Why is life on Earth so diverse??? TEST: Friday 10/28

Evolution Change over time Descent with modification Genetic traits passed on to offspring

Charles Darwin & The Voyage of the Beagle In 1831 he traveled around the world on a ship called the Beagle He noticed that there was great diversity in organisms even in very similar environments The Galapagos Islands had the biggest impact on Darwin’s studies.

Darwin’s Journey

What did Darwin See??

What did Darwin see?????

What did Darwin see????? Glyptodon (fossil)

Evidence of Evolution Darwin saw many things which influenced his theories…… Fossil Record, the Earth was really old (estimated at 4.5 billion years) Lamark’s misconceptions on use and disuse of adaptations (crab) Populations did not grow out of control, there were factors that limited population growth

Evidence of Evolution Did you know???? Fossil Records-fossils being discovered were evidence that the world was much older that once thought. Did you know???? Some fossils were very similar to modern day creatures 99% of species that once lived are now extinct!!!!!!

Fossils show history of life on Earth Relative Dating -The layering of rock can show which fossils are older.

Fossils show history of life on Earth Radioactive Dating -using the half-life of radioactive elements scientists can tell how old a fossil is.

Lamark’s Theory Lamark believed organisms could adapt to fit their environment (ex: fiddler crab) WRONG Problem was that he didn’t know about how traits are passed on genetically His idea that animals are adapted to their environment influenced Darwin’s idea on adaptations

POPULATION GROWTH Darwin’s Observations: Darwin’s Inference: 1. organisms produce so many offspring that their population size would increase exponentially if all individuals that are born reproduce successfully. (Green bean analogy) 2. populations tend to remain stable in size, except for seasonal fluctuations. 3. environmental resources are limited. Darwin’s Inference: Production of more individuals than the environment can support leads to a struggle for existence, with only a fraction of offspring surviving. AHA!!!....Darwin said “It is SURVIVAL OF THE FITTEST”

Theory of Natural Selection “ORIGIN OF SPECIES” In 1859, after 25 years of work, Darwin publishes his work to much ridicule. Theory of Natural Selection Darwin proposes that the diversity of life has evolved because the most fit organism in an environment survives and is able to pass on these fitness traits. Adaptations are characteristics which allow organisms the ability to best survive in their ecosystem. Pinta Island Intermediate shell Hood Island Saddle-backed shell Isabela Island Dome-shaped shell

Darwin’s Theory is supported by…. ARTIFICIAL SELECTION Nature provides variation but humans decide what traits are selected and passed on. Hybridization brings about new variations donkey meets horse.... mule offspring (sterile)

Darwin new there was much variation in nature… Darwin new there was much variation in nature…. Descent with Modification Darwin proposes that after long periods of time, natural selection results in organisms which are very different from their ancestor. Different structures Different niches Different habitats COMMON ANCESTOR

Reasons for…. Descent with Modifications Reason for Genetic Variability Sexual reproduction Mutations Migrations Natural Selection Genetic Drift

Other Evidence for Evolution… Embryology Embryos tend to look very similar at early stages and cells develop into homologous structures.

Embryology

Other Evidence for Evolution… Homologous Structures Traits that are similar in different species because the species share a common ancestor. Same structure, different function

Analagous Structures Analogous Structures: structures similar in function, but not inherited from a common ancestor. Share similar environments. Same function, different structure

Other Evidence for Evolution… Vestigial Organs Traces of organs, inherited from ancestors, that seem to have no functional purpose Hip joint in whales, snakes Ear muscles in humans Male nipples Tailbone

Other Evidence for Evolution… Geographic Distribution Beaver When similar environments produce similar looking organisms that are unrelated. Beaver Muskrat Beaver and Muskrat Coypu Capybara Coypu and Capybara Muskrat Capybara Coypu

Other Evidence for Evolution… Biochemical Evidence All living things use DNA/RNA as their genetic code There is very little difference in DNA sequences of most organisms