-
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
-
Scientific Method?
- Observation
- Hypothesis
- Test the Hypothesis (experiment)
- Analyze results
- reject or fail to reject hypothesis.
- (Never Prove Hypothesis)
-
Alleles?
Different versions of the same gene.
-
Genotype?
the types of genes (alleles) present
-
Homozygous?
two of the same alleles (RR or rr)
-
Heterozygous?
two different alleles (Rr)
-
Phenotype?
physical appearance, determined by the genotype.
-
Dominant Traits?
traits that are expressed, represented by a capital letter.
-
Recessive Traits?
only seen when homozygous, represented by a lowercase letter.
-
Mendelian Genetics
Punnett Squares and probability.
-
Monohybrid cross?
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.
-
Dihybrid crosses?
- Crosses involving two genes simultaneously.
- Ex: Mendel's peas: seed color and seed shape are on different chromosomes.
-
Population?
- A group of individuals of the same species, occupying the same space/environment, that can interbreed.
- Ex: Squirrels in Central Park
-
H-W Equilibrium
an equation, describes relationships between alleles and genotype frequencies (in a population that is not evolving)
-
Evolution
Changes in populations of organisms over time.
-
H-W Assumptions
- No mutations
- No natural selection
- Infinitely large population
- No migration between populations
- Random mating
-
Forces of Evolution?
- Mutation
- Genetic Drift
- Natural Selection
- Migration
- Nonrandom mating
-
Fitness
- 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)
-
Natural Selection
Individuals that survive and reproduce (have greater Fitness) will lead to a change in allele frequencies over time
-
Artificial Selection
- 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
- Directional
- Stabilizing
- Diversifying
- Balancing
-
Directional Selection
Individuals at one extreme of a phenotypic range have greater survival/reproductive success
-
Stabilizing Selection
Individuals with intermediate phenotypes have greater survival/reproductive success
-
Diversifying Selection
Two or more different genotypes/phenotypes are favored; often occurs in heterogeneous environments
-
Balancing Selection
- 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
-
Sexual Selection
- form of natural selection
- directly promotes reproductive success
-
Intrasexual selection
- between members of the same sex
- males directly compete for mating opportunities or territories
-
Intersexual Selection
- between members of the opposite sex
- female choice
-
Genetic Drift
- 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
-
Bottleneck
- 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
-
Founder effect
- small group separates from larger population and establishes new colony
- relatively small founding population expected to have less genetic variation
-
Migration
gene flow occurs when individuals migrate between populations having different allele frequencies
-
Nonrandom Mating
- assortative mating
- disassortative mating
-
Assortative Mating
- Individuals with similar phenotypes are more likely to mate
- increases the proportion of homozygotes
-
Disassortative Mating
Dissimilar phenotypes mate preferntially, favors heterozygosity
-
Inbreeding
- 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
|
|