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How can fossils show us what happened in the past? Agenda for Thursday May 15 th 1.Fossil lab Timeline due tomorrow.

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Presentation on theme: "How can fossils show us what happened in the past? Agenda for Thursday May 15 th 1.Fossil lab Timeline due tomorrow."— Presentation transcript:

1 How can fossils show us what happened in the past? Agenda for Thursday May 15 th 1.Fossil lab Timeline due tomorrow

2 What is variation? Agenda for Friday Feb 13 th 1. Variation lab

3 How do we get variation? Agenda for Wednesday Feb 18 th 1.Theories notes

4 Variation What is variation? Examples. How do we get variation? Can everybody have the same types of variation? Explain. Gene pool – set of genes available in a population

5 Jean Baptiste de Lamarck Use and Disuse Inheritance of Acquired Characteristics – Organisms acquire traits and pass these traits to offspring



8 Lamarck’s Influence Incorrect Not all traits acquired get passed on Important Introduced change over time Realized organisms are changing

9 Charles Darwin Naturalist Traveled on the HMS Beagle (1831-1836) South America, Galapagos Islands, Australia Wrote The Origin of Species


11 Galapagos Islands small group of volcanic islands no land mammals or amphibians Back in England he looked at his findings – Tortoises and Finches

12 Animals

13 The Journey Home Characteristics of many plants and animals vary greatly among the islands Hypothesis: Separate species may have arose from an original ancestor

14 Finches All had differentiated into 14 species different beaks specialized for a particular food source Conclusion – ancestral group of finches colonized islands – Absence of competitors allowed finches to gradually become specialized


16 People influenced Darwin Charles Lyell Malthus – populations can grow exponentially – the are limited by war, disease, or resources This led to Darwin’s idea that there’s a struggle for existence

17 Darwin’s Theory Humans can breed for certain traits – Dogs – Domestic plants Could also happen in nature – Over time this could produce new species

18 Darwin’s Theory Natural selection – organisms best suited for the environment reproduce more successfully – Survival of the fittest Over several generations organisms with favorable traits increase

19 1. Variation within a population 2. Variations are passed on

20 3. More offspring are produced than can survive

21 4. Organisms that survive have favorable variations (adaptations)

22 Modification by Natural Selection Fitness – genetic contribution to next generation Environment “selects” traits – Favorable traits depend on demands of env’t Greater fitness Better adapted Reproduce more

23 Summary of Darwin Natural Selection – organisms best adapted to the environment survive and reproduce the population is the unit of evolution – individuals do not evolve during their lifetimes

24 Theory of Evolution Evolution – change in the inherited traits of a population of organisms over time – NOT new species arising from pre-existing species Part but not all of evolution

25 What is natural selection? Agenda for Thursday Feb 19 th 1.Peppered moth lab 2.Finish theories coloring

26 Cheetahs are able to run faster than 60 miles per hour when chasing prey. How would a biologist explain how the ability to run fast evolved in cheetahs, assuming their ancestors could run only 20 mph?

27 A long time ago, some cheetahs were faster than the others The cheetahs that could run faster were able to catch their prey and were better able to survive The slow cheetahs died off, or weren’t able to reproduce as successfully The cheetahs that survived were the ones that could run faster

28 How does gene pool relate to variation? Agenda for Wednesday May 21 st 1.Finish theories notes

29 I can describe why the majority of the variation in a population is seen as a bell-shaped curve.

30 How did the heavy coat in polar bears evolve if their ancestors had thinner coats? 1. A long time ago, some polar bears had thicker fur than others 2. The thicker coat was favorable 3. The polar bears with thin coats died off. 4. The ones with thicker coats survived and reproduced.

31 Peppered Moths

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