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Evolution of Evolutionary Thought

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Presentation on theme: "Evolution of Evolutionary Thought"— Presentation transcript:

1 You are taking a pretest on evolution first thing-get out a pencil-its scantron

2 Evolution of Evolutionary Thought
SB5a. Trace the history of the theory. SB5d. Relate natural selection to changes in organisms.

3 Jean Baptiste Lamarck (1744-1829)
Theory of evolution in 1809 (before Darwin) Two Ideas about Evolution: Use & Disuse- if you don’t use a part, you lose it. The parts you use the most get stronger. Inheritance of Acquired Traits- the characteristics acquired by an organism during its lifespan are passed onto its offspring. EX: if a person has an arm amputated then her children will not have arms. Does an organism “acquire” characteristics? NO… an organism is BORN with characteristics they don’t grow them during a lifespan. Ex: A giraffe’s neck grows longer to reach higher leaves. Older idea- no longer accepted Jean Baptiste Lamarck ( )

4 Sir Charles Lyell (1797-1875) Wrote Principles of Geology
Believed in gradualism- gradual changes in environment led to gradual changes in organisms. Knew both Lamarck and Darwin, eventually supported Darwin more.

5 Charles Darwin (1809-1882) Naturalist on HMS Beagle for 4 years.
Collected many fossils and animal species from Africa and South America. Most famous research done on Galapagos Islands off coast of S. America. Did not publish until 20 years after his return Was completing research and collecting evidence. Published Origin of Species in book that described natural selection & evolution.

6 Alfred Russell Wallace (1823-1913)
Wrote Darwin letters that prompted Darwin to finish his book- had same basic ideas as Darwin. Did his research on Malay Archipelago Sometimes called “Father of Biogeography” Verified Darwin’s ideas on “struggle for existence”

7 The Theory of Evolution by means of Natural Selection
As outlined by Charles Darwin

8 Darwin believed in two major ideas:
Descent with modification- Most organisms are descended from a common ancestor History of life is like a tree, with multiple branch’s from a common trunk.

9 2. Natural Selection Individuals within a population vary in their traits. More offspring are produced than can survive. Many will get eaten or will not be able to compete for resources. There is competition for limited resources that creates a struggle for existence. Individuals with advantageous traits will survive and reproduce. Those with bad traits will die, taking those bad traits with them. (Survival of the Fittest)


11 Galapagos Tortoises The saddleback tortoise lives on an island with little vegetation, high branches, no grasses. Shell is taller and has neck notch so can reach food sources higher up. The dome tortoise lives on an island with lots of vegetation, low hanging branches, and grasses. Shell is flatter and no neck notch. Both tortoises come from a common ancestor that originated in S. America but over time their populations adapted to the food resources on their respective islands.

12 So what is EVOLUTION? Evolution is the gradual change in a POPULATION over a long period of time. Natural Selection of “the best” traits leads to EVOLUTION.

13 What role does GENETICS play in EVOLUTION
It is the slight MUTATIONS that create VARIATIONS in DNA that can make an organism better (or worse) suited to an environment. Variations can also be created by crossing over or independent assortment during meiosis. These variations are passed on when sperm and egg are made during meiosis. While the mutation/adaptation may happen in an individual EVOLUTION occurs within the POPULATION as a result.

14 Case Study: Malaria and Sickle Cell Anemia in Africa
Malaria very common in Africa b/c of warm humid environment which makes great breeding ground for mosquitoes. Malaria is caused by protist that is transmitted by mosquitoes. Protist enters blood stream, invades round red blood cells and makes copies of itself. Burst from red blood cells, killing the red blood cells. Many people die from Malaria infections every year. Sickle Cell Allele Mutation in DNA caused sickle cell allele to form Sickle cell allele mutates red blood cell to be half-moon shaped instead of round. Fully affected person (SS) would suffer from clotting, pain, sometimes death. Malaria and Sickle Cell Malaria protists cannot enter sickle shaped blood cells. People with sickle cell alleles (RS, SS) are better able to survive a malaria infection so they survive, reproduce and pass sickle cell onto offspring. Eventually large portion of population has sickle cell allele. Evolution: Library: A Mutation Story

15 Pete and Rosemary Grant researched ground finches in Galapagos during the 1970’s and 1980’s. Write a paragraph that describes how the finch populations changed over time. Look back at Darwin’s four postulates for help.

16 During dry years seed coats of plants are tough
During dry years seed coats of plants are tough. This helps prevent dehydration. Beak depth would need to be thick to crack dried up toughened seeds. The birds with thinner beaks couldn’t crack seeds so died out during those dry years. Thicker beaked birds got the seeds, survived, reproduced and passed that trait onto their offspring.

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