Waec 2018 Biology Answers / Biology Obj And Theory Answers Expo

Waec 2018 Biology Answers


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BIOLOGY OBJ:
1-10: BCDCDACDAB
11-20: ADADCBACBC
21-30: CABBDBAADC
31-40: AABCCBCDAA
41-50: AACBABDDAB

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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.

1b) Draw Below Diagram

(1c)
IN A TABULAR FORM MAMMALS AND AMPHIBIANS

MAMMALS

– Mammals give birth to their young ones alive.

– Mammals produce amniotic eggs

AMPHIBIANS

– Amphibians lay eggs
– Amphibians do not produce amniotic eggs

(1d)

– Use of condoms/pills
– withdrawal

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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

(2civ) Nitrogen

(2d)
Holozoic:
Human

Parasitic:
Tapeworm; Venus flytrap

Symbiotic:
Lichen

Saorophytic:
Rhizopus; mushroom; housefly.

Autotropic:
Spirogyra; waterleaf plant; elephant grass.

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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)
(i) Increases soil nutrients
(ii) Improves soil structure.
(iii) Does not corrupt the soil.
(iv) Increases soil humus.

(3e)
(i)z AA
(ii) AO
(iii) BB
(iv) BO

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4a)
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.

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.

4b) Draw The Diagram Below

4ci height of plant
ii size of various parts of the plant such as stems, leaves, flowers, fruits
iii color of parts of plants such as green, white and brown of leaves, stem and root

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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 percent.
Oxygen — 21 percent.
Argon — 0.93 percent.
Carbon dioxide — 0.04 percent.

(6c)
(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.

(6cii)
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.

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.