WAEC Biology Answer (Obj and Essay) – 2020 Expo







========================================================SECTION A========(1a)
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(1bi)CLICK HERE FOR NUMBER 1B DIAGRAM

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The cavity of the middle ear is a narrow air-filled space. A slight constriction divides it into an upper and a lower chamber, the tympanum (tympanic cavity) proper below and the epitympanum above. These chambers are also referred to as the atrium and the attic, respectively. The middle-ear space roughly resembles a rectangular room with four walls, a floor, and a ceiling. The outer (lateral) wall of the middle-ear space is formed by the tympanic membrane.
The middle ear in human can be split into three parts; external, middle and inner. The middle ear lies within the temporCLICK HERE FOR NUMBER 1B DIAGRAM====

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2a) This is a disease caused by the lack of an element in the diet, usually a particular vitamin or mineral2aii)Lack of Calcium causes- Osteoporosis. Rickets. Tetany.Lack of Iodine deficiency- Goiter.Lack of Selenium deficiency. Keshan disease.Lack of Iron deficiency. Iron deficiency anemia.Lack of Zinc- Growth retardation.Lack of Thiamine (Vitamin B1) -Beriberi.Lack of Niacin (Vitamin B3)-Pellagra.Lack of Vitamin C- Scurvy.(Choose any 5)(2bi)
Starch in a tuber of yam is carried out as thus:
-By adding few drops of dilute iodine solution on a raw piece of yam.
-After this, it would be observed that the colour will change blue-black confirming the presence of starch.(2bii)
Glucose in orange fruit requires:
-Putting a small quantity of glucose solution in a test tube, with few drops of Benedict solution (about 2%).
-The mixture is boiled for 4-6minutes.
-After this, a brick-red or orange precipitate is seen confirming the presence of glucose.CLICK HERE FOR NUMBER 2 

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(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 fireCLICK HERE FOR NUMBER 3

========================BONUS ANSWER==========
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| ExamplePisces | cat fish
Amphibians | toad
Reptiles | lizard
Aves | bird
Mammals | man[CLICK HERE FOR NUMBER 4===

======= SECTION C======(6ai)
External fertilization is a mode of reproduction in which a male organism’s sperm fertilizes a female organism’s egg outside of the female’s body.(6aii)
Internal fertilization occurs most often in land-based animals, although some aquatic animals also use this method. There are three ways that offspring are produced following internal fertilization.(6bi)
(i)the foetus will not get oxygen
(ii)the foetus will not get nutrients.
(iii)waste products from your baby’s blood will not be removed(6cii)
[pick three]

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.

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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.

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