Darwin and Evolution

1. Darwin and Evolution

2. History of Evolution Prior to Darwin, it was thought that the world was young & species did not change Lamarck (1744-1829) was first to state that descent with modification occurs and that organisms become adapted to their environments

3. Inheritance of acquired characteristics was the Lamarckian belief that organisms become adapted to their environment during their lifetime and pass on these adaptations to their offspring Lamarck believed that the long necks of giraffes evolved as generations of giraffes reached for ever higher leaves; known as the Law of Use & Disuse (later proven to be false)

4. However, because it is supported by so many lines of evidence, evolution is no longer considered a hypothesis Evolution is one of the great unifying theories of biology

5. Darwin's Background & Voyage: In 1831, at the age of 22, Charles Darwin accepted a naturalist position aboard the ship HMS Beagle & began a five-year voyage around the world He read Principles of Geology by Charles Lyell that stated that the observed massive geological changes were caused by slow, continuous processes (erosion, uplifting...)

6. Darwin carried this book with him on his voyage as he witnessed Argentina coast earthquakes raising the earth several feet, & marine shells occurring far inland and at great heights in the Andes Darwin's many observations led him to the idea that species slowly change over time

7. The Galapagos Islands: Volcanic islands off the South American coast Island species varied from the mainland species, and from island-to-island Each island had either long or short necked tortoises depending on the island's vegetation

8. Finches on the Galapagos Islands resembled a mainland finch, but there were more types Bill shapes are adaptations to different means of gathering food. Galapagos finch species varied by nesting site, beak size, and eating habits

9. Darwin's Theory of Evolution: Evolution is a modification of an existing organism that makes a species more successful An adaptation is a trait that helps an organism be more suited to its environment Darwin decided adaptations develop over time Natural selection was proposed by both Alfred Russell Wallace and Darwin as a driving mechanism of evolution Darwin and Wallace both read an essay by Thomas Malthus that proposed that human populations outgrow resources so there is a constant struggle for existence

10. Fitness – combination of physical traits and behaviors that help an organism survive and reproduce Fitness is a measure of an organism's reproductive success Organisms most fit to reproduce are selected by environment which results in adaptation of the population Fitness arises through adaptation – the better adapted then the longer you survive and the more offspring you produce Every organism’s goal is to pass their traits on to the next generation

11. Natural selection is also called "survival of the fittest" (who survives best and reproduces best)

12. Conditions for natural selection include: a. Variations exist among members of a population b. Many more individuals are produced each generation than will survive c. Some individuals are better adapted so they survive longer & reproduce more offspring d. Members of a population compete for food, space, mates...

13. Variations that make adaptation possible are those that are passed on generation to generation Variation in a species is always present As conditions change some individuals have an advantage over others and will survive better and produce more offspring (survival advantage)

14. If an organism has a survival advantage then natural selection is operating on the population; survival of the fittest Eventually 2 organisms of the species will become so different that they can’t reproduce (breed) together creating 2 new species (speciation) Extinction occurs when previous adaptations are no longer suitable to a changed environment

15. On the Origin of Species by Darwin: After the HMS Beagle returned to England in 1836, Darwin waited over 20 years to publish Darwin was forced to publish Origin of Species after reading a similar hypothesis by Alfred Russell Wallace Both men concluded that modern life forms arose by descent from a common ancestor, gradual modification of earlier forms, and that natural selection is the mechanism by which species change and new species arise

16. This does NOT mean that man came from monkey but that man and monkey have a common ancestor Darwin’s disadvantage was he didn’t know of Mendel’s work so he didn’t know mechanism of how traits are passed from parents to offspring

17. Basic Patterns of Evolution: Nature uses survival and reproduction as a means to strengthen a species and let those best adapted survive Natural selection operates on the gene pool Gene pool - all of the genes in a population- Genetic drift – evolution that occurs by random chance

18. Adaptive Radiation (divergent evolution) is where ancestors give rise to a diversity of species (1 species becomes many species) Convergent Evolution is that 2 very different species evolve due to their living conditions to produce species similar in appearance and behavior Coevolution occurs when 2 different species change in response to each other over time

19. Evolution is like a lottery The traits are like the lottery numbers Which traits (numbers) chosen is chance – those traits best suited to the environment Don’t know ahead of time which traits will be best just as you don’t know which numbers will be picked ahead of time You can be a partial winner – the more traits you have the better you survive and reproduce just like the more numbers you get right the more money you win

20. Natural Selection can affect the distribution of phenotypes of a species in three ways Directional selection – individuals at one end of the curve have better fitness than those in the middle or the end of the curve

21. Stabilizing selection – individuals in the middle of the curve have the highest fitness Disruptive selection – individuals at the upper and lower ends of the curve have better fitness than those in the middle

22. Reproductive Isolation For a new species to evolve, populations must become reproductively isolated from each other so that they can’t interbreed and produce fertile offspring There are three ways reproductive isolation can occur

23. Behavioral Isolation Two populations are able to interbreed, but have different behaviors such as courting rituals to attract mates. These individuals don’t recognize the rituals of the other population

24. Geographic Isolation Two populations are capable of interbreeding, but rivers, mountains, or bodies of water may prevent populations from interbreeding. Over time, the two groups change so much that they can no longer interbreed

25. Temporal Isolation Two or more species reproduce at different times so that they are unlikely to reproduce with each other. Eventually they may become two different species.

26. How Does Evolution Occur: Gradualismsays that evolution occurs at a slow and steady rate Punctuated Equilibrium says that evolution occurs in a pattern of long, stable periods interrupted by brief periods of more rapid change Evolution has proceeded at different rates for different organisms (some organisms have remained basically unchanged for millions and billions of years)

27. Evidence Supporting the Theory of Evolution: Biogeographical Evidence: Biogeography is the study of the geographic distribution of life forms on earth Physical factors, such as the location of continents, determine where a population can spread

28. Fossil Record: Fossil record for some organisms is relatively complete and show an evolution of the organism over time Fossil record shows changes in climate and geography (shark teeth found in present day deserts) Layers near the surface are younger than deeper layers

29. Anatomical Evidence: Organisms have anatomical similarities (body structure) when they are closely related because of common descent Homologous structures in different organisms are inherited from a common ancestor have have similar structures Analogous structures are inherited from different ancestors and have come to resemble each other because they serve a similar function Vestigial Organs (Structures) are remains of a structure that is no longer functional but show common ancestry

30. Embryological Evidence: During development there are similar genes at work among different species All vertebrates have a post-anal tail and paired pharyngeal pouches Organisms that show similarities in their embryonic development may have a common ancestry (due to hox genes)

31. Biochemical Evidence: Almost all living organisms use the same basic biochemical molecules, e.g., DNA, ATP, enzymes ... Similarities in amino acid sequences, DNA codes, shared proteins, etc. can be explained by descent from a common ancestor High number of genes shared in similar groups Orderly addition of genes as organisms develop from the simple to the complex

32. Examples of Evolution in Modern Times: Insect resistance to insecticides Bacterial resistance to antibiotics