WAEC 2018 Biology (Obj & Theory) Answer Expo

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Biology Theory

Number 1 
1i) sperm cell is the male reproductive cell that is expelled along with the seminal fluid or semen when a man ejaculates. In humans, spermatozoa determine the gender of the baby-to-be, which means that they can carry either the X or the Y chromosome.

ii)Palisade cells are found in the mesophyll of a leaf and their main function is the absorption of light so that photosynthesis can take place. The palisade mesophyll consists of chloroplasts with chlorophyll that absorb the light energy.

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(2a)
i) carbon dioxide
ii) Nitrogen

(2b)
(i) CO 2 is used by plants to photosynthesize carbohydrates .
ii) Nitrogen is a major component of chhlorophyll

(2ci)
Variegated leaf is a leaf that has green parts ( where the cells contain chlorophyll) and non green parts ( where there is no chlorophyll).

(2cii)
The green parts

(2ciii)
i) The parts without chlorophyll do not photosynthesise
ii) the cells contain chlorophyll
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(3ai)

renewable resource is a resource which can be used repeatedly and replaced naturally. 

(3aii)

nonrenewable resource is a resource of economic value that cannot be readily replaced by natural means on a level equal to its consumption. 

(3bi)

(i)oxygen

(ii)fresh water

(3bii)

(i)oil

(ii)natural gas

(3c)

(i)Regulated and Planned Cutting of Trees.

(ii)Control over Forest Fire.

(iii)Reforestation and Afforestation.

(v)Check over forest clearance for agricultural and habitation Purposes.

(iv)Proper Utilisation of Forest and Forests Products.

(3d)

(i) Increases soil nutrients 

(ii) Improves soil structure. 

(iii) Does not corrupt the soil. 

(iv) Increases soil humus. 

(3e) 

Hb², Hb², I^a, I^o, I^o, T, t
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4aI)

 A gene is the basic physical and functional unit of heredity. Genes, which are made up of DNA, act as instructions to make molecules called proteins. In humans, genes vary in size from a few hundred DNA bases to more than 2 million bases.

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4aii) HYBRID

In biology, a hybrid, or crossbreed, is the result of combining the qualities of two organisms of different breeds, varieties, species or genera through sexual reproduction.
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(6ai)

Chemosynthesis is the biological conversion of one or more carbon-containing molecules (usually carbon dioxide or methane) and nutrients into organic matter using the oxidation of inorganic compounds (e.g., hydrogen gas, hydrogen sulfide) or methane as a source of energy, rather than sunlight

(6aii)

(i)Bacteria 

(ii)methanogenic archaea

(6b)

Nitrogen — 78%

Oxygen — 21%

Carbon dioxide — 0.04%

(6ci) 

(i) Too much clay deposit. 

(ii) Too much salt deposit. 

(iii) Eusterian vegetation. 

(iv) Mangrove forests. 

(6cii) 

There roof are mainly buttress and prop up roots which may prop up and down, thus anchoring properly to the soil. 

(6di) 

(i) Typhoid fever.

(ii) Dysentery. 

(iii) Cholera. 

(6dii) 

(i)Food poisoning 

(ii) Food spillage. 

(iii) Low market value of food. 

(6e) 

The person need plenty of rest and diet rich in protein, fruits and vegetables and take plenty of water. 

(6f) 

In a tabular form:

Under Tillage:

(i) The soil is prepared. 

(ii) conserve soil nutrients. 

(iii) Good for farm products. 

Under Bush burning:

(i) Fire is used to remove plants. 

(ii) Destroys soil nutrients. 

(iii) A bad farm practice.

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