Ecology

Genetic Variation

Members of a population often vary in their inherited traits

overreproduction

All species can produce more offspring than the environment can support, and many of these offspring fail to survive and reproduce

Natural Selection summary

• Individuals with certain heritable characteristics survive and reproduce at a higher rate than other individuals 

• Natural selection increases the adaptation of organisms to their environment over time 

• If an environment changes over time, natural selection may result in adaptation to these new conditions and may give rise to new species 

Evolution

• Describes the fact that genetic composition has changed over time 

• Is the explanation for life’s unity and diversity 

Homology

A similarity resulting from common ancestry

Vestigial Structures

are remnants of features that served important functions in the organism’s ancestors 

Vestigial Structures

are remnants of features that served important functions in the organism’s ancestors 

Evolutionary Trees

• hypotheses about the relationships among different groups 

Divergent Evolution

branching from a common ancestor- Two or more species diverge from a common ancestor (ex. elephants and wooly mammoths) 

Convergent Evolution

Two or more species share traits NOT due to a common ancestor (ex. birds, bats, butterflies) 

Analogous Structures

• Different structure, similar function 

• Not from a common ancestor 

• Ex. bird wing and insect wing 

Population

a localized group of individuals belonging to the same species

Species

a group of populations who have the potential to interbreed and produce fertile offspring in future

Gene pool

total aggregate of genes in a population at any one time (all alleles at all loci)

Microevolution

is a change in allele frequencies in a population over generations

Three main causes of microevolution

natural selection, genetic drift, and gene flow

Genetic Drift

describes how allele frequencies fluctuate unpredictable from one generation to the next. chance events lead to changes in the gene pool of small areas.

Founder Effect

Occurs when a few individuals become isolated from a larger population allele frequencies in the small founder population can be different from those in larger populations

Bottleneck effect

is a sudden reduction in population size due to chance in the environment, if population stays small it may be further affected by gene drift

Gene flow

consists of movement of alleles among populations (migration) ex. pollen and reduces genetic variation

Natural selection is the only mechanism that

consistently causes adaptive evolution

Relative fitness

the contribution an individual makes to the gene pool of the next generation, relative to the contributions of others

Reproductive Success

generally more subtle and depends on many factors

Sexual Selection

natural selection for mating success, result in sexual dimorphism

Intrasexual selection

competition (male)

Intersexual selection

mate choice (female)

Stabilizing selection

Disruptive selection

directional selection

P=

frequency of the dominant allele in the population

Q=

frequency of the recessive allele in the population

p²

frequency of homozygous dominant individuals

q²

frequency of homozygous recessive individuals

2pq

frequency of heterozygous individuals

Speciation

the origin of new species, is at the focal point of evolutionary theory

microevolution

consists of changes in allele frequency in a population over time

macroevolution

refers to broad patterns of evolutionary change above the species level

What do we actually mean when we talk about species

is a group of organisms that can produce viable fertile offspring

How are different species separated (what do we mean by reproductive isolation)

the existence of biological factors that impede two species from producing viable, fertile offspring.

Prezygotic

barriers that prevent fertilization from happening

Postzygotic

Reasons after fertilization happens that prevents

Habitat isolation

two species encounter each other rarely or not at all because they occupy different habitats even though not isolated by physical barriers

Behavioral isolation

courtship rituals and other behaviors unique to a species are effective barriers

Temporal Isolation

species that breed at different times of the day, seasons, and years cannot mix gamates.

Mechanical isolation

morphological differences can prevent successful mating

gametic isolation

sperm of one species may not be able to fertilize eggs of another

reduced hybrid viability

genes of the different parent species may interact and impair the hybrids development

reduced hybrid fertility

even if hybrids are vigorous they may be sterile

hybrid breakdown

some first gen hybrids are fertile but when they mate with another species offspring of next gen dies off

Allopatric speciation

a population forms a new species while geographically isolated from the parent

sympatric speciation

a subset of a population forms a new species without geographic isolation

punctuated equilibrium

to describe periods of apparent stasis punctuated by sudden change

Gradualism

changes occur slowly and steadily over long period of time