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1.
(a)
Explain briefly how the human ear carries out its function of balancing.
(b)
(i) make a drawing 8 cm - 10 cm long of the structure of the human ear and label fully.
(ii)
Describe briefly the structure of the middle ear in humans.
Explanation
(a)
How the human ear carries out its function of balancing;
- Head movement in any direction affect the fluid/endolymph, In the semi-circular canals, Which are at right angles to each other, The movement forces the sensory/hair cells in the ampulla to set up the impulses, The brain interprets the impulses and relays the impulses to the body muscles for balancing.
(b)
(i) Diagram of the Human Ear;
(b)
(ii) Description of the structure of the middle ear; The middle ear is an air filled chamber, It connects the ear drum of the oval window fenestra ovalis. It contains three bones/hammer/malleus, anvil/incus and stapes/stirrup/ear ossicles. The malleus is attached to the tympanic membrane/tympanum/eardrum. Each of the bones has direct contact with the one next to it, the eustachian tube is formed at the base of the middle ear . The eustachian tube links the ear to the throat/pharynx.
2.
(a)
(i)
What is a deficiency disease?
(ii)
Complete the table below by naming five nutrient deficiency diseases in humans and stating one remedy for each of the diseases.
(b)
Outline a chemical test for
(i)
Starch in a tuber of yam
(ii)
Glucose in orange fruit
Nutrient deficiency disease Remedy
Explanation
(a)
(i)
Deficiency Disease; This is a disease caused by lack of or insufficient or inadequate supply of a specific vitamin or other nutrients/food substances.
(a)
(ii)
Nutrient deficiency diseases Remedy
Goitre/Goiter Consumption of iodizes salt/sea food
Rickets Consumption of a diet rich in calcium/phosphorous/vitamin D
Anaemia/Anemia Eating a diet rich in iron
Kwashiokor Diet of infant should contain protein
Scurvy Consumption of foods/fruits rich in Vitamin C
Pellegra Addition of naicin/vitamin K to diet
Night blindness Consumption of food rich in Vitamin A
Beriberi Consumption of food rich in vitamin B
Stunted growth/cretinism Consumption of food rich in iodine
Marasmus Consumption of protein and carbohydrate
(b) Procedure of Chemical Test for;
(i) Starch in a tuber of yam; The tuber of yam is peeled and sliced, a few drops of iodine solution is added to the peeled yam, blue-black colour formed indicates presence of starch.
(ii) Glucose in orange fruit; Orange fruit is cut and it's juice is extracted into a beaker/test tube, few drops of Benedict's solution/Fehling's solutions A and B is added to equal volume of orange juice, add heat gently, a red/orange/brick-red precipitate shows the presence of glucose. For Benedict's solution when heated shows red/yellow precipitate confirming presence of glucose
3.
(a)
Complete the table below;
Disease Causative organism Vector Control
Cholera
Trypanosome
Female Anopheles mosquito
Ringworm None
(b)
Explain briefly the biological basis of preserving foods using each of the following methods;
(i) salting
(ii) irradiation
(iii) smoking
Explanation
(a)
Disease Causative Organism Vector Control
Cholera Vibrio Cholerae Housefly/Cockroach Good sanitation/good personal hygiene/ any other method of good sanitation/inoculation/vaccination
Trypanosomiaasis/Sleeping sickness Trypanasome Tsetsefly/Glossina Destroying habitat of vector/clearing the vegetation, killing vector/ eradicate flies.
Malaria Plasmodium sp Penale anopheles mosquito Proper sanitation/using spraying recommended insecticide/fumigation, clearing of bushes/drainages of breeding sites/sleeping under nets.
Ringworm Tinea Sp/Fungi/Microsponium None Good personal hygiene, avoid contact with infected persons/material, use of drugs/griseofluvin
(b)
Biological Basis of Preserving Foods by;
(i)
Salting; Removes water/moisture from food by osmosis therefore prevents micro-organisms from growing on food by dehydrating and killing them.
(ii)
Irradation; Involves the exposure of food to high energy gamma rays/x-rays radiation to destroy enzymes that cause spoilage, delay ripening of fruits, sprouting of vegetables therefore allowing long storage periods.
(iii)
Smoking; Reduces the water content of food thereby creating unfavourable conditions for microbial growth and survival also called curing. Smoking contains phenols/carbon that kills microbes on the surface of food.
4.
(a)
Explain briefly;
(i)
independent assortment of genes
(ii)
the reason blood group O in humans can only exist in homozygous form while blood groups A and B can exist both in homozygous and heterozygous forms.
(b)
Complete the table below by naming the classes of vertebrates in their evolutionary trend and giving one example each of the classes.
Classes of vertebrate One example
Explanation
(a)(i) Independent Assortment of Genes; is the random selection of genes during meiosis to produce gametes, where the genes separate/segregate so that only one of a pair is found in any one gamete. In the dihybrid inheritance in heterozygote the pairs of alleles are found on different pairs of chromosome, Only four types of gametes are produced in approximately equal numbers.
(ii) Blood grouping in humans; Is determined by three alternative genes/alleles A, B and O. A person can only possess two alleles of the genes on a pair of homologous chromosomes. Gene O is recessive to both genes A and B which are dominant/co-dominant and possess antigen A and B in the red blood cells hence it is possible to have blood group A as AA (homozygous) or AO (heterozygous) and blood group B as BB or BO, Blood group O can only exist genotypically as OO and does not possess antigen A or B in the red blood cells or in the homozygous recessive state.
(b) Classes of Vertebrates in their Evolutionary Trend;
Class of Vertebrates One Example
Pisces/Osteichthyes/Chondricthyes Tilapia; Tuna, Salmon, Shark, Dogfish, Catfish, Skate, Ray
Amphibia Frog/Toad
Reptilia Snake, Crocodile, Tortoise, Turtle, Lizard, Wall Gecko
Aves Dove, Pigeon, Parrot, Weaver Bird, Hawk, Eagles, Domestic Fowl
Mammalia Human, Monkeys, Rat, Rabbit/Guinea pig
5.
(a)
Explain briefly the following types of fertilization in animals;
(i)
external fertilization
(ii)
internal fertilization
(b)
Name two groups of animal each that exhibit the types of fertilization in (a)
(c)
(i)
If the placenta in a pregnant woman is detached from the uterine wall, give three effect this will have on the foetus
(ii)
Name three other features in the uterus of a pregnant woman that are useful for the development of the foetus
(d)
Explain briefly how the activities of organisms bring bout dynamic equilibrium in the habitat.
(e)
State four problems that organisms in the intertidal zone of a marine habitat could encounter.
(f)
Explain briefly the reasons that the following factors are necessary for germination;
(i) moisture
(ii) viable seeds
(g)
Explain briefly the reason light energy is considered a limiting factor in the production of foods by autotrophs.
Explanation
(a)
(i)
External Fertilization; Involves the release of eggs by the female to the outside environment where a male sheds its sperms on them for fertilization outside the body of the female.
(ii)
Internal Fertilization; Involves the release of eggs inside the body of a female males deposit sperms inside the female where fertilization occurs.
(b)
(i)
Groups of Animal that exhibit external fertilization ;- Fish/pisces, amphibians
(ii)
Groups of Animal that exhibit internal fertilization;- Reptiles, birds/aves, mammals
(c)
(i)
Effect of Detached Placenta on a Foetus;
The exchange of dissolved food substances/oxygen/antibodies between a foetus and the mother will cease, removal of waste products from foetus will cease production of progesterone/hormone will cease might lead to the death of foetus/miscarriage/abortion/still birth. Certain molecules may pass into the body of foetus.
(ii)
Other Features Present in the Uterus of a Pregnant Woman; Umbilical cord, amnion, amniotic fluid, allantois, Chorion
(d)
Dynamic Equilibrium; Nature does not encourage any population exceeding the carrying capacity of the habitat, living organisms play a role in the regulation of the abundance of organisms/population in the habitat. Interaction among various populations lead to competition which may result in the elimination of one species or its restriction to a non-competitive position, Plants sometimes compete by producing toxic chemicals that inhibit neighboring species, there also exists predator-prey relationship/association between animals all these forces act together to achieve dynamic equilibrium in the habitat.
(e)
Problem that Organisms in Intertidal Zones of Marine Habitats could Encounter; Tendency of being carried away by waves drying up/desiccation/exposure to air, varied osmotic balance oxygen deficiency, low light intensity for producers, reduced visibility in animals, fluctuation of water temperature..
(f)
Reasons the following factors are necessary for germination;
(i)
Moisture;- A seed imbibes/absorbs moisture causing the seed to swell and the testa becomes more permeable to oxygen and carbon (IV) oxide. This swelling will rupture the testa before germination starts, the moisture/water activates the enzymes for metabolism leading to germination
(ii)
Viable Seed;- Has a living/healthy embryo, intact healthy cotyledon/endosperm, whole without boring from insect.
(g)
Reason Light energy is Considered a Limited Factor in the Production of Food by Autotrophs; Light energy is obtained from the sun which is an important factor for photosynthesis/photolysis of water that is a process of manufacturing/producing food by autotrophs at optimum temperature/sunlight/solar/light energy green plants/autotrophs will manufacture food.
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