© 2011 Pearson Education, Inc. AP Environmental Science Mr. Grant Lesson 36 Our Planet of Life

© 2011 Pearson Education, Inc. Mastery Check What is biodiversity? Describe three levels of biodiversity. Biodiversity has no single definition. At the species level, it refers to both the number of different species present in an area and to the evenness or relative abundance of those species. At the genetic level, it refers to the genetic variety within a single species. At the ecosystem level, it refers to the number and variety of ecosystems in an area. The concept may be applied at the community, habitat, and landscape levels as well.

© 2011 Pearson Education, Inc. Objectives: Read Withgott & Laposata, Chapter 11 (pgs ) Define the term biological diversity. Characterize the scope of biodiversity on Earth.

© 2011 Pearson Education, Inc. 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.

© 2011 Pearson Education, Inc. Characterize the scope of biodiversity on Earth. Biodiversity can be thought of at three different levels: species diversity, genetic diversity, and ecosystem diversity. Some taxonomic groups (such as insects) hold far more diversity than others. Roughly 1.8 million species have been described so far, but scientists agree that the world holds millions more. Diversity is unevenly spread across different habitats, biomes, and regions of the world.

© 2014 Pearson Education, Inc. Our Planet of Life  Humans are reducing Earth’s diversity of life  Biological diversity or biodiversity  variety of life at all levels of organization  Species diversity  Genetic diversity  Population and community diversity  Biologists employ different working definitions and look at different levels according to their aims and philosophies  Basic concept applies across all levels

© 2014 Pearson Education, Inc. 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  Subspecies = populations of species that occur in different areas and differ slightly from each other  Divergence stops short of separating the species

© 2014 Pearson Education, Inc. Genetic diversity  Encompasses the differences in DNA composition 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

© 2014 Pearson Education, Inc. Ecosystem diversity  Ecosystem diversity  the number and variety of ecosystems  May include different biotic communities or habitats within an area  The open plains of the Serengeti hold a diversity of habitats, including savanna, grassland, wetland  May include habitats, communities, or ecosystems at the landscape level  Sizes, shapes, and connections among patches  An area with a variety of vegetation holds more biodiversity than the same size area with one plant type

© 2014 Pearson Education, Inc. Some groups hold more species than others  Species are not evenly distributed among taxonomic groups  Insects predominate over all other life-forms  40% of insects are beetles  Beetles outnumber all other non-insect animals combined  Groups accumulate species by:  Adapting to local conditions  Populations becoming divided geographically  Low rates of extinction

© 2014 Pearson Education, Inc. Many species await discovery  1.8 million species have been identified and described  Estimates of the total number of species on the planet range from 3 million to 100 million  Most widely accepted estimate of the number of species?  Around 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

© 2014 Pearson Education, Inc.

Biodiversity is unevenly distributed  Living things are not distributed evenly on Earth  Latitudinal gradient  species richness increases toward the equator

© 2014 Pearson Education, Inc. Biodiversity is unevenly distributed  Factors that contribute to higher diversity at the equator:  High plant productivity supports more animals  Climate stability allows specialization, niches, and species coexistence  No glaciation means species never have to leave  Diversity of habitats increases species diversity  Human disturbance can increase habitat diversity locally

© 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.