WAEC 2025 : BIOLOGY {QUESTIONS AND ANSWERS OBJECTIVE AND ESSAY}

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MAY, 23TH ,2025

WAEC 2025 : BIOLOGY {QUESTIONS AND ANSWERS OBJECTIVE AND ESSAY}

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BIOLOGY OBJ

01-10: CACDBCADDB

11-20: ABBDAABDAC

21-30: BABCCCABBA

31-40: BBBAACCBAA

41-50: DBCCCDBCAC

COMPLETED.

(1a)

Excretion is the process by which an organism removes metabolic waste products and toxic substances from its body to maintain homeostasis.

(1bi)

(i) Urea

(ii) Carbon dioxide

(1bii)

(i) Oxygen

(ii) Water

(1c) Image.

(1d)

(PICK ANY 3)

(i) It filters blood to remove waste products like urea.

(ii) It regulates water and salt balance to maintain homeostasis.

(iii) It excretes waste products as urine.

(iii) It helps maintain blood pH by excreting hydrogen ions.

(iv) It produces erythropoietin to stimulate red blood cell production.

(v) It activates vitamin D to support calcium absorption for bone health.

======================

(2a)

In a Tabular form

-Photosynthetic Nutrition-

(PICK ANY TWO)

(i) It uses sunlight as the source of energy.

(ii) It occurs in green plants, algae, and some protists.

(iii) It requires chlorophyll to absorb sunlight.

(iv) Oxygen is released as a by-product during the process.

-Chemosynthetic Nutrition-

(PICK ANY TWO)

(i) It uses energy derived from chemical reactions (e.g., oxidation of inorganic substances like ammonia or hydrogen sulfide).

(ii) It occurs in some bacteria, especially those found in extreme environments like hydrothermal vents.

(iii) It does not require chlorophyll.

(iv) It does not release oxygen as a by-product.

(2bi)

Organisms that feed on dead or decaying organic matter by secreting enzymes and absorbing the digested nutrients.

(2bii)

(PICK ANY TWO)

(i) Rhizopus

(ii) Mucor

(iii) Penicillium

(iv) Aspergillus

(v) Yeast

(vi) Bacillus subtilis

(2biii)

Saprophytes feed by secreting extracellular digestive enzymes onto dead organic material. These enzymes break down complex organic substances into simpler soluble compounds, which the saprophytes then absorb for nourishment.

(2biv)

(PICK ANY THREE)

(i) They help in decomposing waste and recycling nutrients.

(ii) They are used in the production of antibiotics (e.g., Penicillium).

(iii) They play a role in the food and beverage industry (e.g., yeast in bread and alcohol production).

(iv) They are used in scientific research and biotechnology.

(v) Some help improve soil fertility.

(vi) They aid in compost formation and organic farming.

(vii) They can be used in the bioremediation of pollutants.

(2di)

-Butterfly-

Feeds on nectar (fluid feeder).

(2dii)

-Mosquito larva-

Filter feeder, they feed on microorganisms in water

(2diii)

-Mucor-

Saprophytic, they feed on decaying organic matter.

(2div)

-Housefly-

Fluid feeder, they feed on liquefied food using proboscis.

======================

(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 competition, 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.

======================

(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)

Draw the diagram

(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 genotype.

(5a)

(PICK ANY FIVE)

(i) Increases water loss through transpiration and evaporation.

(ii) Denatures enzymes, affecting metabolic activities.

(iii) Causes migration of animals to cooler areas.

(iv) Leads to wilting and possible death in plants.

(v) Reduces reproductive efficiency in organisms.

(vi) Increases risk of dehydration in animals.

(vii) Enhances the spread of temperature-sensitive diseases.

(viii) Reduces oxygen levels in water bodies, affecting aquatic life.

(ix) Disrupts feeding and growth patterns.

(5b)

(PICK ANY FIVE)

(i) Destroys habitats of plants and animals.

(ii) Reduces soil fertility by burning organic matter.

(iii) Increases atmospheric pollution due to smoke.

(iv) Leads to loss of biodiversity.

(v) Kills beneficial soil organisms.

(vi) Increases risk of desertification.

(vii) Causes soil erosion by removing plant cover.

(viii) Reduces agricultural productivity.

(ix) Alters local climate and rainfall patterns.

(5ci)

Countershading is a form of camouflage where the Tilapia's upper body is darker and its underside is lighter. This helps it blend with the dark riverbed when viewed from above, and with the lighter water surface when viewed from below, protecting it from predators.

(5cii)

Seasonal migration in birds is the regular movement of birds from one region to another, usually due to changes in climate or food availability. Birds migrate to warmer regions during cold seasons and return when conditions improve.

(5ei)

(PICK ANY FIVE)

(i) Bacteria

(ii) Viruses

(iii) Fungi

(iv) Protozoa

(v) Algae

(vi) Archaea

(vii) Mycoplasma

(viii) Actinomycetes

(ix) Rickettsiae

(5eii)