our planet of life
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© 2011 Pearson Education, Inc.
Our Planet of Life
AP Environmental Science
Mr. GrantLesson 37
© 2011 Pearson Education, Inc.
Objectives:
• Define the term biological diversity.
• Characterize the scope of biodiversity on Earth.
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Biological Diversity: The variety of life across all levels of biological organization, including the diversity of species, their genes, their populations, and their communities.
Define the term biological diversity.
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Characterize the scope of biodiversity on Earth.
• Biodiversity can be thought of at three different levels: species diversity, genetic diversity, and ecosystem diversity.
• Roughly 1.8 million species have been described so far, but scientists agree that the world holds millions more.
• Some taxonomic groups (such as insects) hold far more diversity than others.
• Researchers make global estimates of biodiversity by extrapolating from local areas and certain taxonomic groups.
• Diversity is unevenly spread across different habitats, biomes, and regions of the world.
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Levels of biological diversity (biodiversity)
• Humans are reducing Earth’s diversity of life
• Biodiversity = variety of life at all levels of organization- Species diversity- Genetic diversity- Population and community
diversity
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Species diversity
• Species = a set of individuals that share certain characteristics and can interbreed- Producing fertile offspring
• Species diversity = the number or variety of species in a particular region- Richness = the number of species- Evenness (relative abundance) = the similarity in
numbers between species• Speciation adds to species richness
- Extinction reduces species richness
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Species diversity and evennessCompared with the boxed area at the top:
Which area has greater species richness? Why?Which has reduced richness? Why?
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The taxonomy of species• Taxonomists = scientists who classify species
- Similarities reflect evolutionary relationships- Genera = groups of related species- 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
• 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 or disease• Inbreeding depression = genetically similar parents
mate and produce inferior offspring- Cheetahs, bison, elephant seals
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Ecosystem diversity
• Ecosystem diversity = the number and variety of ecosystems- Including different communities and habitats in an
area• May include habitats, communities, or ecosystems at
the landscape level- Sizes, shapes, and connections among patches- Beaches, cliffs, coral reefs, ocean waters
• An area with a variety of vegetation holds more biodiversity than the same size area with one plant type
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Some groups have more species than others
• Species are not evenly distributed among taxonomic groups- Insects predominate over all
other life-forms- 40% of insects are beetles
• Groups accumulate species by:- Adapting to local conditions- 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, 1.8 million species have been identified and described
• Most widely accepted estimate of the number of species? - 14 million
• It is very difficult to know how many species exist- Small organisms are easily overlooked- Many species look identical until thoroughly examined- Many remote spots on Earth remain unexplored
• Entomologist Terry Erwin found 163 beetle species living on one tree species
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Biodiversity is unevenly distributed
• Living things are not distributed evenly on Earth
• Latitudinal gradient = species richness increases toward 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, no glaciation- More niches, species
coexistence• Diverse habitats increase species
diversity and evenness- Tropical rainforests and
drylands, ecotones• Human disturbance can increase
habitat diversity- But only at the local level
© 2011 Pearson Education, Inc.
TED Video
Jonathan Drori: Why we're storing billions of seeds (6:38)
Jonathan Drori commissioned the BBC's very first websites, one highlight in a long career devoted to online culture and educational media -- and understanding how we learn.
-In this brief talk from TED U 2009, Jonathan Drori encourages us to save biodiversity -- one seed at a time. Reminding us that plants support human life, he shares the vision of the Millennium Seed Bank, which has stored over 3 billion seeds to date from dwindling yet essential plant species.
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