Chapter 5

Chapter 5

Species Diversity
1. Ecosystem Diversity
  1. The variety of ecosystems within a given region
2. Species Diversity
  1. The variety of species within a given ecosystem
3. Genetic Diversity
  1. The variety of genes within a given species
  2. Genes form blueprint for organism's traits, diversity of genes helps determine species and ecosystem diversity.
Number of Species on Earth
1. Species: A group of organisms distinct from other groups in terms of size, shape, behavior or biochemistry that can interbreed with others in the group to produce viable offspring
2. The number of species is the most common measurement of biodiversity.
  1. This can be hard to determine due to inaccessibility of certain nocturnal, ocean dwelling or microscopic beings.
  2. Current estimates of total species on Earth are between 5-100 million, most likely around 10 million.
Species Richness and Eveness
1. Simply the number of species cannot accurately determine local or regional species diversity.
2. Species Richness: the number of species in a given area
  1. Richness provides general sense of biodiversity.
3. Species Evenness: says whether an ecosystem is numerically dominated by one species or whether all species have similar abundances
  1. Low species evenness implies low biodiversity.
Evolutionary Relationships Among Species
1. Scientists organize species into categories based on how closely related they are.
  1. Phylogenies: branching patterns of evolutionary relationships
    1. Expressed through phylogenetic tree.
    2. Is determined by similarity of traits.
Evolution as the Mechanism Underlying Biodiversity
1. Evolution: change in the genetic composition of a population over time, produces Earth's biodiversity
2. Microevolution: evolution below the species level, i.e. different varieties of the same fruit
3. Macroevolution: genetic changes that create new species, genera, families, classes or phyla- larger categories of organisms into which species are organized.
Creating Genetic Diversity
1. Genes: physical locations on chromosomes within each cell of an organism, determine possible traits that are passed down to offspring.
2. Genotype: complete set of genes in an individual
3. Two Processes of Genetic Diversity
  1. Mutation: occasional mistake in DNA copying process that produces 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 combination of genes producing novel traits
    1. Can provide new immune defenses, increasing survival rate.
4. Phenotype: the actual set of traits expressed in an individual's anatomy, physiology and behavior
Evolution by Artificial Selection
1. Artificial Selection: human induced evolution, i.e. breeding animals to create certain traits
  1. Can result in unwanted resistances (i.e. to antibiotics) or characteristics
Evolution by Natural Selection
1. Natural Selection: Environment induced evolution based on which individuals can survive and reproduce
2. Darwin's Theory of Natural Selection
  1. Individuals produce excess offspring
  2. Not all offspring survive
  3. Individuals differ in traits
  4. Differences in traits can be passed from parent to offspring
  5. Differences in traits imply differences in the ability to survive and reproduce
3. Fitness: an organism's ability to survive and reproduce (trait that implies Natural Selection
  1. Adaptation: a trait that improves an individual's fitness
Evolution by Random Processes
1. Mutation: occurs randomly, if not lethal, adds to genetic variation of population, accumulation of mutations in a population becomes evolution
2. Genetic Drift: change in genetic composition of a population over time as the result of random mating, non- adaptive and random process
3. Bottleneck Effect: reduction in genetic diversity of a population caused by a reduction in its size
4. Founder Effect: change in a population descended from randomly chosen colonizing individuals
Speciation and Extinction Determine Biodiversity
1. Allopatric Speciation: speciation requiring geographic isolation, most common way new species evolve
  1. Geographic Isolation: when a subset of individuals from a larger population colonize a new area, physically separated from the rest of the population.
  2. Reproductive Isolation: Due to physical separation over a period of time, organisms become to different to reproduce viable offspring together
2. Sympatric Speciation: evolution of one species into two species without any geographic isolation
Pace of Evolution
1. Rate of Environmental Change- how fast a species can adapt determines its survival
2. Genetic Variation- species with high genetic variation contain individuals with a wide variety of phenotypes, making it more like for some to survive
3. Population Size- though small populations usually don't have much genetic variation, if there is a mutation, it spreads quickly
4. Generation Time- if a species becomes reproductively mature quickly, it tends to evolve faster
Genetic Engineering: when scientists copy genes from a species with a desirable trait and insert it into another species
Genetically modified organisms: organisms which have been genetically engineered
Evolution Shapes Ecological Niches and Species Distribution
1. Range of Tolerance: a species' limit to abiotic conditions it can tolerate (i.e. temperature, pH, salinity)
2. Fundamental Niche: set of ideal living conditions for a species
  1. This includes abiotic conditions (temperature, etc) and biotic conditions (competition, predators and disease)
3. Realized Niche: the range of abiotic and biotic conditions under which a species actually lives
4. Distribution: areas of the world in which a species lives
5. Niche Generalists: can live in a variety of habitats and feed on a variety of species
6. Niche Specialists: must live in specific habitat or feed on small group of species
Environmental Change and Species Distribution
1. As environments change (i.e. in climate, resources) species move to different areas, their ability to do this differs (i.e. a bird vs. a worm)
Environmental Change and Species Extinction
1. If a species cannot adapt to an environment or change to a more suitable one, it will go extinct
2. Much information on evolution has been procured through studying fossils
  1. Fossils: the remains of organism that have been preserved in rock.
3. According to fossil records there have been five periods of Global Mass Extinction
  1. Mass Extinction: extinction of large number of species over a relatively short time period
  2. The biggest mass extinction was 251 million yrs ago, 90% of marine speciesand 70% of land vertebrates went extinct.
  3. Most famous mass extinction was at the end of the Cretaceous Period, half of all species (i.e. dinosaurs) went extinct, probably due to large meteorite that. A squirrel sized primate that is an ancestor of humans, survived.
  4. We are currently experiencing a sixth mass extinction primarily due to harmful human activities with rapidly onset consequences leaving little time to move or adapt to survive extinction.

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