Evidences of Common Ancestry

Flashcards on Evidences of Common Ancestry

Homologous organs

Organs of different groups of organism that are different in appearance and perform different functions, but are built on same basic pattern and have the common origin.

What homologous organs prove

Presence of homologous organs in different groups of organism proves common ancestry and inter – relationship among different groups and occurrence of divergent evolution.

Analogous organs

Organs of different groups of organism similar in appearance, perform same function but differ in fundamental structure and origin.

What analogous organs prove

Presence of analogous organs in different groups of organisms prove convergent evolution.

Vestigial Organs

Rudimentary or poorly developed organs or any body parts that are non functional, but were functional in ancestors and are fully developed and functional in related forms.

Significance of Vestigial organs

Presence of vestigial organs in some organisms and presence of same functional organ in their ancestor and related groups proves that common ancestry of all living forms.

Atavism or reversion or Dollo’s law

Reappearance or functioning of certain ancestral characters or organs after several generations, which are either completely disappeared or greatly reduced.

Dollo’s law

Living organism exhibit the reappearance of ancestral characteristics.

Connecting link

Organisms which exhibits characters of two different groups (primitive and advanced).

What Connecting link tells

Connecting link tells advanced groups have evolved from simpler ones by descent with modification.

Palaeontology/paleobiology

Study of fossils of plants and animals that lived in the past.

Missing links/Transitional forms

Transitional fossil organisms which possess characters of two different groups of present day living forms.

Biogeographical distribution

The study of distribution of animals and plants in space or on earth.

Discontinuous distribution

Distribution of animals only in some restricted area exhibits discontinuous distribution or STENOTOPIC distribution.

Continuous distribution

Distribution of animals worldwide.

Restricted distribution

Some areas of the world have unique organisms which are not found in any part of the world.

Molecular homology

Similarity in molecular structure of major bio – molecules in different groups of organisms.