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Our Planet of Life

AP Environmental Science

Mr. GrantLesson 37

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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

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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.