EVE 100 Midterm 1 Flashcards

Evolution

The change in heritable charecteristics of biological populaitons over succesive generations

The Modern Synthesis

Unified common descent and natural selection with Genetics to explain evolution comprehensively.

Misconceptions about Evolution

• Just a theory

• huge time scales to generate meanigful chagne

• It is natural selection

• “March in Progress,” resulting in more and orme advanced forms

• are common misunderstandings regarding how evolution operates and the mechanisms involved.

Phylogeny

A hypothesis of the relationships among species, population,, or genes.

Root

Lineage leading to the most recent common ancestor of all species/taxa in phylogeny.

Paraphyletic Group

A group of organisms that includes an ancestor but not all of its descendants, resulting in an incomplete representation of evolutionary relationships.

Polyphyletic Group

A group of organisms that does not include their most recent common ancestor, resulting in a grouping of species based on similar traits rather than shared ancestry.

Monophyletic Group

A group of organisms that includes a single common ancestor and all of its descendants, representing a complete branch of the evolutionary tree.

Polytomy

A branching pattern in a phylogenetic tree where three or more taxa emerge from a single ancestral node, indicating uncertainty about evolutionary relationships.

Cladogram

A diagram that represents the evolutionary relationships among different species, showing how they branch from common ancestors.

Phylogram

A type of phylogenetic tree that uses branch lengths to represent the amount of evolutionary change or genetic distance between taxa.

Chronogram

A type of phylogenetic tree that represents the timing of evolutionary events, where branch lengths are proportional to time.

Plesiomorphy

An ancestral trait shared by a group of organisms, indicating a common evolutionary heritage.

Apomorphy

A derived trait or feature that is specific to a particular lineage, distinguishing it from ancestral forms.

Synapamorphy

A shared derived trait that is used to define a clade and indicates a common evolutionary ancestor.

Homoplasy

A trait that appears similar in different taxa but did not arise from a common ancestor, often due to convergent evolution.

Homoplasy

A trait that is similar in different species but evolved independently, often resulting from adaptations to similar environments or ecological niches.

Homology

A trait that is similar in different species due to shared ancestry, reflecting evolutionary relationships.

Locus

A specific, fixed position on a chromosome where a particular gene or genetic marker is located.

gene

A basic unit of heredity composed of DNA, responsible for encoding proteins and influencing traits in an organism.

allele

one of two or more forms of a gene that arise by mutation and are found at the same place on a chromosome.

genotype

The genetic constitution of an individual organism, representing the combination of alleles inherited from its parents. p

phenotype

The observable physical or biochemical characteristics of an organism, determined by its genotype and environmental influences. These characteristics include traits such as height, eye color, and behavior.

Hardy Weinberg

principle that describes the genetic variation in a population that is in equilibrium. It states that allele and genotype frequencies will remain constant from generation to generation in the absence of other evolutionary influences.

Mutations

changes in the DNA sequence of an organism's genome, which can lead to new traits or variations. Mutations can occur spontaneously or be induced by environmental factors.

Mutation Rates

the probability that an offspring carries a new mutation 

Pleiotropy

a genetic phenomenon where a single gene influences multiple phenotypic traits, showing that genes can have more than one effect on the organism.

Silent mutation

mutation with no effect on phenotype

Neutral Mutation

Mutations with no effect on fitness (reproductive success)

Germline mutations

affect gametes

somatic mutations

affect skin tissue, neurons

Natural Selection

any consistent difference in fitness among different class of biological entities

Conditions for natural selection

1. Reproduction Individuals reproduce to create the next generation

2. Variation Individuals vary in their traits

3. Inheritance Individuals pass on some of their traits to their offspring

4. Differential success Individuals with different traits differ in their survival or reproductive success (fitnessconditions that allow certain traits to become more common in a population over generations.

fitness

= the number of offspring an individual leaves to the next generation

Positive selection

selection for an allele that increases fitness, reduces genetic variation, population will increase over time 

negative selection

a type of selection for an allele that decreases fitness

Selection Coefficient [s]

a measure of differences in relative fitness among genotypes

s>0

fitness advantage s

s<0

fitness disadvantage

Linkage Disequilibrium (LD)

the non-random association of alleles at different loci that occurs in a given population.

Overdominance

occurs when the heterozygote genotype has a fitness advantage over both homozygote genotypes.

heterozygote advantage

a situation in which heterozygous individuals have higher fitness compared to homozygous individuals. This phenomenon can enhance genetic diversity within a population and is commonly observed in various species.

Negative frequency-dependent selection

a type of natural selection where the fitness of a phenotype decreases as it becomes more common in a population. This can maintain genetic diversity by favoring rarer phenotypes. It often leads to a balanced polymorphism, as rare phenotypes receive a selective advantage.

Genetic Drift

a mechanism of evolution that involves random changes in allele frequencies in a population, particularly significant in small populations. It can lead to the loss of genetic variation and can cause alleles to become fixed or lost over time.

Effective Population Size N_E

the size of a population that determines the rate of genetic drift and loss of genetic diversity, often smaller than the actual population due to factors like unequal sex ratios or variation in reproduction. It reflects the number of individuals contributing to the next generation.

Polymorphism

The occurrence of two or more distinct forms, traits, or phenotypes within a population, which can be maintained through various evolutionary processes.

µ

represents the mutation rate in a population, which is the frequency at which new mutations arise in the genetic material.

Population Bottleneck

A sharp reduction in population size due to environmental events or human activities, leading to decreased genetic diversity and an increased risk of extinction.

Founder Effect

A phenomenon that occurs when a small group from a larger population establishes a new population, resulting in reduced genetic variation and potentially differing allele frequencies compared to the original population.

Gene Flow

the incorporation of genes into the gene pool of one population from one or more other populations

• Can counteract the loss of alleles due to drift, restoring genetic variation to local populations (movement) 

• Can homogenize allele frequencies among populations

• Can increase or decrease average fitness of a population

Migration Rate

• Can counteract the loss of alleles due to drift, restoring genetic variation to local populations (movement) 

• Can homogenize allele frequencies among populations

• Can increase or decrease average fitness of a population

p₂-p₁=m(p_m-p₁) the rate at which individuals move between populations, affecting genetic diversity. where m is the ____ rate

Fixation index (F_ST)

A measure of population differentiation due to genetic structure, comparing genetic variation within populations to that between populations. It indicates the degree of genetic diversity lost due to drift and other evolutionary forces.

Random mating

the selection of mates without regard to their genotype or phenotype, ensuring alleles are randomly distributed in offspring.

Inbreeding

the mating of closely related individuals, which can increase the chance of offspring inheriting genetic defects and reduce genetic diversity.

Deleterious Mutations

are harmful changes in DNA that can lead to negative effects on an organism's fitness or health, often reducing reproductive success.