2020 WAEC BIOLOGY ANSWERS
BIOLOGY OBJECTIVE
01-10 CAABDBBBDC
11-20 AACBDDDCBB
21-30 CBACDAABCB
31-40 CABCCBDDCB
41-50 DCBBCBBAAA
INSTRUCTIONS: Answer three (3) Questions in all. Two (2) Questions from SECTION A and one (1) Question from SECTION B
THEORY
(1ai)
When the head moves or changes position,the endolymph fluid in the semi-cricular canals moves and stimulates the nerve endings. The nerve endings then transmit the impulses through vestibular to the cerebellum of the brain where the new position at the head is interpreted and the appropriate responses sent to the muscular system to maintain body balance
(1aii) *[check the image for the diagram]*
(1aiii)
The middle ear in human can be split into three parts; external, mdiddle and inner. The middle ear lies within the temporal bone, and extends from the tympanic membrane to the lateral wall of the inner ear. The main function of the middle ear is to transmit vibrations from the tympanic° membrane to the inner ear via the auditory ossicles.
[Check the images for complete No 1 answers]
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(2ai)
This is a disease caused by the lack of an element in the diet, usually a particular vitamin or mineral.
(2aii)
(Pick any 5)
(i) Lack of Calcium causes- Osteoporosis, Rickets and Tetany.
(ii) Lack of Iodine deficiency- Goiter.
(iii) Lack of Selenium deficiency
(iv)Lack of Iron, deficiency Iron and deficiency anemia.
(v) Lack of Zinc- Growth retardation.
(vi) Lack of Thiamine. (Vitamin B1) -Beriberi.
(vi) Lack of Niacin (Vitamin B3)-Pellagra.
(vii) Lack of Vitamin C- Scurvy
(2bi)This is a physical test:
(i)A chemical test for starch is to add iodine solution (yellow/brown) and look for a colour change.
(ii)In the presence of starch, iodine turns a blue/black colour.
(iii)It is possible to distinguish starch from glucose (and other carbohydrates) using this iodine solution test.
(2bii)
(I)Benedict’s solution is used to test for simple sugars, such as glucose.
(ii)It is a clear blue solution of sodiumand copper salts.
(iii)In the presence of simple sugars, the blue solution changes color to green, yellow, and brick-red, depending.
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3a)
TABULATE
(i) Disease: Cholera
Causative organism: Bacterium (vibro cholerae)
Vector: Housefly
Control: Keeping environment clean
(ii) Disease: Sleeping sickness
Causative organism: Trypanosome
Vector: tse-tse fly
Control: use of antiseptic
(iii) Disease: Malaria
Causative organism: Plasmodium (protozoa)
Vector: Female anopheles mosquito
Control: Draining of swamps
(iv) Disease: Ringworm
Causative organism: Trichophyton and microsporum
Vector: None
Control: Keeping of skin clean and dry
(3bi)
Salting is the dusting of farm products with table salt
(3bii)
Irradiation is the drying of some crops or products using the heat from the sun
(3biii)
Smoking is the drying of some farm products over a smoke of a naked fire
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*BONUS*
(4ai)
This states that during the formation of gamete the distribution of one pair of allele does not affect the distribution of other allelic pair.
(4aii)
Blood group O can only exist in homozygous form because it has no antigen on its red blood cell while blood group A can exist both in homozygous and heterozygous form because of the presence of antigen on their blood cell. therefore they exhibit co-dominance.
(4b)
*Class of vertebrate | Example*
(i) Pisces | cat fish.
(ii) Amphibians | toad.
(iii) Reptiles | lizard.
(iv) Aves | bird.
(v) Mammals | man.
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(6ai)
External Fertilization: This type of fertilization occurs when the sperm from the male animal meets the egg/ovum from the female animal, outside the body of the animal. It is common in pisces and amphibians.
(6aii)
Internal fertilization: a type of fertilization by which the sperm from the male meets the egg/ovum inside the body of the animal. It is common in mammals and birds.
(6bi)
(i) Pisces e.g: Tilapia, Croaker, Titus
(ii) Amphibians e.g.: Frogs, Toads, Newts
(6bii)
Internal fertilization:
(i) Mammals e.g. Man, Rat, Monkeys
(ii) Aves e.g. Parrots,Hawks, Eagles
(6ci)
(i) Malnourished and underdeveloped foetus
(ii) Low supply of oxygen to the foetus due to reduced diffusion
(iii) Leads to the death of foetus and miscarriage of pregnancy
(6cii)
(i) Amnion
(ii) Amniotic fluid
(iii) Umbilical cord
(6d)
Competition in feeding among organisms for scarce resources leads to the death of weaker members of the species and the reproduction of the stronger members, leading to a dynamic equilibrium that balances the rate of death to the rate of birth.
(6e)
(i) Problem of Wave
(ii) Effects of temperature
(iii) Salinity of the Marine
(iv) Humidity
(6fi)
Moisture helps in the germination of seeds by helping to activate the metabolic activities needed for germination, dissolved oxygen content in moisture acts is very beneficial to the biochemical process involved in germination.
(6fii)
Viable seeds are healthy and contain the organic requirements for a healthy germination, and is most times resistant to harsh weather conditions, and lack of nutrients.
(6g)
Light energy is considered a limiting factor in production of food by autotrophs because, photosynthesis which is the main process by which autotrophs produce food cannot take place in the absence of light. The energy from light is solely responsible for the process of photosynthesis.
COMPLETED
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