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The Number of Species on Earth

The Number of Species on Earth. 1.5 million have been named Total # could be 3 million or more New species discovered all the time. The Number of Species on Earth. Scientists group living things on the basis of evolutionary relationships. Three domains Eukarya Bacteria Archaea

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The Number of Species on Earth

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  1. The Number of Species on Earth • 1.5 million have been named • Total # could be 3 million or more • New species discovered all the time

  2. The Number of Species on Earth • Scientists group living things on the basis of evolutionary relationships. • Three domains • Eukarya • Bacteria • Archaea • Eukarya have a nucleus and organelles, Bacteria and Archaea do not.

  3. The Number of Species on Earth Eukaryote cell Bacterial (prokaryote) cell

  4. The Number of Species on Earth • Most of the species on Earth are insects or plants. • Many species of fungi and protists. • Relatively few mammals.

  5. Why are there so many species? • Answer lies in • the different ways in which organisms interact • the idea of the ecological niche

  6. Interaction between Species • Competition • The outcome is negative for both groups • Symbiosis • Benefits both participants • Predation and parasitism • The outcome benefits one and is detrimental to the other.

  7. Competitive Exclusion Principle • Two species that have exactly the same requirements cannot coexist in exactly the same habitat. • E.g. British Red Squirrel and American Grey Squirrel

  8. Competitive Exclusion Principle American Grey Squirrel British Red Squirrel

  9. Niches: How Species Coexist • Flour beetles (Tribolium) • Specific # of beetles of two species placed in flour • Containers maintained at various temp and moisture levels • Periodically beetles counted • One species always wins but which one depends on conditions

  10. Professions and Places: The Ecological Niche and the Habitat • Flour beetles have the same ecological functional niche • Same profession – eating flour • Different habitats • Where it lives

  11. Measuring Niches • Describe the niche • the set of all environmental conditions under which a species can persist • and carry out its life functions • Measuring niche is known as Hutchinsonian niche • E.g. flatworms in streams

  12. Fundamental temperature niche Realized temperature niche

  13. Environmental Factors that Influence Diversity

  14. Example of ecological gradients and changes in plant and animal communities with changes in elevation.

  15. Example of ecological gradients and changes in plant and animal communities with changes in elevation.

  16. Chapter 8: Biogeography

  17. Biotic Provinces • A biotic province is a region inhabited by a characteristic set of taxa, bounded by barriers that prevent emigration and immigration.

  18. Biotic Provinces • All living organisms classified into groups called taxa • Based on evolutionary similarities • Largest group- domain or kingdom • Divisions/phyla • Classes • Orders • Families • Genera • Species

  19. Biotic Provinces • In each major biogeographic area certain families of animals are dominant and fill ecological niches. • For example large herbivores • NA- bison and pronghorn • SA- capybara • Aus- kangaroo • Africa- giraffes and antelope

  20. Biotic Provinces • W/in a realm • Species more likely to be related • Evolved and adapted in the same place for a long time • When a species introduced may be unrelated or distantly related to native species. • Ecological and evolutionary adjustments are yet to take place. • Introduced species may be superior competitor

  21. Biomes • Similar environments provide similar opportunities and similar constraints • Leads to evolution of organisms similar in form and function • Rule of climatic similarity

  22. Example of Convergent evolution- given sufficient time and similar climates species similar in shape and form will tend to occur. Joshua Tree Saguaro from North America Euphorbia of East Africa

  23. Biotic Province vs. Biome • A biotic province is based on who is related to whom. • An evolutionary unit • A biome is based on niches and habitat. • If we know the climate we can make predictions about the biome

  24. Ostrich from Africa Rhea from SA Emu from Australia Divergent evolution- population is divided and each evolves separately

  25. Geographical Patterns of Life within a Continent • Continental drift periodically isolates and remixes groups of organisms • Leads to increase in biodiversity • Complex topography leads to geographic isolation w/in a continent • Life patterns also altered by • Proximity of a habitat to an ocean (large body of water) • Near shore ocean currents • Location relative to mountain ranges • Latitude and longitude

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