2018 WAEC BIOLOGY THEORY/OBJ ANSWERS-MAY/JUNE

Biology OBJ:

1BDDCCBCDBC

11ADCDCCAACC

21CAABBBBCBC

31CABCCACDAA

41ABBDDADDAB

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.

(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 resourcewhich 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)

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.

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 percent.
Oxygen — 21 percent.
Argon — 0.93 percent.

Carbon dioxide — 0.04 percent.

6 c )
i ) They are composed of relatively few species of plants
ii) The salt level of the habitat is high
iii ) High flooding rate
iv ) extreme temperature and salinity fluctuations.
6 cii )

Roots of salt marsh plants help stabilize the sandy substrate and trap and hold nutrients and detritus that flow through with each tidal cycle. This detritus trap helps feed bacteria , algae , and invertebrates . These root tangles also provide critical refuge for small fish and other animals .