BI108 exam 1

Proximate explanation

“how”

ultimate explanation

“why”

Evolution

change in allelic frequencies over generations

heritability

the portion of population variance due to genetic factors

central dogma of biology

flow of info in cells: DNA—→RNA—→protein

gene

sequence of DNA

allele

version of a gene e.g eye color

genotype

combination of alleles

phenotype

physical expression of trait

gonads

reproductive organs

gametes

reproductive cells (1/2 DNA)

meiosis

cell division that produces gametes

recombination

when genetic information is exchanged between homologous chromosomes —> creates genetic variation

law of independent assortment

homologous chromosomes line up randomly

homologous chromosomes

pair of chromosomes with the same genes in the same order, one from each parent

incomplete dominance

when neither allele (Bb) is completely dominant over the other, resulting in a heterozygous individual with an ‘intermediate phenotype’ that blends both traits

epistasis

when the expression of one gene masks/inhibits the expression of another 

pleiotropy

one gene affects multiple traits

ontogeny

the development of an organism over its lifetime

phenotypic plasticity

the ability of a single genotype to produce different phenotypes in response to different environmental conditions

common garder experiment 

2 organisms from different environments placed into the same environment —→ used to differentiate genetic influences from environmental ones 

reciprocal transplant experiment

taking two organisms from different environments and putting them into opposite environment (e.g take snail from environment w predators and snail from environment without and swap them (used to detect phenotypic plasticity vs evolution)

requirements for natural selection

individuals differ from one another, variation is inherited, individuals differ in their success at surviving/reproducing, reproduction is non random

fixation

frequency of an allele reaches 1 while other reaches 0

interbreeding depression

reduced survival rates due to mating between closely related individuals 

deleterious allele

allele that produces maladaptive phenotype

bottleneck effect

when an event wipes out the majority of a population so the rest can only breed with eachother —> results in poor sperm quality and immune system homogeny (e.g new zealand black robin)

example of founder effect

Ellis Van Crevald Syndrome

speciationw

when a single species diverges into two or more new species that can’t interbreed

acquired traits

characteristics that an individual developes during their lifetime (not heritable)

gene flow

movement of alleles between two population

genetic drift

change in allelic frequencies due to random chance

point mutation

one nucleotide replaced with another during replication

frameshift mutation

deletion (one nucleotide deleted) or insertion (one nucleotide inserted)

duplication

section of DNA copied a second time

inversion

section of DNA flipped and inserted into the original position

aneuploidy

entire chromosome duplicated or lost

genome duplication

all DNA in cell is copied

sexual selection

differences in reproductive success causes by competition over mates and related to expression of a trait

anisogamy

different gametes

Bateman’s Principle

male reproductive success increases with # mates while female reproductive success does not

intrasexual selection

between members of same sex

intersexual selection

between sexes, competitive sex evolves exaggerated sexual signals due to mate choice by choosy sex

divergent evolution

single ancectral species splitting into multiple species with different traits

convergent evolution

when unrelated species develop similar traits

homologous traits

traits shared between two or more species with a common ancestor

derived trait

new trait not shared by a common ancestor

analogous trait

same trait derived at different time points

monophyletic group

clade +all ancestors

paraphyletic

common ancestor and some but not all descendants

polyphyletic

no single common ancestor, multiple groups that share an analogous trait

biological species concept

species are reproductively isolated (no gene flow)

morphological species concept

species are consistently morphologically distinct from one another

phylogenetic species concept

spcies are the smallest monophyletic group on a phylogenetic tree

evolution null hypothesis

describes a population where no evolution is happening

Hardy - Weinberg equilibrium

no natural selection, no genetic drift, no gene flow, no mutation, random mating (allele frequencies not changing)

allele frequencies equation

p² +2pq+q² =1