1. Maryam Daman
UOG

2. Patterns of evolution (convergent evolution and divergent evolution)

3. Contents Parallel evolution Co-evolution Convergent evolution Causes
Analogous structures
Significance
Divergent evolution

4. Patterns of evolution
Groups of species undergo various kinds of natural selection and, over time, may engage in several patterns of evolution:
Parallel evolution
Co evolution
Convergent evolution
Divergent evolution

5. Parallel Evolution
Parallel Evolution also involves divergence from a common ancestor, but the descendants evolve similar morphologic characteristics as time goes on. So, parallel evolution is the development of similar characteristics in closely related organisms

7. Co-evolution
It refers to the evolution of two species in response to the evolution of the other. OR One species evolves an adaptation which in turn prompts the other species to evolve one to "Meet" the other.

8. Cont…..
Such evolution often occurs between a predator and its prey like plants and plant-eating insects, or between parasites and hosts, or pollinators and flowering plants.

9. Similarly as trees attain height dinosaurs also attain height to reach the leaves of trees.

10. Convergent evolution
Convergent evolution is the emergence of biological structures or species that exhibit similar function and appearance but that evolved through widely divergent evolutionary pathways.

11. Example of Fish and Whale:
A classic example is how similar a whale looks to a fish, and yet whales evolved from mammals, not fish. But since a whale must move expertly through water just like fish, it evolved a very similar body structure.

12. Causes Similar ecological niches
Marsupial fauna of Australia and the placental mammals of the Old World share a common ancestor that belongs to their own group, and are more closely related to one another than to any other clade but very similar forms evolved in each isolated population.
Selective pressures, combined with variation
Force animals to adapt to their changing environments or perish.

13. Analogous structures
Traits arising through convergent evolution are termed analogous structures.
Bat, bird and insect wings are an example of analogous structures.
Similarity in species of different ancestry that is the result of convergent evolution is called homoplasy.

14. Significance
The Tree of Life contains many remarkable examples of convergent evolution, which attest to the great power of natural selection to adapt different organisms to similar environments.
Sometimes convergent similarities are so striking that they have fooled biologists for decades before being revealed through careful phylogenetic research.
Sometimes convergent evolution modified different body parts to look the same and perform the same function: insect wings were derived from the exoskeleton, while bird wings were derived from forelimbs with an internal skeleton.

15. Cont………
In various species of plants, which share the same pollinators, many structures and methods of attracting the pollinating species to the plant are similar. These particular characteristics enabled the reproductive success of both species due to the environmental aspects governing pollination.

16. Divergent evolution
Divergent evolution is the accumulation of differences between groups which can lead to the formation of new species, usually a result of diffusion of the same species to different and isolated environments.
It blocks the gene flow among the distinct populations allowing differentiated fixation of characteristics through genetic drift and natural selection

17. Example
Diversification of mammals from a common shrew-like ancestor to all modern mammals such as bats, primates, whales, and rhinoceroses.

18. Causes
On a molecular level, this can happen due to random mutation unrelated to adaptive changes.
They either specialize to occupy different niches:
The 23 species of honeycreepers found in Hawaii are all similar in body structure but differ in beak shape.
It is usually a result of diffusion of the same species to different and isolated environments which blocks the gene flow among the distinct populations allowing differentiated fixation of characteristics through genetic drift and natural selection

19. Significance
Divergent evolution leads to speciation, or the development of a new species.
The differences are produced from the different selective pressures. Any genus of plants or animals can show divergent evolution. An example can involve the diversity of floral types in the orchids. The greater the number of differences present, the greater the divergence.

20. Cont………..
On a large scale, divergent evolution is responsible for the creation of the current diversity of life on earth from the first living cells.

21. Thank you