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A Diverse Planet

A Diverse Planet. Evolution & Biodiversity. Home of the Diverse. Ecosystem Diversity Different ecosystems within a region Species Diversity Variety of species within an ecosystem Genetic Diversity Variety of genes within a species. How Many Species?.

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A Diverse Planet

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  1. A Diverse Planet Evolution & Biodiversity

  2. Home of the Diverse • Ecosystem Diversity • Different ecosystems within a region • Species Diversity • Variety of species within an ecosystem • Genetic Diversity • Variety of genes within a species

  3. How Many Species? • The number of species in any given place is the most common measure of biodiversity • Named: 2 million species • Estimate: 5 – 100 million

  4. Measuring Species • Species richness: number of species in a given area (pond, tree canopy, grassland) • Used to give an approximate sense biodiversity

  5. Measuring Species • Species evenness: tells whether an ecosystem is dominated by one species or if there is ‘even’ abundance of all species • High evenness: if all species are represented by similar numbers

  6. Evolutionary Relationships • Species organized into categories that indicate how closely related they are • Phylogenies – branching patterns of evolutionary relationships • Relatedness determined by similarity of traits

  7. Creating Genetic Diversity • Evolution – the change in the genetic composition of a population over time • Microevolution – occurs below the species level (apple, potato varieties) • Macroevolution – gives rise to new species, genera, etc.

  8. Creating Genetic Diversity • Mutation – random change in a gene during replication • Recombination – during reproductive cell division, a piece of one chromosome breaks off and attaches to another; can produce new traits (immune system)

  9. Creating Genetic Diversity • Genotype–the blueprint • Phenotype – the set of traits expressed • Phenotype determined by genotype, but is influenced by environment • Example –turtle, crocodile egg temps can determine gender

  10. Artificial Selection • Humans determine which individuals breed when a preconceived set of traits desired

  11. Natural Selection • The environment determines which individuals survive and reproduce • Proposed by C. Darwin • Differences in traits are associated with differences in the ability to survive and reproduce • N.S. favors combination of traits that improves fitness; process is called adaptation

  12. Random Processes • Changes are not related to differences in fitness • Mutation – if not lethal, can add to the genetic variation of a population • Genetic drift – change in the genetic composition of a population as a result of random mating (impt in smaller populations)

  13. Random Processes • Bottleneck effect – a drastic reduction in the size of a population; genetic composition also reduced • Founder effect – change in a population descended from a small number of colonizing individuals

  14. speciation

  15. Allopatric v. Sympatric Speciation • Allotropic speciation is the process that requires geographic isolation • Similar to the founder effect • Sympatric speciation is evolution of one species into two species in the absence of geographic isolation • Can happen through polyploidy, or • exploiting a new niche may automatically reduce gene flow

  16. Pace of Evolution • Average global rate is 1 new species every 3 million years • It all depends on successful adaptation: • Rate of environmental change • Genetic variation • Population size • Generation time

  17. Ecological Niches • Range of Tolerance – limits to the abiotic conditions they can tolerate • The suite of ideal conditions is termed the fundamental niche of the species • Biotic factors also exist • The range of abiotic and biotic factors under which a species lives is the realized niche

  18. Ecological Niches • Niche generalists – able to live in a variety of habitats or feed on a variety of species • Niche specialists – able to live in a specific habitat or feed on a small group of species

  19. Environmental Change & Species Distribution Pine Spruce Birch Prairie

  20. Environmental Change & Species Extinction • The Fossil Record – remains of organisms preserved in rock • 5 major extinctions have occurred in the past 500 million years • Largest: Permian extinction (90% of marine life) • Most famous: Cretaceous (end of the dinos) • 6th mass extinction: going on now? Some estimates: up to 25% by 2020

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