Biol 213

speciation

process by new species arising

Allopatric Speciation

Geographic divide = no gene flow diff alleles become fixed interbreeding following speciation prevented by poezygotic or postzygotic mechanisms

sympatric speciation

no geographic barrier distructive selection = diff species (something prevents interbreeding)

polyploidization

instantly causes speciation meiosis fails and produces diploid rather than haploid gametes

autopolyploid

2n + 2n (caused by polyploidization) only mates with self

ways of maintaining reproductive isolation

prozygotic + postzygotic

prezygotic

prevents mating eg. habitat isolation

postzygotic

offspring have reduced suvivability/fertility

morphological species concept

-apperance most traditional

morphological species concept advantages

practical, simple

morphological species concept disadvantages

no genetic/evolutionary justification

reproductive species concept advantages

clear criteria/evolutionarly justified

reproductive species concept disadvantages

hard to apply (kinda solved by genomics) n/a for asexual reproduction

phylogenetic species concept

genetic sequencing

phylogenetic

cluster of population that comes from the same branch

phylogenetic species concept advantages

asexual species, any organism, no knowledge of interbreeding required

phylogenetic species concept disadvantages

hard, no obvious boundries

subspecies

geographic speciation = phenotypic variation local varients/selective pressures

ring species

ring shaped boundry that surounds unhabitable terrain

cline/clinical variation

pattern of variation across geographic gradient usually bc gene flow experiences diff conditions

Genetic Drift

-evolution by random change (change in allele frequency due to chance)

-results from random sampling error (not biology)

-stronger drift in smaller populations, reduces genetic variation

-increases variation between populations

locus

spot in a gene with a mutation

founder effect

special case of genetic drift new population started by a small number of individuals

Natural Selection

non random evolutionary change requires phenotypic variation,

selection and inheritance more powerful in large populations (drift is stronger in small populations)

small changes in fitness can affect long term

fitness

reproductive success

heritability

% of trait variation due to genetics

Stabilizing population definition

average individuals have higher fitness, variance decreases between generations, trait mean doesn't change

average individuals have higher fitness, variance decreases between generations, trait mean doesn't change

Stabilizing population definition

disruptive selection

both extremes are favoured, average individuals have lower fitness

both extremes are favoured, average individuals have lower fitness

disruptive selection

frequency dependant selection

fitness of each phenotype depends on how rare/common the phenotype is in the population

fitness of each phenotype depends on how rare/common the phenotype is in the population

frequency dependant selection

Sexual Selection

-by darwin

-sub category of natural selection, definition is debated,

-nonrandom success (intrasexual and intersexual selection)

sperm

produce abudant, energetically cheap, more motile gametes

eggs

produced few, energenically expensive, less motile

dimorphic species

male and female have different phenotypes

intrasexual selection

compitition for mating opportunities within the same sex

Intersexual selection

fitness differences resulting from preferential mating

assortative mating

individuals with similar genotypes/phenotypes mare with eachother more/less than random

outbreeding

mating with individuals more distantly related

inbreeding

mating with close relatives, affects genotypic frequency but doesn't alter allele frequencies

imbreeding depression

greater proportion of offspring are homozygotes recessive mutations (deleterious incresed expression)

hermaphroditic

self fertilizing plants

why would inbreeding or hermaphrodites exist

if pollinators are rare

Phylogeny

history of descent with branching showing relationship between species (common ancestors)

simplest and fewest changes is favoured

two patterns produced by evolution

-similarities are found in extant species

-historical patterns are recorded by fossils

sister groups

common ancestor is not shared by the rest of the phylogenetic tree

phylogram

phylogenetic trees where branch length represents time

cladogram

phylogenetic tree where all branches are equal length

monophyletic

clade on phylogenetic tree that includes a common ancestor and all of its descendants

paraphyletic

section of phylogenetic tree that includes a common ancestor and some (not all) of its descendants

polyphyletic

group on phylogenetic tree that doesn’t show common ancestors

methods used to infer phylogenies

-morphological (character and states, can be homologous or analogous)

-chromosomal

-molecular (ex. dna sequence)

homologous

homologous characters = homologies

shared because of common ancestry

Analogous

analogous characters = homoplasies

-similar in appearance/function but not origin

-shared because of convergent evolution

homoplasies

similar in appearance/function but not origin

homology

shared characteristics because of common ancestry

synapomorphies

homologies are shared by some species but not all

parsimonious

fewest number of changes required (= species are more related)

adaptive radiation

rapid evolution of new species occupying new niches

anagenesis

speciation where ancestor species is replaced by new species (in lineage)

cladogenesis

parent species splits into two species

graduated

slow/steady gradual evolution (often results in anagenesis)

emerges when there’s intense competition for niches, low genetic diversity/small population and high speciation

punctuated

rapid events of branching speciation (results more in cladogenesis, rare)

occurs when there’s colonization of a new area, diversification following a mass extinction or evolution of a new trait

endotherm

organisms that regulate their body temp

often show determinate growth

ectotherms

organisms that conform to environmental temperature

often show indeterminate growth

Allometry

The scaling relationship between biological traits and body size

hypermetric, hypometric, isometric

isometric

a=1

energy increases proportionally with mass

hypermetric

a>1

energy increases with a greater proportion to mass (concave up)

hypometric

a<1

energy increases to a lesser proportion to mass (concave down)

primary goal of managing an energy budget

have energy remaining to reproduce and (sometimes) raise offspring

Life history traits

energy strategies to maximize lifetime reproductive success

shaped by past success, affected by the environment, involves tradeoffs

natural selection usually favours the most offspring strategy

passive care

pre birth energy investment (seed development, gestation)

Active care

post birth energy investment, raising offspring

parity

how often an individual reproduces

semelparity

individuals of the same species can only breed once

ex. pacific salmon

Iteroparity

individuals of the same species can breed more than once in its lifetime

ex Atlantic salmon

Fecundity

avg # of female offspring each living female produces

R0 values

r0 < 1 - pop is decreasing

r0 = 1 - pop is stable

Microevolution

A change in the frequencies of alleles in the gene pool of a population

Population

number of individials alive at a particular time as influenced by births/deaths

(migration is ignored in this course)

Exponential Model of population growth

predicts growth under ideal conditions

-growth rate (r) will always be at Rmax

-rmax is always contstant and positive

Nt +No (1 + r)

r = B - D

Logistic Model of Population Growth

growth based on carrying capacity (K (b=d))

-assumes that growth rate (r) decreases as population increases

-r is influenced by a fraction of k

Rt = Rmax ((K-Nt)/K)

density-dependance

per individual rates of birth/death change as population density changes (usually)

can occur bc predaion, limited food/mates/shelter etc (biotic)

temp, ocean acidity (abiotic)

Ecosystems

community of living organisms interacting with eachother and their environment

has abiotic and biotic components

studied through movement of energy between levels

abiotic

climate/sunlight/air factors

biotic

microbes/plants/animal components in an ecosystem

laws of thermodynamics

1) conservation of energy (can't be created or destroyed can only transfer)

2) law of entropy (energy becomes more spread out)