Bio Exam 1

Evolution

Evolution

A field of study that emerges from the desire to define and systemize life

Barriers to Evolution

Time and ability to spend time comparing and observing species from many locations

Lyell and Hutton

proposed the view that gradual changes over long periods of time lead to geological features on Earth (provides time necessary for evolution)

Lamarack

proposed the idea of changes throughout an organism’s life could be inherited and lead to evolutionary change (mostly INCORRECT)

Wallace & Darwin

Suggested the framework for the idea of evolution via natural selection

Variation

Any difference between organisms with a genetic basis (arises from mutation)

Adaptation

Any heritable trait that helps an organisms survival and reproduction in the current environment (genetic basis)

Convergent Evolution

Similar phenotypes are seen in distantly related lineages (due to similar selective pressures, organisms are not closely related)

Divergent Evolution

Lineages become increasingly different from each other (due to different selective pressures, organisms are closely related)

Fossils

Shows changes in lineage over time and shows extinct organisms are distinct from those of today.

Anatomy

comparison of structural similarities and differences between organisms

Biogeography

Geographic distributions of organisms. Patterns that can be explained via evolution in conjunction with tectonic plate movement

Embryology

Used to compare relatedness

Molecular Evolution

Mutations accumulate the more distantly related organisms become

Species

A group of organisms that are able to breed to product fertile, viable offspring

Ecological Levels

Organism>Population>Ecosystem>Community

Allopatric Speciation

Physical separation between a species, no gene flow, populations will adapt to their separate environment

Adaptive Radiation

Relatively rapid evolution of many species from a single ancestor

Postzygotic barriers

Prevents zygotic development or the resulting offspring is sterile

Prezygotic barriers

Prevent reproduction from occurring (temporal, habitat, behavioral, mechanical

Reinforcement

Less fit hybrids; fewer hybrids will be reproduced and eventually disappear

Fusion

When reproduction barriers weaken and species fuse into one species

Stabilization

Hybrids are fit and can reproduce with each other. The species can either remain separate or hybrid can differentiate into a third species.

Alleles

Different versions of a gene

Gene

Unit of DNA that transmits genetic information

Phenotype

Observable trait of an individual (determined by genotype)

Diploid (2n)

2 copies of each chromosome; somatic cells, made via mitosis

Haploid (n)

1 copy of each chromosome, gametes, made via Meiosis

Gene Pool

Sum of alleles present within a population

Founders Effect

initiates change in allele frequency in an isolated population (going to new environment)

Genetic Drift

Change in allele frequency (change rapidly)(no apparent advantage, random, small populations, gene become fixed)

Hardy Weinberg

Allele and genotype frequencies in a population will stay the same through generations in the absence of natural selection or other evolutionary influences

Hardy Weinberg conditions

No gene flow, no natural selection, no mutation, random mating, no genetic drift

Allele frequency equation

p+1=1

Genotype frequency equation

p²+2pq+q²=1

Microevolution

small-scale changes in allele frequency, changes within the gene pool, eventually genus-level speciation

macroevolution

large scale changes in allele frequency of a population, occurring over long periods of time, give rise to new species

Phylogeny

the evolutionary history and relationship of an organism or group of organisms

Rooted

single common ancestor

Branch Point

Single lineage splitting into two; evolution of a new trait

Basal taxon

Unbranched lineage evolved from a common ancestor (often outgroup)

Sister Taxa

Two lineages stemming from same branch point

Polytomy

A branch with 3 or more lineages (undetermined relationship)

Homologous Structures

Physical traits that are similar due to a common ancestor (similar structure different function)

Analogous Structures

Similar physical or genetic traits that evolved separately in two+ organisms that do NOT share a common ancestor; different structure same function

Molecular Homologies

Analysis of comparable DNA segments; if genes in different organisms share many portions of nucleotide sequence, they are likely homologous

Outgroups

reference species/taxon that is distantly related to the ingroup; serves as a reference

Shared Ancestral Character

Character originated in an ancestor of the taxon

Shared Derived Character

Novel evolutionary character, not present in ancestor, only in the descendants

Monophyletic

consists of a common ancestor and all descendents

Paraphyletic

Consists of an ancestral species and some of the descendants

Polyphyletic

Distantly related species but does not include their most recent common ancestor

Pleiomorphy

Shared Ancestral Character (present in ancestor and descendants)

Apomorphy

A novel derived character

Synapomorphy

Shared derived (shared by last common ancestor and descendants)

Autapomorphy

Unique derived (novel character present in only one group, not in recent common ancestor)

Allele Frequency

The rate an allele occurs within a population; change in response to selective pressures

Genotype Frequency

The rate a specific genotype occurs in a population; change in response to changes in allele frequency

Population Genetics

Measurement of the effect of natural selection on the allele and genotype frequency in a population; the change is evolution

Genetic Drift

Changes in allele frequency due to random chance occurring in all population. Allele fixations can be a result

Founder Effect

Skewed representation of a population; allele frequencies are based on the alleles present in founding individuals

Bottleneck Effect

An event that reduces the population size drastically; only certain individuals survive (allele frequency is based on the alleles present in individuals that survive)

Non-Random Mating

Most species compete for mates; individuals do not have equal opportunities to mate; geographic location can be an affect

Gene Flow

Immigration and Emigration of alleles in and out of a population (affects allele frequency and causes less variations between two populations)

Natural Selection selects for/against phenotypes not alleles

Selection for individuals with greater contribution to the gene pool

Natural Selection works on heritable traits

Selects for traits that are beneficial; selects against traits that are deleterious

Stabilizing Selection

Selective pressures for the average phenotype and against extreme phenotypes (genetic variance decreases)

Directional Selection

Selective pressure for on extreme phenotype and against the other extreme and the average (genetic variance shifts to the new phenotype)

Diversifying Selection

Selective pressure for both extreme phenotypes and against average phenotypes (genetic variance in population will increase)

Frequency-Dependent Selection Positive

Selection for common phenotypes; decreases genetic variance; common phenotype increase relative fitness

Frequency-Dependent Selection Negative

Selection for rare phenotypes; fitness is increased when phenotype is rare; increases genetic variance

Sexual Dimorphism/Selection

Males and females of a species exhibit phenotype differences beyond productive organs

Taxonomy

The classification system used to name organisms

Systematics

Classifies organisms based on evolutionary relationships

Phylogeny

Evolutionary history of organisms and their relationships to other organisms

Sympatric Speciation

New populations inhibit the same geographical range; needs to be complete reproductive isolation

Temporal

Variation in time-of-day mating occurs

Behavioral

Different mating cues

Habitat

Individuals specialize within their environment

Polyploidy(plants)

plants can spontaneously go through a diploid organism to a tetraploid organisms creating a new species

Maximum Parsimony

aid in the tremendous task of describing phylogenies, which means that events occurred in the simplest, most obvious way

Gradual Speciation

species diverge gradually over time in small steps

Punctuated Equilibrium Model

a new species undergoes changes quickly from the parent species, and then remains largely unchanged for long periods of time afterward

Vestigial Structures

structures exist in organisms that have no apparent function at all, and appear to be residual parts from a past common ancestor

Handicap Principle/Good Genes Hypothesis

Phenotype is such a disadvantage that only the fittest males can survive with it

Dispersal Allopatric

Few members move to the new area

Vicariance Allopatric

Geographic barrier divides the population