AP Biology: Unit 7 - Natural Selection

Natural Selection

Process of how organisms having adaptations suited for a particular environment, and from thi, they will have a greater chance of survival and reproduction and passing traits on to next generation

Evolution

Chage in genetic makeup of a population over time

Competition

• Used when they struggle to find the right amount of resources for themselves

• Competing for space, food, shelter, water, nutrients, mates, etc.

• Not all organisms have the same chance of survival

Variation

Genetic differences among organisms within populations such as mutations and sexual reproduction increases variation

Adaptations

Traits that provide an advantage in a particular environment. Individuals wiht adaptations have a greater chance of survival and those having adaptations will increase over time.

Fitness

Ability to survive and reproduce offspring

Reproductive Success

Production of offspring and if there is success over many generations, there is evolutionary fitness

Heretability

Ability to pass on adaptation to successicve generations. Due to selection, traits of an individual that has more reproductive success is found more common

Ecosystem Stability

Determines the rate and direction of evolution (biotic & abiotic environments) can remain more or less stable. They can experience major distruptions and change quickly or slowly over time

Stable vs. Non-stable environment

Stable: Less likely to evolve

Non-stable: more likely to evolve and rate of change is faster

Genetic Variation

Describes an genotypic & phenotypic difference between indviduals & populations (leads to adaptations)

Selective Pressure

Abiotic & biotic factors influencing sustainability (disease, predation, climate, food, etc)

Artificial Selection

Humans select desireable traits (usually for agriculture and animal breeding) causes genetic diversity

Mutation

Random change in someones genetics (chance) in chromosomes

Genetic Drift

Random change in the frequency of a particular allele in a population

• non selective

• migration & geological changes

• genetic makeup of founder popuation

• seperation

Bottleneck Events

Large, diverse populations suddenly reduced to small

Migration/Gene Flow

Movement of individuals causing exchange of alleles between popualtions

• Introduces new genes into popualtion

• Increases variation

Hardy Weinburg Equilibrium

Models for describing and predicting alleles frequencies in an non evolving population

5 Condition for Hardy Weinburg Equilibrium

• large population = no genetic drift

• absense of migration = no gene flow

• no net movement = no genes modified, deleated, or duplicated

• random mating = no sexual selection

• absense of selection = no natural selection

Hardy Weinburg Equilibrium EQUATION

p² + 2pq + q² → used to determine frequencies of genotype/phenotype in a population

• p² = frequencies of heterozygous genotype

• 2pq = frequencies of homozygous resessive

• q² = frequencies of homozygous recessive genotype

Exmples of occurance of evolution

• mutations

• genetic drift

• natural selection

• non-random mating

• gene flow

Morphological homologies

Modified traits that are shared among differnt species

Homologous Structure

Variations in a structure that was present in a common ancestor (human arm, horse leg, bat wings)

Vestigal Structure

Redued or absolute features that serve little/no purpose (bone structure of legs on snakes)

Analogous structures

Evolve independently due to similar environment/condition/selective process

Phylogenetic tree

Branched diagram showing evolutionary relationship among species

Cladogram

Show evolutionary reationships and if any traits were lost or found

Prezygotic

Preventing the production of a fertelized egg

• habitat isolation (rare contact)

• temperal isolation (breeding system)

• behavioral isolation (mating)

• mechanical isolation (reproduction drift)

• gamete isolation (fertilizing egg)

Postzygotic

Pregenting a zygote from developing into a fertile offspring

• Hybrid inevitably: incompatability

• Hybrid sterility: vigourus + sterile

• Hybrid breakdown: first generation are feeble or stable

Allopatric Speciatio

Evolution of new species die to the individuals from the same population being geographically isolated over long periods of time

Sympatric barrier

Evolution of a new species die to individuals being reproductivly isolated

Punctuated Equilibrium

Evolution rapidly after long periods of stasis/no change

Gradualism

Evolution slowly over hundres and thousands of years

Adaptice radiation

Evolution of new species that allowed empty ecological roles or niches to be filled.