apes unit iv: evolution and biodiversity chapter 5
TRANSCRIPT
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APESUnit IV: Evolution and Biodiversity
Chapter 5
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▪ Evolution: Change in genetic composition of a population over time
▪ population: all individuals of the same species occupying the same area.
▪ gene: unit of heritable information -usually associated (at the molecular level) with a specific region located on the chromosome.
▪ allele: - one of two or more slightly different forms, or "variants" of a given gene.
▪ genotype: a selection of the genes that make up an individual.
▪ phenotype: the consequence(s) of all the allelic interactions that give rise to a visibly determinable "type".
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Genetics 101
▪ gene pool: all the genotypes within a population.
▪ Mutation: mistake in copying of genetic code; if mutation in sex cells it is inherited.
▪ Recombination: during cell division part of one chromosome breaks off and attaches to another, which leads to new gene combinations and thus genetic diversity
▪ Evolution by Artificial Selection: Breeding dogs, horses, pea plants
▪ Unintended consequence of agricultural breeding is pesticide/herbicide resistance
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I.Understanding Biodiversity
▪ HHMI: 2014 Lectures 2 and 3
▪ Biodiversity: variety of earth’s species, or varying life forms, the genes they contain, the ecosystems they live in and the ecosystem processes of energy flow and nutrient cycling that sustain life.
▪ Ecosystem Diversity
▪ Species Diversity
▪ Population Diversity
▪ Genetic Diversity
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II. Human Impacts on Biodiversity
Human Impact on Biodiversity
Underlying Causes: population growth, poverty, undervaluing natural capital
Direct Causes: HIPPCO
H=Habitat Destruction, degradation and fragmentation
I: Invasive Species
P=Population growth and increase resource use
P=Pollution
C: Climate Change
O: Overexploitation
▪ Population
▪ Land Transformation
▪ Climate Change
▪ Invasive Species
▪ Diseases
▪ The role of Protected Areas
▪ Synergistic Effects
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Invasive / Alien/Non-Native Species
▪ Native Species: live in their historic range-where they have lived for thousands-millions of years
▪ Alien: Live outside historic range
▪ Some species moved accidentally , some intentionally
▪ Asian Carp
http://www.cbsnews.com/video/watch/?id=5869154n
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Kudzu
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Zebra Mussels▪ feed by drawing water and filtering out most of the
suspended microscopic plants, animals and debris for food.
▪ can lead to increased water clarity and a depleted food supply for other aquatic organisms, including fish.
▪ The higher light penetration fosters growth of rooted aquatic plants which, although creating more habitat for small fish, may inhibit the larger, predatory fish from finding their food.
▪ Zebra mussel infestations may also promote the growth of blue-green algae, since they avoid consuming this type of algae but not others.
▪ Zebra mussels attach to the shells of native mussels in great masses, effectively smothering them
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▪ http://www.nwf.org/What-We-Do/Protect-Wildlife/Invasive-Species/Ballast-Water.aspx
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Population, Pollution and Climate Change
▪ Pollution: DDT
▪ Population: Bald Eagle: saved eagle but shortage of fish mean they eat baby cormorant chicks
▪ Climate Change: Cannot adapt fast enough; Polar Bearhttps://www.youtube.com/watch?v=lPgZfhnCAdI
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Overexploitation: Hunting, Fishing, Illegally killing, capturing and selling wild species
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III. Measuring Biodiversity
▪ Diversity and Abundance▪ Species Richness:
Number of different species▪ Species Evenness:
abundance / proportion of individuals within the species. Are all species represented by similar numbers of individuals?
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III. Measuring Biodiversity
▪ Genetic Diversity and adaptation:
▪ Habitat Fragmentation:
▪ Habitat Islands:
▪ Habitat Corridors:
▪ Island Biogeography: a field within biogeography that examines the factors that affect the species richness of isolated natural communities
▪ Population Bottleneck:
▪ Pika Study:
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▪ Species Richness Influenced by many factors▪ Latitude: richness declines as we move from
equator toward North or South Pole.▪ Time: Longer a habitat exists, the more
colonization and speciation▪ Theory of Island Biogeography: Influence of
SIZE of habitat an d DISTANCE
▪ Conservation: Should we establish several small reserves or a single large reserve?
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IV. Evolution by Natural Selection
▪ Biological Evolution: the process whereby earth’s life changes over time through changes in genetic characteristics of populations. All species descended from earlier, ancestral species.
▪ Proposed by Charles Darwin-On the Origin of Species by Means of Natural Selection. Change in populations (not individuals) genetic makeup over successive generations. Major driving force of adaptation
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Darwin’s Theory▪ Individuals produce an excess of offspring▪ Not all offspring can survive▪ Individual differ in their traits (Genetic Variability )▪ Differences in traits can be passed from parent –
offspring (differential reproduction)▪ Natural Selection: environmental conditions favor
some individuals over others
▪ Fitness: Ability to survive and reproduce
▪ Adaptation/Adaptive Traits: any heritable trait that improves the ability of an individual organism to survive and to reproduce at a higher rate than other individuals in a population under prevailing environmental conditions.
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▪ Differential reproduction: individuals with the trait are able to survive and reproduce at a higher rate than other individuals in the population
▪ Natural Selection at work: Genetic Resistance=ability of one or more organisms in a population to tolerate a chemical designed to kill it. Antibiotic Resistance/Pesticide Resistance
▪ Limitations to adaptation through natural selection▪ Change in enviro condition can lead to adaptation only
for genetic traits already present in a population’s gene pool or for traits resulting from mutations, which occur randomly
▪ Ability to adapt limited by reproductive capacity
▪ Natural Selection acts on individuals but occurs in populations
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▪ Example of Evolution by Natural Selection
Peppered Moth
▪ Coevolution: Populations of two different species interact over a long period of time, change in gene pool of one can lead to change in gene pool of another.
▪ http://www.biotopics.co.uk/newgcse/naturalselection.html
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IV. Evolution by Random Processes
▪ Genetic Drift: Change in allele frequency in a population due to random sampling. Some organisms, by chance, leave behind more offspring
▪ genetic drift with marbles
▪ Population Bottleneck: an evolutionary event in which a significant percentage of a population or species is killed or otherwise prevented from reproducing; some genotypes will be lost and genetic composition of survivors will differ from original group
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Founder Effect
▪ The founder effect is a special case of a population bottleneck, occurring when a small group in a population splinters off from the original population and forms a new one, taking with it only limited alleles from the original population
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Summary
▪ Earth’s biodiversity is the product of evolution, a change in the genetic composition of a population over time
▪ Evolution below the species level is microevolution-variety of apples or potatoes
▪ Genetic changes that give rise to new genera, families, classes in macroevolution
▪ Extinction and speciation are what leads to biodiversity
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V. Speciation and Extinction Determine Biodiversity
▪ Process of Speciaition- Two Phases
Geographic Isolation: groups from same population become physically isolated
Reproductive Isolation: When sexually reproductive organisms becomes so genetically different they cannot mate
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Pace of Evolution
▪ Hundreds to millions of years
▪ Average global rate 1 species every 3 million years.
▪ If populations cannot adapt quickly enough they go extinct
▪ To survive a rapid environmental change, a population must evolve quickly.
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▪ Ecological Niche: role of an organism in ecosystem; its way of life
▪ Niche includes adaptations acquired through evolution, range of tolerance, types and amounts of resources the species uses and interactions with other organisms. Competition limits niche
▪ Limits to Adaptation-ability to adapt limited to gene pool and how fast it can reproduce.
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▪ All species has an optimal environment in which it performs particularly well-a range of tolerance or limit to abiotic conditions they can tolerate.
▪ fundamental niche
▪ realized niche.
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▪ A generalist species: Broad Niches able to thrive in a wide variety of environmental conditions and can make use of a variety of different resources
▪ A specialist species: Narrow Niches can only thrive in a narrow range of environmental conditions or has a limited diet. Often prone to extinction.
▪ Most organisms do not all fit neatly into either group
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IX. Environmental Changes-Physical Evolution
▪ Movement of tectonic plates has determined location of continents and ocean basins▪ Location/latitude of continents
determines climate and thus where plants and animals live▪ Movement of continents has allowed
species to move, adapt to new environments and form new species.
▪ Movement of tectonic plates has allowed species to move, adapt to new climates and form new species
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▪ Volcanic Eruptions: Mt. Saint Helens: Destroy habitat and wipe out populations
▪ Earthquakes: create fissures that separate and isolate populations
▪ Climate Change and Natural Selection: Grizzly and Polar Bear
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▪ Divergence: One species becomes two
▪ Convergence: The evolution of species from different taxonomic groups toward a similar form.
▪ Extinction: Species ceases to exist. They can be ecologically extinct-number are so small they cannot fulfill their role. Over 99 % of all species that have ever lived are now extinct.
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▪ Endemic Species: found only in one area; are most vulnerable to extinction
▪ Background Extinction
▪ Mass Extinction
▪ The 6th mass extinction