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Transcript
Chapter 4 4-1 origins of life. Key Concepts Origins of life- Life started about 3.7 billion years ago. Evolution and evolutionary processes: Micro (small genetic changes) and Macro (long-term, species wide changes) Ecological niches: Species adapting to a specific role in their ecosystem. Species formation: Unique adaptations of small populations. Species extinction: a failure to adapt. Biological Evolution of Life Modern humans (Homo sapiens) appear about 2 seconds before midnight Recorded human history begins 1/4 second before midnight Origin of life (3.6–3.8 billion years ago) Fig. 4-3, p. 66 Biological Evolution Evolution: Change in the genetic make-up of a population over time. Theory of evolution: Life comes from life. All species descended from ancestral species. Microevolution: occurs on a genetic level. Mutations are either advantageous or deleterious. Macroevolution: Successive changes over generations of a population. Microevolution Gene pool: All the genes in an individual. Genetic variability: Genetic diversity amongst a population. Allows for adaptation, key to population survival. Mutations: Random changes in the structure of DNA. Can be advantageous or deleterious. Mutagens: capable of changing DNA. Radiation, certain chemicals. Cigarettes… Natural selection: Certain populations having traits that allow them to be more successful than others. Natural Selection Differential reproduction: Some species reproduce better than others (competitive). Adaptation (adaptive trait): Heritable trait that allows an organism to survive and reproduce. Coevolution: Biological Arms Race. Species gaining a temporary genetic advantage over competitors. Ecological Niches and Adaptation Ecological niche: Species way of life or functional role in an ecosystem. Habitats: Physical location of a species. Fundamental niche: Potential range of a species. Resources it could use. Realized niche: What it does use. Broad and Narrow Niches and Limits of Adaptation Generalist species: broad niches. Variety of potential foods and habitats. Rats, roaches, coyotes, catfish. Specialist species: Very adapted. Limited foods and niches. Pandas, red cockaded woodpeckers… Limits of adaptation: Gene pool, and reproduction speed. 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 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 Fig. 4-5, p. 68-69 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 Misconceptions of Evolution “Survival of the fittest”: Reproductive strength, not individual health. “Progress to perfection” More evolved does not mean better, in fact, the loss of traits often leads to extinction. Speciation What is speciation? -A new species arises when members of one population are isolated. Geographic isolation: members of one population become physically isolated from the other. Reproduction isolation: Members of the separated population can no longer interbreed with the original population. 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 Factors Leading to Extinction Plate tectonics Climatic changes over time Ice ages. Droughts Natural catastrophes Sinking/uplifting Volcanos Meteors Human impacts Habitat degradation Invasive species Extinctions Background extinctions Species disappearing a low rate, mainly by “Natural Causes”. 99.9% of all species. Mass extinctions: Rise in extinction rates above the background level. Mass depletions: High rates, but not that high. Human impacts: During the 20th century, extinction rates increased 100-1,000 times. Humans change the environment faster than species can adapt. Biodiversity = Speciation – Extinction. Biodiversity represents the planets raw genetic material for future evolution. Lack in biodiversity = inability to adapt. “Continental Drift” (Plate Tectonics): The Breakup of Pangaea LAURASIA 225 million years ago 135 million years ago EURASIA AFRICA 65 million years ago Present Fig. 4-8, p. 72 Top 5 best mass extinctions of all time! Ordovician: 500 million years ago. 50% of animal families wiped out. Devonian: 30% of agnathan and placoderm fishes. Permian: 90% of all animal species. 95% of marine species. All trilobites. Triassic: 35% of animal families, lots of reptiles. Cretaceous: up to 80% of all animal species. Mass Extinctions of the Earth’s Past Fig. 4-9, p. 73 Changes in Biodiversity over Geologic Time Terrestrial organisms Cretaceous 400 Quaternary Marine organisms Tertiary Jurassic Triassic Permian Carboniferous Devonian Silurian Ordovician 800 Cambrian 1200 Pre-cambrain Number of families 1600 0 3500 545 500 440 410 355 290 250 205 145 65 1.8 0 Millions of years ago Fig. 4-10, p. 74