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Class 10 Class 12

Identify 'a' and 'b' in the figure given below representing proportionate number of major vertebrate taxa.



In the given figure, 

a represents amphibians, and 

 b represents mammals

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Explain the salient features of Hugo de Vries theory of mutation. How is Darwin theory of natural selection different from it? Explain.

Hugo de Vries based on his work on evening primrose suggested that variations occurred due to mutations. Hugo de Vries gave the name saltation (single step large mutation) to the mutations that brought about speciation. Darwin aboard the H.M.S Beagle observed that all existing living forms share similarities among themselves and also with other life forms that existed millions of years ago of which many are extinct. The evolution of life forms has been gradual and those life forms better fit in environments that leave more progeny. This is called natural selection and is a mechanism of evolution. Mutations are random and directionless while the variations that Darwin talked about were small and directional.
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Which of the following statements is correct

  • Lion and leopard show convergent evolution.

  • Cryptic camouflage is seen in Biston betularia

  • Natural selection is responsible for extinction of dinosaurs.

  • Homo habilis and Homo erectus are closely related.


B.

Cryptic camouflage is seen in Biston betularia

The peppered moth (Biston betularia) is a temperate species of night-flying moth. Peppered moth evolution is often used by educators as an example of natural selection. Peppered moths are cryptically camouflaged against their backgrounds when they rest on the tree trunk.

The peppered moth (Biston betularia) is a temperate species of night-flying moth. Peppered moth evolution is often used by educators as an example of natural selection. Peppered moths are cryptically camouflaged against their backgrounds when they rest on the tree trunk.


Which of the following structures is homologous to the wing of a bird?

  • Wing of a moth

  • Hind limb of a rabbit

  • Flipper of whale

  • Dorsal fin of a shark


C.

Flipper of whale

Wings of bird and flipper of whale are modified forelimbs of the two organisms so have same origin wings help in flying and flippers help in swimming but thus perform the different functions

Wings of bird and flipper of whale are modified forelimbs of the two organisms so have same origin wings help in flying and flippers help in swimming but thus perform the different functions

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(a) Name the primates that lived about 15 million years ago. List their characteristic features.

(b) (i) Where was the first man-like animal found?

(ii) Write the order in which Neanderthals, Homo habilis and Homo erectusappeared on earth.

State the brain capacity of each one of them.

(iii) When did modern Homo sapiens appear on this planet?


(a) Dryopithecus (ape-like) and Ramapithecus (man-like) were the two primates that lived 15 million years ago. These primates were hairy and their walk was similar to that of chimpanzees.

(b) (i) The first man-like animal was found in Africa.

(ii) 

Year

Evolution

Brain capacity

2 million years ago

Homo habilis (Australopithecines) lived in East Africa

650- 800 cc

1.5 million years ago

Homo erectus

900 cc

1,000 - 40,000 years ago

Neanderthal man

1400 cc


(iii) Modern Homo sapiens first appeared primarily in east Africa about 75,000 to 10,000 years ago.
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Analogous structures are a result of

  • convergent evolution

  • shared ancestry

  • stabilising selection

  • divergent evolution


A.

convergent evolution

Analogous organs are those which are similar in function but do not have a common ancestor and thus they are a result of convergent evolution. 

Analogous organs are those which are similar in function but do not have a common ancestor and thus they are a result of convergent evolution. 

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