Conservation Biology Exam 1 Notes

conservation biology: interdisciplinary discipline that studies the negative impacts humans have on species

hypothesis: explanation/answer to a research question that makes testable predictions

biodiversity: diversity of and within species over some defined area; species and their genetic variation

• species richness: total number of species in an area

• speciation: formation of new species

incipient species: close to become separate species from related groups

allopatric speciation: isolation leads to unique populations via mutations and differential selection

• physical barriers prevent populations from interacting (aka no interbreeding)

biological species concept (BSC): species are groups of actually or potentially interbreeding populations which are reproductively isolated from other groups

philosophical and ecological reasons to save species

• inherent (intrinsic) value: people value them because they exists

  • mostly charismatic species (dogs, cats, birds)

• utilitarian value: benefit people directly and indirectly

  • direct: economic and medical

  • indirect: crop pollination, water purification, ecosystem services

• high diversity ecosystems function better than low diversity ecosystems

  • diverse systems more productive and resilient

• economic externalities lead to environmental degradation

global diversity patterns

• temporal patterns: mass extinction events

  • mass extinctions: rapid major reductions in global biodiversity

    • ordovician extinction: 443 MYA

    • devonian extinction: 359 MYA

    • permian extinction: 251 MYA, most intense

    • triassic extinction: 200 MYA

    • cretaceous extinction: 65 MYA, least intense??

  • reasons for mass extinctions:

    • widespread volcanic activity

    • events that alter global atmospheric chemistry, temperature, and climate

• taxonomic patterns: examine number of species alive and taxonomic distribution

  • 1.5 million described species, estimated about 5-10 million

  • most species are invertebrates or plants

    • vertebrates have low diversity compared to other taxa

• spatial patterns: biodiversity hotspots and LDG

  • biodiversity hotspots: unusually high levels of biodiversity

    • found in tropical forests, lakes, and coral reefs; mediterranean climate (wet winter, dry other seasons)

  • Latitudinal Diversity Gradient (LDG): highest diversity near the equator

    • diversity declines with increasing latitude as one moves away from equator

    • hypothesis involves differences in speciation and extinction rates

      • stability hypothesis: tropics have been more stabile than temperate regions

        • increased climatic stability promoters lower extinction rates

      • productivity (energy) hypothesis: tropics have higher incidence of solar radiation

        • increased solar radiation = increased plant growth (higher productivity) = more resources = larger population sizes = lower extinction rates

      • area hypothesis: species diversity is related to area of habitat

        • species-area relationship: more species are found in larger areas

        • most to least diversity: tropics - temperate - boreal

Pleistocene extinction: 2MYA - 12,000YA, many large bodied mammals and birds went extinct in NA and SA

• climate change hypothesis: several ice ages, earth experienced prolonged cooling/warming periods

  • climate change = habitat change = extinctions

  • large species affected because they need more energy/food

  • does not explain why most extinctions occurred at end of Pleistocene

• human overkill hypothesis: human hunting led to extinctions via overharvesting of megafauna

  • shortly after humans arrive, large mammals and birds go extinct

threats to biodiversity

• habitat loss, degradation, and fragmentation

  • humans modify habitats = reduces resources

    • species are poorly adapted to altered habitat

  • main cause of recent extinctions

  • eutrophication: fertilization of aquatic habitats, leads to habitat degradation

  • fragmentation impedes movement and creates edge effects

• overharvesting

  • human activity responsible for conservation crisis

    • how to exploit renewable resource?

  • maximum sustainable yield model: maximizing harvest at population size (p*)

    • harvest Q to maximize yield in sustainable way without causing extinctions

    • need accurate estimate of population size and policy to regulate harvest each year

    • fails due to political pressure of higher quotas and hard to estimate population sizes

      • modification can reduce overexploitation but lowers harvest

• exotic species: species evolved in one place and moved to another place by human activities

  • invasive species: exotic species that attain high abundance and cause negative effects on native species and economic harm

  • exotic species reduce population size of native species

    • can carry novel disease

    • can be super predators

    • can be super competitors

    • can alter disturbance regimes (ex. exotic grasses enhance fire frequency)

  • biotic resistance hypothesis: native species/diversity regulate exotic invasion

    • direct biotic resistance: consumption

    • indirect biotic resistance: competition