1. © 2011 Pearson Education, Inc. AP Environmental Science Mr. Grant Lesson 27 Evolution, Biodiversity, and Population Ecology Evolution: The Source of Earth’s Biodiversity

2. © 2011 Pearson Education, Inc. Objectives: Define the terms evolution and natural selection. Explain natural selection and cite evidence for this process. Describe how evolution influences biodiversity. Discuss reasons for species extinction and mass extinction events.

3. © 2011 Pearson Education, Inc. Evolution: Genetically based change in the appearance, functioning, and/or behavior of organisms across generations, often by the process of natural selection. Natural Selection: The process by which traits that enhance survival and reproduction are passed on more frequently to future generations of organism than those that do not, thus altering the genetic make-up of populations through time. Natural selection acts on genetic variation and is a primary driver of evolution. Define the terms evolution and natural selection.

4. © 2011 Pearson Education, Inc. Explain natural selection and cite evidence for this process.

5. © 2014 Pearson Education, Inc. Evolution: The Source of Earth’s Biodiversity  Species  a population or group of populations whose members share characteristics  They can breed with one another and produce fertile offspring  Population  a group of individuals of a species that live in the same area  Evolution  change over time  Biological evolution  change in populations of organisms over generations  Genetic changes lead to changes in appearance, functioning, or behavior

6. © 2014 Pearson Education, Inc. Evolution: The Source of Earth’s Biodiversity  Genetic changes in evolution may be random  But may be directed by natural selection  Natural selection  process in which traits that enhance survival and reproduction are passed on more frequently to future generations than those that do not  Genetic makeup of future populations is changed

7. © 2014 Pearson Education, Inc. Evolution: The Source of Earth’s Biodiversity  Evolution is one of the best-supported and most illuminating concepts in all science  It is the foundation of modern biology  We must understand it to appreciate environmental science  Understanding how species change over time and adapt to their surroundings is crucial for comprehending ecology and the history of life  Evolutionary processes influence pesticide resistance, agriculture, medicine, health, etc.

8. © 2014 Pearson Education, Inc. Natural selection shapes organisms and diversity  In 1858, both Darwin and Wallace proposed natural selection as the mechanism of evolution  Premises of natural selection:  Organisms struggle to survive and reproduce  Organisms produce more offspring than can survive  Individuals of a species vary in their characteristics due to genes and the environment  Some individuals are better suited to their environment and reproduce more effectively  Organisms with better adapted traits will produce more offspring

9. © 2014 Pearson Education, Inc. Natural selection shapes organisms and diversity  Adaptation  the process where, over time, characteristics (traits) that lead to better reproductive success become more prevalent in the population  Adaptive trait (adaptation)  a trait that promotes reproductive success  Mutations  accidental changes in DNA that may be passed on to the next generation  Non-lethal mutations provide the genetic variation on which natural selection acts  Sexual reproduction also leads to variation

10. © 2014 Pearson Education, Inc. Directional selection  drives a feature in one direction

11. © 2014 Pearson Education, Inc. Selective pressures from the environment influence adaptation  Related species in different environments experience different pressures and evolve different traits.  Divergent Evolution - The process by which a species evolves into two or more descendant or different forms

12. © 2014 Pearson Education, Inc.  Convergent evolution  unrelated species may acquire similar traits because they live in similar environments

13. © 2014 Pearson Education, Inc. Evidence of natural selection is all around us  It is evident in every adaptation of every organism  Artificial selection  the process of selection conducted under human direction  Produced the great variety of dog breeds and food crops

14. © 2014 Pearson Education, Inc. Describe how evolution influences biodiversity.

15. © 2014 Pearson Education, Inc. Evolution generates biodiversity  Biological diversity (biodiversity)  the variety of life across all levels of biological organization  Species  Genes  Populations  Communities  Scientists have described 1.8 million species  Estimates of the total number of species that exist range from 3 million to 100 million  Biodiversity exists nearly everywhere

16. © 2014 Pearson Education, Inc. Speciation produces new types of organisms  The process of generating new species from a single species  Allopatric speciation  species formation due to physical separation of populations  The main mode of speciation  Populations can be separated by glaciers, rivers, mountains  Each population gets its own set of mutations  Natural selection can speed the process

17. © 2014 Pearson Education, Inc. We can infer the history of life’s diversification by comparing organisms  How did the major groups of organisms come to be?  Phylogenetic trees  diagrams that show relationships among species, groups, genes, etc.  Scientists can trace how certain traits evolved  Some traits evolved and were passed on  Other traits evolved more than once (e.g., the ability to fly)

18. © 2014 Pearson Education, Inc. We can infer the history of life’s diversification by comparing organisms  Knowing how organisms are related to one another helps scientists organize and name them  Categories reflect evolutionary relationships  Scientists use physical and genetic characteristics to organize  Each species gets a two- part Latinized scientific name

19. © 2014 Pearson Education, Inc. The fossil record teaches us about life’s long history  Fossil  an imprint in stone of a dead organism  Fossil record  the cumulative body of fossils worldwide  The fossil record shows:  Life has existed on Earth for at least 3.5 billion years  Earlier types of organisms evolved into later ones  The number of species has increased over time  Most species have gone extinct  There have been several mass extinctions in the past

20. © 2014 Pearson Education, Inc. Discuss reasons for species extinction and mass extinction events.

21. © 2014 Pearson Education, Inc. Speciation and extinction together determine Earth’s biodiversity  Extinction  the disappearance of a species from Earth  Species last 1–10 million years  Extinction has historically been a natural occurrence  The loss of a species is irreversible Number of species in existence  speciation  extinction

22. © 2014 Pearson Education, Inc. Speciation and extinction together determine Earth’s biodiversity  Human activity profoundly affects rates of extinction  Biodiversity loss affects people directly  Food, fiber, medicine, ecosystem services

23. © 2014 Pearson Education, Inc. Some species are especially vulnerable to extinction  Extinction can occur when the environment changes rapidly and natural selection can not keep up  Many factors cause extinction:  Severe weather, climate change, changing sea levels  Arrival of new species  Being a small population or specialized species

24. © 2014 Pearson Education, Inc. Some species are especially vulnerable to extinction  Endemic species  a species that only exists in a certain, specialized area  Very susceptible to extinction  Usually have small populations  Island species are often endemic and thus at risk

25. © 2014 Pearson Education, Inc. Some species are especially vulnerable to extinction  Many U.S. amphibians have very small ranges  They are vulnerable to extinction  For example, the Yosemite toad, Houston toad, Florida bog frog  Forty salamander species are restricted to areas the size of a typical county Some U.S. salamander species live on top of single mountains

26. © 2014 Pearson Education, Inc. Earth has seen several episodes of mass extinctions  Background extinction rate  a constant, slow rate of extinction that occurs as a part of evolution  Mass extinction events  episodes that killed off massive numbers of species at once  Occurred five times in Earth’s history  50–95% of all species go extinct at one time  Cretaceous–Tertiary (K–T) event: 65 million years ago  Dinosaurs went extinct  End-Permian event: 250 million years ago  75–95% of all species went extinct

27. © 2014 Pearson Education, Inc. The sixth mass extinction is upon us  Humans are causing the sixth mass extinction event  Resource depletion, population growth, development  Destruction of natural habitats  Hunting and harvesting of species  Introduction of non-native species  Today’s extinction rate is 100–1000 times higher than the background rate and rising  It will take millions of years for life to recover