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Chapter 4

Chapter 4. Evolution and Biodiversity. Chapter 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?

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Chapter 4

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  1. Chapter 4 Evolution and Biodiversity

  2. Chapter 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. Chapter 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. Updates Online The latest references for topics covered in this section can be found at the book companion website. Log in to the book’s e-resources page at www.thomsonedu.com to access InfoTrac articles. • InfoTrac: Life After Earth: Imagining Survival Beyond This Terra Firma. Richard Morgan. The New York Times, August 1, 2006 pF2(L). • InfoTrac: Rhinos Clinging to Survival in the Heart of Borneo, Despite Poaching. US Newswire, March 17, 2006. • InfoTrac: Newfound Island Graveyard May Yield Clues to Dodo Life of Long Ago. Carl Zimmer. The New York Times, July 4, 2006 pF3(L). • NASA: Evolvable Systems • American Museum of Natural History: Tree of Life • PBS: Evolution

  5. Video: Creation Vs. Evolution • This video clip is available in CNN Today Videos for Environmental Science, 2004, Volume VII. Instructors, contact your local sales representative to order this volume, while supplies last.

  6. 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

  7. ORIGINS OF LIFE are either chemical or biological evolution • 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. Chemical Evolution (1 billion years) Biological Evolution (3.7 billion years) Formation of the earth’s early crust and atmosphere Large organic molecules (biopolymers) form in the seas Variety of multicellular organisms form, first in the seas and later on land First protocells form in the seas Single-cell prokaryotes form in the seas Single-cell eukaryotes form in the seas Small organic molecules form in the seas Fig. 4-2, p. 84

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

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

  11. Evolution Types • Microevolution: small changes within a population that give variation within a species dictated by a change in allele frequencies in the gene pool • Gene pool: genes of that population • Allele frequencies: # of genes for traits • Macroevolution: large changes that result in speciation of a species

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

  13. 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

  14. Natural Selection and Adaptations: Leaving More Offspring With Beneficial Traits • Three conditions are necessary for biological evolution: • Genetic variability: DNA must have variances of same traits • Traits must be heritable (passed on) • Trait must lead to differential reproduction. Reproduction of populations who have differing variances of the same trait that are successful

  15. There are three types of selection Stabilizing: The norm is selected while extremes perish Directional: One extreme is selected while one and the norm perish Disruptive: The extremes are selected and the norm perishes

  16. Differential Reproduction in Beetles leads to the survival of the fittest • An adaptive trait is any heritable trait that enables an organism to survive through natural selection and reproduce better under prevailing environmental conditions.

  17. Adaptive Traits are an arms raceCoevolution: 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. Predators become faster and stealthier, while their prey evolves to have other advantages, such as camouflage and speed. • Co-evoltuion also occurs between organisms of symbiotic relationships especially mutualism:Acacia Tree and Ant symbiotic relationship are an example of co-evolution in action

  18. 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

  19. 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. • This change in the genetic makeup of the species is called evolution.

  20. 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.

  21. Contributors to evolution by natural Selection: 1. 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.

  22. 225 million years ago 225 million years ago 135 million years ago 65 million years ago Present Fig. 4-5, p. 88

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

  24. 18,000 years before present Northern Hemisphere Ice coverage Modern day (August) Note: Modern sea ice coverage represents summer months Legend Continental ice Sea ice Land above sea level Fig. 4-6, p. 89

  25. 2. 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.

  26. 3. 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.

  27. 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

  28. Specialist species with a narrow niche Generalist species with a broad niche Niche separation Number of individuals Niche breadth Region of niche overlap Resource use Fig. 4-7, p. 91

  29. 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

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

  31. 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

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

  33. Insect and nectar eaters Fruit and seed eaters Greater Koa-finch Kuai Akialaoa Amakihi Kona Grosbeak Crested Honeycreeper Akiapolaau Maui Parrotbill Apapane Unknown finch ancestor Fig. 4-9, p. 91

  34. SPECIATION, EXTINCTION, AND BIODIVERSITY • Speciation: A new species can arise when member of a population become isolated for a long period of time. • After separation the genetic makeup changes due to selective pressures (density dependent and independent factors) preventing them from producing fertile offspring with the original population if reunited.

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

  36. Adapted to cold through heavier fur,short ears, short legs,short nose. White fur matches snow for camouflage. Arctic Fox Northern population Different environmental conditions lead to different selective pressures and evolution into two different species. Early fox Population Spreads northward and southward and separates Adapted to heat through lightweight fur and long ears, legs, and nose, which give off more heat. Southern Population Gray Fox Fig. 4-10, p. 92

  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: when species disappear at a low rate • as environmental condition slowly change. Rate is 1 -5 species for • each million per year Mass extinction: Significant rise in extinction rates against the bACKGROUND. Typically catastrophic, widespread. There have been 5 • Mass Depletion:High rates but not as high a mass • extinction rates.

  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. Terrestrial organisms Silurian Permian Jurassic Devonian Devonian Cambrian Ordovician Cretaceous Marine organisms Pre-cambrian Carboniferous Number of families Quaternary Tertiary Millions of years ago Fig. 4-13, p. 94

  42. GENETIC ENGINEERING AND THE FUTURE OF EVOLUTIONhttp://listverse.com/2008/04/01/top-10-bizarre-genetically-modified-organisms/ • 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

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

  44. 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

  45. 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

  46. 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

  47. BioPharming • A new field where researchers envision genetically engineered animals to act as biofactories for producing drugs, vaccines, hormones, chemicals, and human body organs

  48. 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

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