chapter 5 evolution of biodiversity
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Chapter 5 Evolution of Biodiversity. Earth is home to a tremendous diversity of species. Ecosystem diversity- the variety of ecosystems within a given region. Species diversity- the variety of species in a given ecosystem. Genetic diversity- the variety of genes within a given species. - PowerPoint PPT PresentationTRANSCRIPT
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Chapter 5Evolution of Biodiversity
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Earth is home to a tremendous diversity of
species
•Ecosystem diversity- the variety of ecosystems within a given region.
•Species diversity- the variety of species in a given ecosystem.
•Genetic diversity- the variety of genes within a given species.
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•Species richness- the number of species in a given area.
•Species evenness- the measure of whether a particular ecosystem is numerically dominated by one species or are all represented by similar numbers of individuals.
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Evolution is the mechanism underlying biodiversity
•Evolution- a change in the genetic composition of a population over time.
•Microevolution- evolution below the species level.
•Macroevolution- Evolution which gives rise to new species or new genera, family, class or phyla.
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Creating Genetic Diversity
•Genes- physical locations on chromosomes within each cell of an organism.
•Genotype- the complete set of genes in an individual.
•Mutation- a random change in the genetic code.
•Phenotype- the actual set of traits expressed in an individual.
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Types Of Evolution
•Evolution by Artificial Selection
•Evolution by Natural Selection
•Evolution by Random processes
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Evolution by artificial and natural selection
• Evolution by artificial selection- when humans determine which individuals breed.
• Evolution by natural selection- the environment determines which individuals are most likely to survive and reproduce.
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Darwin’s theory of evolution by natural
selection• Individuals produce an excess of
offspring.
• Not all offspring can survive.
• Individuals differ in their traits.
• Differences in traits can be passed on from parents to offspring.
• Differences in traits are associated with differences in the ability to survive and reproduce.
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Evolution by Random Processes
•Mutation- occur randomly and can add to the genetic variation of a population.
•Genetic drift- change in the genetic composition of a population over time as a result of random mating.
•Bottleneck effect- a reduction in the genetic diversity of a population caused by a reduction in its size.
•Founder effect- a change in a population descended from a small number of colonizing individuals.
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Speciation
•The creation of a new species
•Can happen in two ways
•Allopatric speciation
•Sympatric speciation
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Speciation and extinction determine biodiversity
•Allopatric speciation- when new species are created by geographic or reproductive isolation.
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• Sympatric speciation- the evolution of one species into two species in the absence of geographic isolation, usually through the process of polyploidy, an increase in the number of sets of chromosomes.
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Speciation and extinction determine
biodiversity
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The Pace of Evolution
•Depends on…
•Rate of Environmental change
•Level of Genetic variation
•Population Size
•Reproductive rate
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Rate of Environmental Change
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Level of Genetic Variation
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Population Size
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Reproductive Rate
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Test Practice
•Would a species with a high rate of env. change, high genetic variation, large population size and fast reproductive rate have a rapid or slow evolution?
•Would a species that had a slow rate of env. change, high genetic diversity, a large population size and a slow reproductive rate experience rapid or slow evolution?
•Justify your answers for both
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Evolution shapes
ecological niches and determines
species distributions
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Niches and Species distribution
•Range of tolerance- all species have an optimal environment in which it performs well. The limit to the abiotic conditions they can tolerate is known as the range of tolerance.
•Fundamental niche- the ideal conditions for a species.
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Niches
•Realized niche- the range of abiotic and biotic conditions under which a species lives. This determines the species distribution, or areas of the world where it lives. (ecosystem)
•Niche generalist- species that live under a wide range of conditions.
•Niche specialist- species that live only in specific habitats.
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The Fossil Record
•Fossils- remains of organisms that have been preserved in rock. Much of what we know about evolution comes from the fossil record.
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The Five Global Mass Extinctions
•Mass extinction- when large numbers of species went extinct over a relatively short period of time.
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The Sixth Mass Extinction
•Scientists feel that we are in our sixth mass extinction, occurring in the last two decades.
•Estimates of extinction rates vary widely, from 2 % to 25% by 2020.
• In contrast to previous mass extinctions, scientists agree that this one is caused by humans.