Evolution

Q1. State Hardy-Weinberg principle of genetic equilibrium. Write any four factors affecting the equilibrium.

Ans:
Hardy-Weinberg principle states that allelic frequencies in a population are stable and remains constant from generation to generation, i.e., gene pool (total number of genes and their alleles in a population) is constant.

Factors:
✓ Genetic drift
✓ Gene flow or gene migration
✓ Genetic recombination
✓ Mutation
✓ Natural selection

Q2. Mention any two examples of evolution by anthropogenic action.

Ans:
1. Industrial melanism:
It is a phenomenon depicted by light-coloured peppered moth (Biston betularia typica) and dark-coloured moth (Biston betularia carbonaria). It is a evolutionary process in which darker individuals came to predominate over lighter individuals since, the industrial revolution is a result of natural selection.

2. Overuse of weedicides and pesticides resulted in the evolution of many resistant varieties of weeds and pests respectively.

Q3. Define saltation.

Ans: Single step large mutation caused speciation is called saltation.

Q4. What are analogous organs? Give two examples.

Ans: The organs which are different in anatomical structure and have different origin but perform similar functions are called analogous organs.

E.g.,
Wings of butterflies and birds.
Eye of octopus and mammals’.
Flippers of penguins and dolphins.
sweet potato (root modification) and potato (stem modification).

Q5. What is divergent evolution? Give examples.

Ans: Some structures developed along different directions due to adaptations to different needs. This is called divergent evolution.

E.g., Forelimbs of some animals like Whales, bats Cheetah and humans.

Q6. List the period, brain size, skeletal structure and dietary preference of
a. Homo habilis
b. Homo erectus

Ans:
a. Homo habilis - The brain size of homo habilis was about 735 cm3, they were fully erect and feed on fleshy meat (carnivores).

b. Homo erectus - The brain size of homo habilis was about 800-1100 cm3, they were fully erect and feed on fleshy meat and plant sources (omnivores).

Q7. List the theories which explain the origin of life.

Ans: Different theories were given to explain the origin of life.

1. Theory of special creation
2. Theory of panspermia/cosmozoic theory
3. Theory of spontaneous generation

Q8. Explain Darwin's theory of evolution.

Ans:
Charles Darwin, based on his observations during a sea voyage around the world in the ship H.M.S Beagle, concluded the following:
✓ Varying degrees of similarities can be observed between existing life forms and those that existed millions of years ago.
✓ There has been gradual evolution of lite forms with new forms arising at different periods of history.
✓ Any population has built-in variations in characteristics which adapt it better to environment.
✓ The characteristics which enable some populations or individuals to survive better in natural conditions climate, food. physical factors) would out-breed others (Survival of the fittest).
✓ Those populations which are better fit (reproductively fit) in an environment will be selected by nature and will survive more (Natural selection).
✓ Adaptability is inherited and fitness is the end result of ability to adapt and get selected by nature.

Q9. Give the diagrammatic representation of Miller's experiment.

Ans: S L Miller and H C Urey performed an experiment in 1953 for chemical evolution.

✓ He created electric discharge in a closed flask containing CH4, H2, NH3 and water vapours at 800 oC.
✓ After few weeks he observed formation of amino acids and complex molecules like sugars, nitrogen bases, pigments and fats in the flask.

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