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Chapter 5

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Stacey Jones

on 21 April 2013

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Transcript of Chapter 5

Chapter 5 Explain the concept of biodiversity and how it is measured. Describe the ways in which evolution can occur. Explain how environmental change affects speciation and extinction. Explain the concept of an ecological niche. Biodiversity exists at three scales: ecosystem diversity, species diversity, and genetic diversity. Environmental scientists measure species diversity both by the number of species in a particular location (species richness) and by how evenly individuals are distributed among those species (species evenness). The greater the number of species, and the more even the distribution, the higher the diversity. Evolution can occur through artificial selection, natural selection, or random processes. Artificial selection occurs when humans determine which individuals will mate and pass on their genes to the next generation to achieve a predetermined suite of traits. Natural selection does not favor a predetermined suite of traits, but simply favors those individuals that are best able to survive and reproduce. Random processes (mutation, genetic drift, bottleneck effects, and founder effects) do not favor a predetermined suite of traits, nor do they favor individuals with the highest fitness. Allopatric and sympatric speciation are two ways in which new species can evolve. Four factors that affect a species’ ability to adapt to environmental change are the rate of environmental change, the amount of genetic variation within the species, population size, and generation time. Evolution by natural selection favors combinations of traits that perform well under particular environmental conditions. As a result, each species has a range of preferred abiotic conditions that constitute its fundamental niche. This fundamental niche is further restricted by biotic factors, including competition, predation, and disease, to form the species’ realized niche. Changes in environmental conditions therefore have the potential to change species’ distributions. Key Terms ecosystem diversity: The variety of ecosystems within a given region.
species diversity: The variety of species within a given ecosystem.
genetic diversity: The variety of genes within a given species.
species richness: The number of species in a given area.
species evenness: The relative proportion of different species in a given area.
phylogenies: The branching patterns of evolutionary relationships.
evolution: A change in the genetic composition of a population over time.
microevolution: Evolution occurring below the species level.
macroevolution: Evolution that gives rise to new species, genera, families, classes, or phyla.
genotype: The complete set of genes in an individual.
mutation: A random change in the genetic code produced by a mistake in the copying process.
recombination: The genetic process by which one chromosome breaks of and attaches to another chromosome during reproductive cell division.
phenotype: A set of traits expressed by an individual.
evolution by artificial selection: A change in the genetic composition of a population over time as a result of humans selecting which individuals breed, typically with a preconceived set of traits in mind.
evolution by natural selection: A change in the genetic composition of a population over time as a result of the environment determining which individuals are most likely to survive and reproduce.
fitness: An individual’s ability to survive and reproduce.
adaptation: A trait that improves an individual’s fitness.
genetic drift: A 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.
geographic isolation: Physical separation of a group of individuals from others of the same species.
reproductive isolation: The result of two populations within a species evolving separately so they can no longer interbreed and produce viable offspring.
allopatric speciation: The process of speciation that occurs with geographic isolation.
sympatric speciation: The evolution of one species into two, without geographic isolation.
genetically modified organism (GMO): An organism produced by copying genes from a species with a desirable trait and inserting them into another species.
range of tolerance: The limits to the abiotic conditions that a species can tolerate.
fundamental niche: The suite of ideal environmental conditions for a species.
realized niche: The range of abiotic and biotic conditions under which a species actually lives.
distribution: Areas of the world in which a species lives.
niche generalist: A species that can live under a wide range of abiotic or biotic conditions.
niche specialist: A species that is specialized to live in a specific habitat or to feed on a small group of species.
fossil: The remains of an organism that has been preserved in rock.
mass extinction: A large extinction of species in a relatively short period of time. Chapter 5.1 Checkpoint ?'s Chapter 5.2 Checkpoint ?'s Chapter 5.3 Checkpoint ?'s Chapter 5.4 Checkpoint ?'s Why is it challenging to determine the number of species on Earth? Because there are so many we haven't discovered yet. Why are estimates of species diversity valuable to environmental scientists? Because they can know how many of each species there is.Because species richness or evenness often declines after a human disturbance, knowing the species richness and species evenness of an ecosystem gives environmental scientists a baseline they can use to determine how much that ecosystem has changed. What is the difference between species richness and species evenness? Why are they both important measures? Species Richness is the number of species in a given area. Species Evenness is the relative proportion of each species in a given area. Because species richness or evenness often declines after a human disturbance, knowing the species richness and species evenness of an ecosystem gives environmental scientists a baseline they can use to determine how much that ecosystem has changed. What is evolution, and what are the three main ways in which it occurs? Evolution is change in the genetic composition of a population over time. Evolution occurs in three primary ways: by artificial selection, by natural selection, and by random processes. How are artificial and natural selection similar? How are they different? Both are a change in the genetic composition of a population over time, they are similar in the process of evolution. but one key difference between the two is the environment determines which individuals survive and reproduce. How does evolution lead to biodiversity? The rate of evolution is different for each species and evolution creates and destroys new and old species which creates a wider biodiversity. How does geographic isolation lead to reproductive isolation? Geographic barriers can split populations. Natural selection may favor different traits in the environment of each isolated population, resulting in different adaptations. Over time, the two populations may become so genetically distinct that they are no longer capable of interbreeding. What factors influence a species’ chances of adapting successfully to a change in its environment? The four factors on successful adaptation: rate of environmental change, genetic variation, population size, and generation time. Why is the pace of human-driven evolution faster than that of natural evolutionary processes? Because humans are faster than nature. How do fundamental niches and realized niches differ? Fundamental niche is the suite of ideal environmental conditions for a species. Realized niche is the range of abiotic and biotic conditions under which a species actually lives. How does environmental change determine species distribution? When does it lead to extinction? It determines what plants/ animals will live and where they will live. When the change is too high for them to adapt too this leads to extinction. How are human activities affecting extinction rates, and why is their impact a particular concern? Humans are destroying many species habitat by cutting down forest to use to make houses, contributing to the rising greenhouse gases causing global climate change, putting roads and homes in the migration paths of animals, over hunting and much more. It is a particular concern because its easier to change than nature herself. Evolution of Biodiversity
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