Evolution

1. Evolution

2. General complexity over time • Fossils resembling clams and shrimp fish  to lizardlike creatures on land  birds  mammals • When animals die, they eventually are covered by a mudslide, and then over time sedimentary rock – layers of minerals and fragments of other rocks deposited over time, covers them.

3. Rocks and Fossils • The older the rocks, the older and more primitive are the animals discovered within them. • Exist as fossils – preserved remnants of a once-living thing. • Gaps in fossil record because fossils usually form in water, not on land • The most common are impressions left in sedimentary rocks, but no always. i.e. woolly mammoths found in glaciers

4. Sidebar: Bringing the Mammoth Back • It is possible to take the DNA of a mammoth and implant it into an elephant egg and give birth to a live mammoth again. Coming soon…same as dodo bird. • http://news.nationalgeographic.com/news/2005/04/0408_050408_woollymammoth.html • “Let’s cuddle” 

5. History of Life on Earth • Earth is 4.6 billion years old • Geologists divide history into four units of time called eras, which are subdivided into periods and epochs • Most bottom rocks are oldest – ones at the top are youngest

7. Radioactive Dating • More accurate way of dating fossils and rocks • Some elements are radioactive and break down at predictable rates called the half-life of an element – the amount of time it takes for one half of the radioactive atoms to disintegrate • i.e. half-life of uranium is 700 million years – breaks down to lead i.e if we have a sample with 25% uranium and 75% lead, 1.4 billion years have passed.

8. The Origin of Life • Pre-photosynthetic organisms, atmosphere likely was composed of CH4, NH3, H2, and H2O vapour • Rains and comets fell on barren rocks forming oceans

9. The Origin of Life • Planet bombarded with energy from ultraviolet light and lightning

10. The Origin of Life • This energy rearranged the chemical bonds of molecules in the atmosphere, creating a large number of organic chemicals built up in the primitive oceans over millions of years.

11. The Origin of Life • HETEROTROPH HYPOTHESIS: Originated by A.I Oparin in 1930’s, stating that the first organisms used organic molecules in the ocean as a food source. • fossil microbe-like objects are dated to be 3.5 billion years old. • Photosynthesis is 2.4 billion years old

12. Stanley Miller Experiment • Early 1950’s – after several days, electricity applied to these gases produced amino acids, the building blocks of proteins. • Proved organic molecules could form from inorganic substances, though not proof how first cell came to being

13. Abiogenesis  • Also known as biopoesis: study of how life arose from inanimate matter • Major question: Which came first, proteins or nucleic acid? • Phospholipids form bilayers in water while under agitation– the same structure as in cell membrane

14. The Origin of Autotrophs • Autotroph: orgainism which makes its own food • First organisms were heterotrophs and anaerobic • As food became scarce, organims that produced own food from sunlight were favoured • Then, as photosynthetic organisms arose, some heterotrophs would start using them as a food source • Oxygen released into atmosphere from autotrophs meant change in atmosphere, and therefore allowing aerobic respiration which releases far more energy than anaerobic respiration

15. Multicellular Organisms • First autotrophs and heterotrophs were single-celled • 570 million year old fossils rare • Fossils younger than this show fossils from all major groups of animals and many groups of plants that are alive today • Worms, corals, shelled animals like clams, animals resembling lobsters, crabs and relatives of today’s starfish

16. Why did they appear so fast? • One hypothesis is that earlier organisms had soft bodies that did not fossilize easily, so it only appears quick • Cambrian Explosion 530 million years ago • Fossil record shows evidence of groups of organisms that became common than became extinct. This historically is the norm – 99% of all things that have ever lived are extinct

17. Extinct

19. Dinosaurs • Roamed for about 200 million years • Died about 60-65 million years ago – most popular theory is an asteroid impact, but could be a combination of other factors as well i.e. volcanic activity, ice age, disease • Scientists have described over 1.7 million of the world's species of animals, plants and algae, as of 2010. • Thought to be 4 to 6 million on earth • http://www.scienceagogo.com/news/20020328223914data_trunc_sys.shtml

20. Theories of Evolution • Until 19th century, people were puzzled by fossils of organisms • Most scientists thought things were distinct and unchanging • Dinosaurs and woolly mammoths could not be explained

21. Jean de Baptiste Lamarck • French naturalist – observations of fossils challenged the common idea that species were fixed types – organisms change through time 1798

22. Jean de Baptiste Lamarck • In 1809, proposed that organisms evolved in response to their environment • Evolve: change from one form to another • First to suggest that animals undergo evolution.

23. Jean de Baptiste Lamarck • Explained two facts: • 1) The fossil record: showed that organisms in the past were different from those living from today • 2) explained why each organism was so well adapted to their environment – organisms ha • Explained two facts: • 1) The fossil record: showed that organisms in the past were different from those living from today • 2) explained why each organism was so well adapted to their environment – organisms have adaptations that suit their particular way of life

24. Jean de Baptiste Lamarck • Explained a mechanism: • Animals have acquired characteristics - the traits that an organism has acquired throughout its lifetime are passed down to their offspring. • For example, if a parent learned to play piano, their child would be born knowing how to play piano • Giraffes have aquired longer necks over time by stretching to reach taller trees. • Even scientists then did not believe him: EPIC FAIL! We now know we have genes, and that new traits are only passed on by on by random, rare mutations

25. Jean de Baptiste Lamarck • They didn’t believe him that species gradually changed through the ages, and on that, they were wrong, not Lamarck

26. DARWIN: DA MAN!!! • 50 years after Lamarck • 1859 wrote on The Origin of Species by Means of Natural Selection • Also stated living things gradually evolve adaptations to the environment • Difference was in the mechanism

27. Charles “Da Man” Darwin • Unlike Lamarck, Darwin recognized the variations among members of a species which are inherited • Natural selection: process by which heritable traits that make it more likely for an organism to survive and successfully reproduce become more common in a population over successive generations.

28. Natural selection • Realized that most organisms produce more offspring that can survive. • There is competition amongst offspring to survive, whether plant or animal, which results in the survival of only a few • Only those organisms most suited for the environment survive to produce offspring “survival of the fittest”

29. Summarizing Natural Selection • 1) Species have the ability to produce a large number of offspring • 2) The resources of the natural world are limited • 3) Therefore, there must be competition for survival among the offspring in each generation • 4) There is great variability within populations of organisms. No two organisms are the same. Much of the variability/variety is inherited • 5) The organisms that survive and produce offspring are those that have inherited the most beneficial traits for surviving in that particular environment • 6) As this process continues through many generations, the population gradually becomes better adapted to the environment

30. Key Points • Variations in a population occur randomly. • They do not arise in response to the environment • Natural selection “selects” from among those traits that already exist within the gene pool.

31. What Darwin didn’t know • Didn’t know about genetics. • Didn’t know about Mendel…the monk’s work was available but remember, no one read it • We now know about random mutations and that they arise “INDEPENDENTLY” of an organism’s needs • Usually they are not useful, but sometimes they are • Only those that are useful will increase an organisms chance of survival

32. TONIGHT’S HOMEWORK • Look over these notes. Summarize the key points.

33. Comparing Darwin and Lamarck • A cheetah’s speed – both would say it’s because of EVOLUTION but: • LAMARCK: “As cheetahs run after their prey, they developed strong legs, which were then passed down to future generations” • DARWIN: “No, you putz, natural selection acted upon variation in the cheetah population. Within the population, some cheetahs had the ability (from birth) to run faster than others, and since it helped them catch prey better, they were able to live to produce offspring and pass the genes onward.

34. Comparing Darwin and Lamarck • The biggest difference is when variation occurs in a population. For Lamarck variations come about as a result of a change in the environment. As prey runs faster, the evolves greater speed. • For Darwin, variations exists independently of the environment, not in response to environmental conditions

35. Evidence of Evolution • Fossils proved that species existed in the past that do not exit now • However, most evolution is slow, and hard to observe

36. Evidence from Structure • Homologous structures: structures with different functions but common ancestry • i.e bird wing and dog arm – still very similar in structure

37. Evidence from Structure • Vestigial Organs: small or incomplete organs that have no apparent function • Remaining parts of once-functioning organs – of a previous ancestor • Whales evolved from four legged ancestor – hip and femur still resides, though not used. Neither affects reproduction of whale either, thus, carries on in future generations Whale

38. Evidence from Embryology • Embryo: a developing organism • Embryology: study of the development of an organism • Developmental stages of many animals look similar…hence proof of common ancestor • The more closely related the species, the more similar embryological patterns shared by organisms

39. Embryology from Biochemistry and Genetics • Genetic code, DNA, is used to code for proteins • A universal genetic code is consistent with the idea that all organisms evolved from a single organism that used that code. • Biochemists compare amino-acid sequences of proteins found in different organisms • More similar organisms – more similar amino-acid sequences and vice versa

40. Observed in Nature • Peppered moths in 1850’s England used to be white to blend with trunks – rarely saw black ones. • With industry in 1900’s, industry darkened tree trunks, black moths started out competing white moths – invisible to predators • Since pollution controls, white moths are making a comeback

41. Observed in Nature • Evidence that a species of fireweed formed by doubling of the chromosome count, from the original stock. • 1989 issue of Scientific American. It's called "A Breed Apart." It tells about studies conducted on a fruit fly, Rhagoletis pomonella, that is a parasite of the hawthorn tree and its fruit, which is commonly called the thorn apple. About 150 years ago, some of these flies began infesting apple trees, as well. The flies feed and breed on either apples or thorn apples, but not both. There's enough evidence to convince the scientific investigators that they're witnessing speciation in action.

42. Controversy • Many people still don’t believe in evolution • They may believe in Intelligent Design or Creationism • The Scopes Monkey trial was the OJ trial of its time. Happened in 1925, it discussed the issue of teaching evolution in school. Involved agnostic defence lawyer Clarence Darrow (thought to be one of the best in history) against five time (failed) Democratic nominee for president William Jennings Bryan (he died five days after winning) • A great movie/book on this topic, though dramatic and a tad inaccurate, is called Inherit the Wind. See the Spencer Tracy version.

43. The Process of Evolution • Evolution tends to work slowly over time • Changes in traits happen through random mutation – this mutation only has chance of staying in the population if it does not negatively affect the ability of the animal to pass on its genes • Over time, natural selection can alter gene frequencies

44. Speciation • Means the formation of new species • Species: a taxonomic rank (the basic rank of biological classification) whose members can interbreed to produce fertile offspring

45. Speciation • Often happens when a population becomes isolated from the rest through geographic isolation: a physical barrier separates a population • No two environments are identical, so selective pressures that occur in one location may be different from the pressures in another location

46. Abert squirrel and Kaibab squirrel • Live on opposite sides of the Grand Canyon • Once part of same population before Colorado River took a separate course 1 million years ago, splitting it in two

47. Abert squirrel and Kaibab squirrel • Different characteristics favoured each on both sides of the canyon • Finally became two different species, where they could no longer interbreed • A.S • K.S

48. Reproductive Isolation • When species which live in the same area breed at different times of the year • i.e. toad species Bufo americanus and Bufo fowleri . The members of these species can be successfully crossed in the laboratory producing healthy, fertile hybrids. However, mating does not occur in the wild even though the geographical distribution of the two species overlaps B.A B.F

49. Adaptive Radiation • When many new species evolve from a single ancestral species • Often occurs when a species enters a new environment where there are few other competing species

50. Adaptive Radiation • i.e. finches in the Galapagos Islands: volcanic islands that lie 1000 km west of South America • Darwin visited them when he was young • Each island was distinct from the other, hence the single species of finch which inhabited each island eventually diverged to different species with differing beaks, feeding habits and behaviours adapted to the local food