WAEC 2020 BIOLOGY QUESTIONS AND ANSWERS

BIOLOGY-OBJ

BIOLOGY-OBJ

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BIOLOGY theory SOLUTIONS

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.

1iii) 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.

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.

(6ci)
(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)
(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.

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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.

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.

*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

(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

4ai)Mendel’s law of independent assortment states that genes do not influence each other with regard to the sorting of alleles into gametes: every possible combination of alleles for every gene is equally likely to occur. The independent assortment of genes can be illustrated by the dihybrid cross: a cross between two true-breeding parents that express different traits for two characteristics.

(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

Pisces | cat fish
Amphibians | toad
Reptiles | lizard
Aves | bird
Mammals | man

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