WAEC 2020/21 Biology Questions /Answers Out

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2020 WAEC BIOLOGY ANSWERS 🇳🇬

1a) The semicircular canals of the inner ear help you with balance. … This movement of the fluid moves the hairs of the canals, creating nerve impulses that travel up to your brain and let it know that your head is off balance. You don’t fall over because your brain tells your muscles to support you.

1b) check images

1bii) The middle ear contains three tiny bones known as the ossicles: malleus, incus, and stapes. The ossicles were given their Latin names for their distinctive shapes; theyare also referred to as the hammer, anvil, and stirrup, respectively.
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2a) This is a disease caused by the lack of an element in the diet, usually a particular vitamin or mineral

2aii)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)

(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.

2a) This is a disease caused by the lack of an element in the diet, usually a particular vitamin or mineral

2aii)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)

2b) i) This is a physical test:
-A chemical test for starch is to add iodine solution (yellow/brown) and look for a colour change.

-In the presence of starch, iodine turns a blue/black colour.

-It is possible to distinguish starch from glucose (and other carbohydrates) using this iodine solution test.

2bii)- Benedict’s solution is used to test for simple sugars, such as glucose.

-It is a clear blue solution of sodiumand copper salts.

-In the presence of simple sugars, the blue solution changes color to green, yellow, and brick-red, depending

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. … Invertebrates utilizing external fertilization are mostly benthic, sessile, or both, including animals such as coral, sea anemones, and tube-dwelling polychaetes

6aii) Internal fertilization occurs most often in land-based animals, although some aquatic animals also use this method. In ovoviparity, fertilized eggs are retained in the female, but the embryo obtains its nourishment from the egg’s yolk; the young are fully developed when they are hatched.

6bi) – Amphibians
– Fish

6bii)- Reptiles
– Birds

6ci) – It can deprive the baby of oxygen

– It can deprive the baby of Food Nutrient

– It can cause heavy bleeding in the mother.

6cii)….

7a) Hormone is a regulatory chemical substance produced in an organism and transported in tissue fluids such as blood or sap to stimulate specific cells or tissues into action.

7b) Adrenaline triggers the body’s fight-or-flight response. This reaction causes air passages to dilate to provide the muscles with the oxygen they need to either fight danger or flee. Adrenaline also triggers the blood vessels to contract to re-direct blood toward major muscle groups, including the heart and lungs.

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