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Natural Selection and Evolution

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Presentation on theme: "Natural Selection and Evolution"— Presentation transcript:

1 Natural Selection and Evolution

2 Charles Darwin Was a naturalist and on Dec. 27, 1831 sailed on the HMS Beagle Nov Darwin Published “The Origin of Species By Natural Selection” where he discussed his theory of Natural Selection and Evolution

3 Natural Selection: “Survival of the Fittest”
Natural Selection means that in any population of individuals with better variations for a particular environment will survive, reproduce, and pass these variations on to the next generation

4 Adaptations Are the changes made by a species caused by genetic variation

5 Mimicry Is a natural adaptation that provides protection for an organism by copying the appearance of another species

6 Camouflage Is a natural adaptation that enables an organism to blend in with its surroundings

7 Evidence for Evolution
Date of the Earth: 4.6 Billion Years old The fossil record supports evolution by comparing fossils from the past with modern day organisms

8 Biological Molecules Contain Evidence
Comparing amino acid and DNA sequences- closer related have more similarities

9 Phylogenetic Tree

10 Anatomy and Development Suggests a Common Ancestry
Vestigial structures are structures that are reduced in size and function (example: appendix and wings on flightless birds)

11 Homologous Structures
Are structures that show a common ancestry (limbs of humans, wings of bats, and fins of whales)

12 Analogous Structures Are structures that are similar in function but different in structure (example: wings of birds and insects)

13 Similarities among vertebrate embryos…
Suggest evolution from a common ancestry

14 Evolution of Species Speciation is the evolution of new species and occurs only with the production of fertile offspring.


16 Geographic Isolation Barrier separates a population into groups

17 Reproductive Isolation
Occurs when formerly interbreeding organisms no longer produce fertile offspring!

18 Polyploid Occurs when any species has any difference of the normal set of chromosomes. This occurs because of mistakes during meiosis.

19 Rates At Which Speciation Occurs

20 Gradualism Is the idea that new species originate through the slow buildup of new adaptations over long time period

21 Punctuated Equilibrium
States that speciation occurs in quick bursts then long time periods in between

22 2 Types of Evolution

23 Divergent Evolution The pattern of evolution in which species once all related to a common ancestor become more and more distinct. Example: Darwin’s Finches

24 Convergent Evolution NON- related organisms evolve similar traits; occurs when two organisms occupy similar environments and face similar selection pressures EXAMPLE: Fish and whale

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