Biology Today — December 2017

EVOLUTION-I

Analysis of various PMTs from 2013-2017

2013

2014

2015

2016

2017

AIPMT/NEET

2

2

1

4

AIIMS

1

2

2

AMU

4

1

Kerala

1

2

K-CET

1

2

2

J & K

1

Class XII

• Life originated on earth millions of years ago and since then innumerable varieties
  of living beings have evolved. Human beings are considered to be the most recent
  and most highly evolved organisms.

THEORIES OF ORIGIN OF LIFE

• The origin of life is explained by various theories put forth by different scientists.
  Some of the important theories are discussed below.

Theory of Special Creation

• It was supported by Father Suarez. It states that : (i) Some supernatural power,
  called God formed living organisms. (ii) Living organisms were formed all of a
  sudden. (iii) They have not undergone any change since their formation.

According to Bible, life was created by God in 6 days.

Day 1

Heaven and

Earth were

formed

Day 2

Sky was

separated

from water

Day 3

Dry land

and plants

Day 4

Sun, Moon

and Stars

Day 5

Fish and

fowl

Day 6

Animals

including

human beings

Theory of Spontaneous Generation (Abiogenesis or Autogenesis)

• It was proposed by Van Helmont (1577-1644). It states that life originated
  abiogenetically only from non-living, decaying and rotting matter like straw, mud,
  etc., by spontaneous generation.


• Van Helmont proposed that living mice will develop when human sweat and wheat
  barn are kept together for 21 days.
  Abiogenesis was experimentally rejected by Francesco Redi. He proved that organisms
  could be formed only from pre-existing organisms, i.e., biogenesis.