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Evolution What is evolution? – It is the process of biological change by which descendents come to differ from their ancestors.

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Presentation on theme: "Evolution What is evolution? – It is the process of biological change by which descendents come to differ from their ancestors."— Presentation transcript:

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2 Evolution What is evolution? – It is the process of biological change by which descendents come to differ from their ancestors

3 Scientists Scientists who began studying evolution: – Linnaeus (1700’s) Developed classification system of organisms Proposed that organisms arose from hybridization

4 Scientists Buffon (1700’s) – Used evidence of past life – Proposed that species shared ancestors instead of arising separately – Proposed earth was much older than 6000 years

5 Scientists Erasmus Darwin (1731) – Proposed all living things were descended from a common ancestor – Later expanded upon by his grandson

6 Scientists Lamarck (1809) – Didn’t believe in extinction – Species evolved instead – Proposed that changes in environment caused behavior to change – Organism passes on these traits to offspring – “Inheritance of acquired characteristics”

7 Charles Darwin Darwin took a trip to the Galapagos Islands aboard the HMS Beagle He studied the inhabitants of the island

8 What did Darwin find?

9 Charles Darwin Findings and conclusions: – Variation among species – Led him to believe species adapt to their environment – Adaptation- feature allows an organism to better survive in an environment – Leads to change in populations over time

10 Examples of Adaptations

11 horned lizard pistol shrimp aye archer fish

12 Charles Darwin Natural Selection – Individuals inherit beneficial adaptations and produce more offspring than others

13 Charles Darwin 4 principles of natural selection: 1. Variation - Differences among organisms 2. Overproduction - More offspring increases chance for survival 3. Adaptation - Certain variations allow to survive better 4. Descent with Modification - Over time, more individuals in the population will have the beneficial traits

14 Natural Selection Variation Adaptation Overproduction Descent with Modification

15 Fossil Evidence No fossil evidence that contradicts evolution has been found Allows us to see transitions of species over time

16 Anatomical Evidence Homologous structures – Features that are similar in structure, but different in function in different organisms – Supports common descent

17 Anatomical Evidence Analogous structures – Structures that perform similar function

18 Anatomical Evidence Vestigial structures – Unused features – Structure had a function in early ancestor – Helps support common ancestry and evolution

19 Molecular Evidence All living things have DNA Organisms carry pseudogenes – Genes that do not function (vestigial) Cells have very similar proteins – Marine worms have same proteins in the eye as vertebrates  Comparison of milk protein in whales and hippos: Hippo TCC TGGCA GTCCA GTGGT Humpback Whale CCC TGGCA GTGCA GTGCT

20 Match the structure Homologous, analogous, or vestigial A C B

21 Population Distributions Normal Distribution – Frequency of a certain phenotype is near the mean

22 Population Distributions Directional Selection – Selection favors phenotypes at one extreme – Population shifts toward advantageous trait

23 Population Distribution Stabilizing Selection – The intermediate is favored and becomes the most common

24 Population Distribution Disruptive Selection – Both extreme phenotypes are favored

25 Genetic Drift Bottleneck Effect – Occurs after an event greatly reduces the size of a population – Ex. Overhunting of elephant seals

26 Genetic Drift Founder Effect – Occurs after a small # of individuals colonize a new area – Ex. Emerald ash borer

27 Sexual Selection Occurs when certain traits increase mating success Two types: – Intrasexual Physical competition among males – Intersexual Displays among males Examples: – Intrasexual – Intersexual Giraffe fight Bird display

28 Long-tailed Widowbird Male Female

29 Evolutionary Classification Cladogram – Evolutionary tree that proposes how species may be related to each other through common ancestors Clade – Group of organisms that share certain traits

30 Evolutionary Classification Bicycle Car Motorcycle Airplane On foot Cladogram for modes of transportation: walkingbicyclemotorcyclecar airplane wheels motor Passengers enclosed wings


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