🧬 Biology — Ecology, Genetics and Evolution

1. Which of the following represents the correct order of increasing complexity in the organisation of an ecosystem?

1. Organism, Community, Population, Ecosystem
2. Organism, Population, Community, Ecosystem
3. Population, Organism, Ecosystem, Community
4. Community, Population, Organism, Ecosystem

Ecological organisation progresses from a single organism, to a population (same species), to a community (different populations), and then to the ecosystem. (JAMB UTME Biology Syllabus (Ecology — the ecosystem: biosphere, community, population); Ndu, Ndu & Ndu, Senior Secondary Biology)

2. In ecology, a population refers to

1. all the living and non-living components found in a habitat
2. all organisms of different species living together in a habitat
3. all the individuals of the same species living in a particular habitat at the same time
4. the non-living physical environment of a habitat

A population is defined as all individuals of one species occupying the same habitat at a given time. (JAMB UTME Biology Syllabus (Ecology — the ecosystem: biosphere, community, population); Ndu, Ndu & Ndu, Senior Secondary Biology)

3. A biological community, as used in ecology, is best described as

1. a single species population in a habitat
2. all the populations of different species living and interacting together in the same habitat
3. only the abiotic components of a habitat
4. a group of producers only within a habitat

A community consists of all the different populations of organisms living and interacting in the same habitat. (JAMB UTME Biology Syllabus (Ecology — the ecosystem: biosphere, community, population); Ndu, Ndu & Ndu, Senior Secondary Biology)

4. According to the Ten Percent Law of energy flow in an ecosystem, when energy is transferred from one trophic level to the next,

1. about 90% of the energy is passed on to the next level
2. all the energy is transferred without any loss
3. only about 10% of the energy is transferred to the next level
4. the amount of energy transferred doubles at each level

Only a small proportion, approximately 10%, of the energy at one trophic level is available to the next, since most is lost as heat during respiration. (Lindeman, R.L. (1942), trophic-dynamic concept; JAMB UTME Biology Syllabus (Ecology — energy flow/trophic levels))

5. Why is energy flow through a food chain considered inefficient?

1. Because producers do not use sunlight for photosynthesis
2. Because most of the energy at each trophic level is lost as heat through respiration
3. Because decomposers store all the energy permanently in the soil
4. Because herbivores never consume all the available plant material

Energy flow is inefficient mainly because a large proportion of the energy at each trophic level is lost as heat during respiration rather than passed on. (JAMB UTME Biology Syllabus (Ecology — energy flow/trophic levels); Lindeman, R.L. (1942))

6. In the nitrogen cycle, the bacterium mainly responsible for fixing atmospheric nitrogen within the root nodules of leguminous plants is

1. Nitrobacter
2. Nitrosomonas
3. Rhizobium
4. a denitrifying bacterium

Rhizobium bacteria live symbiotically in the root nodules of leguminous plants, where they fix atmospheric nitrogen into usable compounds. (JAMB UTME Biology Syllabus (Ecology — nutrient cycling: nitrogen cycle); Ramalingam, S.T., Modern Biology)

7. In the process of nitrification, ammonia is first oxidised to nitrites by Nitrosomonas, after which the nitrites are further oxidised to nitrates by

1. Rhizobium
2. Nitrobacter
3. denitrifying bacteria
4. Escherichia coli

Nitrification occurs in two stages: Nitrosomonas converts ammonia to nitrites, and Nitrobacter then oxidises the nitrites to nitrates. (JAMB UTME Biology Syllabus (Ecology — nutrient cycling: nitrogen cycle); Ramalingam, S.T., Modern Biology)

8. Denitrifying bacteria play an important role in the nitrogen cycle because they

1. fix atmospheric nitrogen gas into ammonia for plants
2. oxidise ammonia into nitrites
3. convert nitrates in the soil back into atmospheric nitrogen gas
4. convert nitrites into nitrates for plant uptake

Denitrifying bacteria break down nitrates in the soil and release nitrogen gas back into the atmosphere, completing the nitrogen cycle. (JAMB UTME Biology Syllabus (Ecology — nutrient cycling: nitrogen cycle); Ramalingam, S.T., Modern Biology)

9. The population of an organism in a habitat will increase in size when

1. mortality and emigration exceed natality and immigration
2. natality and immigration exceed mortality and emigration
3. natality is exactly equal to mortality
4. immigration is exactly equal to emigration

A population grows when the combined rate of births and immigration exceeds the combined rate of deaths and emigration. (JAMB UTME Biology Syllabus (Ecology — factors affecting population size); Stone, R.H. & Cozens, A.B., New Biology for West African Schools)

10. In the food chain: grass → grasshopper → frog → snake, the frog occupies the trophic position of a

1. producer
2. primary consumer
3. secondary consumer
4. decomposer

The grasshopper (primary consumer) feeds on grass, and the frog, which feeds on the grasshopper, is therefore the secondary consumer. (JAMB UTME Biology Syllabus (Ecology — food chains and trophic levels); Ndu, Ndu & Ndu, Senior Secondary Biology)

11. Which of the following is an abiotic component of an ecosystem?

1. Decomposer bacteria
2. Temperature
3. Herbivores
4. Producer plants

Abiotic components are the non-living physical and chemical factors of the environment, such as temperature, light and water. (JAMB UTME Biology Syllabus (Ecology — the ecosystem: biotic and abiotic components); Ndu, Ndu & Ndu, Senior Secondary Biology)

12. Charles Darwin's theory of evolution, set out in On the Origin of Species (1859), proposed that evolutionary change occurs mainly through

1. the inheritance of characteristics acquired during an organism's lifetime
2. natural selection acting on heritable variation within a population
3. spontaneous generation of entirely new species
4. the use and disuse of body organs

Darwin proposed that heritable variation, combined with natural selection, drives evolutionary change over generations. (Darwin, C., On the Origin of Species (1859); JAMB UTME Biology Syllabus (Theories of evolution))

13. Darwin observed that organisms produce more offspring than the environment can support, creating a struggle for existence in which

1. all offspring survive equally regardless of their traits
2. parents protect the weakest offspring from harm
3. organisms best suited (adapted) to the environment survive and reproduce
4. only the largest organisms survive, irrespective of adaptation

This is the basis of 'survival of the fittest': organisms whose variations best suit the environment are more likely to survive and pass on their traits. (Darwin, C., On the Origin of Species (1859); JAMB UTME Biology Syllabus (Theories of evolution))

14. According to Lamarck's theory of evolution, characteristics that an organism develops through the use and disuse of its body parts during its lifetime are

1. lost completely and never passed on
2. passed on to its offspring
3. expressed only in that organism and never inherited
4. irrelevant to the process of evolution

Lamarck's theory of inheritance of acquired characteristics proposes that traits gained through use or disuse during an organism's life are passed to its offspring. (JAMB UTME Biology Syllabus (Theories of evolution — Lamarckism); Stone, R.H. & Cozens, A.B., New Biology for West African Schools)

15. A key difference between Lamarck's and Darwin's explanations of evolution is that Lamarck proposed evolution occurs mainly through

1. natural selection acting on existing heritable variation
2. the inheritance of characteristics acquired by an organism during its own lifetime
3. random mutation of DNA only
4. the sudden appearance of new species with no ancestry

Unlike Darwin, who emphasised natural selection of existing variation, Lamarck argued that traits acquired through use or disuse in an organism's lifetime were inherited. (JAMB UTME Biology Syllabus (Theories of evolution — Lamarckism vs Darwinism); Stone, R.H. & Cozens, A.B., New Biology for West African Schools)

16. The forelimbs of a man, a whale and a bat have the same basic bone arrangement but are adapted for different functions. These are examples of

1. analogous organs, showing convergent evolution
2. vestigial organs with no evolutionary significance
3. homologous organs, showing divergent evolution from a common ancestor
4. mimicry between unrelated organisms

Homologous organs share the same basic structure but differ in function, providing evidence of divergent evolution from a common ancestor. (JAMB UTME Biology Syllabus (Evidence of evolution); Ramalingam, S.T., Modern Biology)

17. The wings of a butterfly and the wings of a bird serve the same function of flight but have completely different structures and origins. Such organs are called

1. homologous organs
2. analogous organs, illustrating convergent evolution
3. vestigial organs
4. identical organs

Analogous organs perform the same function but differ in structure and origin, illustrating convergent evolution rather than a shared ancestor. (JAMB UTME Biology Syllabus (Evidence of evolution); Ramalingam, S.T., Modern Biology)

18. Which of the following is a structural adaptation that helps desert plants (xerophytes) survive dry conditions?

1. Broad, thin leaves with numerous stomata
2. Reduced leaves or spines and thick, water-storing stems
3. Shallow roots that absorb only surface dew
4. Continuous flowering regardless of water availability

Xerophytes reduce water loss through features such as spines instead of broad leaves and thick stems that store water. (JAMB UTME Biology Syllabus (Adaptation of organisms to their environment); Ndu, Ndu & Ndu, Senior Secondary Biology)

19. In evolutionary terms, an organism is described as being 'fit' when it

1. is physically the strongest individual in its species
2. survives and successfully reproduces, passing its genes to the next generation
3. lives the longest life regardless of reproduction
4. can change its body structure within a single lifetime

Evolutionary fitness is measured by an organism's reproductive success, not merely its strength or lifespan. (JAMB UTME Biology Syllabus (Theories of evolution — natural selection); Darwin, C., On the Origin of Species (1859))

20. Natural resources such as forests, wildlife and fresh water, which can be replenished naturally over time if properly managed, are classified as

1. non-renewable resources
2. renewable resources
3. fossil resources
4. extinct resources

Renewable resources can regenerate naturally within a reasonable time if they are not overexploited. (JAMB UTME Biology Syllabus (Conservation of natural resources); Ramalingam, S.T., Modern Biology for Senior Secondary Schools)

21. One major reason for conserving wildlife and forest resources is to

1. increase the rate of soil erosion
2. maintain biodiversity and ecological balance for future generations
3. hasten the extinction of endangered species
4. reduce the amount of oxygen in the atmosphere

Conservation aims to protect biodiversity and maintain ecological balance so that resources remain available for future generations. (JAMB UTME Biology Syllabus (Conservation of natural resources); Ramalingam, S.T., Modern Biology for Senior Secondary Schools)

22. Afforestation, as a method of conserving natural resources, refers to

1. clearing forests for agriculture and timber production
2. planting trees on land that had no previous forest cover
3. burning bush vegetation to create grazing land
4. draining wetlands to create room for construction

Afforestation involves establishing new forests or tree cover on land that was previously unforested, helping to conserve soil and biodiversity. (JAMB UTME Biology Syllabus (Conservation of natural resources); Ramalingam, S.T., Modern Biology for Senior Secondary Schools)

23. Farmers practise crop rotation mainly as a soil conservation method because it helps to

1. exhaust soil nutrients more quickly
2. maintain soil fertility and reduce the build-up of pests and diseases
3. increase the rate of soil erosion
4. encourage continuous cultivation of the same crop on the same land

Rotating different crops on the same land helps replenish soil nutrients and breaks the life cycles of crop-specific pests and diseases. (JAMB UTME Biology Syllabus (Conservation of natural resources — soil conservation); Ndu, Ndu & Ndu, Senior Secondary Biology)

24. Uncontrolled hunting and poaching of wild animals is most likely to result in

1. an increase in the biodiversity of the affected area
2. extinction of the affected species
3. improved population growth of the hunted species
4. no effect on the ecosystem

Poaching and uncontrolled hunting remove individuals faster than populations can replace them, driving species toward extinction. (JAMB UTME Biology Syllabus (Conservation of natural resources); Ramalingam, S.T., Modern Biology for Senior Secondary Schools)

25. Game reserves and national parks are established mainly to

1. promote commercial logging of timber
2. protect wildlife and their natural habitats from over-exploitation
3. encourage unrestricted hunting for tourists
4. convert forest land into farmland

Game reserves and national parks provide protected habitats where wildlife populations can be conserved from over-exploitation and habitat destruction. (JAMB UTME Biology Syllabus (Conservation of natural resources); Ramalingam, S.T., Modern Biology for Senior Secondary Schools)

26. A food chain shows...

1. the one-directional flow of energy from producers through a series of organisms, each feeding on the one before it
2. the random exchange of energy between unrelated organisms in different habitats
3. only the feeding relationships among carnivores
4. the two-way transfer of energy between predators and prey

A food chain represents the unidirectional flow of energy, starting from producers and passing through a sequence of organisms that feed on one another. (JAMB UTME Biology Syllabus (Ecology — food chains, food webs and energy flow); Ramalingam, S.T., Modern Biology for Senior Secondary Schools)

27. Which organisms form the first trophic level of a food chain by manufacturing their own food using light energy?

1. Herbivores
2. Producers (green plants)
3. Carnivores
4. Decomposers

Producers such as green plants are autotrophs that trap light energy through photosynthesis, forming the base of every food chain. (JAMB UTME Biology Syllabus (Ecology — food chains and trophic levels); Ndu, Ndu & Ndu, Senior Secondary Biology)

28. Which of the following correctly arranges levels of ecological organisation from the simplest to the most complex?

1. Community → population → organism → biosphere → ecosystem
2. Population → community → organism → ecosystem → biosphere
3. Organism → population → community → ecosystem → biosphere
4. Biosphere → ecosystem → community → population → organism

Ecological organisation increases in complexity from a single organism through population and community up to the ecosystem and finally the biosphere. (JAMB UTME Biology Syllabus (Ecology — the ecosystem: biosphere, community, population); Ndu, Ndu & Ndu, Senior Secondary Biology)

29. Which bacterium, living in the root nodules of leguminous plants such as beans, fixes atmospheric nitrogen into a usable form?

1. Nitrobacter
2. Escherichia coli
3. Rhizobium
4. Lactobacillus

Rhizobium bacteria in the root nodules of leguminous plants convert atmospheric nitrogen gas into ammonium compounds that plants can absorb. (JAMB UTME Biology Syllabus (Ecology — nutrient cycling: nitrogen cycle); Ramalingam, S.T., Modern Biology)

30. Mendel's Law of Segregation states that...

1. alleles of different genes assort independently of one another
2. dominant alleles always suppress recessive alleles in gametes
3. the two alleles of a gene pair separate during gamete formation so each gamete carries only one allele
4. gametes always carry two alleles of every gene

The Law of Segregation states that allele pairs separate during meiosis, so each gamete receives only one allele for each gene. (JAMB UTME Biology Syllabus (Heredity — Variation in Population); Ramalingam, S.T., Modern Biology for Senior Secondary Schools)

31. What phenotypic ratio is expected in the F2 generation of a monohybrid cross between two heterozygous parents?

1. 1:2:1
2. 9:3:3:1
3. 1:1
4. 3:1

Crossing two heterozygotes (Aa x Aa) gives a genotypic ratio of 1AA:2Aa:1aa, which corresponds to a 3:1 phenotypic ratio of dominant to recessive traits. (JAMB UTME Biology Syllabus (Variation in Population — Heredity); Ramalingam, S.T., Modern Biology)

32. How many chromosomes are present in a normal human somatic (body) cell?

1. 23
2. 44
3. 48
4. 46

Human somatic cells are diploid, containing 46 chromosomes arranged in 23 homologous pairs, one of which is the pair of sex chromosomes. (JAMB UTME Biology Syllabus (Heredity — chromosomes); Ndu, Ndu & Ndu, Senior Secondary Biology)

33. Which sex chromosome combination is characteristic of a normal human male?

1. XX
2. XXY
3. XY
4. YY

A normal human male carries one X chromosome and one Y chromosome (XY), while a normal female carries two X chromosomes (XX). (JAMB UTME Biology Syllabus (Sex determination and sex linkage); Ramalingam, S.T., Modern Biology)

34. The double-helix structure of DNA, held together by complementary base pairing, was described by...

1. Gregor Mendel and Charles Darwin
2. James Watson and Francis Crick
3. Jean-Baptiste Lamarck and Charles Darwin
4. Robert Hooke and Louis Pasteur

James Watson and Francis Crick published the double-helix model of DNA in 1953, showing that the two strands are held together by A–T and G–C base pairing. (Watson, J.D. & Crick, F.H.C., Nature (1953); JAMB UTME Biology Syllabus (Nucleic acids / DNA))

35. In which work did Charles Darwin present his theory of evolution by natural selection, summarised as 'survival of the fittest'?

1. Philosophie Zoologique
2. The Descent of Man
3. Systema Naturae
4. On the Origin of Species

Darwin's On the Origin of Species (1859) proposed that variation, overproduction of offspring and a struggle for existence lead to natural selection of the fittest individuals. (Darwin, C., On the Origin of Species (1859); JAMB UTME Biology Syllabus (Theories of evolution))