Examples of natural selection, Biology

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EXAMPLES OF NATURAL SELECTION -

1. INDUSTRIAL MELANISM -

First studied by Fischer & Ford (1845) on pepperd moth (Biston betularia) of two types : grey moth (B. betularia betularia) and black moth (B. betularia carbonaria); the black moth population in Britain in (1845) was 1% which by 1895 came to 99%, it was thought that due to industrial pollution the grey moth changed into black. When coal run industries were replaced by electric / petroleum run industries the number of grey moths again increased (also correlated as reverse evolution) as pollution did not eliminate the gene of grey color.
As explained by Neo-Darwinians both populations (grey & black) existed together, the environment favoured the one and disfavoured the other at different times resulting into their changed frequency.
Bernard Kettlewell (1950) tested this by releasing equal numbers of grey and black moths in both polluted (Birmingham) and unpolluted (Dorset) areas. Later he captured 19% grey and 40% black moths from polluted areas and 12.5% grey and 6% black from unpolluted areas. This indicates the patterns of differential survival of the moths in respectively areas.

2. SICKLE CELL ANAEMIA -

It is a genetic disorder caused by a single base substitution in a gene.
The mutated gene changes the normal haemoglobin (HbA) to defective haemoglobin (HbS) and also makes the red blood corpuscles sickle shaped.
The persons homozygous for the defective haemoglobin (HbS, HbS) die at an early age. In the heterozygous (HbA, HbS) the cell containing abnormal haemoglobin become sickle-shaped, and unable to bind oxygen efficiently.

3. BIO-INDICATOR PLANTS & ANIMALS -

Plants which are specialized to grow under specific habitual conditions so that their presence in an area can indicate the same.
Prosopis eineraria. P. dilensis, Acacai glandulosa. -Underground water
Impatiens balsamina - Zinc (Zwar zinc mines, Udaipur)
Haplopappus and Astragulus species - Selenium tolerant plant from U.S.A.
Agrostis tenuis - On tailing of lead mines in wales, U.K. the variety from normal pasture couldn't survive on Pb-rich soil.
Tubifix (Animal) - Pollution in water.

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