Chapter 4 Evolution and Biodiversity
Core Case StudyEarth: The Just-Right, Adaptable Planet • 3.7 billion years since life arose • average surface temperature of the earth has remained within the range of 10-20oC Figure 4-1
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
Animation: Stanley Miller’s Experiment PLAY ANIMATION
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
Animation: Evolutionary Tree of Life PLAY ANIMATION
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 • DNA and protein analysis Figure 4-4
EVOLUTION, NATURAL SELECTION, AND ADAPTATION • Biological evolution by natural selection • 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.
Animation: Stabilizing Selection PLAY ANIMATION
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. • Survival of the Fittest
Animation: Disruptive Selection PLAY ANIMATION
Animation: Moth Populations PLAY ANIMATION
Animation: Adaptive Trait PLAY ANIMATION
Hybridization and Gene Swapping: other Ways to Exchange Genes • Hybridization • Can create new species • Occurs when individuals to two distinct species crossbreed to produce fertile offspring • Some species (mostly microorganisms) can exchange genes without sexual reproduction. • Horizontal gene transfer
Limits on Adaptation through Natural Selection • Changes are limited by the population’s gene pool and how fast it can reproduce. • Humans have a relatively slow generation time (decades) and output (# of young) versus some other species.
Common Myths about Evolution through Natural Selection • Organisms do not develop certain traits because they need them. • There is no such thing as genetic perfection.
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.
225 million years ago 225 million years ago 135 million years ago 65 million years ago Present Fig. 4-5, p. 88
Video: Continental Drift PLAY VIDEO
Climate Change and Natural Selection • Changes in climate throughout the earth’s history have shifted where plants and animals can live. Figure 4-6
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
Video: Dinosaur Discovery PLAY VIDEO • From ABC News, Environmental Science in the Headlines, 2005 DVD.
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.
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.
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
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
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
Specialized Feeding Niches • Resource partitioning reduces competition and allows sharing of limited resources. Figure 4-8
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
Video: Frogs Galore PLAY VIDEO • From ABC News, Environmental Science in the Headlines, 2005 DVD.
Evolutionary Divergence • Each species has a beak specialized to take advantage of certain types of food resource. Figure 4-9
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
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.
Animation: Speciation on an Archipelago PLAY ANIMATION
Animation: Evolutionary Tree Diagrams PLAY ANIMATION
Geographic Isolation • …can lead to reproductive isolation, divergence of gene pools and speciation. Figure 4-10
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
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
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
Effects of Humans on Biodiversity • The scientific consensus is that human activities are decreasing the earth’s biodiversity. Figure 4-13
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
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
Genetic Engineering:Genetically Modified Organisms (GMO) • GMOsuserecombinant DNA • genes or portions of genes from different organisms. Figure 4-14
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
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
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
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
Animation: Transgenic Plants PLAY ANIMATION • From ABC News, Biology in the Headlines, 2005 DVD.
How Would You Vote? To conduct an instant in-class survey using a classroom response system, access “JoinIn Clicker Content” from the PowerLecture main menu for Living In the Environment. • 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.
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.