3 Species: a group of individuals that look similar and whose members are capable of producing fertile offspring in the natural environment
4 Morphological Species Concept Morphological Species Concept: the idea that organisms can be classified by differences in their appearanceUsing this concept, scientists can readily communicate about the characteristics, behavior, and relationships of organisms.The morphological concept of species is limited because it does not account for the reproductive compatibility of morphologically different organisms.
6 Biological Species Concept Biological Species Concept: the idea that organisms can be classified by their ability to breed with one anotherUsing both the biological and morphological concepts of species, modern scientists have arrived at the current definition of the term species.
7 Species: a group of individuals that look similar and whose members are capable of producing fertile offspring in the natural environment
8 Variation of Traits in a Population Population: all the members of a species that live in the same area and make up a breeding groupWithin a population, individuals vary in many observable traits.
12 What causes variation in traits? Environmental FactorsHeredityA difference in genotype usually results in a difference in phenotype.Variations in genotypes arise through:MutationGenetic RecombinationIndependent AssortmentCrossing Over
13 Allele Frequencies and Genetic Equilibrium Gene Pool: all the genes for all the traits in a populationAllele Frequency: the percentage of an allele in a gene poolGenetic Equilibrium: the condition in which allele frequencies in a population do not change from generation to generation
15 Hardy & WeinbergHardy and Weinberg outlined the conditions necessary for genetic equilibrium.Godfrey HardyWilhelm Weinberg
16 Hardy-Weinberg Principle Hardy and Weinberg outlined the conditions necessary for genetic equilibrium.1. no mutations occur2. individuals neither enter nor leave the population through migration3. the population is large4. individuals mate randomly5. natural selection does not occur
17 Hardy-Weinberg Principle If one of these conditions does not hold true, allele frequencies of the population may change. In other words, evolution will occur.
19 Disruption of Genetic Equilibrium Evolution occurs when genetic equilibrium is disrupted.
20 1. MutationMutations affect genetic equilibrium by producing totally new alleles for a trait.In addition, mutations can change the frequency of the alleles already present in the gene pool.The occurrence of mutation in most alleles is too low to cause major changes in the allele frequencies of an entire population.
22 2. MigrationMigration: the movement of individual organisms into or out of a population, community, or biomeImmigration: movement of new individuals into a populationEmigration: departure of individuals from a populationGene Flow: the movement of genes into or out of a population
24 3. Genetic DriftGenetic Drift: a shift in allele frequencies in a population due to random events or chanceIn small populations, chance can significantly affect allele frequencies from one generation to the next.
30 Stabilizing Selection Stabilizing Selection: a type of natural selection in which the average form of a trait causes an organism to have an advantage in survival and reproductionThe extreme forms of the trait confer a disadvantage to the organism.Stabilizing selection is most effective in a population that has become well adapted to its environment.Stabilizing selection is the most common type of NS.
34 Disruptive SelectionDisruptive Selection: natural selection in which individuals with either of the extreme forms of a trait have an advantage in terms of survival and reproductionThe average form of the trait confers a selective disadvantage to the organism.
39 SpeciationDisruption of genetic equilibrium leads to changes in the gene pool of a population.Natural selection causes the most significant genetic changes in a population, however, such changes do not necessarily lead to speciation.Speciation: the formation of a new species
42 Isolated PopulationsFor a new species to arise, either interbreeding of the population of fertile offspring must somehow cease among members of a formerly successful breeding population.For this to occur, populations or segments of populations must somehow become isolated.Two Forms of Isolation:Geographic IsolationReproductive Isolation
43 Geographic IsolationGeographic Isolation: the physical separation of populationsExamples: population becomes divided by land or water barrier, colonization of new island, river changes course, highway built across field, etc.
44 Reproductive Isolation Reproductive Isolation: the inability of formerly interbreeding organisms to produce offspringReproductive isolation can occur through disruptive selection.
45 Rates of SpeciationPunctuated Equilibrium: a theory that speciation may occur during brief periods of rapid genetic changeGradualism: a theory that speciation may occur through a gradual change of adaptationsExtinct: the state of a species that no longer existsFor a species to continue to exist, some members must have traits that allow them to survive and pass their genes on to the next generation.
Your consent to our cookies if you continue to use this website.