Evidence for Evolution EQ: How do the various forms of evidence support the theory of evolution?

Evidence for Evolution Biogeography The distribution of plants and animals world wide follows a set pattern Isolated islands have similar plants and animals as the mainland Fossils of the same animal are found on different continents

Biogeography

Evidence for Evolution Comparative Anatomy Homologous structures exist in different species These are structures that are similar in form but different in function Embryological similarities exist The developmental stages of closely related organisms are similar Molecular Biology Compare the DNA of two different species The more similarities that exist the more related the organism are to each other

Homologous Structures

Evidence of Evolution includes The fossil record Geographic distribution of living species Homologous body structures Similarities in early development which is composed of which indicates which implies which implies Physical remains of organisms Common ancestral species Similar genes

Natural Selection Theory Assumptions More offspring are born than can survive There is phenotypic variation within a population Variations are caused by changes or mutations in the DNA Mutations occur by random chance All organisms struggle to survive Nature selects those variations that are best fit for the environment

Evidence for Evolution Fossils are the remain of ancient organisms preserved in the different layers of rocks The law of superposition states that the fossils in the top layers of the earth are younger than the fossils found in the lower layers of the earth Often shows how species changed over time

http://www.youtube.com/watch?v=NyqBYO894eM

Age of Things In 1778 a scientist named Hutton brought up the idea that the earth was very old The rocks, mountains and valleys were all shaped over time by erosion Finally have agreed upon the age of ~ 4.6 billions years Geologic Time Scale The rocks on the bottom are older than the rocks on top of any land feature Allowed scientists to place the age of fossils found in the rocks through relative dating Called the law of superposition

Radioactive Dating Used to date rocks and fossils with more accuracy than relative dating Rocks and bones contain radioactive elements A radioactive element is one that is unstable in its current form and eventually breaks down into a more stable form releasing heat The amount of time for half of the element to break down is its half – life The amount of time it takes for half of the elements to go from unstable to stable

Radioactive Dating Different elements have different half lives allowing scientists to fairly accurately pinpoint when the organism died This is done by comparing how much of an element is still unstable with how much is stable Old form used C14 but it has a large margin of error New form uses K40

Geologic Time Periods Precambrian Life on earth begins – we think Is it possible that life began before this? Earliest fossils of life are dated to 3.5 billion years ago Some evidence suggests it started around 3.8 billion years ago Early animals were single and multicellular Some show evidence of cellular organization like modern jellyfish

Paleozoic Time of major evolution Organisms with shells and skeletons appear Size of individuals increased First invertebrates like the trilobites First jawless fish First fish and forests The earth became inhabitable by organisms much like the ones we see today Ends in mass extinction 90% of all marine species 66% of all reptile and amphibians 30% of all insects

Mesozoic Age of the dinosaurs First mammals and flowering plants The dinosaurs came and went in the mesozoic Were only on the planet for 70 million yrs First mammals and flowering plants Rocky mountains appeared Ended with a major extinction Most likely caused by a meteor crashing in the Gulf of Mexico Changed the climate

Cenozoic Age of the mammal Humans evolved during this time Grasses become abundant First early horses appear Whales and other large mammals appear Humans evolved during this time Variable climates Sea life very similar to today

Age of Civilization Early man appears 2.5 million years ago Many different species of man exist before our present state is reached Possible that more than one species of man was present at any given time

Athropocene Age of Man New geologic Epoch Defined by man’s influence on the environment Started approximately 8000 years ago This is the time in which man began using agriculture to create food 38% of the land is now used for farming Actual start is being debated First purposed in 1870 First scientific papers published using it as an official time period were published in the early part of this century