Darwin & Natural Selection

Transcription

1 Darwin & Natural Selection Early Influential folks Jean-Baptiste Lamarck Scholar who thought about processes that drive evolution Thought species might improve over time because of an inherent drive towards perfection Slide 2 1

2 Early Idea Environmental pressures caused an internal need for change in an individual s body - resulting change was passed to offspring Line of descent = lineage Slide 3 Early Influential folks Georges Cuvier Zoologist and paleontologist Studying fossils- noticed many fossil species had no living counterparts Developed the theory of Catastrophism Slide 4 2

3 Theory of Catastrophism Catastrophic geologic forces shaped Earth s surface Caused species extinctions Remaining species repopulated the earth Slide 5 Early Influential folks Georges Buffon Many talents: author of Histoire naturelle (44 vols!), naturalist, mathematician, cosmologist One of first naturalists to argue that life changed over time According to Ernst Mayr (Harvard prof of Zoology): "Truly, Buffon was the father of all thought in natural history in the second half of the 18th century" Slide 6 3

4 Early Influential folks Charles Lyell Geologist & lawyer Proponent of the theory of uniformity Idea that gradual repetitive processes occurring over long periods of time shaped the earth s surface Slide 7 Early Influential folks Alfred Wallace Saw patterns in where species live and how they might be related Started to think about how natural forces might shape life Slide 8 4

5 Who was Charles Robert Darwin? 12 February April 1882 English naturalist Born in Shrewsbury, Shropshire, England at his family home, The Mount His education gave him: a foundation in the doctrine of Creationwell knowledge of medicine Knowledge of theology Slide 9 What about Charles Darwin? His education led to his interest in natural history. Resulted in taking part in the second voyage of the Beagle Development of theory of natural selection Slide 10 5

6 Where the Beagle &Darwin Sailed HMS Beagle Slide 11 Darwin s Role in Evolutionary Biology Until about 150 years ago, no accurate explanations for how evolution occurred Humans noticed evolutionary changes for thousands of years, (since human began breeding plants and animals) Plants and animals over thousands of years, selected and bred to produce more seeds or meat or milk - artificial selection Slide 12 6

7 For example! Slide 13 The Crocoduck! (What the?) The CROCODUCK! Poster child for the folks who do NOT understand how evolution works! Heh! Slide 14 7

8 Darwin s Times makes if tough! social climate of time was not always receptive to radical scientific ideas understood he must get other scientists to not automatically reject new and different ideas if his evolution idea was to be accepted Slide 15 And of course all new ideas have their issues Slide 16 8

9 Darwin s Role included Darwin did not invent the idea of evolution but gets most of the credit for explaining how evolution works Understanding people cannot refute the effects of artificial selection (hard data & examples ) Slide 17 Darwin s time: no organized government funding of education and research anyone wanting to conduct research had to be rich, or required rich sponsors a small leap for Darwin to people to accept the idea that nature performs natural selection, only not intentionally Slide 18 9

10 Darwin s Book- part 2 The 2 nd part of his book focused on how nature selects for traits in organisms Darwin called this process natural selection - the basic mechanism bringing about the diversity of life on the earth Slide 19 Darwin s Natural Selection natural selection mechanism had several components Slide 20 10

11 Darwin Observed: All species produce more offspring than are needed to maintain their populations (replace the parents), and not all of the offspring survive In any species, there are differences between individuals that are passed from generation to generation (Inherited genetic variation) Some individuals in a population have more offspring than others Slide 21 Darwin Inferred: Individuals who inherited a set of characteristics that best allowed them to survive in their environment were the ones who had more offspring - Differential reproductive success Because those offspring make up a larger proportion of the next generation, their traits become more common in the next generation Slide 22 11

12 Mice living in White Sands, New Mexico white sand dunes and little vegetation Mice living here come in three colors: Black Gray White Natural Selection An Example Slide 23 Predators easily pick out the black & gray mice on a white background white mice harder to see on the white sands Natural Selection An Example (cont.) Slide 24 12

13 Over time, the majority of the mice who survive and live long enough to reproduce are white (most of the offspring are white) Natural Selection An Example (cont.) Slide 25 Natural Selection An Example (cont.) The white offspring must live long enough to reproduce and pass their white genes on to their offspring Does that mean that "white coat color" is automatically a better color for a mouse? Not if the mouse lives somewhere white is a disadvantage If they are easy to see they become predator lunch duh! Slide 26 13

14 Some Interesting ideas Credit should be jointly shared between Darwin and Alfred Wallace because they came up with a similar theory about natural Selection at the same time Poor forgotten Alfred! Slide 27 Interesting Thoughts what if?? If Darwin had known about Genes and DNA If Darwin had known about Gregor Mendel (genetic work with peas) This means Darwin didn't know how a trait can be passed from parent to offspring About that letter from Alfred Russel Wallace Slide 28 14

15 More Interesting stuff Recent work in the Galápagos Islands says population evolutionary changes occur much faster than Darwin ever suspected For more info: read The Beak of the Finch by Jonathan Weiner Slide 29 More Idea to Ponder Natural selection is not the only mechanism of evolution. It is one of many possible HOWEVER it is the only one that leads to adaptation Lichen spider Slide 30 15

16 Natural Selection some thoughts Evolution is a change in the gene pool of a population over time A population is a group of organisms of the same species that reproduce together Slide 31 Natural Selection happens when there is variation in the DNA of different individuals that is acted on by the environment Slide 32 16

17 So! Last but Not Least Natural Selection & Evolution happen in a population if two conditions are met: 1. Genetic variation 2. Environment pressure that favors one combination of DNA over others Slide 33 Museum of Life: Darwin s Finches Slide 34 17