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

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Presentation on theme: "Why is life on Earth so diverse??? TEST: Friday 10/28."— Presentation transcript:

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

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

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

4 Darwins Journey

5 What did Darwin See??

6 What did Darwin see?????

7 Glyptodon (fossil)

8 Evidence of Evolution Darwin saw many things which influenced his theories…… 1. Fossil Record, the Earth was really old (estimated at 4.5 billion years) 2. Lamarks misconceptions on use and disuse of adaptations (crab) 3. Populations did not grow out of control, there were factors that limited population growth

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

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

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

12 Lamarks Theory Lamark believed organisms could adapt to fit their environment (ex: fiddler crab) Lamark believed organisms could adapt to fit their environment (ex: fiddler crab) Problem was that he didnt know about how traits are passed on geneticallyProblem was that he didnt know about how traits are passed on genetically His idea that animals are adapted to their environment influenced Darwins idea on adaptationsHis idea that animals are adapted to their environment influenced Darwins idea on adaptations WRONG

13 Darwins Observations: 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. POPULATION GROWTH AHA!!!....Darwin said It is SURVIVAL OF THE FITTEST Darwins Inference: Production of more individuals than the environment can support leads to a struggle for existence, with only a fraction of offspring surviving.

14 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

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

16 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

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

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

19 Embryology

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

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

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

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

24 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


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