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Evolution, Biodiversity, and Community Processes. La Ca ñada High School Dr. E. What types of Life exist on the Earth?. Types of Organisms. Prokaryotic Kingdom : single-celled organisms containing no internal structures surrounded by membranes (therefore there is no nucleus)
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Evolution, Biodiversity, and Community Processes La Cañada High School Dr. E
Types of Organisms • Prokaryotic Kingdom: single-celled organisms containing no internal structures surrounded by membranes (therefore there is no nucleus) • Monera – bacteria and cyanobacteria
Endosymbiotic Theory Chloroplast Plants and plantlike protists Aerobic bacteria Ancient Prokaryotes Photosynthetic bacteria Nuclear envelope evolving Mitochondrion Primitive Photosynthetic Eukaryote Animals, fungi, and non-plantlike protists Primitive Aerobic Eukaryote Ancient Anaerobic Prokaryote
Types of Organisms • Eukaryotic Kingdoms: all organisms consisting of cells which contain membrane-bound nuclei • Protista - mostlyone-celled organisms – have characteristics of all three other Eukaryote Kingdoms • Fungi - organisms which decompose stuff • Plantae - organisms which use photosynthesis to make their own food • Annuals completelife cycle in one season • Perennialslive for more than one season • Animalia - organisms which must get organic compounds from food they eat - most are able to move • Invertebrates – no backbone • Vertebrates – Fish, Amphibians, Reptiles, Birds and Mammals
Fossils 1600's - Danish scientist Nicholas Steno studied the relative positions of sedimentary rocks • Layering is the most obvious feature of sedimentary rocks • formed particle by particle and bed by bed, and the layers are piled one on top of the other • any sequence of layered rocks, a given bed must be older than any bed on top of it • Law of Superposition is fundamental to the interpretation of Earth history, because at any one location it indicates the relative ages of rock layers and the fossils in them.
Half-life for a given radioisotope is the time for half the radioactive nuclei in any sample to undergo radioactive decay
Evolutionary Bush One life-form splits into two and those branches split (independently) to make more. Time Phenotypic ‘distance’
Evolutionary Bush -- thousands of earlier and later branches.
At any given moment (e.g. the ‘present’), all we see is current diversity…all extinct forms are gone (99.9%) Time
WRONG WRONG
Charles Darwin • 1809-1882 • British naturalist • Proposed the idea of evolution by natural selection • Collected clear evidence to support his ideas
Darwin’s Observations • Most species produce more offspring than can be supported by the environment • Environmental resources are limited • Most populations are stable in size • Individuals vary greatly in their characteristics (phenotypes) • Variation is heritable (genotypes)
Darwin’s finches • 13 species of finches in the Galápagos Islands • Was puzzling since only 1 species of this bird on the mainland of South America, 600 miles to the east, where they had all presumably originated
Darwin’s finches • Differences in beaks • associated with eating different foods • adaptations to the foods available on their home islands • Darwin concluded that when the original South American finches reached the islands, they adapted to available food in different environments
What did Darwin say? • Organisms reproduce more than the environment can support • some offspring survive • some offspring don’t survive • competition • for food • for mates • for nesting spots • to get away from predators
Survival of the fittest • Who is the fittest? • traits fit the environment • the environment can change, so who is fit can change Peppered moth
Stephen Jay Gould (1941-2002) • Harvard paleontologist & evolutionary biologist • punctuated equilibrium • prolific author • popularized evolutionary thought
Punctuated Equilibrium • Rate of speciation is not constant • rapid bursts of change • long periods of little or no change • species undergo rapid change when they 1st bud from parent population Time
Gradualism • Gradual divergence over long spans of time • assume that big changes occur as the accumulation of many small ones
Adaptive Radiation • When one species splits into many species to fill open habitats. • Darwin’s finches
Speciation When a group becomes geographically isolated over time it will become reproductively isolated = new species formed. • One species can evolve into two or more species • 2 step process • Geographical isolation • Reproductive isolation
Ammospermophilus spp Geographic isolation • When a population becomes divided by a natural barrier. • Mountains, river, body of water, landslides • Groups can’t interbreed or intermix • Become adapted to a different environment Harris’s antelope squirrel inhabits the canyon’s south rim (L). Just a few miles away on the north rim (R) lives the closely related white-tailed antelope squirrel
Reproductive Isolation • Differences in isolated groups become so great, they can no longer interbreed • Physical changes • Behavioral changes • Biochemical changes
Speciation Evolution of new species
Four causes of evolutionary change: • Mutation: fundamental origin of all genetic (DNA) change.
Four causes of evolutionary change: • Mutation: fundamental genetic shifts. • Genetic Drift: isolated populations accumulate different mutations over time. In a continuous population, genetic novelty can spread locally.
Four causes of evolutionary change: But in discontinuous populations, gene flow is blocked.
Four causes of evolutionary change • Mutation: fundamental genetic shifts. • Genetic Drift: isolation accumulate mutations • Founder Effect:sampling bias during immigration. When a new population is formed, its genetic composition depends largely on the gene frequencies within the group of first settlers.
Founder Effect.-- Human example: your tribe had to live near the Bering land bridge…
Founder Effect.-- …to invade & settle the ‘New World’!
Four causes of evolutionary change: • Mutation: fundamental genetic shifts. • Genetic Drift: isolation accumulation of mutations • Founder Effect: immigrant sampling bias. • Natural Selection: differential reproduction of individuals in the same population based on genetic differences among them.
Four causes of evolutionary change: • Mutation: fundamental genetic shifts. • Genetic Drift: isolation accumulation of mutations • Founder Effect: immigrant sampling bias. • Natural Selection: reproductive race • These 4 interact synergistically
Number of Individuals Small Large Size of individuals Modes of Action • Natural selection has three modes of action: 1. Stabilizing selection 2. Directional selection 3. Diversifying selection
Number of Individuals Small Large Size of individuals 1. Stabilizing Selection Acts upon extremes and favors the intermediate