Observations That Explain Evolution Ecological pressures that lead to accelerated natural selection. Differential predation - leads to a change in the types and amounts of mature individuals that can breed and leave offspring Artificially imposed environmental conditions - antibiotics and the emergence of drug resistant bacteria – the antibiotics select for only those with the R-factor that infers immunity – as the resistant bacteria multiplies it becomes the dominant strain Emergence of super infections… MRSA

Homology Homology refers to common physical structures that are result of common ancestry. – developmental homology - comparison of embryological development to infer common ancestry – anatomical homologies - limbs, spine, shoulders,... structures that have similar function but show variations in the structural theme

Homology – vestigial organs - tail and appendix in humans structures that show homology but have little or no function to the organism – molecular homology - common gene sequences shared between all living things are the basis of phylogeny (genetic tree of life) basis of the inference that ALL life is connected through common ancestry

Biogeography Similar species are found in areas that are in close proximity to each other whereas similar niches separated by great distances might have species that look similar but are very different – Eutharians (animals that complete their development in the womb) and marsupials from Australia. Although they make look similar they are not closely related. parallel evolution

Biogeography Endemic species - those species that are found only in an isolated area (geographical isolation) – Created by divergent evolution and geographical isolation