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7 Characteristics of Life?
- 1. Cells and Organization
- 2.Energy use and Metabolism
- 3. Response to Environmental Changes
- 4. Regulation and Homeostasis
- 5. Growth and Development
- 6. Reproduction
- 7. Biological Evolution
- Test the Hypothesis (experiment)
- Analyze results
- reject or fail to reject hypothesis.
- (Never Prove Hypothesis)
Different versions of the same gene.
the types of genes (alleles) present
two of the same alleles (RR or rr)
two different alleles (Rr)
physical appearance, determined by the genotype.
traits that are expressed, represented by a capital letter.
only seen when homozygous, represented by a lowercase letter.
Punnett Squares and probability.
Hommozygous Dominant crossed with a homozygous recessive.
Law of Dominance
In the monohybrid cross (mating of two purebred organisms that differ in only one character), one version disappeared. There is a change in genotype, all are heterozygous.
- Crosses involving two genes simultaneously.
- Ex: Mendel's peas: seed color and seed shape are on different chromosomes.
- A group of individuals of the same species, occupying the same space/environment, that can interbreed.
- Ex: Squirrels in Central Park
an equation, describes relationships between alleles and genotype frequencies (in a population that is not evolving)
Changes in populations of organisms over time.
- No mutations
- No natural selection
- Infinitely large population
- No migration between populations
- Random mating
Forces of Evolution?
- Genetic Drift
- Natural Selection
- Nonrandom mating
- Relative likelihood that a genotype will contribute to the gene pool of the next generation as compared with other genotypes
- Measure of Reproductive Success
- The ability to survive and reproduce
Types of Selection?
- Phenotypes can be selected by humans to reproduce (artificial selection)
- Adaptation that increases survival and reproduction in a particular environment (natural selection)
Individuals that survive and reproduce (have greater Fitness) will lead to a change in allele frequencies over time
- Does not depend on the ability to survive or reproduce based on environmental conditions.
- Human induced
4 Observations of Natural Selection
- Individuals within populations vary
- Some of the variation among individuals can be passed to offspring
- Populations of organisms produce more offspring than will survive
- Survival and reproduction are not random
Patterns of Natural Selection
Individuals at one extreme of a phenotypic range have greater survival/reproductive success
Individuals with intermediate phenotypes have greater survival/reproductive success
Two or more different genotypes/phenotypes are favored; often occurs in heterogeneous environments
- increases genetic diversity
- creates a balanced polymorphism (2+ alleles are kept in balance and maintained in the population)
- Has heterozygote advantage, and negative frequency-dependent selection
- form of natural selection
- directly promotes reproductive success
- between members of the same sex
- males directly compete for mating opportunities or territories
- between members of the opposite sex
- female choice
- changes in allele frequencies due to random change
- Allele frequencies may "drift" randomly from one generation to the next
- happens regaurdless of fitness
- faster in smaller populations
- populations reduced dramatically and then rebuilds
- randomly eliminated members without regard to genotype
- surviving members may have allele frequencies different from original population
- new population likely to have less genetic variation
- small group separates from larger population and establishes new colony
- relatively small founding population expected to have less genetic variation
gene flow occurs when individuals migrate between populations having different allele frequencies
- assortative mating
- disassortative mating
- Individuals with similar phenotypes are more likely to mate
- increases the proportion of homozygotes
Dissimilar phenotypes mate preferntially, favors heterozygosity
- choice of mate based on genetic history
- does not favor any particular allele but it does increase the likelihood the individual will be homozygous
- negative consequences with regard to recessive alleles
- lower mean fitness
- inbreeding depression
Neutral Theory of Evolution
- much of the modern variation in gene sequences is explained by neutral variation rather than adaptive variation
- sequencing data supports this data