WAEC SSCE - Biology - 2003 (Essay)
Question 1 Report
(a) Name three main parts of the human brain
(b) State the functions of the following:
(i) Cerebrum
(ii) Hypothalamus
(iii) Medulla Oblongata.
(c)(i) List three organs of a higher plant that can respond to stimulus
(ii) What is tactic movement?
(d) Explain the following terms, giving one example in each case:
(I) Phototaxis
(ii) Hydrotaxis
(iii) Chemotaxis.
(a) Three main parts of the human brain are:
- Forebrain (cerebrum)
- Midbrain
- Hindbrain, which includes the cerebellum and medulla oblongata
(b) Functions of parts of the brain
(i) Cerebrum
- It is the seat of consciousness and sensory perception.
- It controls voluntary actions of the body.
- It is responsible for intelligence, memory, reasoning, learning, judgement and imagination.
- It receives, interprets and stores information from the sense organs.
(ii) Hypothalamus
- It regulates body temperature.
- It regulates water balance and osmoregulation.
- It controls hunger, appetite, thirst and feeding.
- It controls sleep and wakefulness.
- It controls the pituitary gland.
- It is associated with emotions such as anger and aggression.
(iii) Medulla oblongata
- It controls involuntary activities such as breathing and heartbeat.
- It controls the diameter of blood vessels and blood pressure.
- It controls swallowing, coughing, sneezing, yawning and vomiting.
- It helps control digestive activities, including peristalsis and salivation.
(c)(i) Three organs of a higher plant that can respond to stimuli are:
- Root
- Stem
- Leaf
Other examples include flowers and tendrils.
(c)(ii) Tactic movement
Tactic movement, or taxis, is the directional movement of the whole body of a free-living organism from one place to another in response to an external stimulus. The movement may be positive, towards the stimulus, or negative, away from the stimulus.
(d) Explanation of terms with examples
(i) Phototaxis
Phototaxis is the directional movement of a whole organism in response to light. Example: Euglena moves towards light; this is positive phototaxis.
(ii) Hydrotaxis
Hydrotaxis is the directional movement of a whole organism in response to water or moisture. Example: A woodlouse moves towards a region of high humidity.
(iii) Chemotaxis
Chemotaxis is the directional movement of a whole organism in response to a chemical substance. Example: Antherozoids of moss or fern swim towards chemicals secreted by the archegonium.
Answer Details
(a) Three main parts of the human brain are:
- Forebrain (cerebrum)
- Midbrain
- Hindbrain, which includes the cerebellum and medulla oblongata
(b) Functions of parts of the brain
(i) Cerebrum
- It is the seat of consciousness and sensory perception.
- It controls voluntary actions of the body.
- It is responsible for intelligence, memory, reasoning, learning, judgement and imagination.
- It receives, interprets and stores information from the sense organs.
(ii) Hypothalamus
- It regulates body temperature.
- It regulates water balance and osmoregulation.
- It controls hunger, appetite, thirst and feeding.
- It controls sleep and wakefulness.
- It controls the pituitary gland.
- It is associated with emotions such as anger and aggression.
(iii) Medulla oblongata
- It controls involuntary activities such as breathing and heartbeat.
- It controls the diameter of blood vessels and blood pressure.
- It controls swallowing, coughing, sneezing, yawning and vomiting.
- It helps control digestive activities, including peristalsis and salivation.
(c)(i) Three organs of a higher plant that can respond to stimuli are:
- Root
- Stem
- Leaf
Other examples include flowers and tendrils.
(c)(ii) Tactic movement
Tactic movement, or taxis, is the directional movement of the whole body of a free-living organism from one place to another in response to an external stimulus. The movement may be positive, towards the stimulus, or negative, away from the stimulus.
(d) Explanation of terms with examples
(i) Phototaxis
Phototaxis is the directional movement of a whole organism in response to light. Example: Euglena moves towards light; this is positive phototaxis.
(ii) Hydrotaxis
Hydrotaxis is the directional movement of a whole organism in response to water or moisture. Example: A woodlouse moves towards a region of high humidity.
(iii) Chemotaxis
Chemotaxis is the directional movement of a whole organism in response to a chemical substance. Example: Antherozoids of moss or fern swim towards chemicals secreted by the archegonium.
Question 2 Report
(a) What is a cell?
(b) Describe the structure and state the function of each of the following:
(i) Nucleus
(ii) Mitochnodrion.
(c)(i) Make a labelled diagram 8 cm to 10 cm long of the Euglena.
(ii) List. three animal-like features and two plant-like features of Euglena.
(a) A cell is the smallest structural and functional unit of life. It is the basic unit from which living organisms are built and is capable of carrying out life processes.
(b)(i) Nucleus
- Structure: The nucleus is usually spherical or oval and is surrounded by a double nuclear membrane containing pores. It contains nucleoplasm, chromatin materials (chromosomes/genes) and a nucleolus.
- Functions: It controls the activities of the cell, contains hereditary materials, and controls or initiates cell division.
(b)(ii) Mitochondrion
- Structure: A mitochondrion is an oval or rod-shaped organelle bounded by a double membrane. Its inner membrane is folded into cristae, enclosing a fluid-filled matrix containing enzymes and ribosomes.
- Function: It is the site of aerobic (tissue) respiration, where energy is released from food in the form of ATP.
(c)(i) Labelled diagram of Euglena, 9 cm long
(c)(ii) Animal-like features of Euglena
- It possesses a flagellum for movement.
- It has a contractile vacuole for osmoregulation.
- It has a gullet/reservoir through which it can take in food; it can feed heterotrophically when light is absent.
Plant-like features of Euglena
- It contains chloroplasts and manufactures food by photosynthesis.
- It possesses pyrenoids/paramylum granules for food storage.
Answer Details
(a) A cell is the smallest structural and functional unit of life. It is the basic unit from which living organisms are built and is capable of carrying out life processes.
(b)(i) Nucleus
- Structure: The nucleus is usually spherical or oval and is surrounded by a double nuclear membrane containing pores. It contains nucleoplasm, chromatin materials (chromosomes/genes) and a nucleolus.
- Functions: It controls the activities of the cell, contains hereditary materials, and controls or initiates cell division.
(b)(ii) Mitochondrion
- Structure: A mitochondrion is an oval or rod-shaped organelle bounded by a double membrane. Its inner membrane is folded into cristae, enclosing a fluid-filled matrix containing enzymes and ribosomes.
- Function: It is the site of aerobic (tissue) respiration, where energy is released from food in the form of ATP.
(c)(i) Labelled diagram of Euglena, 9 cm long
(c)(ii) Animal-like features of Euglena
- It possesses a flagellum for movement.
- It has a contractile vacuole for osmoregulation.
- It has a gullet/reservoir through which it can take in food; it can feed heterotrophically when light is absent.
Plant-like features of Euglena
- It contains chloroplasts and manufactures food by photosynthesis.
- It possesses pyrenoids/paramylum granules for food storage.
Question 3 Report
(a)(i) What is respiration?
(ii) Name two types of respiration.
(iii) Write in words the equation representing the type of respiration that occurs in the muscle during strenuous exercise.
(b) Name two diseases that can affect the above mentioned system.
(c) Mention the structures used for gaseous exchange in the following organisms:
(i) Amoeba
(ii) Cockroach
(iii) White mangrove
(iv) Hibiscus.
(a)(i) Respiration is the biochemical process by which food substances (mainly glucose) are broken down (oxidised) in living cells to release energy for the body's activities.
(ii) Two types of respiration: aerobic respiration and anaerobic respiration.
(iii) The type occurring in muscles during strenuous exercise is anaerobic respiration. In words:
Glucose \(\rightarrow\) lactic acid + energy
(b) Two diseases affecting the respiratory system: tuberculosis and pneumonia (asthma and bronchitis are also acceptable).
(c) Structures used for gaseous exchange
- (i) Amoeba: the entire cell surface membrane (general body surface).
- (ii) Cockroach: tracheae (spiracles and tracheal tubes).
- (iii) White mangrove: pneumatophores (breathing roots) with lenticels.
- (iv) Hibiscus: stomata (in leaves) and lenticels (in stem).
Answer Details
(a)(i) Respiration is the biochemical process by which food substances (mainly glucose) are broken down (oxidised) in living cells to release energy for the body's activities.
(ii) Two types of respiration: aerobic respiration and anaerobic respiration.
(iii) The type occurring in muscles during strenuous exercise is anaerobic respiration. In words:
Glucose \(\rightarrow\) lactic acid + energy
(b) Two diseases affecting the respiratory system: tuberculosis and pneumonia (asthma and bronchitis are also acceptable).
(c) Structures used for gaseous exchange
- (i) Amoeba: the entire cell surface membrane (general body surface).
- (ii) Cockroach: tracheae (spiracles and tracheal tubes).
- (iii) White mangrove: pneumatophores (breathing roots) with lenticels.
- (iv) Hibiscus: stomata (in leaves) and lenticels (in stem).
Question 4 Report
(a) Describe the processes that occur from the time a pollen grain is deposited on the stigma of a flower to the . formation of a zygote.
(b) Explain the importance of the amniotic sac to the mammalian embryo.
(c) The following are the names of some common diseases; malaria, typhoid, amoeboid dysentry, tuberculosis, tetanus, leprosy, cholera, yellow fever, poliomyelitis, measles, common cold, small pox, influenza, chicken pox, whooping cough and trypanosomiasis. Use the format below to classify the diseases according to their causative organisms.
| Viral diseases | Bacteria diseases | Protozoa diseases |
(a) From pollination to the formation of a zygote
When a pollen grain is deposited on the stigma, it absorbs sugary fluid and germinates, growing out a pollen tube. The pollen tube grows down through the tissues of the style towards the ovary, its direction controlled by chemical substances (chemotropism) and its path softened by enzymes it secretes. The tube nucleus leads at the tip, while the generative nucleus divides to form two male gametes. The tube reaches an ovule and enters it through the tiny opening called the micropyle. The tip of the tube then bursts and releases the two male gametes into the embryo sac. One male gamete fuses with the egg cell (fertilisation) to form the zygote (2n), which later develops into the embryo. The second male gamete fuses with the two polar nuclei to form the endosperm nucleus (3n). This union of two gametes is called double fertilisation.
(b) Importance of the amniotic sac to the mammalian embryo
- It is filled with amniotic fluid that acts as a shock absorber, protecting the embryo from mechanical injury and pressure.
- It keeps the embryo moist and prevents it from drying up.
- It allows the embryo to move freely and grow evenly.
- It helps to maintain a constant temperature and pressure around the embryo.
(c) Classification of the diseases by causative organism
| Viral diseases | Bacterial diseases | Protozoan diseases |
|---|---|---|
| Yellow fever, poliomyelitis, measles, common cold, small pox, influenza, chicken pox | Typhoid, tuberculosis, tetanus, leprosy, cholera, whooping cough | Malaria, amoebic dysentery, trypanosomiasis |
Answer Details
(a) From pollination to the formation of a zygote
When a pollen grain is deposited on the stigma, it absorbs sugary fluid and germinates, growing out a pollen tube. The pollen tube grows down through the tissues of the style towards the ovary, its direction controlled by chemical substances (chemotropism) and its path softened by enzymes it secretes. The tube nucleus leads at the tip, while the generative nucleus divides to form two male gametes. The tube reaches an ovule and enters it through the tiny opening called the micropyle. The tip of the tube then bursts and releases the two male gametes into the embryo sac. One male gamete fuses with the egg cell (fertilisation) to form the zygote (2n), which later develops into the embryo. The second male gamete fuses with the two polar nuclei to form the endosperm nucleus (3n). This union of two gametes is called double fertilisation.
(b) Importance of the amniotic sac to the mammalian embryo
- It is filled with amniotic fluid that acts as a shock absorber, protecting the embryo from mechanical injury and pressure.
- It keeps the embryo moist and prevents it from drying up.
- It allows the embryo to move freely and grow evenly.
- It helps to maintain a constant temperature and pressure around the embryo.
(c) Classification of the diseases by causative organism
| Viral diseases | Bacterial diseases | Protozoan diseases |
|---|---|---|
| Yellow fever, poliomyelitis, measles, common cold, small pox, influenza, chicken pox | Typhoid, tuberculosis, tetanus, leprosy, cholera, whooping cough | Malaria, amoebic dysentery, trypanosomiasis |
Question 5 Report
(a) What is a balanced diet?
(b) (i) Name four classes of food other than proteins
(ii) Give one example of food substance for each class named
(c)(i) State three functions of proteins in humans.
(ii) Describe the appearance of a child with protein deficiency.
(d)(i) Name one organelle in a living cell that produces enzymes.
(ii) Mention two enzymes that act on proteins.
(a) A balanced diet is a diet that contains all the classes of food (carbohydrates, proteins, fats and oils, vitamins, mineral salts, water and roughage) in the correct proportions needed by the body for proper growth, energy and health.
(b)(i) Four classes of food other than proteins, with (ii) one example each
| Class of food | Example |
|---|---|
| Carbohydrates | Rice (yam, bread, garri) |
| Fats and oils | Groundnut oil (butter, palm oil) |
| Vitamins | Orange (vitamin C source) |
| Mineral salts | Table salt (milk for calcium) |
(c)(i) Three functions of proteins in humans
- For growth and building of new cells and tissues.
- For repair of worn-out or damaged tissues.
- For the formation of enzymes, hormones and antibodies (and can be oxidised to give energy).
(ii) Appearance of a child with protein deficiency (kwashiorkor)
- Swollen belly and puffy (oedematous) face, hands and feet due to fluid retention.
- Thin, wasted limbs with poor muscle development and stunted growth.
- Reddish-brown, sparse hair; pale, scaly skin; and general weakness with a miserable, irritable look.
(d)(i) Organelle that produces enzymes: the ribosome (site of protein/enzyme synthesis).
(ii) Two enzymes that act on proteins: pepsin and trypsin (erepsin/peptidase also acceptable).
Answer Details
(a) A balanced diet is a diet that contains all the classes of food (carbohydrates, proteins, fats and oils, vitamins, mineral salts, water and roughage) in the correct proportions needed by the body for proper growth, energy and health.
(b)(i) Four classes of food other than proteins, with (ii) one example each
| Class of food | Example |
|---|---|
| Carbohydrates | Rice (yam, bread, garri) |
| Fats and oils | Groundnut oil (butter, palm oil) |
| Vitamins | Orange (vitamin C source) |
| Mineral salts | Table salt (milk for calcium) |
(c)(i) Three functions of proteins in humans
- For growth and building of new cells and tissues.
- For repair of worn-out or damaged tissues.
- For the formation of enzymes, hormones and antibodies (and can be oxidised to give energy).
(ii) Appearance of a child with protein deficiency (kwashiorkor)
- Swollen belly and puffy (oedematous) face, hands and feet due to fluid retention.
- Thin, wasted limbs with poor muscle development and stunted growth.
- Reddish-brown, sparse hair; pale, scaly skin; and general weakness with a miserable, irritable look.
(d)(i) Organelle that produces enzymes: the ribosome (site of protein/enzyme synthesis).
(ii) Two enzymes that act on proteins: pepsin and trypsin (erepsin/peptidase also acceptable).
Question 6 Report
(a) List four adaptive features of animals that climb rain forest trees.
(b) State five important uses of water to organisms in the tropical rain forest.
(c) Describe how temperature as an ecological factor can be measured
(d)(i) Name two scientists who have contributed to the study of evolution.
(ii) List five evidences to support the occurrence of evolution.
(a) Four adaptive features of animals that climb rain forest trees
- Long, curved claws or nails for gripping bark and branches.
- Prehensile (grasping) tail or limbs for holding on to branches.
- Opposable digits (fingers and toes) for firm grasping.
- Adhesive pads/suckers on toes (as in tree frogs) and strong, well-developed limb muscles for climbing and leaping.
(b) Five important uses of water to organisms in the tropical rain forest
- Water is the medium (raw material) for photosynthesis in green plants.
- It is a solvent and medium for transport of dissolved food, minerals and wastes within organisms.
- It is needed for germination of seeds and for turgidity/support in plants.
- It serves as a habitat for aquatic organisms and for drinking by animals.
- It aids temperature regulation (cooling by transpiration and sweating) and biochemical reactions.
(c) Measuring temperature as an ecological factor: temperature is measured using a thermometer. Air (atmospheric) temperature is read from a mercury or alcohol thermometer placed in shade; soil temperature is taken with a soil thermometer buried at the required depth; and maximum-minimum (six's) thermometers record the highest and lowest temperatures over a period. Readings are taken in degrees Celsius.
(d)(i) Two scientists who contributed to the study of evolution: Charles Darwin and Jean-Baptiste Lamarck (Alfred Russel Wallace also acceptable).
(ii) Five evidences supporting the occurrence of evolution
- Fossil records showing gradual change of organisms over time.
- Comparative anatomy (homologous and vestigial structures).
- Comparative embryology (similar early embryonic stages).
- Geographical distribution of organisms.
- Cell biology / biochemistry (similar cell structure and molecules such as DNA and proteins).
Answer Details
(a) Four adaptive features of animals that climb rain forest trees
- Long, curved claws or nails for gripping bark and branches.
- Prehensile (grasping) tail or limbs for holding on to branches.
- Opposable digits (fingers and toes) for firm grasping.
- Adhesive pads/suckers on toes (as in tree frogs) and strong, well-developed limb muscles for climbing and leaping.
(b) Five important uses of water to organisms in the tropical rain forest
- Water is the medium (raw material) for photosynthesis in green plants.
- It is a solvent and medium for transport of dissolved food, minerals and wastes within organisms.
- It is needed for germination of seeds and for turgidity/support in plants.
- It serves as a habitat for aquatic organisms and for drinking by animals.
- It aids temperature regulation (cooling by transpiration and sweating) and biochemical reactions.
(c) Measuring temperature as an ecological factor: temperature is measured using a thermometer. Air (atmospheric) temperature is read from a mercury or alcohol thermometer placed in shade; soil temperature is taken with a soil thermometer buried at the required depth; and maximum-minimum (six's) thermometers record the highest and lowest temperatures over a period. Readings are taken in degrees Celsius.
(d)(i) Two scientists who contributed to the study of evolution: Charles Darwin and Jean-Baptiste Lamarck (Alfred Russel Wallace also acceptable).
(ii) Five evidences supporting the occurrence of evolution
- Fossil records showing gradual change of organisms over time.
- Comparative anatomy (homologous and vestigial structures).
- Comparative embryology (similar early embryonic stages).
- Geographical distribution of organisms.
- Cell biology / biochemistry (similar cell structure and molecules such as DNA and proteins).
