Waec 2025 Biology Theory and Objective Answers…
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*WAEC BIOLOGY ANSWERS*
SECTION A. ANSWER ANY QUESTIONS.
*NUMBER ONE*
(1a)
Excretion is the biological process by which living organisms remove metabolic waste products from their body to maintain internal balance and prevent harm.
(1b)
-Mammals-
(PICK ANY TWO)
(i) Urea
(ii) Carbon dioxide
(iii) Water
(iv) Uric acid
(v) Creatinine
(vi) Excess salts
-Plants-
(PICK ANY TWO)
(i) Oxygen
(ii) Water vapor
(iii) Tannins
(iv) Alkaloids
(v) Resins
(vi) Latex
(1c)
Check the image below
(1d)
(PICK ANY THREE)
(i) Removal of nitrogenous wastes like urea
(ii) Regulation of water and salt balance (osmoregulation)
(iii) Regulation of blood pH
(iv) Secretion of erythropoietin to stimulate red blood cell production
(v) Regulation of blood pressure through renin
(vi) Activation of vitamin D for calcium absorption
*WAEC BIOLOGY ANSWERS*
*NUMBER THREE*
(3a)
Carbon dioxide (CO₂) and oxygen (O₂) are balanced through the processes of photosynthesis and respiration. Plants take in CO₂ during photosynthesis and release O₂. Animals and humans breathe in O₂ and release CO₂ during respiration. This cycle maintains the balance of both gases in nature.
(3b)
(PICK ANY FIVE)
(i) Light intensity
(ii) Soil type
(iii) Water availability
(iv) Temperature
(v) Wind
(vi) pH level of the soil
(vii) Availability of nutrients
(viii) Human activities
(3ci)
Overcrowding in an ecosystem refers to a situation where the number of organisms exceeds the carrying capacity of the environment, leading to competition for limited resources such as food, water, and space.
(3cii)
(PICK ANY FIVE)
(i) Increased competition for food and space
(ii) Spread of diseases
(iii) High mortality rate
(iv) Migration of some organisms
(v) Decrease in reproductive rates
(vi) Poor growth and development
(vii) Accumulation of waste
(viii) Stress and aggressive behavior among organisms
(ix) Depletion of natural resources
(3di)
Density-dependent factors are environmental factors whose effects on the population vary with population density, such as CompetitionCompetition,
disease, and predation. WHILE Density-independent factors affect the population regardless of its size or density, such as natural disasters, temperature, and pollution.
(3dii)
(PICK ANY TWO)
(i) Predation
(ii) Disease
(iii) Competition for resources
(iv) Parasitism
(v) Availability of mates
(vi) Accumulation of waste products
(3diii)
Density-dependent factors limit population through crowding effects like disease or competition. Density-independent factors, such as weather, affect populations regardless of size. Together, they influence balance and stability in an ecosystem.
*WAEC BIOLOGY ANSWERS*
*NUMBER FOUR*
(4a)
(PICK ANY TWO)
(i) Genetic recombination resulting in inheritance of two recessive alleles (tt).
(ii) Poor nutrition during the child’s developmental years.
(iii) Hormonal imbalance, especially low levels of growth hormone.
(iv) Genetic mutations affecting height-related genes.
(v) Chronic illnesses or medical conditions during growth.
(vi) Lack of physical activity or inadequate health care.
(4aii)
(4aiii)
Genotype: tt
(4bi)
Genotype is the genetic makeup of an organism in terms of the alleles present, e.g, TT, Tt, or tt.
(4bii)
(PICK ANY TWO)
(i) Genetic recombination during meiosis.
(ii) Mutations in genes or chromosomes.
(iii) Environmental influences such as diet or climate.
(iv) Random fertilization during sexual reproduction.
(v) Crossing over during meiosis.
(vi) Effects of diseases or infections during development.
(4ci)
An allele is an alternative form of a gene found at the same locus on homologous chromosomes.
(4cii)
In a Tabular form
-Genotype-
(PICK ANY TWO)
(i) It refers to the genetic makeup of an organism.
(ii) It is determined by the combination of alleles inherited from parents.
(iii) It cannot be observed directly.
(iv) It remains constant throughout the life of the organism.
(v) It can be represented using letters such as TT, Tt, or tt.
-Phenotype-
(PICK ANY TWO)
(i) It refers to the observable characteristics of an organism.
(ii) It is influenced by both genotype and environmental factors.
(iii) It can be seen and measured (e.g., height, skin color).
(iv) It may change due to environmental conditions.
(v) It is the physical expression or outcome of the individual traits.
SECTION B. COMPULSORY PART.
NO 5.
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