Evolution and Systematics Exam 1

Evolution

the changing of characteristics in a population over time (NOT in individuals)

What are the two theories of how biodiversity occurs?

Special creation and evolution

catastrophism

the world came about suddenly and quickly through sudden dramatic changes (great flood), related to special creation

gradualism

large effects come from small changes over long time periods

Uniformitarianism

rates of change have been the same throughout history

Was Darwin the first person to propose evolution?

No, he only proposed the mechanism

Lamarckism

inheritance of acquired traits, doesn’t explain the hierarchy of species

Who discovered the correct mechanism for evolution?

Codiscovered by Wallace and Darwin

Natural selection

the process that promotes maintenance and spread of traits promoting survival and fecundity

What 3 things will always cause evolution?

individuals vary, variation has a heritable component, and individuals with certain attributes survive and reproduce best

What two ideas are the foundation of modern biology?

gradualism and evolution by natural selection

What ideas came about during the Darwinian revolution?

• evolution is not purposeful or goal-driven

• an intelligent designer is not needed for biodiversity

• evolution does not necessarily favor more complex/bigger

Artificial selection

process of changing traits of domestic animals by humans by promoting the survival and reproduction of individuals with desirable traits

What three elements cause evolution via natural selection?

1. individuals vary

2. variation has a heritable component

3. humans choose to to breed individuals with desired traits

orthogenesis

evolution is a straight line leading to humans (less to more complex)

Who were Darwin’s two bulldogs?

Thomas Huxley and Alfred Wallace

Thomas Huxley

Stood in for Darwin during public debates

Saltation

Evolution occurs in big steps, new species are formed without intermediates

Hopeful Monsters

brand new, highly functioning organisms resulting from a single evolutionary step (saltation)

Thomas Hunt Morgan

developed concepts of Mendelian genetics with fruit flies

Bean Bag Genetics

genes are discrete traits of inheritance distributed on chromosomes, mutation and crossing over of genes is the source of new traits. Fails to consider complex interactions of genes

Mutationists

evolution occurs via mutation without natural selection

What groups did biology divide into by the 20th century?

lamarckists, saltationists, mutationists, and darwinians

What did the new synthesis combine?

Mendelian genetics and natural selection

What is the raw material of natural selection?

Variation

Heritable Variation

Variation arising from differences in traits that are passed from parents to offspring

What are the sources of heritable variation?

Mutation and gene flow

Mutation

random changes to genetic code

Gene flow

genes that code for traits moving from one population to another

Fitness

lifetime reproductive success of an individual

Example of fitness consequences

mouse color affecting predation based on the habitat it lives in

Adaptation

attunement to the environment or a trait that increases fitness in a particular environment

Directional selection

selection away from the current phenotype to a single new one or selection for the replacement of one allele with another

purifying/stabilizing selection

selection for the current phenotype

Disruptive Selection

selection for 2 distinct phenotypes, selection against intermediate for 2 different allele states

Example of Natural selection

light colored moth, then the industrial revolution made everything dark, all the moths became dark- directional selection

exaptation

trait that evolved for one reason but is now used for another

Example of exaptation

feathers evolved for insulation but are now used for flight, see red to be red

gene

sequence of dna that specifies a functional product

Allele

version of a gene

locus

location of a gene on a chromosome

Genotype

combination of alleles that an individual has at a locus

Phenotype

observable characteristics of an organism

What conclusions did mendel come to?

• inheritance is particulate- individuals have two alleles and can be homo/heterozygous

• some alleles are dominant and some are recessive

• the law of segregation

the law of segregation

alleles at locus separate into 2 gametes

Why did Mendel work in an ideal scenario?

• each trait was determined by 1 gene

• each gene was unlinked

• each trait was controlled by a simple dominant/recessive system

Linkage disequilibrium

nonrandom association of alleles on different loci

Law of independant assortment

alleles of each gene segregate independently

Hardy Weinburg Model assumes

there is no evolution

What does the Hardy Weinburg model allow the calculation of?

The gene frequency in the following generation

What is the hardy weinburg equation?

1=p²+2pq+q²

What are the old and new definitions for evolution (genetically)?

• old: change in characteristics of a population over time

• new: change in gene frequency of a population over time

Darwinian fitness

reproductive success relative to the average reproductive success in a population

Selection Coefficient

fitness reduction of one genotype relative to another

What are the 3 theories for why there is heterozygosity in the wild?

mutation selection balance, heterozygote advantage, and frequency dependent selection

Mutation selection balance

natural selection perpetually removes less fit alleles, mutation perpetually removes less fit alleles, mutation perpetually introduces more fit alleles, deletarious alleles always exist at low frequencies

Heterozygote advantage

the heterozygote is the most fit, for example sickle cell anemia

frequency dependent selection

fitness of alleles changes with allele frequency. High fitness when rare, low when common.

Genetic drift

evolution due to chance events AKA sampling error

Founder events

new populations are founded with few individuals, there is almost always a change in gene frequency. Examples are tay-sachs and huntingtons