S2 Biology 2nd Term Past Paper PDF

**[SCHEME OF WORK]** **[WEEKS]** **[TOPICS]** ------------------------- ---------------------------------------------------------- **** EXCRETION **** Tissues And Supporting Systems **** Components Of The Mammalian Skeleton **** Axial Skeleton **** Perp...

**[SCHEME OF WORK]** **[WEEKS]** **[TOPICS]** ------------------------- ---------------------------------------------------------- **** EXCRETION **** Tissues And Supporting Systems **** Components Of The Mammalian Skeleton **** Axial Skeleton **** Perpendicular Skeleton **** Joints **** Alimentary Canal /Digestive System **** Feeding Habits/ Feeding in man, Amoeba and Hydra. **** Circulatory System **** **[M]**ethods of transporting Higher Animals **** Revision **** **[EXCRETION]** Excretion is defined as the removal of waste products of metabolism from the body of an organism(animal/plant) which in turn if left without elimination from the body causes damage to body cells and organs. Waste substances include: \- By product formed during metabolic processes in the body. \- Excess substances, which cannot be stored in the body. \- Unwanted materials present in food, which are absorbed into the body. **[N/B]** : **Metabolism** is the sum total of all on-going chemical reactions in the body occurring at a particular time. Animals and plants have excretory organs and give out excretory product. Examples of common excretory products include: a. Urea. b. Uric acid. c. Carbon(iv) oxide. **[Organisms , Their Excretory Organs And Their Excretory Products]** +-----------------------+-----------------------+-----------------------+ | **ORGANISMS** | **EXCRETORY | **EXCRETORY PRODUCT** | | | ORGAN/STRUCTURE** | | +=======================+=======================+=======================+ | a. Protozoans | Contractile vacuole | - Carbon(iv) oxide | | | | | | | | - Ammonium salt | | | | | | | | - Water | +-----------------------+-----------------------+-----------------------+ | b. Earthworm | Nephridia/nephridium | - Water | | | | | | | | - Carbon(iv) oxide | | | | | | | | - Urea | +-----------------------+-----------------------+-----------------------+ | c. Flatworm | Flame cells | -urea | | | | | | | | \- water | +-----------------------+-----------------------+-----------------------+ | d. fish | Gills | - carbon(iv)oxide | | | | | | | | - water | | | | | | | | - Urea | +-----------------------+-----------------------+-----------------------+ | e. Insects | Malphigian tubules | - Carbon(iv) oxide | | | | | | | | - Uric acid | +-----------------------+-----------------------+-----------------------+ | f. Mammals | Kidneys, skin, lungs, | - \- Sweat | | | liver | | | | | - Carbon (iv) oxide | | | | | | | | - Uric acid | | | | | | | | - Hormones | | | | | | | | - Water | | | | | | | | - Urea | | | | | | | | - | +-----------------------+-----------------------+-----------------------+ | g. Flowering plants | Stomata, Lenticels | - Water | | | | | | | | - Carbon(iv)oxide | | | | | | | | - oxygen | +-----------------------+-----------------------+-----------------------+ | h. Birds | Kidney, Lungs | - Uric acid | | | | | | | | - Carbon(iv)oxide | | | | | | | | - Water | +-----------------------+-----------------------+-----------------------+ | i. Reptiles | Kidney | - urine containing | | | | urea | | | | | | | | - Salt | | | | | | | | - Water | | | | | | | | - Hormones | | | | | | | | - Uric acid | +-----------------------+-----------------------+-----------------------+ | j. Crustaceans | Green gland | - Water | | (Shrimp, cray | | | | fish, Crab) | | - Carbon(iv)oxide | | | | | | | | - Urea | | | | | | | | - Ammonium salt | +-----------------------+-----------------------+-----------------------+ | k. Trees | Bark | - Gums | | | | | | | | - Tannis | | | | | | | | - Mucillage | | | | | | | | - Antocyannis | | | | | | | | - Crystals | | | | | | | | - Alkaoid | | | | | | | | - Resins | +-----------------------+-----------------------+-----------------------+ [ I**mportance of Excretion (Need for excretion)**] The importance of excretion expresses the essential need for excretion. They include: 1\. Removal of waste product of metabolism (waste product of metabolism are generally poisonous to cells of the body). 2\. Excretion helps to maintain water balance in the body. 3\. Excretion helps to maintain salt balance in the body( homeostasis ). 4\. It prevents the fatal interaction of waste product with the normal activity in the body. 5\. To remove poisonous or unwanted substances. 6\. It helps in controlling body temperature. 7\. It saves protozoa like amoeba from bursting \- The earthworm makes use of the nephridia as it excretory organ. \- Each segment of the body contains these necessary organs are a pair of tube except the first three segments and the last three segment of the body. \- Each of the nephridium of an earthworm has a funnel cavity called nephrostrome which is lined up with cilia hairs. \- These nephrostrome open to the outside through a small pore called nephridiopore. \- The nephridiopore opens into the body of the segment of the front. \- The nephrostrome then leads a long coiled tube made up of a ciliated tube, a ciliated tube and a muscular ciliated tube which opens to the exterior. \- Each neprhridium is surrounded by a capilliary network. \- The waste product mainly urea are excreted from the blood capilliaries surrounding nephridia. \- Waste products are also removed from the fluid in the blood and passed into the funnel. \- Fluid containing waste products moves through the long tube of the nephridia. \- Along the way, salt and other substances that are useful to the body are re-absorbed through the walls of the tubes. \- The unabsorbed substances including water collect in a nuis tubes as urine. \- The excretory pores relaxes to allow urine to the exterior. **[Title: Excretory system in earthworm]** **[Excretion in insects]** \- The organ responsible for excretion in insect is the malphigian tubule \- The malphigian tubules are fine,slender,long-out grown from the exterior of the small intestine of the insect. \- They are found floating between glands and organs in most part of the thorax and abdomen. \- They are found in sex groups each consisting of up to 12 tubules \- They consists of two parts, the distal(free) and the proximal end. **[Mechanism Of Excretion In Insects]** \- Nitrogenous waste products and water which are liberated at the haemocoel are absorbesd at the distal end of the malphigian tubule. \- They are then converted to uric acid as it passes through the malphigian towards the gut. \- During this process, large volume of water is absorbd as the uric acid reaching the end of the proximal part o thef tubules become solid crystals. \- In the hind gut more water is re-absorbed by the recticle \- Thus, the urine with feaces which eventually leaves the \_\_\_\_\_\_\_\_ highly concentrated and almost a dry solid. **[TITLE: External features of the malphigian tubules.]** **[Excretion In Mammals]** \- Basically, mammals make use of kidneys, lungs , liber,skin as their organs of excretion. \- The lungs excrete water vapor and carbon(iv) oxide. \- The liver excrete \_\_\_\_\_\_\_\_\_\_ pigment \_\_\_\_\_\_\_ /this is a product \_\_\_\_\_\_\_\_ from the decomposirion of haemoglobin /the skin,water,salt and urea \- The skin also excretes water and salt. \- The kidney however excretes water,mineral salt, urea, uric acid and creatinine. \- Yet with all these organs ,the kidney is the basic excretory organ in mammals. **[STRUCTURE OF THE KIDNEY]** \- It is a bean- shapes reddish brown organ. \- It is located at the posterior end of the abdomen- longtitude in the kidney has two distinct region /the outer cortex and inner medulla) \- Through these regions, several millions of urinary tubules ( nephron) which are the basic units of the excretory system. \- These nephron opens at the tips of a triangular shaped masses of tissue called pyramids. \- The pyramid in turn opens at turn opens to a funnel shaped cavity called pelvis \- The kidney has many capillaries which are branches of the renal artery and renal vein. **[URINARY TUBULE IN HUMANS]** **[Structure Of The Urinary Tubule In Humans]** \- Each urinary tubule begins with the cortex region in the kidney as a cup shaped structure called bowman's capsule. \- Bowman's capsule houses numerous cappiliaries called Glomerulus. \- The bowman's capsule opens into a short coiled tube called the proximal convoluted tubule. \- The urinary tubule (nephron) is seen to straighten out or straighten up as it enters into the inner medulla and forms the Henle's loop or loop of Henle. \- After which it re-enters the cortex again where it forms the distal convoluted tubule. \- The tubule bends again and completes its course in the medulla. \- As the tubule gets into the pelvis, it widens and pours its content into a wider connective tube duct. \- This duct eventually joins up and opens into the pelvis at apex(top) of the pyramid. \- It should be noted that this tubule(urinary) is closely associated with several network of capilliaries. \- The capilliary glomerulus will join to form a blood vessel holding out of Bowman's capsule. \- These vessels branches into a capilliary network around the urinary tubules before rejoining to form a branch network of renal vains. **[Processes (Of /Involved) In Formation Of Urine]** For the urine to be formed , it must pass through three different and distinct phases; These phases include Ultra filtration process, Selective re-absorption, Hoormonal secretion. \- Occurs at the Bowman's Capsule \- This involves a filtration process in which useful materials and substances are filtered in through the Bowman's capsule. \- The materials or substances filtered include mainly;water, urea, nitrogenous compound,mineral salts, sugar glucose and plasm solute. \- These materials majorly come from the blood. renal arteries and circulates through the capillaries forming the glomerulus at the bowman's capsule. \- As the filtrate (glomerular filtrate ) flows within the tubules and gets into the proximal convoluted tubule(**PCT**) and henle loop , selective reabsorptions is initiated occurring more in the PCT. \- It occurs basically in the P.C.T and less the Henle's loop. \- Selective re-absorption involves re-absorption of useful materials (like water, sugar, amino acids and salts) back into the blood by active transport against a concentration gradient. **[Hormonal Secretion Process Involved In Formation Of Urine.]** \- As re-absorption continues, the fluid in the tubule becomes more concentrated. Hormonal secretion by the brain is effected on the distal convoluted tubule. \- It involves a relative reabsorb ion of more water or from the glomerular filtrate within the urinary tubules of the action of the secretion of ADH( anti diuretic hormone) \- The filtrate now becomes even more concentrated. \- The liquid after this process is actually urine which gradually trickles down into the renal pelvis. \- From the ureter, the urine passes into the urinary bladder. \- The bladder when full being muscular contracts ,as sensation to urinate is heightened. **[Excretion In Flowering Plants ]** \- Flowering plants have special excretory system. The waste materials in plants are disposed of through various parts of the plants. Plants waste /excretory product) include the following; carbon(iv ) oxide ,tannis,acids,resins,mucilliage, alkanoids, crystals of salts, \_\_\_\_\_\_\_\_ , gum, antocyannin, oxygen. \- The main excretory organs of plants are the stomata of the leaves and lenticels at the bark of the stem.\\ **[The Main Excretory Wastes Of Plants]** \- Carbon(ii) oxide (Co2) is excreted by diffusion or through stomata or lenticels. \- Oxygen(02) ; this is excreted during photosynthesis and is eliminated by diffusion through the stomata or lenticels. \- Water (H20) ; this is excreted by diffusion out of the stomata or lenticels and through gultation or transpiration. \- Oils an resins; theses are stored in the cells cytoplasm where they are kept from the system until they are eliminated. \- Latex; it is stored in a tuber like system in tissue and are kept harmless until they ooze off. The plant when \_\_\_\_\_\_\_\_\_\_\_ the plant is damaged. \- Tannins, gums, antocyannins, muccilliage; these are pigments and are converted into compounds. **[MODULE TWO: TISSUES AND SUPPORTING SYSTEMS.]** Living organisms essentially are plants and animals and \_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_of tissues and supporting systems. This system enables them to carry out simple life activities such as movement or locomotion*.* SKELETON(Definition): Skeleton is defined as the bony frame work of the body which provides support, shape and protection of soft tissue and organs in animals. Generally, skeleton enables animals to move from one place to another and also skeleton have their particular forms and components. **[Forms And Components And Skeletal Materials ]** \- There are basically three (3) forms of skeletal materials namely 1\. Cuticle 2\. Cartilage 3\. Bones **[Features Of A Cuticle]** \- It comprises of chitin They are located outside(external) of the body. Cuticle are exoskeleton. They are found generally in arthropods( crayfish ,crabs, prawn, insects, spider ,scorpion) Cartilages are tissues found in the skeleton of complex vertebrates. They consist essentially living cells called chrondoplast, carbohydrate and proteins. Cartilages are tough and flexiblethat has great tensil stress. They generally act as shock absorber that helps cushion the effects of bone moving against bones during movement. Examples of organisms which possess cartilage are ; cartilaginous fishes like sharks, rays and mammals **[Type Of Cartilage]** **- Hyaline cartilage** **- Fibro cartilage** **- Elastic cartilage** **[1. Hyaline cartilage:] These type of cartilages are found in** **Of the body like: the trachea and bronchi, surface of moral joints and and also the protruding part of the nose which support.** **[2. Fribo -- cartilage:] This is a tougher cartilage than the hyaline cartilage, and it is found in regions of the body like: the small bones (vertebra) of the vertebral column.** **[3. Elastic cartilage:] This category of cartilages are found in the external ear (pinna) and epidermis.** **[Features of the Bone]** **- The bone is the strongest tissue.** **- It is a tissue and a major component of the vertebral column.** **- The bone consists of bones is made up of two third of the mass of the bone and it is the mineral part of a bone.** **- Structurally, the bone is made up of a hard outer layer (shaft) and a spongy hollow can y filled with bone marrow.** **[Figure above show longitudinal section of the thigh bone.]** **[Figure above shows the transverse section of a compact bone.]** **[Types of skeleton.]** **- There are three (3) types of skeleton and they are:** **[- Hydrostatic skeleton]** **- It is the type of skeleton possessed by soft-bodied animals.** **- They use fluid pressure to provide support and movement as the fluid presses against their muscular body walls.** **- This fluid pressure causes the muscles to contract there by creating pressure against the fluid.** **- This in turn helps to maintain the shape and form of animals. Examples include:- earthworms and anemones.** **[Exoskeleton]** **- It is a kind of skeleton found outside (external) part of the body of some animals.** **- They have the poly saccharide (chitin) in their structure.** **- The chitin helps in support giving shape and protection to the animals.** **- 9weExoskeleton is found largely in arthropods (crayfishes , shrimps) animals. It is also found in invertebrates like hydra, euglena, tapeworm, paramecium.** **[3. Endoskeleton: ]** MODULE 3 **[COMPONENTS OF THE MAMMALLIAN SKELETON]** **The skeletal system of bones in mammals and rabbits are grouped into two namely:-** **1. Axial skeleton (central).** **2. Appendicular skeleton (jointed appendages) skeleton.** **[Axial skeleton]** The Axial skeleton is made up of:- 1\. The skull. 2\. The vertebral column (backbone). 3\. The ribs and breast bone. **[The Skull.]** \- The mammanlian skull is made up of several flat bones which are joined together by means of joints called secture joint. The components of the skull are: [- Cranium/ Brain box:] This holds or houses the brain. [- Facial skeleton:] This is the part of the skull that supports the eyes, nose and muscles of the cheeks. [- Jaws:] The jaws are the part of the skull which are made up of the upper jaw (maxilla) and lower jaw (mandible) which contains the teeth. 1\. - It gives cape to the brain. 2\. - It protects the brain. 3\. - It protects the vital organs in the head. 4\. -!It bears the teeth. \- It is also regarded as or called the spinal column or \- It is regarded as the central supporting systems of the skeleton. \- It protects the spinal cord. \- It is made up of five groups or types of bone called vertebrae in mammals. \- The following are the group of vertebrae in man and their location in the body. **[Types of Vertebrae and And their Location]** Cervical vertebrae Found in the **neck region.** Thoracic vertebrae Found in the **chest region.** Lumbar vertebrae Found in the **upper region of the abdomen** Sacral vertebrae Found in the **upper region of the abdomen** Caudal vertebrae Found at the **tail region.** [ ] **Distribution of vertebrae in man, rabbits and rats** **Type of vertebrae** **Man** **Rabbit** **Rat** ----------------------- --------- ------------- -------------- **Cervical** **7** **7** **7** **Thoracic** **12** **12** **13** **Lumbar** **5** **7** **6** **Sacral** **5** **3 -- 4** **4** **Caudal** **4** **16** **27 -- 30** **Total** **33** **45 - 46** **57 -- 60**