Ch 15: Theory of evolution

Evolution Development of new organisms from pre-existing ones Heritable change in the characteristics within a population from one generation to the next Charles Darwin published “on the origin of species” in 1859 Text outlined descent with modification

Descent with modification (DwM) Every species must have descended by reproduction from preexisting species Species must be able to change over time

Natural selection Mechanism for DwM Four main parts of Darwin’s reasoning Overproduction: more offspring produced than can survive Genetic variation: individual within a population have different traits Struggle to survive: individuals compete Some variations improve chance for survival and reproduction Adaptation: trait that makes an individual successful in its environment

Natural selection 4. Differential reproduction: organisms with best adaptations are most likely to survive and reproduce Through inheritance, adaptations become more frequent in a population This leads to change in a population Fitness: measure of an individual’s heredity contribution to the next generation More than survival Must reproduce offspring that will reproduce in turn

Contributors to Darwin Before Darwin’s time, most scientist thought the earth and it’s organisms were permanent and unchanging Earth was thought to only be thousands of years old How old is it actually? About 4.5 Billion years old Geologists started to identify the actual age of the earth by looking at the rock strata: rock layers Oldest layers on bottom

Contributors French anatomist Georges Cuvier

Fossil record Fossil: remains or traces of past life Fossils show that different organisms have appeared at different times and places on Earth Superposition: oldest rocks on the bottom

How old is it? Relative vs absolute age Which is older: A fossil at A or F? If a radioactive isotope has a half-life of 50 years, how much is left after 250 years if the original amount was 5,000 mg? Half-lifes Mass remaining 5000 mg 1 (50 years) 2500 mg 2 (100 years 1250 mg 3 (150 years) 625 mg 4 (200 years) 312.5 mg 5 (250 years) 156.25 mg

Transitional species Intermediate species between ancestral species and later descendants Page 304

Biogeography Studies why living things are found where they are Unrelated organisms with similar features

Comparative anatomy Homologous structures: found in related species that share a common ancestor May have different functions but similar structure Analogous structures: related functions, but different structure

Vestigial structures Structures with no current function May have been functional in ancestral species

Evolution in action Evolution is continuous and ongoing Scientists can study evolutionary patterns today Case study: anole lizards

Convergent evolution Process by which different species evolve similar traits

Divergence and radiation Divergent evolution: process in which descendants of a single ancestor diversify into species that each fit into different parts of their environment

Adaptive radiation Many species evolve from a single ancestral species

Artificial selection Selective breeding of organisms for specific traits DONE BY HUMANS!!! This is in contrast to natural selection in which the environment places pressure on certain traits

Coevolution When two or more species have evolved adaptations to each other’s influence Why are flowers different colors? Why do they have different scents? Why are flowers shaped differently? Why do we keep having to develop new antibiotics? Methicillin Resistant Staphylococcus aureus MRSA