Our Planet of Life

1. AP Environmental Science Mr. Grant Lesson 37 Our Planet of Life

2. Objectives: • Define the term biological diversity. • Characterize the scope of biodiversity on Earth.

3. Define the term biological diversity. Biological Diversity: The variety of life across all levels of biological organization, including the diversity of species, their genes, their populations, and their communities.

4. 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.

5. 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

6. 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

7. Species diversity and evenness Compared with the boxed area at the top: Which area has greater species richness? Why? Which has reduced richness? Why?

8. 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

9. 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

10. 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

11. 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

12. 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

13. Insects outnumber all other species

14. 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

15. 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

16. 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

17. TED Video 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. Jonathan Drori: Why we're storing billions of seeds (6:38) -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.