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2025 WAEC GCE FIRST Series Biology Questions and Answers

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 2025 WAEC GCE 1st Series Biology Questions and Answers Expo Runz

 

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BIOLOGY OBJ
01-10: ACABDCBDBB
11-20: ABDBBBDBAB
21-30: AACDCBCBAC
31-40: ADDAADCCBC
41-50: DBDBDCBBDA

COMPLETED

 

THEORY QUESTIONS

 

ANSWERS:

WAEC GCE BIOLOGY THEORY

(1ai)
Homeostasis refers to the intrinsic regulatory mechanisms employed by biological organisms to maintain a stable internal environment despite external fluctuations.

(1aii)
(i)Kidneys
(ii)Liver
(iii)Hypothalamus

(1b)
Under type of neuron
(i)Sensory Neuron
(ii)Motor Neuron
(iii)Inter Neuron

Under function of neuron
(i)Transmits sensory information from receptors to the central nervous system
(ii) Conveys signals from the CNS to effectors, such as muscles and glands
(iii)Integrates information between sensory and motor neurons within the CNS

(1c)

 

(2a)
UNDER PRIMARY SUCCESSION

(i) Occurs in areas where no soil or vegetation existed before, such as after a volcanic eruption or glacier retreat.
(ii) Starts from scratch, with no remaining vegetation or soil.

UNDER SECONDARY SUCCESSION

(i) Occurs in areas where soil and vegetation were previously present, but were disturbed or damaged, such as after a forest fire or clear-cutting.
(ii) Starts with remaining vegetation, such as seeds, roots, or stumps.

 

*WAEC GCE BIOLOGY THEORY*

(4a)
[img]https://i.imgur.com/wnLOeF1.jpeg[/img]

(4b)
Type of Inheritance Illustrated The type of inheritance illustrated in this cross is -incomplete dominance. In this form of inheritance, neither allele is completely dominant over the other, resulting in a blending of traits in the phenotype of the offspring.

(4c)
Mechanism of Incomplete Dominance In incomplete dominance, the alleles for a trait blend together in the phenotype of the heterozygous offspring. In this case, the red allele (R) does not completely mask the expression of the white allele (r). Instead, when an R allele is combined with an r allele, the resulting phenotype is an intermediate color—in this case, pink flowers. This occurs because the expression of the alleles produces a phenotype that is a mixture of both parental traits, rather than one being dominant over the other.

(4d)
Test Cross with F1 Offspring A test cross involves breeding an individual of unknown genotype with a homozygous recessive individual to determine the genotype of the former. Let’s analyze the outcomes based on the F1 offspring (Rr), which are pink flowered.

(4di)
Genotype of the Parent The genotype of the parent used in the test cross is rr (homozygous recessive).

(4dii)
Phenotypes of the Result of the Cross The phenotypes of the result of the cross will be: – Pink flowers (Rr) – White flowers (rr)

(4diii)
Genotypes of the Result of the Cross The genotypes of the result of the cross will be: – Rr (pink) – rr (white)

(4div)
Genotypic Ratio of the Offspring Obtained The genotypic ratio of the offspring obtained from the test cross will be: – 1 Rr : 1 rr This means that there is a 50% chance for each genotype, resulting in a genotypic ratio of 1:1 for Rr (pink) and rr (white). This comprehensive analysis illustrates the principles of inheritance and the effects of dominant and recessive alleles on phenotypic expression.

 

(5)
Oviparous animals lay eggs that develop outside the mother’s body. The young are nourished by yolk in the egg.

Examples: Birds, reptiles, and amphibians.
Viviparity:

Viviparous animals give birth to live young that develop inside the mother’s body. The young are nourished via a placenta or other maternal tissue.
Examples: Mammals, including humans.

(5b)
(I) Bird
(ii) Reptiles
(iii) Amphibians

(5c)

(5d)
(I) Nitrogen Fixing Bacteria: Convert atmospheric nitrogen (N₂) into a form that plants can use (ammonia, NH₃).
(ii) Nitrifying Bacteria: Convert ammonia (NH₃) into nitrites (NO₂-) and then into nitrates (NO₃-), which are usable by plants.
(iii) Denitrifying Bacteria: Convert nitrates (NO₃-) back into atmospheric nitrogen (N₂), completing the cycle.

 

(5e)
[img]https://i.imgur.com/G8uvCtx.jpeg[/img]

(5f)
Under Below the soil
(i)Radicle
(ii)Hypocotyl

Under Above the soil
(i)Cotyledon
(ii)Epicotyl

(5g)
(i) The sense organ used for smelling is the olfactory epithelium, located in the nasal cavity.
(ii) The sense organ sensitive to touch is the skin, which contains various receptors for tactile sensations.

 

(6a)
Explanation of Reproductive Methods

(i) Oviparity

Oviparity is a mode of reproduction in which animals lay eggs that develop and hatch outside the mother’s body.

The embryo receives no direct nourishment from the mother.

Example: Birds, reptiles, amphibians.

(ii) Viviparity

Viviparity is a reproductive method where embryos develop inside the mother’s body and receive nourishment directly from her before birth.

Example: Humans, mammals, some sharks.

(6b)
Three Classes of Oviparous Animals

1. Aves (Birds) – e.g., hen, pigeon.

2. Reptilia (Reptiles) – e.g., lizard, snake.

3. Amphibia (Amphibians) – e.g., frog, toad.