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13 The Changing Biosphere

13 The Changing Biosphere. When we finish this chapter you should be able to: Define natural selection Explain how geographical isolation and reproductive isolation lead to the evolution of new species Discuss how mutations increase diversity. 13.1 Clues from the past: The fossil record.

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13 The Changing Biosphere

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  1. 13 The Changing Biosphere When we finish this chapter you should be able to: Define natural selection Explain how geographical isolation and reproductive isolation lead to the evolution of new species Discuss how mutations increase diversity

  2. 13.1 Clues from the past: The fossil record Biosphere is constantly changing (slowly) Abiotic: Geologic and Atmospheric (climate) changes ex: oxygen added to atmosphere over time warming and cooling cycles (ice ages)

  3. Biotic: Fossil record shows how a organisms have changed over time.  Evolution Old species become adapted (evolve) to new conditions or become extinct. Ex: dinosaurs New species arise under new climate conditions to replace old Ex: Horse: from forest browser to grassland grazer

  4. Well adapted species can survive for long periods of time Ex: Opossum – only marsupial (pouched) animal left in N. America Living fossils – well adapted species survive unchanged for long periods of time Ex: Coelacanth (lobed fin fish) unchanged for 100 million years is missing link between fish and four legged animals (amphibians, etc.)

  5. 13.1 Section Review • Describe some of earth’s ongoing changes that affect the abiotic part of the biosphere • Compare the composition of earth’s primitive atmosphere with our present-day atmosphere • How does horse evolution show adaptations to a changing environment

  6. 13.2 Evolution through Natural Selection Population- organisms of a species – that interbreed in nature Members have Variations: differences in their traits due to their different genes, that help them survive and reproduce

  7. Over production (compared to limited resources - food, etc.) leads to natural selection of best adapted ones, to pass on their genes

  8. Adaptations – traits which help an organism to survive – new traits arise through mutation: change in the genes Pandas thumb

  9. Isolation - New species arise when some of the individuals become isolated and stop interbreeding with the rest Geographic isolation – separation of a population by mountain range, river, etc. separated group changes differently from original group ex: grand canyon: Abert squirrel and kaibab squirrel (north rim) Leads to Reproductive Isolation (new species can’t breed with old)

  10. Convergent Evolution Different animals adapted to similar lifestyles ex: mouse deer (goat) agouti (rodent) royal antelope (deer) each is small, brown – live in tropical rainforest Also Auk (north pole) and penguin (south pole)

  11. 13.2 section review • Explain how natural selection is similar to people breeding animals. • List 3 adaptations that help mammals, like us, survive in their environment. • Compare the terms geographic isolation and reproductive isolation. • Explain convergent evolution by comparing fish and whales

  12. 13.3 diversity and mutations Gene pool – the collection of all variations for different genes for traits in a population – get mixed during sexual reproduction Mutation – change in a gene, creates new or variation in traits - only mutations in egg cells can be passed on - usually negative and fatal – occasionally beneficial

  13. Peppered Moth England / Industrial revolution – darkening of trees from soot Moth population evolved from light color to dark color over 100 years. (Now evolving back)

  14. Human Adaptation In what type of environment would webbed feet be an advantage? Quechua Indians of the high Andes in S. America have larger lungs, and more red blood cells to carry O2 in the thin air at high altitude

  15. Rate of Evolutionary Change Two theories: Gradualism – gradual changes over a long period of time. Vs. Punctuated Equilibrium – long stable periods with brief periods of changes (1000 years) How would climate change contribute to these?

  16. Preserving Diversity Greater diversity (variety) in traits allows populations to adapt to changes, rather than become extinct. Ex: Cheetah – endangered with little genetic diversity - one disease could wipe out entire species Ex: Depleted Fish stocks – due to overfishing – cod, blue-fin tuna, swordfish Avoid also – grouper, snapper, Chilean sea bass Better – salmon, mahi-mahi, tilapia, striped bass, halibut

  17. 13.3 section review • How do mutations affect species diversity? • What role do mutations play in natural selection? • Describe the main difference between gradualism and punctuated equilibrium • What can you do at the supermarket top preserve the diversity of the marine ecosystem?

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