Morphological and comparative anatomical evidence

Phylogeny –

• The study of ancestor is called phylogeny.
• The phylogenetic history can be revealed by comparative study of external and internal structures.
• Comparative anatomy and morphology shows similarities and differences among organisms of today and those that exited years ago.
• Homologous organs
• Analogous organs

Homologous organs –

• The organs whose structure or origin is same but functionally different.

example – vertebrate hearts or brains, in plants, the thorns and tendrils of bougainvillaea and cucurbita, the forelimbs of whale, bats, cat and human share similarities in the pattern of forelimb bones.

• All the animals have similar anatomical structure in their forelimb bones such as humerus, radius, ulna, carpals metacarpals and phalanges.
• Though the forelimbs have similar anatomical structure but they perform different functions.
• The same structure developed along different directions due to adaptations to different needs.
• Homology is based on divergent evolution.
• Homology indicates common ancestry.

Divergent evolution :-

• Due to different needs, some structures developed differently. This is called divergent evolution.

Analogous organs :-

• The organs which are anatomically different but functionally similar are called analogous organs

For example- wings of butterfly and birds.
Other example include

1. Eye of octopus and mammals
2. Phyllodes and leaves
3. Butterfly wings and bat wings

Due to sacde function different structures evolve similarly , this is called

Convergent evolution:-

Sweet potato (root modification) and potato ( stem modification)

Biochemical evidence :-

The similarities in proteins and genes performing a common given function among diverse organism given clues to common ancestry

The most convincing evidence of descent from a common ancestor comes from the similarities in the biochemical composition and physiological activities of organisms.

1. Enzymes and hormones: in the same manner similar or identical enzymes and hormones, are found in large number of animals groups. For example, trypsin- the protein splitting enzyme, is found in animals from protozoa auto mammals and amylase from sponges to man.
2. chromosomes :the essential component of nucleus in every living cell is the chromosomes. The chemical composition of DNA is basically the same in all living beings except for differences in the sequence of nitrogenous bases.
3. Genetic code: it is surprising to note that the same genetic code having triplet code is found from viruses to man.
4. All of these organisms store energy in the form of ATP.
5. All the these factors of biochemistry provide evidence for evolution.

Biogeographical evidences :-

• Species restricted to a region develop unique features.
• Also species present in widely separated region show similarity of ancestry.

Adaptive radiation :-

Adaptive radiation is the relatively fast relatively fast evolution of evolution of many species from a single common ancestor. Adaptive radiation generally occurs when an organism enters a new area and different traits affect its survival. An example of adaptive radiation is the development of mammals after the extinction of dinosaurs.

1. Darwin’s finches :-

• Darwin observed many varieties of finches in the same island.
• All varieties had evolved from original seed – eating finches.
• With alteration in beaks some became insectivorous and some vegetarian.

Marsupials of australia :-

Within the australian continent, many different marsupials or pouched animals are seen.

These have evolved from a common ancestral stock.

Placental animals in australia :-

A variety of placental mammals have evolved from the australian with respect to their need.