Evolution Chapter 4 How Did We Become Such a Powerful Species So Quickly? 3 Main Adaptive Traits Opposable Thumbs Ability to Walk Upright Intelligence (Complex Brains) Fig. 4-1, p. 63 How Do We Know Which Organisms Lived in the Past? Fossil record Radiometric dating Ice cores DNA studies Fig. 4-2, p. 65 Origins of Life Considerable evidence suggests that life developed in 2 phases over the past 4.6-4.7 billion years. Chemical evolution (1 billion yrs) Biological evolution (3.7 billion years) Question #1: What is biological evolution by natural selection, and how has it led to the current diversity of organisms on earth? Include the importance of variation within the gene pool and mutation on microevolution and how this relates to adaptations. Biological Evolution Biological Evolution Theory of Evolution • Microevolution Mutations Natural Selection 1) 2) 3) Variation exists for a trait Traits is heritable – can be passed on to offspring Individuals w/ trait are better able to survive, reproduce & spread the trait In a polluted environment… Adaptations Natural selection works on individuals, Evolution occurs in populations! Adaptations Coevolution How microevolution occurs… Genes mutate, Individuals are selected, and Populations evolve! Question #2: How does the formation of new species (speciation) and extinction of species affect biodiversity? Explain the mechanism of speciation and how this increases biodiversity. Macroevolution Speciation • Increases biodiversity Extinction • Decreases biodiversity Speciation – Extinction = Current Biodiversity Mechanism of Speciation Geographic Isolation • 2 groups from same species become physically separated for long time period Reproductive Isolation • Mutation & natural selection act on separated populations • Each group adapts to different environmental conditions • Over time, leads to formation of 2 new species Geographic Isolation can Lead to Speciation Arctic Fox Northern population Early fox population Spreads northward and southward and separates Adapted to cold through heavier fur, short ears, short legs, short nose. White fur matches snow for camouflage. Different environmental conditions lead to different selective pressures and evolution into two different species. Gray Fox Southern population Adapted to heat through lightweight fur and long ears, legs, and nose, which give off more heat. Fig. 4-7, p. 71 Question #3: Define ecological niche. Distinguish between fundamental niche and realized niche. List the factors that determine the realized niche. Ecological Niches and Adaptation Ecological Niche (Occupation) Habitats (Address) Fundamental Niche Realized Niche Question #4: Distinguish between a specialist and a generalist. Evaluate the conditions that favor these two approaches. Generalist Species Broad Niches • can live in many places • can eat a variety of foods • can tolerate a wide range of environmental conditions Cockroaches: Nature’s Ultimate Survivors Fig. 4-A, p. 69 Specialist Species Occupy narrow niches (may only have 1 possible habitat) • use few food types • can only tolerate a narrow range of environmental conditions • more prone to extinction when environment changes • reduces competition & allows for sharing of limited resources Specialized Feeding Niches for Birds Black skimmer seizes small fish at water surface Scaup and other diving ducks feed on mollusks, crustaceans, and aquatic vegetation Flamingo feeds on minute organisms in mud Herring gull is a tireless scavenger Brown pelican dives for fish, which it locates from the air Avocet sweeps bill through mud and surface water in search of small crustaceans, insects, and seeds Louisiana heron wades into water to seize small fish Dowitcher probes deeply into mud in search of snails, marine worms, and small crustaceans Oystercatcher feeds on clams, mussels, and other shellfish into which it pries its narrow beak Ruddy turnstone searches under shells and pebbles for small invertebrates Knot (a sandpiper) picks up worms and small crustaceans left by receding tide Piping plover feeds on insects and tiny crustaceans on sandy beaches If resources are limited, natural selection favors specialized species. Evolutionary Divergence of Honeycreepers Fruit and seed eaters Insect and nectar eaters Greater Koa-finch Kuai Akialaoa Amakihi Kona Grosbeak Crested Honeycreeper Akiapolaau Maui Parrotbill Unknown finch ancestor Apapane Fig. 4-6, p. 70 Broad and Narrow Niches Generalist species • Better able to survive rapidly changing environmental conditions Specialist species • Benefit under constant environmental conditions (reduces competition) Number of individuals Niches of Specialist and Generalist Species Specialist species with a narrow niche Niche separation Generalist species with a broad niche Niche breadth Region of niche overlap Resource use Fig. 4-4, p. 68 Limits on Adaptation A population’s ability to adapt is limited by it’s gene pool & the speed with which it can reproduce Natural selection can only work on currently existing traits (beneficial adaptations are rare) Rapid reproducers are able to adapt much more quickly to changes in environment Question #5: How is “survival of the fittest” different from the idea of “progress to perfection”? Evolution Misconceptions Survival of the “fittest” refers to reproductive success – not strength! Evolution doesn’t lead to genetic perfection, just works to select for best traits for the current environmental conditions. • Organism best suited to environment, survives & reproduces. Helpful traits are then passed on! Question #6: How can genetic engineering affect our ecosystems? Future of Evolution Genetic Engineering (gene splicing) Genetically Modified Organisms (GMOs) Ethical concerns Ecological Lesson Whenever we intervene in nature, we must pause & ask “What happens next?” Evaluate possible unintended consequences of biotechnology.