Evidence of Evolution Chapter 15 Part II
1. Fossil Record • Are able to observe links between modern forms and ancestors (ex. transition species) • Relative age- age compared to other fossils by referring to the geologic time scale and records of known fossils • Absolute age- use of radiometric dating to date rocks
2. Biogeography • Geographical distribution of species • New organisms arise in same geographic area where similar forms already lived • Example) Australia – has native wolves, cats, mice, moles, and anteaters. Most mammals are marsupials (animals evolved in isolation)
3. Anatomy and Embryology • Homologous structures- anatomical structures that occur in different species that originated in most recent common ancestor • may have different functions but look similar
Common Ancestor: Bat Human
Analogous Structures-a body part similar in function to another organism due to environmental pressuresEx) the wings of a fly, a moth, and a bird developed independently as adaptations to a common function – flying
Vestigial structures- a part of an organism with little or no function but which had a function in an ancestral species
Comparative Embryology- Study of structures that appear during embryonic development • Ex)All vertebrate embryos go though a stage in which they have gill pouches on the sides of their throats
4. Molecular Biology (DNA and Proteins) • Comparison of DNA, RNA, and amino acid sequences • Greater the number of similarities, the more closely the species are related through a common ancestor • Shows the common descent of the most diverse organisms.
Evidence of Evolution:fossil evidence, homologous structures, embryology, vestigial organs, biochemical • Bones in bird’s wing and human’s arm are similar in structure. • All organisms use ATP to transfer energy. • There are similarities in structure among the early stages of fish, birds and humans. • Humans, unlike rabbits, have no known use for their appendix. • Horses have increased in size and decreased in number of toes since the Eocene.
Patterns of Evolution • 1. Coevolution • 2. Convergent Evolution • 3. Divergent Evolution
1. Coevolution • When two or more species have evolved adaptations that influence each other (evolutionary “arms race”) • Examples: • Predator-prey • Parasite-host • Plant-animal pollinator (bee and flower) • Humans have developed and used antibiotics to kill bacteria, bacteria have evolved to become antibiotic resistant
2. Convergent Evolution • Organisms appear to be similar but are not closely related at all • The environment selects similar traits • Result in analagousstructures • Ex) dolphin and shark
3. Divergent Evolution • Two or more biological characteristics become more and more dissimilar in response to different habitats
Adaptive radiation- a new population in a new environment (island) will undergo evolution until the population fills many parts of the environment Ex) Galapagos finches
Artificial Selection • The intentional breeding (by humans) of certain traits, or combination of traits, over others