Evolution, Speciation and Ecology: Questions & Answers

Posted on Jan 10, 2026 in Biology

Evolution, Speciation and Ecology Q&A

Fixism and diversity of living things (4 marks)

Question: How does Fixism explain the diversity of living things?

Answer: Fixism claims that species were created as they are now and that they do not change. Therefore, the diversity we find today is the diversity that has always existed.

Convergent evolution: similar wings in birds & butterflies (4 marks)

Question: Explain why two very different species, such as birds and butterflies, can have similar wings responsible for the same function. Which evidence of evolution is it?

Answer: When different species face similar environmental pressures or ecological roles, they may independently evolve similar structures that serve the same function. This phenomenon is an example of convergent evolution.

Darwin: competition and its consequences (4 marks)

Question: According to Darwin, why do individuals compete against each other? What are the consequences of this constant competition?

Answer: The primary cause of competition is the limited availability of resources in an environment. The consequence is that only the fittest—those better adapted to their environment—are more likely to survive and reproduce.

Punctuated equilibrium, Neo-Darwinism and neutralism (5 marks)

Question: Compare the theory of punctuated equilibrium with Neo-Darwinism and neutralism. What are their similarities and differences?

Answer: All three are evolutionary theories, but they emphasize different mechanisms and tempos of change:

  • Punctuated equilibrium: Proposes that evolutionary change occurs relatively rapidly in short bursts associated with speciation events, separated by long periods of stasis.
  • Neo-Darwinism: Emphasizes gradual evolutionary change driven by natural selection acting on genetic variation over long timescales (slow and gradual process).
  • Neutralism (Neutral Theory): Proposes that most mutations are selectively neutral—neither advantageous nor disadvantageous—and that genetic drift rather than natural selection often governs their frequency in populations.

Barriers that can lead to genetic isolation (4 marks)

Question: Name four barriers that can lead to genetic isolation.

Answer: Examples of barriers that can lead to genetic isolation include:

  • Geographical barriers
  • Sexual barriers
  • Physiological barriers
  • Chromosomal barriers
  • Ethological barriers

Note: Multiple types of barriers can contribute to reproductive isolation; more than four examples are listed here for completeness.

Abiotic vs biotic factors with examples (4 marks)

Question: Differentiate, with examples, between abiotic and biotic factors.

Answer:

  • Abiotic factors: Non-living chemical and physical components of an environment that affect ecosystems. Examples: temperature, pH, salinity, humidity, wind, etc.
  • Biotic factors: Living components of an environment that affect ecosystems. Examples: disease (pathogens), competition, predation, mate availability, etc.

Definition of biomass (2 marks)

Question: Define biomass.

Answer: Biomass is the total dry weight of organic matter in organisms or ecosystems (i.e., all biologically produced organic matter such as carbohydrates, proteins, and other tissues).

Habitat versus ecological niche (3 marks)

Question: Explain, using an example, the difference between the habitat and the ecological niche of a species.

Answer: A species’ habitat is the physical environment where it lives. A species’ ecological niche describes its role or function within that habitat. For example, a lion’s habitat is the African savannah; its ecological niche includes its role as an apex predator and hunter.

Consequences of removing decomposers or autotrophs (4 marks)

Question: What would happen if an ecosystem did not have bacteria and fungi? And what if it did not have autotrophic organisms?

Answer:

  • No bacteria and fungi (decomposers): Dead organic matter would not be efficiently recycled into inorganic compounds. Over time, soils would become depleted of nutrients and plants would lack essential nutrients.
  • No autotrophic organisms (primary producers): There would be no organisms capable of converting inorganic inputs (light, carbon dioxide) into organic matter. As a result, primary production would cease and most life would be unsustainable.

Formation of oil and natural gas (5 marks)

Question: Outline the formation of oil and natural gas.

Answer: Oil and natural gas form from the decay of marine organisms on the ocean floor. The process includes:

  1. Accumulation of organic matter (remains of marine organisms) on the seabed.
  2. Deposition of sediments on top of the organic layer, creating anoxic (low-oxygen) conditions that inhibit decomposition.
  3. Burial, compaction, and heating of the organic-rich sediments over geological time.
  4. Transformation of the compacted and heated organic matter into hydrocarbons (oil and natural gas).
  5. Migration and accumulation of these hydrocarbons within porous reservoir rocks where they can be trapped and extracted.