Biology [2 Mark Question Answer]

(i) Natural selection
During the struggle for existence, only those individuals which have advantageous variations survive while the ones which lack these variations are wiped out. Nature selects only those variations which are suitable for existence. This process is called natural selection.
(ii) Charles Darwin

Common name: Peppered moth
Scientific name: Biston betularia

Stage A: Australopithecus
Stage B: Homo sapiens sapiens Characteristic features of stage B (Homo sapiens sapiens):

Bipedal locomotion with four reversed curves in the spine

Forehead steep, reduced brow ridges

Stage A: Australopithecus
Stage B: Homo sapiens sapiens
Stages of human evolution in their correct sequence:
Australopithecus → Homo habilis → Homo erectus → Neanderthal man → Cro-Magnon man → Homo sapiens sapiens

(a) Use and disuse:
Parts of the body which are used extensively become larger and stronger, while those which are not used deteriorate.
(b) Inheritance of acquired characters:
An organism could pass its modifications to its offspring.

Industrial melanism : This term refers to the phenomenon where the frequency of dark-colored varieties of animals, particularly moths,increases in industrial areas. This is an example of natural selection, where darker moths had a survival advantage in polluted environments due to their better camouflage against soot-covered surfaces.

Adaptive characters: These are traits or features in an organism that have evolved as a response to specific environmental pressures, enhancing the organism's chances of survival and reproduction. Examples include the long necks of giraffes for feeding on tall trees or the camouflage in chameleons.

Vestigial organs: These are organs or structures in an organism that have lost much or all of their original function through the course of evolution. Examples include the human appendix or the hind limb bones in whales. They are considered evidence of an organism's evolutionary history.

Natural selection or Survival of fittest : This is a key mechanism of evolution proposed by Charles Darwin. It suggests that individuals best adapted to their environment are more likely to survive and reproduce. Over time, this leads to the evolution of species as advantageous traits become more common in the population.

Biological evolution : This refers to the process through which different species of organisms develop and diversify from earlier forms during the history of the earth. This process is driven by factors like genetic variation, reproduction, and natural selection, leading to changes in the traits and characteristics of organisms over generations.