Chapter 5

Chapter 5

Earth is home to diversity of species
1. Ecosystem Diversity: the variety of ecosystems within a given region
2. Species Diversity: the variety of species within a given ecosystem
3. Genetic Diversity: the variety of genes within a given species
  1. Genes form the blueprints for organism's traits. With genetic diversity, it helps determine the species of diversity and ecosystem diversity
How many species?
1. the number of species in any place is the measure of biodiversity
  1. It is hard to determine how many species there actually are because many organisms live in inaccessible locations
  2. Scientists have estimated around 5 to 100 million species
Species Richness and Evenness
1. Species Richness: the number of species in a given area
2. Species Evenness: whether a particular ecosystem is numerically dominated by one species or whether all of its species have similar abundances
  1. High species evenness means higher levels of biodiversity while low species evenness is the opposite
3. Species evennes and richness declines after human disturbance
Evolutionary relationships
1. organizing species into categories of how closely they are related
2. Phylogenies: the branching patterns of evolutionary relationships
  1. determined by the similarity of their traits
Evolution is the mechanism underlying biodiversity
1. Evolution: a change in the genetic composition of a population over time
2. Microevolution: evolution below the species level (i.e. different varieties of the same vegetables
3. Macroevolution: genetic changes that create new species, genera, families, classes, or phyla-larger categories of organisms into which species are organized
Genetic Diversity
1. Genes: physical locations on chromosomes within each cell of an organism
2. Genotype: complete set of genes in an individual
3. Phenotype: The actual set of traits in an individuals anatomy, physiology and behavior
4. Two processes of genetic diversity:
  1. Mutation: occasional mistake in DNA copying process that reduces a random change in genetic code
    1. Most are detrimental but some improve chances of survival or reproduction
  2. Recombination: as chromosomes are duplicated during reproductive cell division, a piece of a chromosome breaks off and attaches to another chromosome, creating new combinations of genes producing novel traits
    1. This can help the immune systems defense
Evolution by Artificial Selection
1. Evolution by Artificial Selection: when humans determine which individuals breed, typically with a certain set of traits
  1. However it can produce unwanted results (i.e. weeds with mutations repelling herbicides)
Evolution by Natural Selection
1. Evolution by Natural Selection: the environment determines which species survive and reproduce
2. Fitness: an individuals ability to survive and reproduce
  1. Adaptation: traits that improve an individual's fitness
3. Darwin's Theory
  1. not all offspring survive
  2. individuals produce an excess of offspring
  3. individuals differ in their traits
  4. differences in traits can be passed on from parents to offspring
  5. differences in traits are associated with differences in the ability to survive and reproduce
Evolution by Random Processes
1. Mutation: occur randomly; if not lethal, they can add to genetic variation of a population
2. Genetic Drift: change in genetic composition of a pop. over time as a result of random mating
3. Bottleneck Effect: a reduction in the genetic diversity of a pop. caused by a reduction in its size
4. Founder Effect: a change in population descended from a small number of colonizing individuals
Allopatric versus Sympatric Speciation
1. Geographic Isolation: ex. of evolution creates new species; when a subset of individuals from a bigger pop. colonize in a new area that is physically separated from the rest of the pop.
2. Reproductive Isolation: when two pop.s will be separated over time and will become so different that even if the physical barriers were removed, they couldn't interbreed and produce offspring
3. Allopatric Speciation: speciation requiring geographic isolation
4. Sympatric Speciation: evolution of one species into two species without geographic isolation
Pace of Evolution
1. Rate of change: to survive- the pop. must evolve quickly.
2. Genetic Variation: species with high genetic variation contain individuals with a wide variety of phenotypes
3. Pop. Size
  1. Genetic Engineering: scientists can copy genes from a species with a certain trait and insert them into another species
  2. Genetically Modified Organisms: organisms which have gone through the process of genetic engineering
Evolution Shapes Ecological Niches and Determines Species Distributions
1. Range of Tolerance: limits to the abiotic conditions they can tolerate (ex. temp., humidity, salinity, pH)
2. Fundamental Niche: the ideal conditions of the species
3. Realized Niche: the range of abiotic and biotic conditions under which a species actually lives
4. Distribution: the areas of the world in which the species lives
5. Niche Generalists: species which can live in a variety of habitats or feed on a variety of species
6. Niche Specialists: species must live in a specific habitat or feed on a small group of species
Environmental Changes and Species Distributions
1. 5 Global Mass Extinctions
  1. Mass Extinction: extinction of a large number of species one a short time period
  2. Greatest Mass Extinction: 251 million years ago, 90% marine species and 70% land vertebrates went extinct
  3. Better known Extinction: end of Cretaceous period (65 million years ago), around one half of Earths species went extinct
  4. Currently in the 6th mass extinction, due to harmful human activities, depleting the world from 2-25% of species
2. Fossils: the remains of organisms that have been preserved in rocks
3. Environmental changes: if species cannot adapt to the changes or move to a better environment they they will eventually go extinct
  1. The average lifespan of a species is around 1-10 million years

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