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

© 2011 Pearson Education, Inc. Reading and Objectives: Read: Withgott & Laposata, Chapter 3... Evolution: The Source of Earth’s Biodiversity (pgs ) Define the terms evolution and natural selection. Objectives: 1.Reading Mastery Check 2.Explain natural selection and cite evidence for this process. 3.Describe how evolution influences biodiversity. 4.Discuss reasons for species extinction and mass extinction events.

© 2011 Pearson Education, Inc. Mastery Check Describe the steps involved in allopatric speciation. When a population is split into two populations that become geographically and reproductively isolated from each other, they may evolve over time, in their different environments and under different selective pressures, into different species. This is called allopatric speciation.

© 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.

© 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

© 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

© 2011 Pearson Education, Inc. Because organisms produce excess young, individuals vary in their traits, and many traits are inherited, some individuals will prove better at surviving and reproducing. Their genes will be passed on and become more prominent in future generations. Explain natural selection and cite evidence for this process. 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

© 2014 Pearson Education, Inc.  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

© 2011 Pearson Education, Inc. Mutations and recombination provide the genetic variation for natural selection. 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

© 2011 Pearson Education, Inc. Directional selection  drives a feature in one direction

© 2011 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

© 2011 Pearson Education, Inc.  Convergent evolution  unrelated species may acquire similar traits because they live in similar environments

© 2011 Pearson Education, Inc. We have produced our pets, farm animals, and crop plants by artificial selection. Artificial selection  the process of selection conducted under human direction -Produced the great variety of dog breeds and food crops

© 2014 Pearson Education, Inc. Describe how evolution influences biodiversity. Natural selection can act as a diversifying force as species adapt to their environments in a myriad of ways.  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

© 2014 Pearson Education, Inc. Speciation by geographic isolation (or other means) produces new 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

© 2014 Pearson Education, Inc. The branching patterns of phylogenetic trees reflect the historical pattern in which lineages of organisms have emerged. 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)

© 2014 Pearson Education, Inc. The fossil record informs us about life’s 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

© 2014 Pearson Education, Inc. Discuss reasons for species extinction and mass extinction events. Extinction may occur when species that are highly specialized or have small populations encounter rapid environmental change.  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

© 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

© 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

© 2014 Pearson Education, Inc. Earth’s life has experienced five known episodes of mass extinction, due to asteroid impact and possibly volcanism and other factors.  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

© 2014 Pearson Education, Inc. Today, human impact may be initiating a sixth mass extinction.  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

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© 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.

© 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

© 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

© 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