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MHT-CET : Biology Entrance Exam

MHT - CET : Biology - Evolution Know More

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Types of Adaptations

Fossorial Adaptation

These are subterrenian adaptations shown by diggers. Thus, fossorial adaptation is the adaptation for burrowing.

Scansorial Adaptation
These are adaptations shown by animals living on trees. Example: Scansorial adaptation is found in sloth.

Volant Adaptation

Volant adaptation refers to adaptation for flying. Example: Birds, bat, etc. show volant adaptation.

Cursorial Adaptation:
Cursorial adaptation refers to adaptation for running. Example: Horse shows cursorial adaptation.

Different Theories of Evolution

a.      Organic Evolution 'Descent with modification' by Charles Darwin.

b.      Jean Baptise de Lamarck put forth the theory of evolution of inheritance of acquired characters.

c.       Weismann's theory of continuity of germplasm - This theory provided the strongest criticism to Lamarckism. It was proposed by August Wiesmann in 1904. It stated that germ cells and somatic cells form the organism.

d.      The principle of natural selection as mechanism of evolution by Charles Darwin and Alfred Wallace.

e.      Mutation theory proposed by Hugo De Vries in 1905.

f.        Isolation theory proposed by M. Wagner.

 

Vestigial Organs
In the human body, there are 100 vestigial organs. Example: Vermiform appendix, coccyx or tail bone, canines, wisdom teeth, nictitating membrane, auricular muscles, male mammary glands, etc. Some vestigial organs in other animals are splint bones in the hind limbs of horse, wings and feathers in flightless birds, etc.

Different Stages in the Evolution of Horse

Eohippus

-

Eocene epoch

Mesohippus

-

Oligocene epoch

Miohippus

-

Oligocene epoch

Parahippus

-

Miocene epoch

Merychippus

-

Miocene epoch

Hipparion

-

Pliocene epoch

Pliohippus

-

Pliocene epoch

Equus

-

Modern horse

 

Evolutionary Trends in Horse Evolution

1.      There was an increase in size.

2.      There was an increase in the length of the neck.

3.      There was an increase in the face length.

4.      There was an increase in the length and size of III digit.

5.      The size of the brain increased. The brain also became more complex.

6.      Molarisation of premolars took place.

7.      There was a change in gait from plantigrade gait to unguligrade gait.

8.      Lateral digits disappeared to form splint bones.

9.      The hoof on the middle digit got enlarged.

 

Different Eras

Archaeozoic era
Era of invisible
life

Proterozoic era
Era of early life

Palaeozoic era
Era of ancient life

Mesozoic era
Era of medieval
life

Cenozoic era
Era of modern life

1500 million
years old

First life in
the form of
unicellular
organisms
evolved

925 million
years old

Simple marine
invertebrates
evolved

Fishes and
amphibians
evolved

Reptiles evolved

Age of
mammals, birds
and modern insects

 

Palaeozoic Era

Cambrian
period

Ordovician
period

Silurian
period

Devonian
period

Carboniferous
period

Permian
period

550 million
years old

480 million
years old

Origin of
primitive
terrestrial
ferns

350 million
years old

300 million
years old

250 million
years old

 

Age of
giant molluscs

 

Age of fishes

Age of
amphibians

 

 

 

 

Origin of
first land
vertibrates

Origin of
Reptiles

 

 

Mesozoic Era

Triassic
period
190 million years old

Jurassic
period
155 million
years old

Cretauous
period
120 million
years old

Origin of primitive mammals

Age of giant reptiles

 

 

Cenozoic Era

 

 

Tertiary Period

 

Palaocene
epoch
70 million
years old

Eocene
epoch
50 million
years old

Oligocene
epoch
35 million
years old

Miocene
epoch
25 million
years old

 Pliocene
 epoch
10 million
years old

 

 

Quarternary Period

 

 

 

 

 

 

 

 

 

  Pleistocene
  epoch
  evolution of   primitive man

Holocene epoch
Age of man
20,000 years old

 

 

 

 

 

 

 

Examples of Connecting Links

1.      Protopterus is connecting link between bony fishes and amphibians.

2.      Ornithorhynchus is connecting link between reptilia and mammalia.

3.      Peripatus is connecting link between Annelida and Arthropoda.

4.      Neopilina is connecting link between Annelida and Mollusca.

Palaeontological Evidence
It is the evidence based on comparative study of fossils of different animals. Leonardo de Vinci for the first time reported fossils. George Cuvier established palaeontology in 1800.

Types of Fossils:

a.      Petrified fossils:
Example: teeth, bones, shells, big trees.

b.      Mould fossils:
Example: wings of insects, leaves, jelly fishes.

c.       'Unaltered fossils:
Example: snow preserved mammoth, rhinoceros

d.      Compressed fossils:
Example: plant fossils

e.      Print fossils


Age of Fossil
The age of fossils is determined by the age of rock which can be calculated by radioactive substances present in it. Different methods used to determine the age of fossils are:
a) Uranium Lead Method
b) Radioactive Carbon Method

Drawbacks of Darwin's Theory

1.      It did not explain the causes of heritable and non-heritable variations.

2.      It did not explain the presence of vestigial organs.

3.      It did not clearly explain the role of natural selection in evolution.

4.      It did not explain the origin of new characters.

 

Neo Darwinism
Neo Darwinism is the combination of Darwin's theory and De-vries theory of mutation. The theory states that:

1.      Variation is raw material of evolution.

2.      Variation occurs due to the change in gene pool.

3.      Change in gene pool occurs because of mutation and recombination.

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