Ch 11 - Wikispaces 11 Biodiversity and Conservation Biology ... Bengal tiger = Panthera tigris ... Copyright 2008 Pearson Education, Inc.,

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  • Copyright 2006 Pearson Education, Inc., publishing as Benjamin Cummings

    PowerPoint Slides prepared by

    Jay Withgott and Heidi Marcum

    Copyright 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

    Ch 11

    Biodiversity and

    Conservation Biology

    Part 2: Environmental Issues

    and the Search for Solutions

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    Central Case: Saving the Siberian tiger

    The largest cat in the world

    The Russian Far East mountains house the last remaining tigers

    Nearly became extinct due to hunting, poaching and habitat destruction

    International conservation groups saved the species from extinction

    - Research, education, zoos, and captive breeding programs

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    Biodiversity encompasses several

    levels

    Humans are reducing Earths diversity of life

    Biodiversity sum total of all organisms in an area

    - Split into three specific levels:

    - Species diversity

    - Genetic diversity

    - Ecosystem diversity

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    Species diversity

    Species Diversity = the number or variety of species in the world or in a particular region

    - Richness = the number of species

    - Evenness or relative abundance = extent to which numbers of individuals of different species are equal or skewed

    - Speciation generates new species and adds to species richness

    - Extinction reduces species richness

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    The taxonomy of species

    Taxonomists = scientists who classify species

    - Physical appearance and genetics determines a species

    - Genera = related species are grouped together

    - Families = groups of genera

    Every species has a two-part scientific name: genus and species

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    Subspecies: the level below a species

    Subspecies = populations of species that occur in different areas and differ slightly from each other

    - Divergence stops short of separating the species

    - Subspecies are denoted with a third part of the scientific name

    Siberian tiger =

    Panthera tigris

    altaica

    Bengal tiger =

    Panthera tigris

    tigris

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    Genetic diversity Encompasses the differences in DNA among

    individuals within species and populations

    The raw material for adaptation to local conditions

    Populations with higher genetic diversity can survive

    - They can cope with environmental change

    Populations with low genetic diversity are vulnerable

    - To environmental change

    - Disease

    - Inbreeding depression = genetically similar parents mate and produce inferior offspring

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    Ecosystem diversity

    Ecosystem diversity = the number and variety of ecosystems

    Also encompasses differing communities and habitats

    Rapid vegetation change and varying landscapes within an ecosystem promote higher levels of biodiversity

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    Some groups contain more species than

    others

    Species are not evenly distributed among taxonomic groups

    - Insects predominate over all other life-forms

    - 40% of all insects are beetles

    Groups accumulate species by

    - Adaptive radiation

    - Allopatric speciation

    - Low rates of extinction

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    Insects outnumber all other species

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    Measuring biodiversity is not easy

    Out of the estimated 3 - 100 million species on Earth, only 1.7 - 2 million species have been successfully catalogued

    Very difficult to identify species

    - Many remote spots on Earth remain unexplored

    - Small organisms are easily overlooked

    - Many species look identical until thoroughly examined

    Entomologist Terry Erwin found 163 beetle species specialized on one tree species

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    Biodiversity is unevenly distributed

    Living things are distributed unevenly across Earth

    Latitudinal gradient = species richness increases towards the equator

    Canada has 30 - 100 species of

    breeding birds, while Costa Rica

    has more than 600 species

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    Latitudinal gradient has many causes

    Climate stability, high plant productivity, and no glaciation

    Tropical biomes support more species and show more species evenness

    - Diverse habitats increase species diversity

    Human disturbance can increase habitat diversity

    - But only at the local level

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    Biodiversity losses and species

    extinction

    Extinction = occurs when the last member of a species dies and the species ceases to exist

    Extirpation = the disappearance of a particular population from a given area, but not the entire species globally

    - Can lead to extinction

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    Extinction is a natural process

    Paleontologists estimate 99% of all species that ever lived are now extinct

    Background rate of extinction = natural extinctions for a variety of reasons

    - 1 extinction per 1 to 10 million species for mammals and marine species

    - 1 species out of 1,000 mammal and marine species would go extinct every 1,000 to 10,000 years

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    Earth has experienced five mass

    extinctions

    In the past 440 million years, mass extinctions have eliminated at least 50% of all species

    After every mass extinction the biodiversity returned to or exceeded its original state

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    The current mass extinction is human

    caused

    During this Quaternary period, we may lose more than half of all species

    - Hundreds of human-induced species extinctions, and multitudes of others, teeter on the brink of extinction

    The current global extinction rate is 100 to 1,000 times greater than the background rate

    - This rate will increase tenfold in future decades due to human population growth and resource consumption

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    People have hunted species to extinction for

    millennia

    Extinctions followed human arrival on islands and continents

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    Current extinction rates are higher than

    normal

    The Red List = an updated list of species facing high risks of extinctions

    - 23% of mammal species

    - 12% of bird species

    - 31 - 86% of all other species

    Since 1970, 58 fish species, 9 bird species, and 1 mammal species has gone extinct

    - In the U.S., in the last 500 years, 236 animal and 17 plant species are confirmed extinct

    - Actual numbers are undoubtedly higher

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    Biodiversity loss is more than extinction

    Decreasing numbers are accompanied by smaller species geographic ranges

    Genetic, ecosystem, and species diversity are being lost.

    The Living Planet Index summarizes trends in populations

    - Between 1970 and 2003, the Index fell by 30%

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    Biodiversity loss has many causes

    Reasons for biodiversity losses are multifaceted, complex, and hard to determine

    - Factors may interact synergistically

    Four primary causes of population decline are:

    - Habitat alteration

    - Invasive species

    - Pollution

    - Overharvesting

    Global climate change now is the fifth cause

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    Habitat alteration causes biodiversity loss

    The greatest cause of biodiversity loss

    - Farming simplifies communities

    - Grazing modifies the grassland structure and species composition

    - Clearing forests removes resources organisms need

    - Hydroelectric dams turn rivers into reservoirs upstream

    - Urbanization and suburban sprawl reduce natural communities

    - A few species (i.e., pigeons, rats) benefit from changing habitats

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    Habitat alteration has occurred in every

    biome

    Particularly in tropical rainforests, savannas, and tropical dry forests

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    Invasive species cause biodiversity loss

    Introduction of non-native species to new environments

    - Accident