Bio 104 test 1

The study of how genes within a population affects evolution

Evolution over generations (can even create a new species if there is enough genetic variation)

The proportion of a particular geno/phenotype in a population

Always expressed as a proportion and always combines to equal 1

The frequency of alleles in a population 

• The number doubles bc there are two alleles for each gene 
• ex. 1,000 individuals= 2,000 alleles

The frequency of genotypes and alleles in a population won't change unless there are outside forces acting upon it

If changes do occur, evolution is occurring

When there are no net changes in the genotype/alleles over time in a population

P2+2pq+Q2= 1

Random mating, no net mutations, no migration, large population size, no natural selection

Non-random mating, gene flow, mutations, natural selection, genetic drift

Non-random mating of individuals that are more closely related than if they were chosen at random 

Increases the frequency of homozygous genotypes 

Can lead to inbred depression, which decreases fitness

Choosing a mate based on phenotype 

Changes genotype frequency only at loci involved with mating choice

A change in DNA 

Only mutation in reproductive cells are inherited

Does not always lead to something harmful: only if the polypeptides are majorly changed

Random changes in a small population

When a phenomenon (natural disaster, disease, famine) leaves only a small subset of population alive

Only the alleles present in survivors can be passed on to new generations

Genetic drift when a small group goes off and establishes a new population somewhere else

Only the alleles present in founders will be passed on to new generations of that population

Ex. Finland

When genes from one population go to another 

Ex. a group of birds flies from their population up North to another population of the same species down South

Members more adapted to the environment have better fitness 

Over time, the number of favorable alleles in the population increases

Natural selection preserves individuals with favorable phenotypes and eliminates the unfavorable

Disruptive, Stabilizing, directional

Extreme changes in 2 or more of the rarer phenotypes, and a decline in the medium phenotype

Very rare

Selects against phenotype extremes, favors the average phenotype

Phenotypes begin to increase at one of the extremes (in response to environment)

A mutation that is not expressed

Genetic variations among individuals in a population that may or may not produce distinct phenotypes

Natural selection maintains homozygous genes when heterozygous may be more beneficial 

Ex. People with one dominant and one recessive allele for sickle cell anemia have a higher malaria survival rate

When a phenotype has greater selective value when it's rare

Ex. The cichlid have 2 mouth variants: left and right. There are times when left is more frequent than right and vice versa. This is because the fish get used to looking for a cichlid with a right/left mouth, and so the cichlid evolves to keep them on their toes. 

(It is variation to keep the species going)

When a genetic variation has no impact on fitness and consequently is not adaptive

A neutral variation could be beneficial/harmful in another environment

Genetic variation in a species across populations 

Ex. the height of the yarrow depends on what elevation it's at

Gradual changes in a species phenotype by population as a result of geographic influences

All forms of life evolved from older versions over time 

This is the cornerstone of biology and links many disciplines

Accumulation of genetic chances within a population between generations

Agriculture- evolution of pesticide resistant bugs

Conservation management- helping to save rare and endangered species 

Bioremediation- Evolving micro-organisms in polluted soils for clean up

Evolutionary modification that increases the likelihood of surviving and reproducing

Variation, overproduction, limites on reproduction, and differential reproductive success 

Variation- individuals in a population show variation in their traits

Overproduction- Inidividuals have to create more offspring than can survive

Limits on reproduction- organisms have to compete for limited resources, and not all survive to reproduce 

Differential reproductive succes- individuals with more favorable characteristics are more likely to survive and reproduce

It took Darwin's ideas and integrated them into different fields of biology

Natural selection

Fossils can be found in sedimentary rock, with the oldest at the bottom. 

It shows how unicellular organisms turned into the organisms they are today 

Fossil record is biased towards aquatic animals and the few terrestrial organisms conductive to fossil formation (deprivation of O2 to preserve body parts without deterioration)

Organisms with hard body parts are more likely to be fossilized than those with soft body parts

Similar environmental conditions result in independent evolution of similar structures in different organisms

Structures that don't have any function 

Ex. the fused tailbone in humans, wisdom teeth, muscles that move ears

A group of populations that are difference form other species by morphology, behavior, genetics, etc.

The variety of living organisms and the ecosystems to which they belong

Includes species, communities, genetic variations

The study of biodiversity

Tests and posts evolutionary relationships of hypotheses

Naming, describing, and classifying species

Arranging organisms into groups based on evolutionary relationships

• Binomial system
• Uses Latin
• Italicized, or underlined if written by hand 
• Genus comes first, then species

A formal group of organisms at any level

Species

Domain, Kingdom, Phylum, Class, Order, Family, Genus, Species

Bacteria, archaea, eukaryotes

A type of phylogenetic tree in which every branch represents a clade

A group of organisms with a common ancestor

Characteristics that reflect those of shared ancestors

• Not all similar traits are homologous
• Ex: the body forms of sharks and dolphins are analogous

Ancestral

Monophyletic, paraphyletic, polyphyletic

Includes an ancestral species and its descendants that share common characters

Contains a common ancestor and some, not all, of it's descendants share ancestral characteristics

The branching point on a cladogram

2 or more species that share a common ancestor

The most closely related group

The cladogram with the fewest amount of changes (# of hypothesized character changes) to explain it

Statistical method used to make decisions, especially when analyzing molecular data 

Ex. The probability that nucleotide sequencing in DNA and RNA change at a constant rate over time

A population is declared a separate species if it has been evolving long enough for statistically significant differences in traits to evolve 

Limitations: Needs DNA sequencing to confirm

Prevents fertilization from taking place 

Types of barriers: Temporal, habitat, behavioral, mechanical, gamete isolation

When 2 groups reproduce at different times

Species that live in the same geographic region, but mate in different habitats

Ex: birds with overlapping regions, but one mates in forests and the other mates in fields

Distinct series of signals for mating 

Ex. birds who collect shiny things to attract mates

Structural differences in reproductive organs

The sperm and egg can meet, but can't fuse to form a zygote 

Molecular/chemical mechanisms prevent fusion

Zygotes are produced, but the offspring is not viable 

Ex: a horse and a donkey create a mule, which is sterile

Creates an F2 individual that is sterile

Phenetics, evolutionary taxonomy, phylogenetic systems

The evolution of a new species, beginning when a population becomes isolated and their gene pools divide

Allopatric and sympatric

Occurs in different geographical locations, mostly in animals

Also occurs when a population migrates/is dispersed and colonizes in new area

Ex: the desert pupfish that originally lived in one big pool and got separated into different species when the pool dried up and sectioned them off

Speciation between 2 populations in the same geographic range, occurs when reproductive isolating mechanisms evolve at the beginning of speciation. Mostly in plants 

Occurs in two ways: change in ecology, polyploidism 

Change in ecology: The cichlid, males evolved to have specific patterns for their females. If the female can't see, she will sometimes mate with a male of another species by accident 

Polyploidism: sometimes plants mutate and have more than 2 chromosomes in a set

Choosing a mate based on color or another characteristic

Darwin suggested that sexual selection could lead to the evolution of a new species

Long periods of stasis interrupted by rapid speciation (can sometimes be triggered by environment)

Evolution proceeds continuously over time

Phyletic gradualism and punctuated equilibrium

The permanent end of a lineage

When extinction occurs, it opens up a new adaptive zone that provide new opportunities for the species that remain

Low-level, continuous extinction

Rare, occurred only 5-6 times in Earth's history

Each mass extinction is followed by a period of adaptive radiation of survivors 

Humans are causing the biggest mass extinction on Earth

Evolutionary diversification of many related species from one or few ancestral species in a relatively short period 

Ex. the honey creeper, silverswords

A species consists of one or more populations whose members do not interbred with other species

Limitations: only applies to species that reproduced sexually