Lecture 24

Lecture 24 - Lecture 24: Biodiversity, Extinction and the...

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Lecture 24: Biodiversity, Extinction and the Atmosphere Biodiversity Levels of biodiversity Threats to biodiversity Importance of biodiversity Extinction The Atmosphere Fossil Fuels and the Greenhouse Effect Ozone Problem Conclusions
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Biodiversity Biodiversity What is biodiversity? _____________ is the variety and variability of life forms (both contemporary and extinct) Biodiversity includes genetic and ecosystem diversity in a defined area and over time (richness in numbers and individuals of different species in an environment)
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Global plant biodiversity _____________________ 1. Bryophyta (mosses, bryophytes): 24,000 sp. 2. Polypodiophyta (ferns): 8,500 sp. 3. Lycopodiophyta (club mosses): 1225 sp. 4. Equisetophyta (horsetails): 29 sp. 5. Psilotophyta (whisk ferns): 4 sp. 6. Cycadophyta (cycads): 105 sp. 7. Pinophyta (conifers): 600 sp. 8. Ginkgophyta (ginkgo): 1 sp. 9. Gnetophyta (gnetops): 70 sp. 10. Magnoliophyta (_________ plants): 245,000 species!
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Concepts of Biodiversity Two hypotheses: 1. R___________ ”: Each species is important in their own small way. Lose one (like a rivet on an airplane) and little happens; but the ecosystems weakens. Lose several species, and at one point the whole ecosystem fails. 2. “ R_________ ”: Most species are superfluous, as only are critical to the survival of the ecosystem. Species like passengers on a plane: even with only a few, the plane can still fly.
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Evidence Crop production ____________ with biodiversity Increased ecosystem resilience to stress with _______________ species diversity Full productivity can be reached by a few select species in terms of biomass, but most ecosystems have far more species than necessary, thus random loss will not cause system collapse.
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Levels of diversity S____________ occurs when a population diverges from another to become a separate species. Rate of speciation: __________ in tropics and in deserts; slower in temperate regions Rates of speciation are ______ in aquatic habitats, yet individuals species tend to survive for a long period of time. Rates of speciation are __________ in areas of environmental stress. Higher diversity of species in tropical rainforests
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Threats to biodiversity _____________ are the current major cause of species loss and habitat degradation. Widespread and concentrated habitat destruction caused by humans Native species often lost, exotic weeds invade habitat Naturally occurring species loss: Selective and random, infrequent and scattered Native species reduced in numbers (but not lost) Habitats disrupted, but not destroyed Re-colonization is by native species
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Significance of biodiversity Without a biologically viable world, humans would not exist Biodiversity provides an array of services that maintain life on earth Biodiversity provides humans with ___________ benefits : Crops, domestic animals, medicines,
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Lecture 24 - Lecture 24: Biodiversity, Extinction and the...

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