FORM FOUR BIOLOGY EXAM – TOPIC: ORGANIC EVOLUTION
Time: 3 Hours
Instructions:
- Answer all questions in Sections A and B.
- Answer two (2) questions only from Section C.
- All diagrams must be neat and properly labeled.
SECTION A (16 Marks)
1. Multiple Choice Questions (10 Marks)
Choose the most correct answer:
- The scientist who proposed the theory of inheritance of acquired characteristics is:
- a) Charles Darwin
- b) Gregor Mendel
- c) Jean-Baptiste Lamarck
- d) Thomas Malthus
- Which of the following is considered a vestigial organ in humans?
- a) Heart
- b) Appendix
- c) Liver
- d) Lungs
- The process by which unrelated organisms independently evolve similarities when adapting to similar environments is called:
- a) Divergent evolution
- b) Convergent evolution
- c) Adaptive radiation
- d) Co-evolution
- Which of the following provides the most direct evidence for evolution?
- a) Fossil records
- b) Comparative anatomy
- c) Embryology
- d) Biogeography
- The term "survival of the fittest" is most closely associated with:
- a) Lamarck
- b) Darwin
- c) Mendel
- d) Wallace
- Which of the following is an example of homologous structures?
- a) Wings of birds and insects
- b) Forelimbs of humans and bats
- c) Fins of fish and flippers of whales
- d) Eyes of octopus and humans
- The concept that evolution occurs in rapid bursts followed by long periods of stability is known as:
- a) Gradualism
- b) Punctuated equilibrium
- c) Adaptive radiation
- d) Speciation
- Which of the following is NOT a mechanism of evolution?
- a) Natural selection
- b) Genetic drift
- c) Mutation
- d) Photosynthesis
- The scientist who emphasized the role of population growth and resource limitation in evolution was:
- a) Lyell
- b) Malthus
- c) Lamarck
- d) Darwin
- Structures that have no apparent function but resemble structures their ancestors possessed are called:
- a) Analogous structures
- b) Homologous structures
- c) Vestigial structures
- d) Adaptive structures
2. Matching Items (6 Marks)
Match the items in List A with the correct responses from List B:
List A | List B |
---|---|
(i) Natural selection | a) Sudden heritable change in DNA |
(ii) Homologous structures | b) Development of similar traits in unrelated species |
(iii) Vestigial organs | c) Structures with similar origin but different functions |
(iv) Mutation | d) Process leading to the formation of new species from a common ancestor |
(v) Convergent evolution | e) Remnants of organs that had functions in ancestors |
(vi) Adaptive radiation | f) Differential survival and reproduction of organisms |
SECTION B (54 Marks)
3. Lamarck vs. Darwin Theories (6 Marks)
Explain the main differences between Lamarck's and Darwin's theories of evolution.
4. Fossil Record Evidence (6 Marks)
Describe how the fossil record provides evidence for organic evolution.
5. Homologous and Analogous Structures (6 Marks)
Discuss the significance of homologous and analogous structures in understanding evolutionary relationships.
6. Role of Mutations (6 Marks)
Explain the role of mutations in the process of evolution.
7. Genetic Drift (6 Marks)
Describe the concept of genetic drift and provide an example of how it can affect a population.
8. Biogeography Importance (6 Marks)
Discuss the importance of biogeography in supporting the theory of evolution.
9. Speciation Process (6 Marks)
Explain the process of speciation and the factors that can lead to the formation of new species.
10. Adaptive Radiation (6 Marks)
Discuss the concept of adaptive radiation with a suitable example.
11. Comparative Embryology (6 Marks)
Explain how comparative embryology supports the theory of evolution.
SECTION C (30 Marks)
Answer two (2) questions from this section.
12. Mechanisms of Evolution (15 Marks)
- Describe the mechanisms of evolution, including natural selection, genetic drift, gene flow, and mutation. (12 marks)
- Discuss how these mechanisms can lead to changes in allele frequencies within a population. (3 marks)
13. Evidence for Evolution (15 Marks)
Explain the evidence for evolution (use seven points).
14. Importance of Evolution (15 Marks)
Discuss the importance of evolution.
FORM FOUR BIOLOGY EXAM – ANSWERS: ORGANIC EVOLUTION
Time: 3 Hours
Instructions:
- Answers for all questions in Sections A and B are provided below.
- Answers for two questions from Section C (Questions 12 and 13) are provided as per instructions.
- Diagrams are described due to the inability to draw directly in HTML.
SECTION A (16 Marks)
1. Multiple Choice Questions (10 Marks)
- The scientist who proposed the theory of inheritance of acquired characteristics is:
- a) Charles Darwin
- b) Gregor Mendel
- c) Jean-Baptiste Lamarck
- d) Thomas Malthus
Explanation: Lamarck proposed that organisms acquire traits during their lifetime and pass them to offspring, e.g., giraffes stretching necks to reach higher leaves.
- Which of the following is considered a vestigial organ in humans?
- a) Heart
- b) Appendix
- c) Liver
- d) Lungs
Explanation: The appendix has no significant function in humans but is homologous to structures in other animals, indicating evolutionary history.
- The process by which unrelated organisms independently evolve similarities when adapting to similar environments is called:
- a) Divergent evolution
- b) Convergent evolution
- c) Adaptive radiation
- d) Co-evolution
Explanation: Convergent evolution results in analogous structures, like wings of birds and insects, due to similar environmental pressures.
- Which of the following provides the most direct evidence for evolution?
- a) Fossil records
- b) Comparative anatomy
- c) Embryology
- d) Biogeography
Explanation: Fossils show physical remains of ancient organisms, documenting changes over time, e.g., transitional forms like Archaeopteryx.
- The term "survival of the fittest" is most closely associated with:
- a) Lamarck
- b) Darwin
- c) Mendel
- d) Wallace
Explanation: Darwin used this term to describe natural selection, where organisms best adapted to their environment survive and reproduce.
- Which of the following is an example of homologous structures?
- a) Wings of birds and insects
- b) Forelimbs of humans and bats
- c) Fins of fish and flippers of whales
- d) Eyes of octopus and humans
Explanation: Homologous structures share a common origin, like the forelimbs of humans and bats, despite different functions.
- The concept that evolution occurs in rapid bursts followed by long periods of stability is known as:
- a) Gradualism
- b) Punctuated equilibrium
- c) Adaptive radiation
- d) Speciation
Explanation: Punctuated equilibrium, proposed by Gould and Eldredge, suggests rapid evolutionary change during speciation followed by stability.
- Which of the following is NOT a mechanism of evolution?
- a) Natural selection
- b) Genetic drift
- c) Mutation
- d) Photosynthesis
Explanation: Photosynthesis is a metabolic process, not a mechanism altering allele frequencies, unlike natural selection, genetic drift, or mutation.
- The scientist who emphasized the role of population growth and resource limitation in evolution was:
- a) Lyell
- b) Malthus
- c) Lamarck
- d) Darwin
Explanation: Malthus’s work on population growth inspired Darwin’s concept of competition for limited resources driving natural selection.
- Structures that have no apparent function but resemble structures their ancestors possessed are called:
- a) Analogous structures
- b) Homologous structures
- c) Vestigial structures
- d) Adaptive structures
Explanation: Vestigial structures, like the human appendix, are remnants of functional structures in ancestors, supporting evolutionary history.
2. Matching Items (6 Marks)
List A | List B |
---|---|
(i) Natural selection | f) Differential survival and reproduction of organisms |
(ii) Homologous structures | c) Structures with similar origin but different functions |
(iii) Vestigial organs | e) Remnants of organs that had functions in ancestors |
(iv) Mutation | a) Sudden heritable change in DNA |
(v) Convergent evolution | b) Development of similar traits in unrelated species |
(vi) Adaptive radiation | d) Process leading to the formation of new species from a common ancestor |
Explanation: Each term is matched with its definition, reflecting key evolutionary concepts, e.g., natural selection drives differential survival, and homologous structures indicate common ancestry.
SECTION B (54 Marks)
3. Lamarck vs. Darwin Theories (6 Marks)
Answer:
- Lamarck’s Theory (Inheritance of Acquired Characteristics): Traits acquired during an organism’s lifetime (e.g., stretched neck from reaching high leaves) are passed to offspring. Use and disuse of organs lead to their development or reduction.
- Darwin’s Theory (Natural Selection): Variations exist naturally; organisms with advantageous traits survive and reproduce, passing those traits to offspring. Environment selects for favorable traits, not acquired ones.
- Key Differences: Lamarck emphasized acquired traits and use/disuse; Darwin focused on natural selection acting on inherent variations. Lamarck’s theory lacks genetic evidence, while Darwin’s is supported by modern genetics.
Explanation: Lamarck’s ideas were disproven as acquired traits (e.g., muscle from exercise) are not heritable, whereas Darwin’s natural selection aligns with genetic inheritance.
4. Fossil Record Evidence (6 Marks)
Answer:
- Chronological Record: Fossils show a sequence of organisms over time, with simpler forms in older layers and complex ones in newer layers.
- Transitional Forms: Fossils like Archaeopteryx (reptile-bird traits) and Tiktaalik (fish-tetrapod traits) show intermediate stages between groups.
- Extinction and Divergence: Fossils document extinct species (e.g., dinosaurs) and branching patterns, supporting common ancestry and evolutionary change.
Explanation: Fossils provide a tangible timeline of life’s history, showing gradual changes and linking modern species to ancient ancestors.
5. Homologous and Analogous Structures (6 Marks)
Answer:
- Homologous Structures: Share common embryonic origin but different functions, e.g., forelimbs of humans (arms), bats (wings), and whales (flippers). Indicate common ancestry and divergent evolution.
- Analogous Structures: Similar functions but different origins, e.g., wings of birds and insects. Result from convergent evolution due to similar environmental pressures.
- Significance: Homologous structures support shared ancestry; analogous structures show how different lineages adapt similarly, reinforcing natural selection’s role.
Explanation: These structures reveal evolutionary relationships (homologous) and environmental influences (analogous), providing complementary evidence for evolution.
6. Role of Mutations (6 Marks)
Answer:
- Definition: Mutations are random changes in DNA, introducing new alleles into a population.
- Source of Variation: Mutations create genetic diversity, which natural selection acts upon, e.g., a mutation conferring antibiotic resistance in bacteria.
- Evolutionary Impact: Beneficial mutations increase fitness and spread; neutral mutations may persist; harmful mutations are often eliminated. Over time, mutations drive evolutionary change.
Explanation: Mutations are the raw material for evolution, providing novel traits that natural selection or other mechanisms can shape.
7. Genetic Drift (6 Marks)
Answer:
- Concept: Genetic drift is random change in allele frequencies, especially in small populations, due to chance rather than selection.
- Effects: Can lead to loss or fixation of alleles, reducing genetic diversity. Significant in small populations, e.g., bottleneck or founder effects.
- Example: A hurricane decimates a small island bird population, leaving only a few survivors with a specific allele. This allele becomes more common by chance, altering the population’s genetic makeup.
Explanation: Genetic drift highlights the role of chance in evolution, particularly in small populations, and can lead to significant evolutionary outcomes.
8. Biogeography Importance (6 Marks)
Answer:
- Distribution Patterns: Biogeography studies species distribution, showing unique species on isolated regions, e.g., marsupials in Australia.
- Common Ancestry: Similar species on nearby islands (e.g., Galápagos finches) suggest divergence from a common ancestor, supporting evolution.
- Environmental Adaptation: Species distributions reflect adaptations to local environments, consistent with natural selection driving evolutionary change.
Explanation: Biogeography illustrates how geographic isolation and environmental factors shape species diversity, aligning with evolutionary theory.
9. Speciation Process (6 Marks)
Answer:
- Definition: Speciation is the formation of new species when populations diverge and become reproductively isolated.
- Process: Begins with isolation (geographic or reproductive), leading to genetic divergence via mutation, selection, or drift. Over time, populations cannot interbreed.
- Factors: Geographic barriers (e.g., rivers), reproductive barriers (e.g., different mating seasons), and genetic changes (e.g., mutations altering traits).
Explanation: Speciation explains biodiversity, showing how isolated populations evolve distinct traits, like Darwin’s finches on different islands.
10. Adaptive Radiation (6 Marks)
Answer:
- Concept: Adaptive radiation is the rapid diversification of a single ancestor into multiple species, each adapted to different ecological niches.
- Conditions: Occurs in new or underutilized environments with diverse resources, e.g., after extinction events or colonization of islands.
- Example: Darwin’s finches in the Galápagos evolved different beak shapes from a common ancestor, adapting to varied food sources (seeds, insects, cactus).
Explanation: Adaptive radiation demonstrates how natural selection drives rapid speciation in response to ecological opportunities.
11. Comparative Embryology (6 Marks)
Answer:
- Concept: Comparative embryology compares embryo development across species, revealing similarities indicating common ancestry.
- Evidence: Vertebrate embryos (e.g., fish, birds, mammals) show similar early stages, like gill slits and tails, reflecting shared evolutionary origins.
- Support for Evolution: These similarities suggest conserved developmental genes from a common ancestor, modified over time for different adult forms.
Explanation: Embryological similarities provide strong evidence for evolution, showing how diverse species share developmental pathways.
SECTION C (30 Marks)
Answering Questions 12 and 13 as examples.
12. Mechanisms of Evolution (15 Marks)
- Mechanisms of Evolution (12 Marks):
- Natural Selection: Organisms with traits better suited to the environment survive and reproduce, increasing favorable allele frequencies. E.g., darker moths surviving predation in polluted areas.
- Genetic Drift: Random changes in allele frequencies, especially in small populations. Includes bottleneck (population crash) and founder effects (small group starts new population). E.g., reduced diversity in cheetah populations.
- Gene Flow: Movement of alleles between populations via migration, increasing genetic diversity or homogenizing populations. E.g., pollen transfer between plant populations.
- Mutation: Random DNA changes create new alleles, providing raw material for evolution. E.g., mutations conferring pesticide resistance in insects.
Explanation: These mechanisms interact to drive evolutionary change, with natural selection and mutation being primary drivers, while drift and gene flow modify allele distributions.
- Changes in Allele Frequencies (3 Marks):
- Natural selection favors beneficial alleles, increasing their frequency.
- Genetic drift randomly alters allele frequencies, potentially fixing or eliminating alleles.
- Gene flow introduces new alleles, altering frequencies; mutations create new alleles, shifting genetic variation.
Explanation: Allele frequencies change as these mechanisms act on genetic variation, leading to evolutionary divergence or adaptation.
13. Evidence for Evolution (15 Marks)
Answer:
- Fossil Records: Show a timeline of life, with transitional forms (e.g., Tiktaalik) linking major groups, indicating gradual change.
- Homologous Structures: Similar structures with different functions (e.g., vertebrate forelimbs) suggest common ancestry and divergent evolution.
- Analogous Structures: Similar functions in unrelated species (e.g., bird and insect wings) show convergent evolution due to similar environments.
- Vestigial Structures: Reduced structures (e.g., human appendix) indicate evolutionary remnants of functional ancestral traits.
- Comparative Embryology: Similar embryonic stages (e.g., gill slits in vertebrates) suggest shared developmental pathways from a common ancestor.
- Biogeography: Species distributions (e.g., Galápagos finches) reflect evolutionary divergence in isolated regions, supporting adaptation and speciation.
- Molecular Biology: DNA and protein similarities (e.g., cytochrome c across species) indicate shared ancestry, with closer relatives showing greater similarity.
Explanation: These seven lines of evidence collectively demonstrate evolution’s occurrence, showing how species change over time and share common origins.
No comments
Post a Comment