🌸Chapter 6
EVOLUTION
( 2 Marks)
1. What is evolution?
Answer:
Evolution is the gradual development of complex organisms from simpler forms of
life over a long period of time through changes in genetic composition and
adaptation to the environment.
2. Define organic evolution.
Answer:
Organic evolution refers to the process by which living organisms have evolved
from pre-existing life forms through modification and natural selection over
geological time.
3. What is the theory of spontaneous
generation?
Answer:
It states that life originated spontaneously from non-living matter such as
mud, water, and decaying organic material. This idea was later disproved by
Louis Pasteur.
4. Describe Louis Pasteur’s
experiment disproving spontaneous generation.
Answer:
Pasteur boiled nutrient broth in an S-shaped flask. Air could enter but dust
and microbes were trapped in the neck. No life appeared until the neck was
broken, proving that life comes from pre-existing life.
5. What is the chemical evolution
theory?
Answer:
According to Oparin and Haldane, life originated from inorganic molecules (like
CH₄, NH₃, H₂O, H₂) under high temperature, lightning, and UV radiation forming
simple organic molecules which later formed complex life.
6. What was demonstrated by Miller
and Urey’s experiment?
Answer:
Miller and Urey showed that simple organic molecules like amino acids could be
formed from inorganic gases under conditions similar to primitive Earth
(electric discharge, water vapor, methane, ammonia, hydrogen).
7. What is biogenesis?
Answer:
The theory of biogenesis states that life originates only from pre-existing
living organisms, not from non-living matter.
8. What is meant by the term
‘primordial soup’?
Answer:
It refers to the mixture of organic molecules in Earth’s primitive oceans that
gave rise to the first life forms through chemical evolution.
9. Name two gases absent in Earth’s
primitive atmosphere.
Answer:
Oxygen (O₂) and ozone (O₃) were absent in the primitive atmosphere.
10. Who proposed the idea of
chemical evolution?
Answer:
A.I. Oparin (Russia) and J.B.S. Haldane (England) independently proposed the
idea of chemical evolution.
11. What are fossils?
Answer:
Fossils are the preserved remains, impressions, or traces of organisms that
lived in the past, found in sedimentary rocks.
12. What is fossilization?
Answer:
It is the process through which living organisms are preserved as fossils over
geological time due to sedimentation and mineralization.
13. How do fossils support
evolution?
Answer:
Fossils show progressive changes from simple to complex organisms over
geological time, providing direct evidence of evolution.
14. What is a connecting link? Give
an example.
Answer:
Connecting links are organisms showing features of two different groups, e.g., Archaeopteryx
(between reptiles and birds).
15. What are vestigial organs? Give
examples.
Answer:
Vestigial organs are remnants of structures that were functional in ancestors
but are now reduced and non-functional, e.g., appendix, nictitating membrane in
humans.
16. What are homologous organs?
Answer:
Organs with similar structure but different functions are homologous, e.g.,
forelimbs of a human, whale, and bat.
17. What are analogous organs?
Answer:
Organs with similar function but different structure and origin are analogous,
e.g., wings of bat and wings of insect.
18. How do homologous organs provide
evidence for evolution?
Answer:
They indicate common ancestry among different organisms showing divergent
evolution.
19. How do analogous organs provide
evidence for evolution?
Answer:
They show that unrelated species can evolve similar traits under similar
environmental pressures (convergent evolution).
20. What is adaptive radiation? Give
an example.
Answer:
Adaptive radiation is the evolution of different species from a common ancestor
in response to different habitats, e.g., Darwin’s finches in Galápagos Islands.
21. What is convergent evolution?
Answer:
It is the evolution of similar features in unrelated groups of organisms due to
similar environmental conditions, e.g., dolphins (mammal) and sharks (fish).
22. What is divergent evolution?
Answer:
It is the evolution of different features from a common ancestral form, leading
to homologous organs.
23. Name the scientist who proposed
the theory of natural selection.
Answer:
Charles Darwin proposed the theory of natural selection.
24. What is natural selection?
Answer:
It is the process by which organisms better adapted to their environment
survive and reproduce, while others perish.
25. What are Darwin’s finches?
Answer:
These are 14 species of finches from the Galápagos Islands showing variation in
beak shape and size adapted to different food sources.
26. Define artificial selection.
Answer:
Artificial selection is the process by which humans breed plants and animals
for desired traits, e.g., dogs, cabbage varieties.
27. What is mutation theory of
evolution?
Answer:
Proposed by Hugo de Vries, it states that sudden heritable changes (mutations)
in organisms cause evolution, not gradual variations.
28. What is genetic drift?
Answer:
Random change in allele frequency in small populations due to chance events,
leading to evolution.
29. What is founder effect?
Answer:
When a few individuals colonize a new area, their gene pool may not represent
the parent population, causing evolution (genetic drift).
30. What is Hardy-Weinberg
principle?
Answer:
It states that allele frequencies in a population remain constant from
generation to generation unless influenced by evolutionary forces.
31. Write the Hardy-Weinberg
equation.
Answer:
p2+2pq+q2=1p^2 + 2pq + q^2 = 1p2+2pq+q2=1, where p and q are the
frequencies of dominant and recessive alleles.
32. Name five factors that can
disturb Hardy-Weinberg equilibrium.
Answer:
Mutation, genetic drift, gene flow, natural selection, and non-random mating.
33. What is gene flow?
Answer:
Movement of genes or alleles between populations due to migration, leading to
variation.
34. What is reproductive isolation?
Answer:
It is the inability of two groups of organisms to interbreed and produce
fertile offspring, leading to speciation.
35. Define speciation.
Answer:
Speciation is the process by which new species arise from existing ones through
isolation and genetic divergence.
36. What is microevolution?
Answer:
Small changes in gene frequency within a population over a short time that can
lead to new varieties or species.
37. What is macroevolution?
Answer:
Large-scale evolutionary changes that result in the formation of new genera,
families, or higher taxa.
38. Name the earliest human
ancestor.
Answer:
Australopithecus is considered one of the earliest ancestors of modern
humans.
39. Who proposed the mutation theory
of evolution?
Answer:
Hugo de Vries.
40. What is the difference between
microevolution and macroevolution?
Answer:
Microevolution involves small genetic changes within a species, while
macroevolution leads to formation of new species or groups.
41. What is the significance of
fossils in evolution?
Answer:
Fossils help trace evolutionary history, showing transition forms and age of
organisms through dating.
42. What are analogous structures?
Give an example.
Answer:
Structures performing similar functions but different in origin, e.g., wings of
bird and insect.
43. What is adaptive radiation? Give
another example besides Darwin’s finches.
Answer:
Adaptive radiation is evolution of several species from a common ancestor;
e.g., Australian marsupials.
44. Name the scientist who proposed
the law of inheritance of acquired characters.
Answer:
Jean Baptiste Lamarck.
45. What is Lamarckism?
Answer:
The theory that characteristics acquired during an organism’s lifetime can be
inherited by offspring.
46. Why was Lamarck’s theory
rejected?
Answer:
It lacked experimental evidence; acquired traits do not alter genes and hence
cannot be inherited.
47. Name the ancestor of modern man
discovered in Africa.
Answer:
Australopithecus africanus discovered in Africa.
48. What is the scientific name of
modern man?
Answer:
Homo sapiens.
49. Name any two species of genus
Homo other than Homo sapiens.
Answer:
Homo habilis and Homo erectus.
50. What is the significance of
Hardy-Weinberg principle in evolution?
Answer:
It serves as a baseline to study evolutionary changes by comparing expected and
observed allele frequencies.
