Bio Exam 2 - Professor Fischetti

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What is this curve?

What curve is this?

What is happening when a graph flattens out?

It has reached Carrying Capacity/Steady State

What is it called when exponential growth eventually creates too many individuals for the environment to support?

Struggle for Existence

Morphological/Phenotypic Variation

Variation in the form of structure of the organism

Continuous Variation

Infinite number of possible measurements between extremes

Discontinuous Variation

Variation can be categorized (qualitative). Ex: eye color, hair color, height, rows of scales

How do you know which allele is dominant?

The trait expressed in the Heterozygote is the dominant allele’s trait.

If a population is evolving…

allele or genotype frequencies change from generation to generation

If a population is not evolving…

it is in Hardy-Weinberg Equilibrium

If calculated x² is greater than critical x², is the population evolving?

The population is evolving

Ontogeny

The change an individual experiences over a lifetime.

Mendel’s Laws

Segregation, Independent Assortment, Law of Dominance

Hardy-Weinberg Equilibrium

Genotype frequencies are due to random chance

HWE Assumption: No Natural Selection

All genotypes will have equal fitnesses (fixed)

Assortative Mating

Mating occurs between same phenotype or genotype

Disassortative Mating

Mating occurs between different phenotype or genotype

HWE Assumption: No Migration/Gene Flow

There must be no allele differences in HWE

HWE Assumption: No Mutation

There must be no variation in HWE

HWE Assumption: Mating is Random

Cannot has assortative or disassortative mating

Microevolution

chenges within populations

Macroevolution

occurs above the species level

Phylogenetic Trees (or Cladograms)

Nodes, Leaves, Branches

Node

implies a common ancestor for species on branches above the node

Leaves

equally related to their most closely shared node

Branch

Connection between nodes and/or leaves

Phenotypes

Physical (morphological, structural) attributes of an organism influenced by its genotype and environment.

Hardy-Weinberg Equilibrium

A principle that gives predictions for the null hypothesis regarding genetic variation.

Cryptic Variant

A variant that blends in with its environment.

Conspicuous Variant

A variant that stands out in its environment.

Carrying capacity

The maximum population size that an environment can sustain.

J Curve or Exponential Curve

A specific shape of a growth curve reflecting unlimited resources, resulting in population doubling.

Struggle for existence

The concept inferred by Darwin that populations produce more offspring than the environment can support.

Homozygous dominant genotype frequency

In Hardy-Weinberg equilibrium, the expected frequency if p = 0.6 is 0.36.

Expected number of heterozygous individuals

Using the HWE formula 2pq, the expected number of heterozygous individuals (Dd) in a population of 1,000 where p=0.6 and q=0.4 is 480.

Chi-square value conclusion

If the chi-square value is 0.0, the conclusion is that the population is not evolving.

Nonrandom mating

A violation of Hardy-Weinberg equilibrium that changes genotype frequencies but not necessarily allele frequencies.

Stabilizing selection

A mode of selection where the average phenotype is favored and extremes are selected against.

Heterozygote advantage

A phenomenon maintaining both alleles and preventing fixation due to their fitness differences.

Exponential growth

Population growth pattern that occurs in environments with abundant resources.

Fixation

When an allele’s frequency reaches 1.0 (100%) in a population due to strong selective pressure.

Directional selection

A mode of selection where a population shifts toward one extreme trait.

Standard deviation

A statistical measure that decreases as a population becomes more specialized for a specific environment.

Disruptive selection

A mode of selection where individuals with extreme traits survive better than those with average traits.

Genetic Drift

The effect of chance on a population’s allele and genotype frequencies.

Mutation

A chemical error during DNA replication leading to new traits.

Natural selection

The process where certain traits increase survival and reproduction rates.

Migration or gene flow

The movement of individuals or gametes between populations, introducing new alleles.

Allele A

An allele expected to decrease in frequency over time due to low fitness.

Sickle Cell Anemia

A genetic disorder where a deleterious recessive allele persists due to stabilizing selection.

Strength of selection (S)

Calculated as S = 1 - W, where W is the fitness of an individual or phenotype.

Gene

A basic unit of inheritance.

Allele

Different forms of the same gene.

Genotype

The combination of alleles found in an individual.

Mendel's Laws

The principles of segregation and independent assortment.

Gene Pool

The total number of copies of a gene within a population.

Frequency sum in population genetics

All allele frequencies in a population must add up to 1.

Darwin’s finches

An adaptive radiation of 14 species traced back approximately 5 million years.

Hardy-Weinberg Equilibrium

A principle to test whether a population is evolving.

Assortative mating

Mating that occurs between individuals of the same phenotype or genotype.

Disassortative mating

Mating that occurs between individuals of different phenotypes or genotypes.

Genetic bottleneck

Temporary reduction in population size due to environmental events that limits genetic diversity.

Microevolution

Small-scale changes within populations over time.

Macroevolution

Large-scale evolutionary changes occurring above the species level.

Phylogeny

The evolutionary history of an organism.

Phylogenetic trees

Diagrams that represent the evolutionary relationships between species based on shared traits.

Monophyletic group

A group that shares a common ancestor.