Fossil Evidences

What are the Four Types of Evidence for Evolution

Homologus Organs :

• These organs are similar in structure but disimilar in functions.
• Homologous organs are found in forms showing adaptive radiation from a common ancestor so these give evidence of ‘divergent evolution’.
• Ex. forelimbs of mammals, bat’s wing, a cat’s paw.
• In plants homologous organs may be a thorn or a tendril as they arise in the axillary position. If homology is seen at the molecular level.  This is called molecular homology.

Analogous Organs :

• These organs are perform similar function but quite different in origin and development.
• Analogous organs are also called homoplastic organs.
• Analogous organs like wings of insects, birds and bats illustrate ‘convergent evolution’.
• Ex. – Wings of birds, wings of insects show the same function but their origin and development is different.

Vestigial Organs :

• Vestigial organs are useless organs found in the body. These are present in reduced form.
• Ex. wings of kiwi, limbs of snakes, the nictitating membrane of the eye, body hair and the muscles that move the ears.
• During the period of evolution vestigial organs have become functionless.

Fossil Evidences :

• Fossils are the remains of the organisms that found in the ancient period. We can determine fossil’s age through the period of rock by radioactive material. Histological time scale is a chronological order of evolution history based upon the study of fossils.
• Study of fossils known as palaeontology.

Petrification :

• Hard parts are preserved in this type of fossil.

Archaeopteryx :

• A fossil bird show both reptilian and avian features – It had wing  like birds, thecodent dentition and tail like reptiles. Hence, archeopteryx is a connecting link between birds and reptiles.

Connecting links :

Embryological Evidences:
The study of embryo from variours organisms reveals similarity in the early stages of embryo development & this theory suggests that these organism have evolved from common ancestors.
Eg. Embryos of fish, turtle, bird, pig & man shows the similarity during embryo development.