• EXCRETION
• TISSUES AND SUPPORTING SYSTEMS
• COMPONENTS OF THE MAMMALIAN SKELETON
• JOINTS
• ALIMENTARY CANAL/DIGESTIVE SYSTEM
• FEEDING HABITS
• FEEDING IN AMOEBA, HYDRA AND MAN
• TRANSPORT SYSTEMS
• CIRCULATORY SYSTEM IN MAMMALS
• MECHANISM OF TRANSPORT IN HIGHER PLANTS

Excretion

Biology, SS 2, Second Term Week: 1

Topic: Excretory System

Introduction

Every organism, from the smallest protist to the largest mammal, must rid itself of the potentially harmful by-products of its own vital activities.

Excretion is the removal of waste products from the chemical reactions that occur inside all living things (organisms). In other words, excretion is the removal of harmful and unwanted toxic waste products of metabolism.

The Chemical reactions of a human are called cell metabolism. The normal waste product from mammals is urea. It is released in urine and sweat. Carbon Dioxide is also something that is excreted from mammals when breathing out. Excretion is important for living things because a build up of the waste products from these chemical reactions is very dangerous for the body because it can, in excess, be poisonous.

The process by which the water content and the ion concentration is regulated and kept constant in the cells is known as osmoregulation. This process results in maintaining the osmotic pressure in the blood and tissue fluids.

The two physiological processes, excretion and osmoregulation are interconnected as they both are responsible for bringing about homeostasis in the body. The physiological mechanisms involved are intimately bound with each other, so much so, in higher vertebrates like mammals, kidneys perform both functions, excretion and osmoregulation.

Note: The terms secretion and egestion are often confused with excretion. Hence it is important to understand clearly what they mean.

Secretion

Secretion is the production of useful chemical substances like hormones, enzymes or other molecules by the cells of glands like the bile, endocrine glands like the islets of Langerhans or unicellular glands like the epithelial mucosal lining of the large intestine.

Egestion

Egestion is expelling the undigested wastes from the body. Food which is not digested and thus is not assimilated by the body is passed to the last part of the alimentary canal called the rectum and egested out in the form of faeces or excreta.

The excretory system is a passive biological system that removes excess, unnecessary or dangerous materials from an organism, so as to help maintain homeostasis within the organism and prevent damage to the body. It is responsible for the elimination of the waste products of metabolism as well as other liquid and gaseous wastes.

Importance of Excretion

Waste products produced in the body by metabolic activities must not be allowed to remain in the body because of the following reasons:

(i) The excretory products are harmful to the body and so must be removed.

(ii) Some are poisonous and must never be allowed to accumulate within the body

(iii) Excretion helps to maintain water balance in the body

(iv) Excretion also helps to maintain salt balance, i.e. homeostasis in the body

(v) Waste products when not removed can interfere with normal metabolic activities of the body.

Excretory Systems or Organs of Some Organisms

Organisms	Excretory systems/organs
(i) Protozoa, e.g. Amoeba	Contractile vacuole, by diffusion
(ii) Flatworms, e.g. tapeworm	Flame cells
(iii) Annelids, e.g. earthworms	Nephridia
(iv) Insects	Malphighian tubules
(v) Crustaceans	Green glands
(vi) Fishes	Kidneys
(vii) Amphibians, e.g. toad	Kidneys
(viii) Reptiles	Kidneys
(ix) Birds	Kidneys and lungs
(x) Mammals	Kidneys, skin, liver and lungs
(xi) Flowering plants	Stomata and lenticels

Different excretory organs or systems have different excretory products they remove. This depends on the complexity of the animal concerned. The excretory organs or systems are the waste products they remove are stated in the table below.

Excretory organs or systems	Waste products excreted
(i) Contractile vacuole	Carbon dioxide, ammonia and water
(ii) Flame cells	Carbon dioxide, ammonia and water
(iii) Nephridia	Water, urea, carbon dioxide and nitrogenous wastes
(iv) Malphighian tubules	Wastes, carbon dioxide and uric acid
(v) Green glands	Water, urea, carbon dioxide and ammonia salts
(vi) Gills	Carbon dioxide, water and urea
(vii) Skin	Sweat containing urea, salts and water
(viii) Liver	Bile salts, water and urea
(ix) Lungs	Carbon dioxide and water vapour
(x) Kidneys	Urine containing urea, salts, water, hormones and uric acid
(xi) Stomata and lenticels	Water, carbon dioxide and oxygen
(xii) Bark of trees	Tannins, mucilage, gum, crystals, anthocyanin, alkaloid, resin, oil and latex.

Based on excretory product animals can be grouped into 3 major groups:

Ammonotelic animals: The organisms whose principle excreta is ammonia are called ammonotelic animals and the process of elimination of ammonia is called ammonotelism. Ammonia is highly toxic, cannot be stored in body for long time. It is readily soluble in water hence it is principle excreta in aquatic crustaceous, annelidans, molluscans, echinoderms, bony fishes and larval form of amphibians.

Uricotelic animals: Organisms whose principle excreta is uric acid are called uricotelic animals and the process of elimination of uric acid is called uricotelism. Uric acid is least toxic, a least soluble in water. Hence it is principle excreta in those organisms which conserve water. Eg:‐ Insects, land snail, reptiles and birds.

Ureotielic animals: Animals whose principle excreta is urea are called ureotielic animals and the process of elimination of urea is called ureotelism. Urea is less toxic than ammonia and more toxic than uric acid. In ornithine cycle ammonia reacts with Co₂ to form urea in liver. Ureotoelic animals are cartilaginous fishes, adult amphibians and all mammals.

Excretory Mechanism in Some Organisms

Contractile Vacuoles – Amoeba (Kingdom Protista)

The water content in the organism has to be regulated as there is a constant inflow of excess water. This is because the cell membrane surrounding the animal is semi permeable and as the protoplasm contains a higher concentration of salts than the water outside, water enters the cell by osmosis. This water is more than what is actually required by the animal. To counter this, excess water collects into the contractile vacuole as fast as it enters the body. The vacuole slowly grows larger until it reaches the maximum size. Then the endoplasm in the area surrounding the vacuole contracts and the fluid contents which contain traces of urea and carbon dioxide are discharged out into the surrounding pond water. Thus the contractile vacuole functions effectively as an organelle that performs both excretion and osmoregualtion.

Flame Cells in Flatworm  (Phylum Platyhelminthes)

A flame cell is a specialized excretory cell found in the simplest freshwater invertebrates, including flatworms, rotifers and nemerteans. Flame cells function like a kidney, removing waste materials. Bundles of flame cells are called protonephridia.

Metabolic waste products of flat worms are excreted generally in the form of NH₃ by diffusion across the general body surface. Flatness is helpful in diffusion. However flat worms release excess water as well as some excretory products through flame cells.

Excretion in Mammals – Human

The body excretes three main waste materials. These are Carbon Dioxide, Urea and Water. Excretion is a very important feature to us because without it toxic substances will build up in our bodies and kill us. It also helps in maintaining the composition of body fluids.

There are four types of excretory organs used by mammals. These are: lungs, skin, liver and kidneys.

The Lungs

The lungs excrete water vapour and carbon dioxide.

 The Liver

The largest internal organ in humans, the liver is also one of the most important. It has many functions, among them the synthesis of proteins, immune and clotting factors, and oxygen and fat-carrying substances. Its chief digestive function is the secretion of bile, a solution critical to fat emulsion and absorption. The liver also removes excess glucose from circulation and stores it until it is needed. It converts excess amino acids into useful forms and filters drugs and poisons from the bloodstream, neutralizing them and excreting them in bile (A bitter, neutral, or slightly alkaline fluid secreted by the liver and passed through a duct into the gallbladder, where it is stored). The LIVER excretes BILE PIGMENTS called BILIRUBIN (derived from the decomposition of haemoglobin).

Test Questions

1. ________ is the removal of waste products from the chemical reactions that occur inside all living things (organisms).
2. The bile pigment excreted by the liver is called _____
   a) bile
   b) bilirubin
   c) pigments
   d) urea
3. Nephridia is the excretory organ found in _____
   a) annelids
   b) crustacean
   c) fish
   d) plants
4. Organisms whose principle excreta is uric acid are called _____ animals
   a) uric
   b) urinal
   c) urethra
   d) uricotelic
5. ______ is expelling the undigested wastes from the body.
6. ______  is the production of useful chemical substances like hormones, enzymes or other molecules by the cells of glands like the bile, endocrine glands like the islets of Langerhans or unicellular glands.
7. Name the excretory organ found in the following
   a) flatworm
   b) crustaceans
   c) fishes
   d) flowering plants 
   e) Protozoa
   f) Insects
8. The process by which the water content and the ion concentration is regulated and kept constant in the cells is known as ______
9. The _______ is a passive biological system that removes excess, unnecessary or dangerous materials from an organism, so as to help maintain homeostasis within the organism and prevent damage to the body. 
10. The normal waste product from mammals is urea. It is released in _____ and ______

Answers

1. Excretion
2. B
3. A
4. D
5. Egestion
6. Secretion
7. Flame cells
   Green glands
   Kidneys
   Stomata
   Contractile Vacuole
   Malphigian tubule
8. Osmoregulation
9. Excretory System
10. Urine and Sweat

Components Of The Mammalian Skeleton

Biology SS2 Second Term, Week 3

Topic: Vertebrate Skeleton

Introduction

The skeleton of vertebrates is composed primarily of bone. Cartilage covers articular surfaces between bones and connects the ribs to the sternum. The skeleton is divided into two major parts:

1.    The axial skeleton includes the skull, mandible, hyoid, ribs, sternum, and vertebrae

2.  The appendicular skeleton includes the girdle, limb and feet bones

The Human Skeleton

The Axial Skeleton

The axial skeleton forms the central axis of the body. It consists of the skull, the vertebral column, the ribs and the sternum or breastbone.

The Axial and Appendicular Skeleton

The Skull

The skull consists of 28 different bones (including the ossicles of the ear). The bones of the skull can be divided into two main groups: the cranium which encloses and protects the brain and the facial bones.

The Skull

The Cranium: The cranium consists of eight flat bones which are rigidly attached to each other with dentate sutures (joints with teeth-like protrusions). They envelop and protect the brain. The frontal bone forms the forehead and portions of the eye sockets (or orbits). The occipital bone, at the base of the skull contains a large opening, called the foramen magnum, through which the spinal cord passes. On each side of the opening is the occipital condyle, by means of which the skull articulates with the first neck or cervical vertebra (the atlas). The organs of hearing are situated in the temporal bone, one on each side. The openings leading into these organs can also be seen on each side.

The Facial Bones: The facial skeleton consists of fourteen irregular bones, which are all (with the exception of the lower jawbone) firmly attached to the cranium by means of sutures. They include the nasal bones, the two jawbones and the cheek bones. The lower jaw articulates with the temporal bone part of the cheek bone, just in front of the ear. This allows for the necessary movement of the lower jaw when food is bitten off and chewed. Both upper and lower jaws have alveolar pockets into which teeth fit.

Cranial and Facial bones

The Vertebral Column

Vertebral column is also called back bone or spine and encloses the spinal cord. It is a flexible, curved, vertical rod, and consists of a row of 33 movably articulated ring like bones called vertebrae. Between each of the two bones the space is supplemented by pads of fibro-cartilage called the intervertebral discs. The vertebrae are held together by ligaments which prevent their dislocation, but permit a degree of movement, making the backbone flexible. The adult vertebral column measures 60-70 cm in length.

The vertebrae are grouped and named according to the region they occupy.

·Seven cervical vertebrae form the neck or cervical region.

·Twelve thoracic vertebrae form the back of the thorax or chest.

·Five lumbar vertebrae form the lumbar region or loins.

·Five sacral vertebrae form the sacrum.

·Four caudal vertebrae form the coccyx or tail.

The vertebrae in the three upper regions remain separate or distinct throughout life, and are called the movable vertebrae. Those in the two lower regions, the sacrum and coccyx, are united in the adult to form two bones and are called, the fixed vertebrae.

Vertebral column

With the exception of the first two cervical vertebrae, all the movable vertebrae have similar structure; a typical vertebra is a bony ring. Its hole is called the vertebral foramen. The front border of the vertebral foramen is very thick. It is known as the body or centrum.

The remaining boundary of the vertebral foramen is thin. It is termed as the vertebral arch. Each half of a vertebral arch has a vertically narrow side, the pedicel, and a broader hind part, the lamina. The two laminae meet in the midline of the back. The upper and lower margins of the pedicel have concavities called the vertebral notches. When vertebrae are articulated together, adjacent notches form apertures– the intervertebral foramina, for the exit of the spinal nerves. The vertebral arch gives off processes to which the muscles are attached. The processes include a median spinous process and paired articular processes and transverse processes. The spinous process projects back and often also downward from the junction of the laminae. The articular processes of the adjacent vertebrae meet to form synovial joints. They provide limited movement between vertebrae. The vertebral foramina of all the vertebrae when intact form a vertebral canal that encloses the spinal cord.

In between the adjacent vertebrae, there are elastic pads of fibrocartilage- the intervertebral discs. This provides mobility to the vertebrae, check undue friction and take up shocks. Displacement of intervertebral disc is called slip-disc and is dangerous.

The Cervical Vertebrae

The neck region consists of 7 cervical vertebrae. The cervical vertebrae are the smallest of the bones, and except the first and the second, which are peculiar in shape, the cervical vertebrae possess the following characters in common. The first cervical vertebra is called atlas. It is almost ring like. It provides up and down or nodding movement to the skull on it. The second cervical vertebra is termed as axis. Its centrum bears an odontoid process, which allows side to side or turning movement to the atlas and skull together on it.

Cervical vertebrae

The bodies of other cervical vertebrae are small and oblong in shape broader from side to side than from backward. The neural arch is large. The spinous processes are divided or bifid terminally. The transverse processes are perforated by foramina for the passage of the vertebral arteries. Thus this important blood vessel is protected as it passes through the vulnerable region of the neck.

The Thoracic Vertebrae

In vertebrates, thoracic vertebrae compose the middle segment of the vertebral column, between the cervical vertebrae and the lumbar vertebrae. In humans, there are twelve thoracic vertebrae and they are intermediate in size between the cervical and lumbar vertebrae; they increase in size going towards the lumbar vertebrae, with the lower ones being a lot larger than the upper. They are distinguished by the presence of facets on the sides of the bodies for articulation with the heads of the ribs, and facets on the transverse processes of all, except the eleventh and twelfth, for articulation with the tubercles of the ribs. By convention, the human thoracic vertebrae are numbered T1-T12, with the first one (T1) located closest to the skull and the others going down the spine towards the lumbar region.

Thoracic Vertebrae

Appendicular Skeleton

The appendicular skeleton is made up of the limbs and limb girdles which is directly concerned with movement in animals.

The limbs: There are two pairs of limbs in every animal, these are the forelimbs and the hind limbs. In man, the forelimbs are free and are called hands. In other animals except Ape and Gorilla, both the fore and hind limbs are used for walking. The forelimbs consists of the arm(humerus, ulna and radius) and the hands(carpals, metacarpals and phalanges) while the hind-limbs consists of the legs(femur, fibula and tibia) and the feet(tarsals, metatarsals and phalanges).

Limb Girdles: Generally, there are two limb girdles and they support the weight of the body. They are:

The Pectoral (Shoulder) Girdles: This  is a group of large flat bones in the shoulder region to which the forelimbs are attached.

The Pelvic (Hip) Girdles: This is another group of large flat bones in the hip region to which hind limbs are attached.

Test Questions

1. The skull consists of ___ different bones
   a) 38
   b) 28
   c) 18
   d) 48
2. The _____  is a group of large flat bones in the shoulder region to which the forelimbs are attached.
3. The pelvic girdle is found in the ____
4. There are two pairs of limbs in animals and these are _____ and ____ limbs
5. The ______ skeleton is made up of the limbs and limb girdles which is directly concerned with movement in animals

Answers

1. B – 28
2. Pectoral Girdle
3. Hip
4. Fore and Hind 
5. Appendicular

Circulatory System In Mammals

Biology, SS 2, Second Term, Week 10

Topic: Circulatory System In Mammals

Introduction

Circulatory system refers to the continuous movement or flow of blood round the body involving the heart and the blood vessels.

Higher organisms e.g. man, require blood to carry materials to and from different parts of their body. There is need for organisms to transport oxygen from the lungs to other living cells within the organisms and also, dissolved food materials absorbed in the villi to other parts of the body which need them. Circulation is the process by which absorbed food materials are carried through arteries, capillaries and veins to all parts of the body where they are utilized for body functioning. Materials which are transported by blood in human body are water, salts, hormones, oxygen, digested food, etc. waste materials also removed from the body through blood circulation.

Parts of the Circulatory System

The organs that are responsible for blood circulation in the body are together called the circulatory system. The circulatory system consists of the blood vessels and the heart.

The Heart

The heart pumps blood to all part of the body through the circulatory system. The heart is a muscular organ that lies in the chest cavity and is almost conical in shape. It is made up of four chambers. These four chambers include two upper chambers which are the right auricle and left auricle; and two lower chambers, the right ventricle and left ventricle. Blood enters the heart at the auricles and leaves from the ventricles. The heart is constantly beating, contracting and relaxing. There are about 70-75 beats per minute although this beating rate may vary with individuals. Beating rate is faster in children than in adults.

Blood Vessels

These are channels or routes through which blood passes to different parts of the body. There are three types of blood vessels; the arteries, veins and capillaries.

1. Arteries: These are the blood vessel that carry blood away from the heart to all parts of the body except the pulmonary artery.
2. Veins: These are blood vessels that carry blood to the heart from all parts of the body except the pulmonary vein.
3. Capillaries: These are tiny networks of blood vessels that connect arteries to veins. Blood flows out from the heart through arteries to all parts of the body, through capillaries and then into the veins, and back to the heart where circulation continues.

Characteristics of Capillaries

1. They are small, very thin walled vessels which lie between the cells of human organs.
2. They connect the arteries with the veins
3. They allow food and oxygen to pass from the blood to the body cells
4. They also collect waste materials from cells
5. They allow the exchange of materials between the blood and cells.

Importance of Circulatory system

1. Helps in excretion of waste products from the body
2. Digested food materials like glucose, amino acids, fatty acids and glycerol are carried from the intestine to the tissues where they are stored or used up, water and oxygen are also carried by the blood.
3. Protection of the body against diseases e.g. white blood cells
4. Regulation of the body temperature: the blood helps in the distribution of heat produced in muscles and organs like liver, to other parts of the body.
5. Helps in blood clotting in wounds e.g. blood platelets
6. Sustains life by supplying nutrients to cells.

Types of Circulatory System

Circulatory system in animals can be grouped into three major categories:

a. Closed and opened circulatory systems

b. Single and double circulatory systems

c. Pulmonary and systematic circulatory systems.

Closed and Opened Circuclatory System

i. Closed Circulatory System:

The closed circulatory systems are made up of blood vessels called arteries from the heart which branch many times into small units called capillaries but eventually join up with other vessels called veins that are connected to the heart. By this design, blood is therefore always confined within the cavities of the vessels and the heart and never comes into direct contact with the cells of the body.

Some invertebrates like annelids and all the vertebrates have closed circulatory systems. In mammals, for example, there is no mixing of oxygenated blood in the heart. While oxygenated blood is confined to the left part of the heart, deoxygenated blood is confined to the right side.

ii. Opened Circulatory System: In this system, the blood vessels lead out of the heart but end in blood spaces called haemocoels within the body cavity. In these spaces, the blood comes into direct contact with the cells after which it is returned to the heart, Arthropods and some molluscs have opened circulatory systems.

Single and Double Circulatory Systems

i. Single circulatory system: In a single circulatory system, the blood only passes through the heart once every time it makes one complete movement round the body. This system is common in fish which has only two-chambered heart – one auricle and one ventricle.

ii. Double circulatory system: In double circulatory system, the blood passes through the heart twice every time it makes one complete movement round the body. Each time the blood passes through the heart, it goes through a separate pathway. This is found in mammals.

The double circulation gives rise to the two pathways involved in double circulatory system called pulmonary and systemic circulation.

Pulmonary and Systemic Circulation

i. Pulmonary Circulation: The pulmonary circulation involves the movement of blood between the heart and the lungs. In other words, it involves the movement of blood from the heart to the lungs for oxygenation.

ii. Systemic Circulation: The systemic circulation involves the movement of blood between the heart and all other parts of the body besides the lungs. In one complete circulation, blood from any part of the body enters the heart for the first time, it is then sent to the lungs for oxygenation. From the lungs, it is brought back to the heart for the second time before it can be redistributed to all parts of the body. This is the sequence involved in double circulation.

Pulmonary and systemic circulation can be represented mathematically by linear equation as:

Pulmonary circulation = Heart + Lungs

Systemic circulation = Heart + Body

The appearance of heart twice in the two equations represents the double circulation of blood in mammals.

Practice Questions

1. _____ are tiny networks of blood vessels that connect arteries to veins
2. _____ are the blood vessel that carry blood away from the heart to all parts of the body except the pulmonary artery
3. _____ refers to the continuous movement or flow of blood round the body involving the heart and the blood vessels.
4. ____ are blood vessels that carry blood to the heart from all parts of the body except the pulmonary vein.
5. In the open circulatory system, the blood vessels lead out of the heart but end in blood spaces called _____within the body cavity

Answers

1. Capillaries
2. Arteries
3. Circulatory
4. Veins
5. Haemocoels

Alimentary Canal/Digestive System

Biology, SS 2, Second Term, Week: 5

Topic: Digestive System

Introduction

The digestive system or alimentary canal or tract is concerned with the breakdown of complex food substances and its conversion in to simpler components, its absorption through the blood stream and assimilation in the cells and tissues producing desired effects of growth. Digestion is the breakdown of food into smaller components that can be more easily absorbed and assimilated by the body. We have two types of alimentary tracts, namely, the complete and incomplete alimentary tract.

· The incomplete tract has just an opening into the outside world which is referred to as the mouth. This serves the purpose of ingestion and egestion. An example of an organism with incomplete alimentary tract is a planarian.

·   The complete alimentary tract has two openings to the outside world. It contains both the mouth and the anus. The mouth serves the purpose for ingestion while the anus serves the purpose for egestion. Example of this group is bird, earthworm, goat and human.

In complete digestive tract, each tract performs different functions and at the end each tract is specialized on what it does. For example when we put yam into our mouth, the teeth breaks it down into smaller particles and pushes it to the esophagus where peristalsis takes place; it is further transported to the stomach where the churning of the food takes place. It further goes to the small intestine, where digestion of food is completed and absorption takes place in the villi while the large intestine absorbs water from the food materials and the remnant are passed through from the Anus away from the body when food is taken in, the incoming food, does not mix with the outgoing undigested food materials.

Alimentary Canal of Planaria
The planaria is a free living flat slender small worm. The tract has a mouth, muscular pharynx and intestine, that is ventrally placed. Its pharynx protrudes from its mouth, whenever it wants to attack a prey. The pharynx leads to the intestine which has three main branches one anterior and two posterior giving rise to a lateral diverticula’s that eventually forms a gastro vascular cavity which is lined with phagocyte cells, glandular storage cells and gland cells. 

Planarian feeds on small crustaceans, nematodes, insects and rotifers and this makes it a carnivorous animal. It kills its prey by entangling them in mucus gland, it then sucks them in small bits into its intestine. Digestion is intracellular and food is distributed to all the body parts by a process known as diffusion.

Adaptive features of alimentary system of a flatworm and their functions

· They (e.g. planarian) have a simple alimentary canal that has just an opening to the outside world. It consists of a mouth on the ventral side of the small intestine.

· The pharynx is muscular and large. It helps to push the food inside it to the small intestine.

· The small intestine with branches enables the digested food to diffuse to all parts of the body while the undigested food is egested from the mouth which really makes it a primitive organism.

Alimentary System of an Earthworm

The alimentary system of an earthworm consists of a long straight tube that is divided two openings: the mouth-through which food enters and the anus-through which undigested food leaves the body. The alimentary canal of the earthworm includes the following parts: mouth, pharynx, oesophagus, crop, gizzard, intestine, caecum, rectum and anus.

The pharynx secretes mucus to lubricate food particles.
The oesophagus has a pair of oesophageal glands that secrete calcium arborvitae that removes excess calcium that has been absorbed in the earthworm’s food. The oesophagus has a narrow tubular wall that transfers the ingested food to the crop.

The crop is a temporary place where it stores its food before they are passed into the gizzard for digestion.

The gizzard has a thick muscular wall with stones, which aids the grinding of food particles.

The intestine is long and straight where extra cellular digestion of food takes place.

Enzymes are released to chemically breakdown the food and the soluble pieces are absorbed.

Anus: The undigested food and soil is egested through the anus as ‘worm casts’.

The Alimentary Canal

Advancement of the alimentary canal of Earthworm over that of planaria

·The Earthworm has a long and straight intestine, which makes it efficient for digestion and absorption of food while the planarian has diffused intestinal branches.

·The earthworm has two openings, which is the mouth and the anus, while the planarian has just one opening, which serves as the mouth.

·The earthworm has a thick muscular gizzard, which it used for the grinding of food particles during digestion which planarian lacks.

·The earthworm absorbs food in the form of blood, while planarian diffuses  food after digestion has taken place.

·The crop of the earthworm serves as a temporary storage of food before digestion takes place while the planarian lacks these products.

Alimentary Canal of Grasshopper or Cockroaches

The alimentary canal is divided into three main portions:

• Foregut
• Midgut
• Hindgut

Foregut

It consists of the mouth surrounded by the mouthparts. The mouth cavity is called the pharynx. It continues as the oesophagus that is short, narrow and thin-walled. The canal then enlarges into crop which is also thin-walled. The crop opens into short, muscular organ, the gizzard or the proventriculus. A pair of Salivary glands lies outside and below the crop.

Each salivary gland is branched, the secretions of all the branches pouring into a common duct. The two ducts, one of each side, open into the mouth cavity at the labium. The entire foregut is lined with chitin. In the gizzard, the chitin (a polysaccharide forming the major constituent in the exoskeleton of arthropods and in the cell walls of fungi) forms teeth and plate to facilitate grinding of the food.

Midgut

Midgut consists entirely of stomach or ventriculus. At the junction of the gizzard and stomach are six pairs of gastric caecae. These are pouch-like structures arranged in a ring-like manner around the anterior end of the stomach. The anterior lobe of each pair of the caecae extends over the proventriculus and the posterior lobe extends over the ventriculus.

The caecae secrete digestive juices and pour them into the stomach. The midgut is not lined by chitin or cuticle but by a peritrophic membrane. This membrane protects the stomach wall from abrasions and is fully permeable to enzymes and digested food.

Hindgut

Hindgut is a coiled structure consisting of anterior ileum, middle colon and posterior rectum. The rectum opens to the exterior through the anus. The hindgut is lined with cuticle. At the junction of the stomach and ileum are attached numerous long tubules called the Malpighian tubules.

Mechanism of Digestion

Digestion starts at the mouth with the mandibles and the maxillae chewing the food. It is also acted upon by enzymes of salivary juice, the salivary carbohydrases which partially digest the food. The food is then swallowed with the help of lubrication provided by the salivary juice.

The food then enters the oesophagus and then into the crop. Here, the masticated food is temporarily stored.

The food then passes into the gizzard which acts as the grinding chamber. At the junction of the gizzard and the stomach is a valve called the pyloric valve. It allows the passage of only the thoroughly digested food into the stomach and also, prevents the regurgitation of food from the stomach.

The grinded food then enters the stomach. The digestive enzymes secreted by the gastric caecae act upon the food in the stomach. These enzymes include amylase, maltase, invertase, tryptase and lipase. The digested food is absorbed through the stomach walls into the surrounding space which is called the haemocoel. From here, it is transported to the different body parts.

In the hindgut, absorption of water takes place and the undigested food is formed into almost dry pellets. These are excreted through the anus as faeces.

Test Questions

1. The ____ secretes mucus to lubricate food particles.
2. Digestion starts at the ____
3. The food then passes into the gizzard which acts as the ______
4.  _______ is the breakdown of food into smaller components that can be more easily absorbed and assimilated by the body
5. The _____ is a temporary place where it stores its food before they are passed into the gizzard for digestion.
6. _____ is a coiled structure consisting of anterior ileum, middle colon and posterior rectum.

Answers

1. Pharynx
2. Mouth
3. Grinding chamber
4.  Digestion 
5. Crop
6. Hindgut

Feeding Habits

Biology SS 2 Second Term

Week: 7

Topic: Feeding Habits

Introduction

Modifications and Mechanisms of Feeding in some Animals

There are five modifications and mechanisms of feeding associated with some organisms. These feeding mechanisms include:

Absorbing Mechanisms, e.g. tapeworm

The tapeworm is an endoparasite which carries out parasitic feeding on its host i.e., the man. It has no mouth but absorbs digested food from the intestine of its host. The body of the tapeworm is modified and adapted for parasitic feeding as follow:

1. The alimentary canal is absent, hence food is absorbed through its entire body surface
2. The tapeworm has hooks and suckers which are used for attachment to the intestine of the host to avoid dislodgement
3. The body has thick cuticle which resists digestive enzymes of the host
4. The flat body surface of the tapeworm provides a large surface area for the absorption of already digested food
5. The entire body surface is used also for the absorption of food  

Biting and Chewing Mechanism, e.g. Grasshopper or Cockroach

The grasshopper or cockroach has mouth parts adapted for biting and chewing. These insects have four different mouth parts which are modified and adapted for biting or chewing food. These mouth parts are:

Labrum: The grasshopper has labrum or upper lip which prevents the food from falling off the mouth

Mandibles: It possesses a pair of mandibles which are heavy, toothed and jaw-like structure used for cutting and chewing food materials.

Maxillae: The grasshopper also has a pair of maxillae which is also a biting blade. This breaks down the food which the mandibles have chewed into smaller particles

Labium: The labium (lower lip) prevents the wastage of food from the mouth.

Sucking Mechanisms

There are three popular organisms which exhibit sucking mechanism. These are mosquito, butterfly and housefly. These insects have different modifications of mouth parts adapted for feeding on food through the mechanism of sucking.

Piercing & sucking mouth parts in mosquitoes  

In mosquito, mouth parts are piercing & sucking type i.e. they are adapted for piercing the tissues of animal or plants to suck blood or plant juice.

The mouth parts consist of labium, labrum-epipharynx, hypopharynx, mandibles & maxillae.

Labium: The labium is modified to form a long, straight, fleshy tube called proboscis. It has a deep labial groove on its upper side. At the distal end of labium is a pair of small tactile labella which are reduced labial palps.

Function: The labial groove lodges all other mouthparts. During piercing, labella guide the mandibles & maxillae. The whole labium bends back to allow needle like mouthparts to go in the flesh.

Labrum (epipharynx): The labrum is long & needle like with ventral groove. The epipharynx is fused with the labrum forming labrum- epipharynx.

Function: It covers the labial groove dorsally from inside. This structure appears C – shaped in transverse section having a groove called food channel.

Hypopharynx: Food channel is closed below by a long, pointed & flattened plate, like a double edged sword, called hypopharynx. It possesses a salivary duct, opening at its tip.

Function: Through this duct saliva is poured to prevent coagulation of blood during sucking.

Mandibles & maxillae: Within the labial groove lies paired, long, needle shaped mandibles & maxillae. Mandibles end in sharp tiny blades, while maxillae into saw like blades bearing teeth.

Function: Mandibles & maxillae act as piercing organs.

In male the labrum-epipharynx & the labium are the same as in the female, but the mandibles & maxillae are very short & functionless & the hypopharynx is fused with the labium.

Mechanism of feeding: The normal foods of both sexes are nectar of flower & juices of plants, but the female possesses modified mouth parts for obtaining additional meals of blood of vertebrates. A female mosquito sits on a vertebrate & presses its labellae of proboscis against the skin. Labellae act as a guide for the piercing mandibles & maxillae.  The labium bends back and mandibles & maxillae pierce deep into the skin in order to puncture the blood capillaries.

Saliva, acting as an anticoagulant, is injected down the hypopharynx into the wound. The labrum-epipharynx & hypopharynx together form a feeding tube to suck up blood. The suction is caused by the pharynx by which blood comes into the mouth.

Butterfly

The butterfly feeds on liquid food like nectars of flowers. It has its mouth parts modified for sucking in the following ways:

• It possesses a long coiled proboscis (galea) used for sucking nectars of flowers
• The insect is capable of recoiling the long proboscis under its head when not in use
• There is the non-functioning of the other mouth parts due to the type of food taken by the insect

Housefly

The housefly feeds on liquid food materials. It has mouth parts modified for sucking in the following ways:

• The housefly possesses enlarged labella which are sucking structures for liquid food.
• The housefly has the ability to feed on solid food, e.g. sugar by pouring out its saliva to change the food to a liquid state.
• It has a sucking mechanism called sponging in which the mouth is places on the liquid food and it will start to rush into the mouth
• The labella have fine channels which aid rapid absorption of liquid food into the mouth.

Grinding Mechanism

Grinding mechanism is common among mammals, e.g. man, cattle, sheep, goat, etc. These animals are capable of grinding the food before swallowing. This grinding is aided by the presence of hard and strong teeth made of enamel and dentine.

The animals are adapted to the grinding mechanism by the following features:

• They possess different sets of teeth
• The teeth are hard and strong to withstand biting, chewing or grinding and cracking of food
• They possess incisors which are sharp with flat edges used for cutting off bits of food
• Animals have pointed canine teeth which are used for tearing food
• There is presence of premolars and molars with undulating and wide surfaces used for grinding of food
• The absence of front teeth (incisors) in sheep (a herbivore) is a special adaptation as it helps to grip the grasses during feeding by the animal

Trapping and Absorbing Mechanism

The trapping and absorbing mechanism are common among the insectivorous or carnivorous plants such as bladderwort and sundew. Bladderwort and sundew have structures which enable them to adapt to this mode of feeding.

• Sundew, for example, traps insects by undergoing nastic movements in response to touch from the body of the insects
• The sundew leaf has long hairs which carry digestive glands
• Insect on landing on these hairs causes other hairs to curl over the insect and cover it
• The sundew is capable of secreting a fluid rich in enzyme to digest the insect externally
• The protein so synthesised is easily absorbed by the carnivorous plant into its body

Feeding Habits

Filter feeders: These are aquatic animals that use a body structure similar to a filter basket to gather plants and animals suspended in the surrounding water. The filter feeder siphons water into its mouth and then filters it to obtain small organisms to digest. The tube sponge is a filter feeder. Other examples include flamingos, tube worms, clams, barnacles, and baleen whales.

Fluid feeders: Animals which feed on any fluid materials are classified as fluid feeders. There are two major groups of fluid feeders, these are wallowers e.g. tapeworm and suckers e.g. mosquito. They obtain food by sucking or licking nutrient-rich fluids from live plants or animals. Fluid feeders have mouth parts that are adapted to pierce or rip skin or leaf tissue. The same or other mouth parts are used to suck or lick the blood or sap that is their food. Examples of fluid feeders include mosquitoes, ticks, aphids, spiders, bees, butterflies, vampire bats, and hummingbirds.

Substrate feeders: These live in or on their food source and eat their way through it. Examples of substrate feeders include caterpillars and earthworms. Caterpillars eat their way through the green tissues of leaves. Earthworms eat their way through the soil, ingesting soil particles containing partially decayed organic material as they go.

Test Questions

1. Give an example of an  insect which exhibits sucking mechanism.
2. Mandibles & maxillae act as ______ organs 
3. What are Substrate Feeders?
4. Grinding mechanism is common among _____
5. List three types of feeding habits

Answers

1.  Mosquitoes, Butterfly
2. Piercing
3. They live in or on their food source and eat their way through it
4. Mammals  
5. Filter feeders
   Substrate feeders
   Fluid Feeders                                                                                                  

Feeding in Amoeba, Hydra and Man

Biology, SS 2, Second Term, Week: 8

Topic: Feeding in Amoeba, Hydra and Man

Amoeba Feeding

Amoeba feeds on microscopic organisms such as single-celled algae and bacteria. When the amoeba encounters a suitable organism, the cytoplasm flows round the prey and engulfs it, with a drop of water, in a food vacuole. The cytoplasm secretes enzymes into the food vacuole. The enzymes digest the soft parts of the prey and the soluble products are absorbed back into the cytoplasm. Any undissolved residue is left behind as the amoeba flows on.

Feeding in Hydra

Hydra feeds on a variety of small aquatic animals, such as Daphnia and Cyclops, which it catches by means of lots of tiny stinging cells on its tentacles. Scattered over the outer layer tentacles are a great many of these stinging cells called cnidoblasts. Smaller numbers occur on the main body. Each cnidoblast contains a capsule (nematocyst) from which projects a small “trigger” called a cnidocil. Inside each capsule is a tiny hollow thread. It is inverted like a finger of a glove which is pushed into the hand part. These threads are the food-catching apparatus.

Feeding in Mammals

Mammals may eat animals, vegetation, or a mixture of the two. Different words are used to describe mammals and the type of feeding:

• Carnivore: A mammal that eats other animals (flesh or meat eaters).
• Herbivore: A mammal that eats plants.
• Omnivore: A mammal that can eat both plants and meat.

When mammals eat, the food is first broken down into smaller pieces in the mouth. The teeth carry out this mechanical process. There is a row of teeth in the top jaw and a row of teeth in the bottom jaw. When the jaws are moved, the teeth met in different ways so that the food the animal eats is crushed.

Dentition

Dentition refers to the number, arrangement and conformation of teeth in an organism.

Types of Dentition

There are two main types of dentition. These are:

1.    Homodont dentition: In this type of dentition, the organisms have the same type of teeth. No set of teeth is specialised for any function. All the teeth are of the same shape, size and functions. Examples of homodont dentition are found in fishes, amphibians and reptiles.

2.    Heterodont dentition: In this type of dentition, the organisms possess teeth of different shapes, sizes and functions. Examples of organisms having heterodont dentition are mammals, e.g. rabbits, man, dog, cattle, etc.  

There are different kinds of teeth in the mouths of mammals. These are incisors, canines, premolars and molars. The type of teeth possessed by an animal is closely related to the type of food it eats.

Mammals again have two sets of teeth. These are milk teeth and permanent teeth

1.    Milk Teeth: This is the set of teeth possessed by the young ones (i.e. children in the case of human) and it is made up of the incisor, canine and premolar teeth (i.e. without the molar). Milk teeth later fall off to be replaced by the permanent teeth.

2.    Permanent Teeth: This is the set of teeth possessed by adult mammals and is usually four types. They remain till old age and may number up to 32 in man.

Types of Teeth

• The incisors are at the front of the mouth.
• The canines are behind the incisors on each side (although they are missing in some mammals).
• The premolars are at the sides of the mouth.
• The molars are right at the back of the mouth, on each side.

Structure of a Tooth

A typical tooth such as the canine or incisor is made up of three regions which are the crown, the neck and the root.

• The crown is the part of the tooth that is above the gum·
• The root is the part of the tooth that is embedded in the socket of the gum·
• The neck is the narrow junction between the crown and the root.
• Incisors and canine have one root each while premolars and molars may have two or three roots each.
• Enamel is white in colour. It is the hardest substance in the human body and covers the outer portion of the crown. It is made up of mineral salts (of calcium and magnesium) and keratin. It can withstand high pressure.
• Cement is the layer present covering the root portion of the tooth. It is made up of mineral salts and water and is almost as hard as bone.
• Periodontal membrane or ligament – It consists of fibres which extend across the cement and anchor the tooth in the bony socket. They also allow a certain degree of movement while chewing thereby acting as shock absorbers.
• Dentine is yellow and is a bone-like material which is present along the full height of the tooth. It is enclosed by the enamel in the crown portion and cement in the root portion. Dentine can also be composed of living cells which show divisions with new cells being added to it regularly.
• Pulp cavity is the innermost region of the teeth and shows the presence of blood vessels and nerve endings. The blood vessels serve to nourish the tooth and the nerves transmit messages of heat, cold and pain to the brain and back. The pulp cavity in the root portion is also referred to as the root canal. The number of root canals may range from 1 to 3 depending on the type of tooth. The blood vessels and the nerves enter the root canal through a small hole at the tip of the root canal.

Dental Formula

The dental formula refers to the numbers and types of teeth present in the mouth of an animal. The numbers and types of teeth present in the jaw of an animal is a reflection of special adaptation of mammalian teeth for feeding.

Teeth of a carnivore – the dog

The teeth in carnivores are well designed for dealing with flesh and bones

Incisors: These are small and designed to meet together to grip the prey and pull the meat apart.

Canines: These are large, sharp and pointed. They may be used for holding and killing the prey, and also for tearing the meat apart.

Premolars and molars: These are powerful teeth that meet together and can crush flesh and bone.

Carnassials: These do not meet, but pass each other, rather like a pair of scissors, so that the meat iscut into pieces and the bones cracked.

Jaw hinge: This only allows up and down movement to provide a firm scissor action. There is nosideways movement.

The dental formula for dog:

Puppy (temporary teeth) not presents at birth – but complete by 60 days.

I – 3/3  C- 1/1  P – 3/3  M – 0/0 = 14 x 2 = 28

Adult (permanent teeth) – emerge at about 4 months of age

I – 3/3   C – 1/1   P – 4/4   M – 2/3 = 21 x 2 = 42

Teeth of a herbivore

The teeth in herbivores are well designed for dealing with plant material. It indicates that in the upper right (or left) half of the jaw there are no incisors or canines (i.e. there is a diastema), three premolars and three molars. In the lower right (or left) half of the jaw are three incisors, one canine, three premolars and three molars

The dental formula for sheep:

Temporary teeth

I – 0/4  C – 0/0  P – 3/3  M – 0/0 = 10 x 2 = 20

Permanent teeth

I – 0/4  C – 0/0  P – 3/3  M – 3/3 = 16 x 2 = 32

In sheep the permanent teeth are not completely erupted until 3.5 – 4 years of age

Teeth of an omnivore – the Human

Incisors: Used for biting – apples, for example.

Canines: Not as large and powerful as those of a dog, although they can be used for tearing.

Premolars and molars: Used for chewing and crushing food. These teeth slide over each other as the jaw moves from side to side.

Jaw hinge: The hinge joint in a Human skull allows some sideways movement, so the bottom jaw can move both up and down and from side to side.

The dental formula for man where I = incisors, C = canines, P = premolars and M = molars:

Man (adult): I – 2/2   C – 1/1   P – 2/2   M – 3/3 = 16 x 2 = 32

During the life span of man, he grows two sets of teeth. This condition is called diphyodont. The teeth, which appear during the infancy, number only 20 and are temporary. They start falling from around the age of 5. They are thus called deciduous teeth (also called milk teeth). In each jaw there are 10(4 incisors, 2 canines and 4 pre-molars).

The permanent teeth take the place of the milk teeth after they fall. The types of teeth remain the same. In addition to these 20 teeth, the permanent set have 12 molars which are present 3 on each side. Thus, a total of 32 teeth are present in the normal human adult.

Dental Care

Keeping your teeth and gums healthy requires good nutrition and regular brushing and flossing. The teeth can therefore be cared for in the following ways:

• Brush your teeth twice a day—in the morning and before bed—and floss once a day. This removes plaque, which can lead to damaged teeth, gums, and surrounding bone.
• Use toothpaste that contains fluoride, which helps prevent tooth decay and cavities. Ask your dentist if you need a mouthwash that contains fluoride or one with ingredients that fight plaque. Look for toothpastes that have been approved by the American Dental Association.
• Avoid foods that contain a lot of sugar. Sugar helps plaque grow.
• Avoid using tobacco products, which can cause gum disease and oral cancer. Exposure to tobacco smoke (secondhand smoke) also may cause gum disease as well as other health problems.
• Practice tongue cleaning. You can use a tongue cleaner or a soft-bristle toothbrush, stroking in a back-to-front direction. Tongue cleaning is particularly important for people who smoke or whose tongues are coated or deeply grooved.
• Schedule regular trips to the dentist based on how often you need exams and cleaning.

Practice Questions

1. A mammal that eats other animals (flesh or meat eaters) is called _____
   a) herbivores
   b) carnivores
   c) omnivores
   d) savages
2. Permanent teeth in the normal human adult is __
   a) 22
   b) 32
   c) 42
   d) 33
3. One of the following is not a type of teeth ___
   a) Molar
   b) Premolar
   c) Cay-nine
   d) Incisor
4. The dental formulae for adult dog of 4months of age is ____
5. _____ is yellow and is a bone-like material which is present along the full height of the tooth.
   a) Dentine
   b) Dentist
   c) Dental
   d) Enamel
6. ____ is the hardest substance in the human body and covers the outer portion of the crown
   a) Dentine
   b) Incisor
   c) Crown
   d) Enamel
7. _____ refers to the number, arrangement and conformation of teeth in an organism.
   a) Teeth
   b) Dental
   c) Dentition
   d) Tooth
8. ____ are used for chewing and crushing food.
   a) molars
   b) canine
   c) premolars
   d) a & c
9. One of the following is not a way to care for your teeth
   a) Chew gum regularly
   b) Brush your teeth twice a day
   c) Avoid foods that contain a lot of sugar
   d) Use toothpaste that contains fluoride
10. ____ is used for biting
    a) molars
    b) premolars
    c) canine
    d) incisors

Answers

1. B
2. B
3. C
4. I – 3/3   C – 1/1   P – 4/4   M – 2/3
5. A
6. D
7. C
8. D
9. A
10. D

Transport Systems

Biology, SS 2, Second Term, Week: 9

Topic: Transport Systems

Introduction

Organisms need to be able to move materials such as respiratory gases, nutrients, waste products and heat both into and out of, and within its body.

A transport system is a means by which materials are moved from an exchange surface or exchange surfaces to cells located throughout the body system.

Specialized exchange surfaces are biological structures whose features are such that they permit the highly efficient transfer of materials e.g. respiratory gases, across them via mechanisms such as diffusion or active transport. Although many micro-organisms accept materials directly through their cell membrane.

Mass flow is the movement of a fluid in one direction, usually through a system of tube-like vessels. Examples of mass flow in mass transport systems include the movement of blood and the movement of xylem and phloem through plants.

Need for Transportation

The need for transportation in living organisms includes:

1.    Transport is necessary for every cell of the organism to obtain all the essential materials for its metabolism, e.g. nutrients, oxygen, water etc.

2.    It is also necessary to remove and dispose metabolic wastes, e.g. carbon dioxide, water, urea etc.

3.    In plants, transport is necessary to move mineral salts and water from the roots to the stems and leaves.

4.    Transport is also required to move hormones in plants and animals from where they are produced to the area of need.

5.    Glucose from the leaves and storage organs are some of the substances being regularly transported in plants

Features of Transport Systems

Transport systems in many different types of organisms have lots of common features, such as:

Contains a transport medium in which materials of various sizes and shapes can be conveyed. This medium is usually water-based. Water acts as a solvent for a wide range of substances and flows easily at the temperatures of living organisms. Examples of transport media in animal transport systems include blood, lymph and hemolymph.

A structure or ‘system’ of vessels that contain or enclose the transport medium and extend via a branching network, to all locations to which materials carried must be transported. This doesn’t apply to ‘Open Circulatory Systems’, which may have some vessels but the transport medium is not retained within them at all times. 

A mechanism for moving the transport medium through the system, e.g. through a network of vessels. Movement of a fluid through a system requires a difference in pressure between parts of the system.

i.Animal Transport Systems sometimes include a pumping organ such as the heart in mammals, birds and some other creatures. They may also use other mechanisms such as muscular contraction of muscle tissues as well as, or instead of, a heart.

ii.    Plant Transport Systems tend to rely on passive physical process e.g. evaporation of water.

·    Mechanism(s) to maintain the mass flow movement of the transport medium in one direction. The pressure difference that moves the transport medium through the system is helpful but not necessarily sufficient to prevent back-flow. Some of the vessels in the circulation systems of animals include valves that prevent black-flow of the fluid contained in the vessel.

Materials for Transportation

The following things are transported by blood:

§  Nutrients (e.g. glucose, amino acids, etc.)

§  Antibodies: Antibodies are produced by white blood corpuscles and transported by the blood to all parts of the body for tissue respiration or for storage in storage organs.

§  Carbon dioxide: Animals breathe in oxygen and breaths out CO_2. Metabolic process of respiration going on in the body cells constantly releases carbon (IV) Oxide and water. These diffuse in exchange of oxygen across the capillary wall into the blood stream. The release of carbon (IV) Oxide from the body of animals helps to maintain the adequate internal body temperature of animals.

§  Hormones: Hormone is produced by the endocrine glands of the animal body. It is transported by blood to the action sites. These action sites are where these hormones are needed and used.

§  Oxygen: Oxygen is the principal gas that holds the lives of animals. The red blood cells contain haemoglobin. This haemoglobin combines with oxygen to form what is called Oxyhaemoglobin. The oxyhaemoglobin assists in distributing oxygen to cells and tissues where they are needed in the body.

§  Urea: Waste products arising from body metabolism of animals are carried by blood to the kidney, skin and so on for excretion. In the other words, urine is transported from the kidney to the bladder and then excreted from the body through the possible part of the body.

§  Heat (not a molecules, unlike all the others)

§  Excess salts: These are also produced from cells and excreted by the skin and kidney

§  Water: This is a universal solvent. All living things both plants and animals needs water for survival. The total amount of water in a man of average weight (70 kilograms) is approximately 40 litres, averaging 57 percent of his total body weight. Water is transported from one part of human body to the other. Water is also released as sweat through the skin pores. It is a very important class of food needed by animals.

Media of Transportation

In all organisms, a liquid or fluid is the medium of transportation of materials. Generally, there are four major media of transportation which are:

Cytoplasm

Cytoplasm is used as the medium of transportation of materials in lower unicellular organisms such as Amoeba and Paramecium. Materials such as glucose, amino acids, oxygen, water and carbon dioxide are transported from one part of the cell to another through cytoplasm.

Cell sap or Latex

Cell sap or latex is used as the medium of transportation of materials in plants. Cell sap is a concentrated solution found in the vacuole of cells which serves as a stronger solution. As a result of this the cell sap is able to transport water and dissolved mineral salts from the soil through the root hairs to the upper parts of the plants.

Blood

The blood is a powerful medium of transportation of materials in most animals especially vertebrates. The blood in its fluid state is able to move large materials over the entire body through blood vessels like arteries, veins and capillaries from where they are produced or obtained to their point of destination.

Lymph

Lymph is one of the media of transportation in higher animals. it is a fluid similar in composition to tissue fluid, although it contains extra lymphocytes, there is no red cell present. It returns fluid to the main veins through opening in the subclavian (left jugular) vein below the neck. Example of lymph vessel is the lateal which transports fatty acids and glycerol.

Practice Questions

1. A ____ is a means by which materials are moved from an exchange surface or exchange surfaces to cells located throughout the body system.
   a) Transport system
   b) Circulatory system
   c) Respiratory system
   d) none of the above
2. ____ is the principal gas that holds the lives of animals
   a) carbon(iv)oxide
   b) oxygen
   c) nitrogen
   d) a & b
3. ____ is not a medium of transportation in Organisms
   a) lymph
   b) blood
   c) cell sap
   d) water
4. Oxygen in the blood combines with haemoglobin to form _____
5. Hormone is produced by the _______ of the animal body
6. One of the following is not a material transported by the blood
   a) urea
   b) nutrient
   c) antigens
   d) Oxygen
7. Excess salts is excreted by the ____
   a) skin
   b) kidney
   c) bladder
   d) a & b
8. The total amount of water in a man of average weight (70 kilograms) is approximately ___ litres
   a) 40
   b) 50
   c) 60
   d) 45
9. _____ is a concentrated solution found in the vacuole of cells which serves as a stronger solution
   a) hypoglycemic solution
   b) cell membrane
   c) cell sap
   d) nucleus
10. Another name for cell sap is ____

Answers

1. A
2. B
3. D
4. Oxyhaemoglobin
5. Endocrine glands
6. C
7. D
8. A
9. C
10. Latex

Tissues And Supporting Systems

Biology, SS 2 Second term

Week 2

Topic: Supporting Tissues and Systems

Introduction

Living organisms including plants and animals need tissues to enable them carry out life processes such as movement, respiration, etc. For example, without the various bones and tissues, vertebrates may not be able to stand, respire, move and carry out their life processes.

Skeleton

Skeleton is the bony framework of the body which provides support, shape and protection to the soft tissues and tissues in animals.

The human skeleton consists of 206 bones. We are actually born with more bones (about 300), but many fuse together as a child grows up. The longest bone in our bodies is the femur (thigh bone). The smallest bone is the stirrup bone inside the ear. Each hand has 26 bones in it. Your nose and ears are not made of bone; they are made of cartilage, a flexible substance that is not as hard as bone. The bones support your body and allow you to move. Bones contain a lot of calcium (an element found in milk and other foods). Bones manufacture blood cells and store important minerals.

Biological Significance of Skeleton

1. Support and Shape: The skeleton is a support structure, providing shape to the body. It also acts as the protective framework that is needed to keep the body organs safe.
2. Protection: The bones of the skeleton protect the delicate internal organs and the soft tissue of the body, keeping the inner body safe from trauma due to falls or injuries.
3. Movement: The bones are connected to skeletal muscles that permit the body to move. Bones act as levers and when the muscles contract they pull on a bone and allow it to move.
4. Blood Cell Production: Haemopoiesis, or blood cell formation, takes place in the red bone marrow. Blood cells are essential to life and play a huge role in keeping the body healthy as well.
5. Mineral Storage: Skeletal bones are able to store phosphorous and calcium, which may then be released in the necessary amount, to keep the body at a level of homeostasis, or a state of balance.

Skeletal Components

The skeleton is composed of fibrous and mineralized connective tissues that give it firmness and flexibility. It consists of bone, cartilage, tendons, joints, and ligaments.

1. Bone: A bone is a type of mineralized connective tissue that contains collagen and calcium phosphate, a mineral crystal. Calcium phosphate gives bone its firmness. Bone tissue may be compact or spongy. Bones provide support and protection for body organs.
2. Cartilage: This is a form of fibrous connective tissue that is composed of closely packed collagenous fibers in a rubbery gelatinous substance called chondrin. Cartilage provides flexible support for certain structures in adult humans including the nose, trachea, and ears. In mammals, there are three types of cartilages:
3. Hyaline cartilage: This is found in trachea and bronchi which keep them open and the surface of moveable joints
4. Fibro-cartilage: It is tougher than hyaline cartilage and it is found in the discs between the small bones (vertebra) of the vertebral column
5. Elastic cartilage: This is found in the external ear (pinnae) and epiglottis

Difference between Bones and Cartilages

Bone	Cartilage
Bones is made up of living and non-living cells	Cartilage is made up of mainly living cells
It is not flexible, especially in adult	It is very flexible both in adults and young ones
It can never be replaced by a cartilage	It can easily be replaced by bone
It is made up mainly of mineral salts	It is not made up mainly of mineral salts
It is a stronger and more rigid tissue	It is not so strong but it is a flexible tissue

1. Tendon: This is a fibrous band of connective tissue that is bonded to bone and connects muscle to bone.
2. Ligament: This is a fibrous band of connective tissue that joins bones and other connective tissues together at joints.
3. Joint: This is a site where two or more bones or other skeletal components are joined together.

Types of Skeleton

The three types of skeleton are hydrostatic skeleton, endoskeleton and exoskeleton. Hydrostatic skeleton is found in cold-blooded animals including invertebrates. We human beings have endoskeleton. Exoskeleton is found in insects.

Hydrostatic Skeleton

It is found in soft-bodied and cold-blooded animals. This skeleton has a coelom, which is a fluid-filled cavity. This coelom is surrounded by muscles and the rigidity caused by the fluid and the muscles serve as a supporting structure for the organisms. The fluid pressure along with the motion of the supporting muscles helps the organisms to change shape and move. Echinoderms, cnidarians, annelids, nematodes and some other organisms use the hydrostatic skeleton for movement. The Earthworm which is an annelid is boneless. With the help of hydrostatic skeleton it burrows through the ground. Examples of echinoderms are the star fish and the sea urchin. The Jelly fish is a cnidarians.

Endoskeleton

The simplest definition for endoskeleton is that it is the skeleton found inside the body. It forms the frame work for the animal. The tissues and muscles are formed around the skeletal system and the muscular forces are transmitted to this skeleton. The Endoskeleton supports the animal structure. It is composed of mineralized tissues. In Phylum Chordata, Porifera and Echinodermata endoskeleton is present. The animals that come under Phylum Chordata are all vertebrates including human beings.

Exoskeleton

These are skeletons found outside the body. It forms a protective covering for the animals. It supports as well as protects the animals. All crustaceans have exoskeleton. Crabs, spiders, lobsters, insects are all crustaceans. Most invertebrates do possess cuticle which is composed of chitin. Chitin is a non-living substance commonly found covering the outer part of the body of some animals.  Animals with exoskeleton are usually small. This is because large animals could not be supported by exoskeleton and need bones to support them. Animals with exoskeleton have a head and abdomen and in some cases, a thorax. The exoskeleton is soft and thin at the joints where it has to bend. The large exoskeletons are called shells. Tortoise is one animal that has a shell and endoskeleton.

Test Questions

1. ____ is the name of the skeleton found inside the body
   a) Exoskeleton
   b) Hexoskeleton
   c) Endoskeleton
   d) Hydrostatic skeleton
2. The human skeleton consists of ___ bones
   a) 306
   b) 206
   c) 106
   d) 406
3. ______ is a non-living substance commonly found covering the outer part of the body of some animals.
   a) Chitin
   b) Keratin
   c) Cartilage
   d) Skeleton
4. _____ is a fibrous band of connective tissue that joins bones and other connective tissues together at joints.
5. ______ is a form of fibrous connective tissue that is composed of closely packed collagenous fibers in a rubbery gelatinous substance called chondrin.
6. _____ is tougher than hyaline cartilage and it is found in the discs between the small bones (vertebra) of the vertebral column
   a) Fibro – cartilage
   b) Elastic – cartilage
   c) Cartilage
   d) Bone
7. The longest bone in the body is called _____

Answers

1. C
2. B
3. A
4. Ligament
5. Cartilage
6. A
7. Femur

Joints

Biology SS2 Second Term

Week 4

Topic: Joints

Introduction

The human skeleton consists of more than 200 bones. The individual bones are attached in such a way that a large variety of co-ordinated movements are made possible in different parts of the body. These movements are made possible by skeletal muscles, the fact that the bones act as levers, cartilage which reduces friction and ligaments which prevent dislocation and the presence of movable joints. The site or place where two or more bones of the skeleton are attached to each other is called a joint or place of articulation.

A joint or place of articulation is formed where two or more bones come in close contact in the body and are attached to each other by ligaments.

Types of Joints

Joints can be classified according to the degree and type of movement they allow. The following types of joints can be recognized:

1. Fibrous (or Immovable) Joints

These joints are firmly held together by a thin layer of strong connective tissue. There is no movement between the bones such as the sutures of the skull and the teeth in their sockets.

2. Cartilaginous Joints

Cartilaginous joints are joints where the articular surfaces of the bones forming the joints are attached to each other by means of white fibro-cartilaginous discs and ligaments which allow only a limited degree of movement. Examples are the cartilaginous between the vertebrae, the cartilage in the symphysis which binds the pubic bones together at the front of the pelvic girdle and the cartilage in the joint between the sacrum and the hip bone.

A cartilaginous joint between two vertebrae

3. Synovial Joints

These are freely movable joints. Most of the joints in the body are of the synovial type. The following are the main characteristics of a synovial joint:

• The ends of the bones are covered with a layer of smooth hyaline cartilage, called articular cartilage in the joint regions. This reduces friction at the point.
• The joint is completely enclosed by a bag-like capsular ligament which holds the joint together and helps to contain the synovial fluid.
• The capsular ligament is lined with a synovial membrane. This membrane secretes synovial fluid into the synovial cavity and acts as a seal, waterproofing the joint. The synovial fluid lubricates the joint.
• In addition to the capsule, the bones are also attached and held together by strong, tough ligaments made of dense connective tissue. These ligaments prevent dislocation during normal movement. The articulating surfaces of adjacent bones are reciprocally shaped.
• Synovial joints can be subdivided into the following groups according to the type of movement they carry out:

4. Ball-and-Socket Joints

These joints are formed where the rounded head of one bone fits into the hollow, cup-shaped socket of another bone such as the shoulder joint and the hip joint. Such joints allow freedom of movement in all directions.

5. Hinge Joints

These joints occur where the convex surface of one bone fits into the concave surface of another bone, so making movement possible in one plane only. Examples of these joints are the knee and the elbow joints. Hinge joints have ligaments mainly at the sides of the joints.

      6. Gliding Joints

This type of joint allows for gliding movements between flat surfaces as the surfaces slide over one another. Only a limited amount of movement is allowed such as the joints between the carpal bones, the joints between the tarsal bones and those between the articular processes (zygapophyses) of successive vertebrae.

7.   Pivot Joints

This is the Rotation of one bone around another. A bony ring rotates round the pivot (axis) of another bone such as the ring-like atlas rotating around the odontoid process of the axis, allowing the head to turn from side to side.

Top of the neck
(atlas and axis bones)

Structure of Joints

Joints consist of bones, muscles, cartilage, tendons, ligaments and other connective tissue. Muscles keep the bones in place and also through contraction or extension help move the bones. Cartilage prevents the bone ends from rubbing directly on to each other. Cartilage is not as hard and rigid as bone, but is stiffer and less flexible than muscle. Tendons are bands of fibrous tissue that connect muscles to bones. Ligaments are bands of fibrous tissue that connect the ends of bones together to form a joint.

The Human Joint Structure

The human joint structure

• Cartilage reduces friction. Acts as a shock absorber.
• Synovial fluid lubricates the joint.
• Synovial membrane produces synovial fluid.
• Tendon joins muscle to bone enabling movement.
• Ligament joins bone to bone, stabilising the joint.

Supporting Tissues in Plants

The development of stable supporting elements has been an important prerequisite for the evolution of large terrestrial organisms. Animals have endo- or exoskeletons that correspond in function to the woody stems or trunks of plants. The strength of tissues protects also against enemies. The hard shell of many seeds prevents a chewing to pieces or puncturing by animals and avoids that parasites like fungi or bacteria force their way into them.

 Extensive specialized supporting tissues exist only in vascular plants. Vascular plants have up to four types of supporting tissue:

1. The collenchyma, a tissue of living cells,
2. The sclerenchyma, a tissue of nearly always dead cells, and
3. The vascular tissue consisting of both living and dead cells. It is responsible for the transport and dispersal of water, nutrients and assimilates.
4. Parenchyma

Parenchyma

The cells of parenchyma are large, thin-walled, and usually have a large central vacuole. They are often partially separated from each other and are usually stuffed with plastids.

In areas not exposed to light, colourless plastids predominate and food storage is the main function. The cells of the white potato are parenchyma cells.

Where light is present, e.g., in leaves, chloroplasts predominate and photosynthesis is the main function.

Sclerenchyma

The walls of these cells are very thick and built up in a uniform layer around the entire margin of the cell. Often, the cell dies after its cell wall is fully formed. Sclerenchyma cells are usually found associated with other cells types and give them mechanical support.

Sclerenchyma is found in stems and also in leaf veins. Sclerenchyma also makes up the hard outer covering of seeds and nuts.

Collenchyma

Collenchyma cells have thick walls that are especially thick at their corners. These cells provide mechanical support for the plant. They are most often found in areas that are growing rapidly and need to be strengthened. The petiole (“stalk”) of leaves is usually reinforced with collenchyma.

Vascular Tissues

Vascular tissues do not only fulfill supporting functions. Their conductive functions are more important. They consist of water-conducting xylem and food-conducting phloem. Only the xylem has still supporting functions. Xylem and phloem are combined in a structure that is called vascular bundle.

• Xylem:

Xylem conducts water and dissolved minerals from the roots to all the other parts of the plant. In angiosperms, most of the water travels in the xylem vessels. These are thick-walled tubes that can extend vertically through several feet of xylem tissue. Their diameter may be as large as 0.7 mm. Their walls are thickened with secondary deposits of cellulose and are usually further strengthened by impregnation with lignin. The secondary walls of the xylem vessels are deposited in spirals and rings and are usually perforated by pits.

In woody plants, the older xylem ceases to participate in water transport and simply serves to give strength to the trunk. Wood is xylem. When counting the annual rings of a tree, one is counting rings of xylem.

• Phloem

The main components of phloem are

• Sieve elements and
• Companion cells.

Sieve elements are so-named because their end walls are perforated. This allows cytoplasmic connections between vertically-stacked cells. The result is a sieve tube that conducts the products of photosynthesis — sugars and amino acids — from the place where they are manufactured, e.g., leaves, to the places where they are consumed or stored; such as roots, growing tips of stems and leaves, flowers, fruits, tubers, corms, etc.

Sieve elements have no nucleus and only a sparse collection of other organelles. They depend on the adjacent companion cells for many functions.

Companion cells move sugars, amino acids and a variety of macromolecules into and out of the sieve elements, then pass on to the cells of their destination.

Uses of Fibres to the Plants

1. All fibres give strength and support to plants
2. They serve mechanical functions when they grow older such as rigidity, flexibility and elasticity
3. They protect the fragile part of the plants
4. They are sclerenchymatous in nature
5. When they are associated with wood or xylem, they are known as wood fibres.

Functions of Supporting Tissues in Plants

Supporting tissues provide the following functions to plants:

1. Strength: The sclerenchyma and collenchyma tissues provide the necessary strength required by plants
2. Rigidity: The supporting tissues like collenchyma, sclerenchyma and wood fibres provide the necessary materials to make the plant strong against any external forces.
3. Protection: Some supporting tissues are known to protect the delicate parts of the plants body, e.g. cambium and phloem vessel
4. Flexibility: Some supporting tissues also provide the necessary materials which make the plants flexible thereby preventing the plants from being broken by the bending and twisting movements caused by strong winds
5. Conduction: Some supporting tissues especially xylem and phloem tissues are known to also conduct water and manufacture food respectively within the plant.

Test Questions

1. ______  joints are joints where the articular surfaces of the bones forming the joints are attached to each other by means of white fibro-cartilaginous discs and ligaments which allow only a limited degree of movement.
2. What is the name of the joint found in the shoulder?
3. What parts of plant are responsible for strength?
4. _____ tissue(s) is responsible for conducting water and manufacture of foods in plants
   a) phloem
   b) collenchyma
   c) xylem
   d) a & c
5. Sieve elements and companion cells can be found in the ____
   a) xylem
   b) scelerenchyma
   c) phloem
   d) collenchyma
6. The site or place where two or more bones of the skeleton are attached to each other is called a _____
7. _____ reduces friction and acts as a shock absorber.
8. ____ fluid is used to lubricate joint.
   a) Binomial 
   b) Synovial
   c) Joint
   d) Tendon
9. _____  conducts water and dissolved minerals from the roots to all the other parts of the plant.
   a) phloem
   b) xylem
   c) collenchyma
   d) scelerenchyma
10. Another name for fibrous joints are _____ joints
    a) immovable
    b) movable
    c) strong
    d) weak

Answers

1. Cartilaginous
2. Ball and socket joint
3. Scelerenchyma and Collenchyma
4. D
5. C
6. Joint
7. Cartilage
8. B
9. B
10. A

Mechanism Of Transport In Higher Plants

 Biology, SS 2, Second Term, Week: 11

Topic: Transport System in Plant

Introduction

In a simple plant like an alga, materials enter or leave the cells in the body by diffusion. In higher land plants, special conducting tissues, known as vascular tissues carry out transport.

Two main types of vascular tissue are used in transport – xylem and phloem.

·Xylem transports water and minerals.

·Phloem transports organic molecules such as the products of photosynthesis.

Xylem

There are four types of xylem cells:

Xylem vessels: Consist of dead hollow cells because the walls are lignified and the cell contents disintegrate. The lignin makes the cell wall impermeable so they are in effect waterproof. It also makes the vessels extremely strong and prevents them from collapsing. They have a wide lumen and are linked end to end to create a long, hollow tube since the end cell walls have one or many perforations in them. This allows the transport of large volumes of water. The sidewalls have bordered pits (unlignified areas) to allow lateral movement of water. Xylem vessels are found in angiosperms.

Tracheids: Similar to vessels but with narrower lumens and connected by pits. They have tapered ends so that they dovetail together. Tracheids are found in conifers.

Parenchyma: Living cells with thin cellulose walls. They can store water, which makes them turgid and so gives them a supporting role.

Fibres: They provide strength because their walls are lignified (and therefore, dead).

Movement in the root

Water enters through the root hair cells and then moves across into the xylem tissue in the centre of the root. Water moves in this direction because the soil water has higher water potential, than the solution inside the root hair cells.

This is because the cell sap has organic and inorganic molecules dissolved in it. The root hairs provide a large surface area over which water can be absorbed.

Minerals are also absorbed but, their absorption requires energy in the form of ATP because they are absorbed by active transport. They have to be pumped against the concentration gradient.

Water taken up by the root hair moves across the cortex of the root either via the cytoplasm of the cells in between the root hair cell and the xylem (the symplast pathway) or through the cell walls of these cells (the apoplast pathway). The root hair cell will have higher water potential than the cell next to it. As always, water moves by osmosis to where the water potential is lower. In this way, as water is always being absorbed by the root hairs, water will always move towards the centre of the root.

When the water reaches a part of the root called the endodermis, it encounters a thick, waxy band of suberin in the cell walls. This is the Casparian strip and it is impenetrable. In order to cross the endodermis, the water that has been moving through the cell walls must now move into the cytoplasm.

Once it has moved across the endodermis, it continues down the water potential gradient until it reaches a pit in the xylem vessel. It enters the vessel and then moves up towards the leaves.

Movement in the Xylem

Water evaporates from the mesophyll cells into air spaces in the leaf. If the air surrounding the leaf has less water vapour than the air in the intercellular spaces, water vapour will leave the leaf through stomata.

This process is called transpiration and will continue as long as the stomata are open and the air outside is not too humid. On dry, windy days when water vapour is continually diffusing out and being removed, transpiration will increase in rate.

Although this loss of water can cool the plant, it is essential that the plant does not lose too much water. Therefore water must be continuously supplied to the leaves. The xylem ensures that this happens. Xerophytes are plants which are well adapted to living where conditions are very dry. They may have rolled up leaves – for example, Marram grass which exposes the waterproof cuticle on the outside and the stomata open into an inner humid space. Other Xerophytes store water in their stems and reduce the surface area of their leaves, which become spines – for example, Cactus.

Water is removed from the top of xylem vessels into the mesophyll cells down the water potential gradient. This removal of water from the xylem reduces the hydrostatic pressure exerted by the liquid so the pressure at the top is less than at the bottom. This pushes the water up the tube. The surface tension of the water molecules, the thin lumen of the xylem vessels and the attraction of the water molecules for the xylem vessel wall (adhesion), helps to keep the water flowing all the time and to keep the water column intact.

Pressure to push water up can also be increased from the bottom. By actively pumping minerals from cells surrounding the xylem into the xylem itself, more water is drawn into the xylem by osmosis.

This increase in water pressure, called root pressure, certainly helps in the process but is less important than the simple movement of water down the water potential gradient, ultimately from the soil at the bottom, to the air at the top. This is because moving water this way does not require energy (it is passive).

Phloem

There are four types of phloem cells:

• Sieve tube elements: These are living, tubular cells that are connected end to end. The end cell walls have perforations in them to make sieve plates. The cytoplasm is present but in small amounts and in a layer next to the cell wall. It lacks a nucleus and most organelles so there is more space for solutes to move. The cell walls are made of cellulose so solutes can move laterally a well as vertically. Next to each sieve tube element is a companion cell.
• Companion cell: Since the sieve tube element lacks organelles, the companion cell with its nucleus, mitochondria, ribosomes, enzymes etc., controls the movement of solutes and provides ATP for active transport in the sieve tube element. Strands of cytoplasm called plasmodesmata connect the sieve tube element and companion cell.
• Parenchyma: Provides support through turgidity.
• Fibres: Provides support for the sieve tube elements.

Movement in the Phloem

This process is called translocation and involves the movement of organic substances around the plant. It requires energy to create a pressure difference and so is considered an active process.

Sucrose is loaded into the phloem at a source, usually a photosynthesizing leaf. For this to occur, hydrogen ions are pumped out of the companion cell using ATP. This creates a high concentration of hydrogen ions outside the companion cell. Sucrose is loaded (moved into companion cells) by active transport, against the concentration gradient.

However, the protein carrier involved in the loading, has two sites, one for sucrose and one for a hydrogen ion. When it is used to pump sucrose into the companion cell, hydrogen will move in the opposite direction, back down its concentration gradient. This is why a high concentration of ions is needed outside the cell.

The sucrose can then diffuse down the concentration gradient into the sieve tube element via the plasmodesmata that connects the companion cell with the sieve tube element. This lowers the water potential of the sieve element so water enters by osmosis.

At another point sucrose will be unloaded from the phloem into a sink (e.g. root). It is likely that the sucrose moves out by diffusion and is then converted into another substance to maintain a concentration gradient. Again, water will follow by osmosis.

The loading and unloading result in the mass flow of substances in the phloem. There is evidence to support this theory; the rate of flow in the phloem is about 10,000 times faster than it would be if it was due only to diffusion, the pH of the phloem sap is around 8 (it is alkaline due to loss of hydrogen ions), and there is an electrical potential difference across the cell surface (negative inside due to the loss of positively charged ions).

Transpiration

Transpiration is defined as the removal of excess water from plants into the atmosphere in form of water vapour. Plants are capable of loosing excess water through:

1.    The stomata in the leaves and this is called stomata transpiration

2.    The cuticle in the leaf surface in what is called cuticular transpiration

Conditions Affecting the Rate of Transpiration

The rate at which water vapour is lost by a plant depends on a number of factors which are:

1.    The size of the stomata pores

2.    Humidity

3.    Temperature

4.    Light

5.    Wind

6.    Soil water

Importance of Transpiration to plants

Transpiration has the following importance or advantages to plants:

1.    It enables plants to absorb water and mineral salts from the soil

2.    It facilitates the movement of soil water

3.    The evaporation of water due to transpiration from the plants cools the plants

4.    It helps to remove excess water from the plants

Translocation

Translocation is the process by which manufactured food substances are transported from where they are manufactured to tissues where they are needed or stored. Translocation normally begins from the leaves to other parts of the plant. Phloem is the tissue through which these manufactured food substances are translocated.

Substances or materials comm only translocated in plants include:

1.    Sugar

2.    Glucose

3.    Oil

4.    Resins

5.    Proteins or amino acids

6.    Alkaloids

7.    Hormones

Practice Questions

1. _____ is the process by which manufactured food substances are transported from where they are manufactured to tissues where they are needed or stored.
   a) Translocation
   b) Relocation
   c) Movement
   d) immigration
2. All these cells exist in the xylem except
   a) tracheids
   b) xylem vessels
   c) roots
   d) fibres
3. One of these substances is not translocated in plants
   a) Glucose
   b) Oil
   c) Resins
   d) Water
4. Conditions affecting the rate of transpiration are
   a) humidity
   b) light
   c) soil water
   d) all of the above
5. There are two main vascular tissues used in support. They are _____ and ____
6. Why is Transpiration important to plants?

Answers

1. A
2. C
3. D
4. D
5. Xylem, Phloem
6. State the importance above