Charles Darwin and Natural Selection Notes. Biology - Ms. Spinale/Mrs. Kaye

Transcription

1 Charles Darwin and Natural Selection Notes Biology - Ms. Spinale/Mrs. Kaye

2 Charles Darwin In 1831, Charles Darwin set sail on the HMS Beagle. He was 22 years old. His journey lasted for 5 years. He collected thousands of specimens and observations around South America, Antarctica, and Australia.

3 Charles Darwin He noticed that organisms that lived in temperate areas of South America were more similar to organisms living in tropical areas of South America than to organisms living in temperate areas of Europe.

4 Charles Darwin He spent 20 years analyzing his data and published a book titled, On the Origin of Species.

5 Descent with Modification Darwin s idea that all organisms on Earth are related through descent from some unknown ancestral type that lived long ago.

6 Descent with Modification

7 Alfred Wallace vs. Charles Darwin Wallace mailed Darwin a draft that described the theory of evolution in Darwin worked feverishly for almost a year and published his book in 1859.

8 Alfred Wallace vs. Charles Darwin Darwin is considered to be the, Father of Evolution, over Wallace because, Darwin s explanations were more detailed. Darwin s explanations contained extensive supporting evidence. Darwin s journals showed that he had been working for at least 15 years.

9 Evolution by Natural Selection Observations: There is a lot of variation within species. Examples of variation include size, coloration, strength, behavior, etc. Some of these variations get passed on. Variations - differences in inherited traits.

10 Evolution by Natural Selection All individuals within a population are not exactly the same. Example: some zebras are faster than others. Variations arise through mutations. Mutation - a change in the genetic code (DNA) that may result in a hereditary change in a characteristic.

11 Evolution by Natural Selection Many mutations have no negative effects. Example: eye color. Mutations are caused by a variety of things...to be discussed later.

12 Selective Breeding Darwin figured that if humans can bring about change in populations, maybe nature can also bring about changes. Change eventually might lead to new species.

13 Selective Breeding

14 Selective Breeding

15 Galapagos Island Darwin studied two finches. The medium ground finch and the cactus finch. His study lasted 12 years. He recorded body and beak sizes. During this time, there were two extreme dry spells and many finches died.

16 Galapagos Island The finches that survived had larger beaks that were thicker than before.

17 Galapagos Island Those with larger/thicker beaks were better able to eat the hard, dry seeds left by the drought.

18 Species Species - a group of organisms whose members very closely resemble each other because they share many key characteristics. Individuals of the same species have the ability to mate and produce fertile offspring.

19 Species Population - a group of organisms of the same species.

20 Infertiles Ligers and mules are not considered their own species because they are infertile; they cannot mate and produce offspring.

21 Darwin s Theory If there are no limits to population growth, organisms will produce very rapidly. This includes an unlimited supply of water, food, and space, and no disease or predators.

22 Darwin s Theory Darwin decided that it is true that all organisms deal with this struggle. Some make it and pass on their traits through reproduction, and others die and do not reproduce. This keeps the population constant.

23 Darwin s Theory Individuals within a population have small differences, called variations, that can be inherited. These differences may decide which organisms survive and which ones die because of their fit into the environment.

24 Adaptations Adaptation - the beneficial inherited traits that allow some members of a population to survive and reproduce. If an organism doesn t have the adaptation, then they are less likely to survive and reproduce (so their traits are not passed on).

25 Adaptations Organisms do not acquire these characteristics to help them survive. Organisms are simply lucky enough to have been born with a better version that fits the environment in which they live.

26 Adaptations Individuals do not evolve, populations evolve. If the change is big enough, it can be recognized as a distinct new species, different from its ancestral form.

27 Selective Pressures - Competition Plants and animals have to compete with each other for limited resources. Example: plants in the jungle. All need sunlight, water, and nutrients. Those that are able to get these things more efficiently will pass on their genetics to the next generation.

28 Selective Pressures - Competition The difference in ability to compete with limited resources leads to evolution.

29 Selective Pressures - Competition

30 Selective Pressures - Predation Predation forces both predators and prey to adapt to survive. This results in a constant battle between both sides. Predators must use strong characteristics to eat.

31 Selective Pressures - Predation Prey must use strong characteristic to flee. Both get passed down on both sides of the war.

32 Selective Pressures - Other Space. Food/water. Disease. Climate/weather. Human impact (hunting, pollution).