Evolution: 1) the evidence a) Evidence for evolution can be divided into 3 major categories: i) Homology homology refers to characteristics that are similar as a result of common ancestry. You're very similar. Similarity is the common descent. This is evidence of different species being related to one another at one point. A homologous characteristic is a trait that a species has that is shared with other species from descent. (1) Structural homology is underlying similarity despite a different lifestyle. Bat wings and whale wings have the same structural component, in spite of different bones and digits etc. They share the same structure but they look very different because they are different species and the wings have adapted to new lifestyles. The bat adapted to flight and the whale flipper have adapted to swimming lifestyle. (2) Homology vs. convergent evolution. Convergent evolution is similar trait between two species, but not from the same ancestor this can happen because the species goes through the same conditions and so natural selection causes this similarity. Ex. Wings in bats vs. wings in birds (limbs are homologous). Wings in bats vs. wings in insects (this is convergent evolution.) Flight in bats and birds is due to convergent evolution. (3) Homology: vestigial organs. Evolution is a remodelling process. One consequence is there are times when once upon a time there was a trait that was advantageous but now it's not. The result is if there are mutations to this trait there is no disadvantage there is no penalty to this trait being reduced. We have sometimes structures that are not functional that represent earlier time of evolutionary history that had some advantage. Fossil basilosaurus. Why would a marine animal need a pelvis? (an adaptation for travel on land). (4) Embryological homology: the developmental genes that produce tails etc are still within our genome but they have no value. It is present in a brief period of time in our embryonic period and these points to our common ancestors. (5) Genetic homology: itself DNA is a homology. DNA very similar between closely related organisms. Lineages that diverge longer ago in time accumulate greater differences among one another. (6) Homologies and the tree of life: homologies produce patterns that agree with evolution and diversification from a common ancestor. (a) Morphological similarity: in species that diverge recently from a common ancestor. (b) Developmental (c) Molecular-scale: protein and DNA sequence. Haemoglobin. ii) Biogeography: explaining patterns of descent w/modification. Refers to the study of the geographical distribution of the species. Geographic isolation also promotes diverges to accumulate. Ex. If you got two islands of castaways competing in survival. If islands closer not b very hard for individuals from one island to move to another. So this might not be difficult. Pair bonding and pair mating. You don't get genetic divergence. If you have these two more isolated then its very rare for individuals to exchange genetic material. Any genetic changes that occur in one population are not expressed in another. So over time genetic divergence emerges in these different species. Can act as an agent to promote
evolutionary change. Biogeography if we have a parent population of a species and over time it disperses through large difference. If we were to accept that all of these populations originate from a common ancestor what we would expect to see is that populations close together more similar than populations further apart. (1) Speciation on islands: most resemble the closest mainland, not other islands far away. iii) Fossils: supports our understanding of evolutionary history. Eg. Divergence of mammals 65 Million Years Ago INDEPENDENT lines of evidence agree that mammals diverged. "missing links" or intermediate transitional forms. Archaeopteryx had bird like and reptile like features. (1) Predictions from evolutionary theory: transitional forms. The fossil evidence for transitional forms continues to accumulate, further supporting evolutionary theory.