Evolution and Biodiversity

1. Evolution and Biodiversity

2. Overview Questions • How do scientists account for the development of life on earth? • What is biological evolution by natural selection, and how can it account for the current diversity of organisms on the earth? • How can geologic processes, climate change and catastrophes affect biological evolution? • What is an ecological niche, and how does it help a population adapt to changing the environmental conditions?

3. Overview Questions (cont’d) • How do extinction of species and formation of new species affect biodiversity? • What is the future of evolution, and what role should humans play in this future? • How did we become such a powerful species in a short time?

4. Rest assured, you are not alone!

5. Core Case StudyEarth: The Just-Right, Adaptable Planet • During the 3.7 billion years since life arose, the average surface temperature of the earth has remained within the range of 10-20oC. Figure 4-1

6. In the Beginning…according to Science • Chemical Evolution- (hypothesis) the first organic (life forming) molecules formed from inorganic molecules and energy; formed protocells • Lightening; Heat (geothermal); Radiation (UV-sun) • Produced by Stanley Miller and Harold Urey • Biological Evolution-the change in a populations’ genetic make-up through successive generations (takes time; not on an individual basis) • Evidence from fossils (comparative anatomy) and DNA

7. ORIGINS OF LIFE • 1 billion years of chemical change to form the first cells, followed by about 3.7 billion years of biological change. Figure 4-2

8. Biological Evolution • This has led to the variety of species we find on the earth today. Figure 4-2

9. Modern humans (Homo sapiens sapiens) appear about 2 seconds before midnight Recorded human history begins about 1/4 second before midnight Age of mammals Age of reptiles Insects and amphibians invade the land Origin of life (3.6-3.8 billion years ago) First fossil record of animals Plants begin invading land Evolution and expansion of life Fig. 4-3, p. 84

10. How Do We Know Which Organisms Lived in the Past? • Our knowledge about past life comes from fossils, chemical analysis, cores drilled out of buried ice, and DNA analysis. Figure 4-4

11. EVOLUTION, NATURAL SELECTION, AND ADAPTATION • Biological evolution by natural selection involves the change in a population’s genetic makeup through successive generations. • genetic variability • Mutations: random changes in the structure or number of DNA molecules in a cell that can be inherited by offspring.

12. The Theory Evolution • Evolution Theory- the idea that all species descended from earlier, ancestral species • Explains HOW life has changed and why life is so diverse • Gene Pool- a populations’ genetic make-up (all the genes found in the individuals in a population) • Microevolution- small genetic changes that occur in a population • Macroevolution- long-term, large scale changes; cause 2 outcomes: • New species are formed from ancestral species • Other species are lost through extinction

13. How Evolution Occurs • Mutation- a random change in the structure (alleles) or number of DNA molecules in a cell; 99% fatal; • Mutagens-radiation (gama, x-ray, UV) or natural or man-made chemicals • Abnormalities- mistakes made during the copy process when cells divide or during reproduction • Natural Selection- the process through which some individuals exhibit traits that increase their chances of survival and ability to produce offspring; 3 required conditions • Variability of trait in species • Must be heritable, able to be passed from one generation to another • Differential Reproduction- increase the number of offspring or survivability of offspring of an individual

14. Adaptation • Natural Selections Causes (1) alleles or sets of alleles that are beneficial to become more common in successive generations and (2) other less beneficial alleles to become less common • Adaptation- the improved ability of an organism to survive and reproduce; a specific trait that increases these chances is called and adaptive trait; often caused by the environment and do one of the following: • Species adapt through natural selection • Migrate to another area • Become extinct

15. Natural Selection and Adaptation: Leaving More Offspring With Beneficial Traits • Three conditions are necessary for biological evolution: • Genetic variability, traits must be heritable, trait must lead to differential reproduction. • An adaptive trait is any heritable trait that enables an organism to survive through natural selection and reproduce better under prevailing environmental conditions.

16. Directional Selection Average New average Previous average Snail coloration best adapted to conditions Natural selection Number of individuals Number of individuals Average shifts Coloration of snails Coloration of snails Directional Natural Selection Proportion of light-colored snails in population increases

17. Stabilizing Selection Stabilizing Natural Selection Natural selection Dark snails eliminated Light snails eliminated Snails with extreme coloration are eliminated Number of individuals Number of individuals Coloration of snails Coloration of snails Average remains the same, but the number of individuals with intermediate coloration increases

18. Disruptive Selection Diversifying Natural Selection Intermediate-colored snails are selected against Snails with light and dark colors dominate Natural selection Light coloration is favored Dark coloration is favored Number of individuals Number of individuals Coloration of snails Coloration of snails Number of individuals with light and dark coloration increases, and the number with intermediate coloration decreases

19. Fig. 5-5 p. 101 Natural Selection • Coevolution- the hypothesis that the population of two interacting species (over a long-term) can cause changes in the gene pool that affect changes in the gene pool of the other species

20. Coevolution: A Biological Arms Race • Interacting species can engage in a back and forth genetic contest in which each gains a temporary genetic advantage over the other. • This often happens between predators and prey species.

21. Hybridization and Gene Swapping: other Ways to Exchange Genes • New species can arise through hybridization. • Occurs when individuals to two distinct species crossbreed to produce an fertile offspring. • Some species (mostly microorganisms) can exchange genes without sexual reproduction. • Horizontal gene transfer

22. Limits on Adaptation through Natural Selection • A population’s ability to adapt to new environmental conditions through natural selection is limited by its gene pool and how fast it can reproduce. • Humans have a relatively slow generation time (decades) and output (# of young) versus some other species.

23. Common Myths about Evolution through Natural Selection • Evolution through natural selection is about the most descendants. • Organisms do not develop certain traits because they need them. • There is no such thing as genetic perfection.

24. GEOLOGIC PROCESSES, CLIMATE CHANGE, CATASTROPHES, AND EVOLUTION • The movement of solid (tectonic) plates making up the earth’s surface, volcanic eruptions, and earthquakes can wipe out existing species and help form new ones. • The locations of continents and oceanic basins influence climate. • The movement of continents have allowed species to move.

25. 225 million years ago 225 million years ago 135 million years ago 65 million years ago Present Fig. 4-5, p. 88

26. Climate Change and Natural Selection • Changes in climate throughout the earth’s history have shifted where plants and animals can live. Figure 4-6

27. Catastrophes and Natural Selection • Asteroids and meteorites hitting the earth and upheavals of the earth from geologic processes have wiped out large numbers of species and created evolutionary opportunities by natural selection of new species.

28. ECOLOGICAL NICHES AND ADAPTATION • Each species in an ecosystem has a specific role or way of life. • Fundamental niche: the full potential range of physical, chemical, and biological conditions and resources a species could theoretically use. • Realized niche: to survive and avoid competition, a species usually occupies only part of its fundamental niche.

29. Generalist and Specialist Species: Broad and Narrow Niches • Generalist species tolerate a wide range of conditions. • Specialist species can only tolerate a narrow range of conditions. Figure 4-7

30. SPOTLIGHTCockroaches: Nature’s Ultimate Survivors • 350 million years old • 3,500 different species • Ultimate generalist • Can eat almost anything. • Can live and breed almost anywhere. • Can withstand massive radiation. Figure 4-A

31. Specialized Feeding Niches • Resource partitioning reduces competition and allows sharing of limited resources. Figure 4-8

32. Avocet sweeps bill through mud and surface water in search of small crustaceans, insects, and seeds Ruddy turnstone searches under shells and pebbles for small invertebrates Herring gull is a tireless scavenger Brown pelican dives for fish, which it locates from the air Dowitcher probes deeply into mud in search of snails, marine worms, and small crustaceans Black skimmer seizes small fish at water surface Louisiana heron wades into water to seize small fish Piping plover feeds on insects and tiny crustaceans on sandy beaches Oystercatcher feeds on clams, mussels, and other shellfish into which it pries its narrow beak Flamingo feeds on minute organisms in mud Scaup and other diving ducks feed on mollusks, crustaceans,and aquatic vegetation Knot (a sandpiper) picks up worms and small crustaceans left by receding tide (Birds not drawn to scale) Fig. 4-8, pp. 90-91

33. Evolutionary Divergence • Each species has a beak specialized to take advantage of certain types of food resource. Figure 4-9

34. SPECIATION, EXTINCTION, AND BIODIVERSITY • Speciation: A new species can arise when member of a population become isolated for a long period of time. • Genetic makeup changes, preventing them from producing fertile offspring with the original population if reunited.

35. Speciation, Extinction, and Biodiversity • Speciation • Geographic isolation • Reproductive isolation

36. Geographic Isolation • …can lead to reproductive isolation, divergence of gene pools and speciation. Figure 4-10

37. Extinction: Lights Out • Extinction occurs when the population cannot adapt to changing environmental conditions. • The golden toad of Costa Rica’s Monteverde cloud forest has become extinct because of changes in climate. Figure 4-11

38. Extinction • Background extinction- due to environmental changes; occurs slowly • Mass extinction- catastrophic and or widespread; • Adaptive radiation- occurs just after a mass extinction when many niches are available in the changed environment

39. Species and families experiencing mass extinction Bar width represents relative number of living species Millions of years ago Era Period Extinction Current extinction crisis caused by human activities. Many species are expected to become extinct within the next 50–100 years. Quaternary Today Cenozoic Tertiary Extinction 65 Cretaceous: up to 80% of ruling reptiles (dinosaurs); many marine species including many foraminiferans and mollusks. Cretaceous Mesozoic Jurassic Extinction Triassic: 35% of animal families, including many reptiles and marine mollusks. 180 Triassic Extinction Permian: 90% of animal families, including over 95% of marine species; many trees, amphibians, most bryozoans and brachiopods, all trilobites. 250 Permian Carboniferous Extinction 345 Devonian: 30% of animal families, including agnathan and placoderm fishes and many trilobites. Devonian Paleozoic Silurian Ordovician Extinction 500 Ordovician: 50% of animal families, including many trilobites. Cambrian Fig. 4-12, p. 93

40. Effects of Humans on Biodiversity • The scientific consensus is that human activities are decreasing the earth’s biodiversity. Figure 4-13

41. GENETIC ENGINEERING AND THE FUTURE OF EVOLUTION • We have used artificial selection to change the genetic characteristics of populations with similar genes through selective breeding. • We have used genetic engineering to transfer genes from one species to another. Figure 4-15

42. Genetic Engineering:Genetically Modified Organisms (GMO) • GMOsuserecombinant DNA • genes or portions of genes from different organisms. Figure 4-14

43. Phase 1 Make Modified Gene E. coli Genetically modified plasmid Insert modified plasmid into E. coli Cell Extract Plasmid Extract DNA Plasmid Gene of interest DNA Remove plasmid from DNA of E. coli Identify and remove portion of DNA with desired trait Insert extracted (step 2) into plasmid (step 3) Identify and extract gene with desired trait Grow in tissue culture to make copies Fig. 4-14, p. 95

44. Phase 2 Make Transgenic Cell A. tumefaciens (agrobacterium) Foreign DNA E. Coli Host DNA Plant cell Nucleus Transfer plasmid copies to a carrier agrobacterium Agrobacterium inserts foreign DNA into plant cell to yield transgenic cell Transfer plasmid to surface of microscopic metal particle Use gene gun to inject DNA into plant cell Fig. 4-14, p. 95

45. Phase 3 Grow Genetically Engineered Plant Transgenic cell from Phase 2 Cell division of transgenic cells Culture cells to form plantlets Transfer to soil Transgenic plants with new traits Fig. 4-14, p. 95

46. Transgenic cell from Phase 2 Cell division of transgenic cells Culture cells to form plantlets Transfer to soil Transgenic plants with new traits Phase 3 Grow Genetically Engineered Plant Stepped Art Fig. 4-14, p. 95

47. How Would You Vote? • Should we legalize the production of human clones if a reasonably safe technology for doing so becomes available? • a. No. Human cloning will lead to widespread human rights abuses and further overpopulation. • b. Yes. People would benefit with longer and healthier lives.

48. THE FUTURE OF EVOLUTION • Biologists are learning to rebuild organisms from their cell components and to clone organisms. • Cloning has lead to high miscarriage rates, rapid aging, organ defects. • Genetic engineering can help improve human condition, but results are not always predictable. • Do not know where the new gene will be located in the DNA molecule’s structure and how that will affect the organism.

49. Controversy Over Genetic Engineering • There are a number of privacy, ethical, legal and environmental issues. • Should genetic engineering and development be regulated? • What are the long-term environmental consequences?

50. Case Study:How Did We Become Such a Powerful Species so Quickly? • We lack: • strength, speed, agility. • weapons (claws, fangs), protection (shell). • poor hearing and vision. • We have thrived as a species because of our: • opposable thumbs, ability to walk upright, complex brains (problem solving).