UCSB EEMB 2 Final Exam

Evolution

the process by which different kinds of living organisms are thought to have developed and diversified from earlier forms during the history of the earth

Lamarck

-invertebrate zoology

-first comprehensive theory of evolution - use/disuse model (giraffes)

-inheritance of acquired characteristics

-importance of environments

Lyell

"Principles of Geology"

-countless small changes occurring over vast periods of time, all according to known natural laws

-earth is ancient and develops slowly

Malthus

-pop growth will always overtake the food supply

Cuvier

comparative anatomy and extinction

Hardy-Weinberg principle

-Allele and genotype frequencies in a population will remain constant from gen to gen in the absence of other evolutionary influences

To remain at H-W equilibrium

1. large breeding pop

2. random mating

3. no change in allele freq due to mutation

4. no immigration or emigration

5. no natural selection

general equation to calculate individual allele frequencies in a two-allele system (H-W)

freqB = p = (2N[BB] + N[Bb])/2N

*Bb will never be greater than 50%

Effective population size

size of population that can mate

Extinction vortex

mutual reinforcement occurs among biotic + abiotic processes that drives a population to extinction

Gene flow

transfer of genetic variation from one pop to another

mutational metdown

accumulation of harmful mutations in a small pop --> loss of fitness + decline in pop size

-caused by genetic drift

negative/positive assortative mating

neg: avoid mating with similar individuals

pos: opposite ^

balancing selection

multiple alleles are maintained in the gene pool of a population at frequencies higher than expected from genetic drift alone

-could be due to heterozygote advantage, coevolutionary dynamics (other species exhibits a common trait in first species), negative assort mating, spatially (temporally fluctuating selection)

-leads to negative frequency - dependent selection: allele more common decreases fitness

Continuous variation

variation in phenotypic traits that can't be grouped into discrete categories (ex. weight, height, etc)

directional selection

mode of natural selection, extreme phenotype favored over others: causes allele frequency to shift over time

ex. dark moths when smog increases

disruptive selection

-pushing for both extremes, but average may stay the same

-mating with who you look like

frequency-dependent selection

the fitness of a phenotype depends on how common it is in the population

-ex: if a predator loves large bunnies, there's pressure to be smaller

-favored allele switches over

time

Types of selection on graphs

Genetic equilibrium

an allele or genotype in a pool where freq remains constant from gen to gen

Heterozygote advantage

(over-dominance) heterozygous genotype has higher relative fitness to either homozygote

ex. sickle cell

selective sweep

the reduction or elimination of variation due to a recent fixation due to strong positive natural selection

anisogamy

sexual reproduction by the fusion of dissimilar gametes

-smaller gamete usually male

coevolution

influence of closely associated species on each other in their evolution

fecundity

ability to produce an abundance of offspring or new growth

aka fertility

Fisherian/runaway selection (sexy sons)

sexual selection mech to account for the evolution of exaggerated male ornamentation by persistent, directional female choice

fundamental asymmetry of sex

tendency for females to invest more in their offspring

good genes hypothesis

female's choice in mate are honest indicators of the male's ability to pass on genes that will increase survival or reproductive success of her offspring

intrasexual selection

members of the same sex compete to mate

intersexual selection

competitive sex shows off and opposite sex chooses

isogamy

sexual reproduction by the fusion of similar gametes

Muller's ratchet

Mutation meltdown!

-accumulation of deleterious mutations in asexual pops that drive to extinction (irreversible)

Red Queen Hypothesis

organisms are constantly struggling to keep up with one another in an evolutionary race between predator/prey species

sensory exploitation hypothesis

male secondary sexual characters as adaptations to exploit female responses that evolved in non-sexual contexts

sperm competition

females have multiple potential mating partners

-competitive process between spermatozoa of two or more different males to fertilize the same egg

allopatric speciation

aka geographical isolation: biological pops of the same species become isolated from each other to an extent that prevents or interferes with gene flow

autopolyploidy

polyploidy in which the chromosome complement consists of more than two copies of homologous chromosomes

allopolyploidy

individual or strain whose chromosomes are composed of more than two genomes each of which has been derived more or less complete but possibly modified from one of two or more species

-mating of diff species

When does polyploidy occur?

When complete haploid sets of chromosomes are added to a diploid genome

-improper split of sister chromatids or homologous chromosomes

biological species concept

explanation for how species form. Species = pop of orgs that can breed to produce fertile offspring

fusion

process in which several uni-nuclear cells combine to form a multi-nuclear cell

genetic divergence

process in which 2+ pops of an ancestral species accumulate independent genetic changes (mutations) through time

-often after they have been reproductively isolated for a while

hybrid zone

a narrow geographic region where two genetically distinct populations or species are found in close proximity and hybridize to produce offspring of mixed ancestry

-hybridization: mating organisms of different varieties or species to create a hybrid

morphological species concept

characterizes a species by body and other structural features (sexual + asexual)

-useful when gene flow is unknown

parapatric speciation

Rare! pops are separated by an extreme change in habit then develop different distinct characteristics and lifestyles

peripheral isolate model

aka parapatric speciation, a form of allopatric speciation. A small pop at extreme edge of of species range is separated off

reproductive isolation

mech that keeps species from mating with others

post-zygote isolation

prevents formation of fertile offspring

pre-zygotic isolation

prevents the fertilization of eggs

reinforcement

process of speciation where natural selection increases the reproductive isolation between two pops of species. Occurs as a result of selection acting against production of hybrid individuals of low fitness

speciation

formation of new and distinct species in course of evolution

sympatric speciation

evolution of a new species from a surviving ancestral species while both continue to inhabit the same geographic region

ex. resident and transient orcas

adaptative radiation

diversification of a group of organisms into forms filling different ecological niches

background extinction rate

aka normal extinction rate, the standard rte of extinction in earth's geological and biological history before humans became a primary contributor to extinctions

dispersal

-movement of individuals from birth site to breeding site (natal disp)

-from breed to breed (breeding disp)

gradualism

evolution proceeds by imperceptibly small steps over long periods of time

punctuated equilibrium

the hypothesis that evolutionary development is marked by isolated episodes of rapid speciation between long periods of little or no change

standing diversity

# of taxa at a given time and place

turnover

rate at which a thing is depleted and replaced

vicariance

geographical separation of a population typically by a physical barrier such as a mtn range or a river

-results in a pair of closely related species

Types of fossil

Intact - DNA

Trace - ecology

Casts - morphology

α = ?

Ω = ?

α = origination rate

Ω = extinction rate

α + Ω = turnover

Diversity (t + 1)

= Diversity (t) + α - Ω

analogous traits

similarity due to convergent evolution, not common ancestry

homologous traits

features that are inherited from a common ancestor

clade

group of organisms evolved from a common ancestor

consensus tree

provides estimate for level of support for each clade

convergent evolution

the independent evolution of similar traits in distantly related organisms due to adaptation to similar environments and lifestyles

homoplasy

character shared by a set of species but not present in their common ancestor

monophyletic

(of a group of organisms) descended from a common evolutionary ancestor

node

a common ancestor of the branches

paraphyletic group

descendents from a common ancestor but not including all the descendent groups

parsimony principle

choose the simplest scientific explanation that fits the evidence

phylogeny

evolutionary development and diversification of a species

Plesiomorphy

evolutionary trait that is homologous within a particular group of organisms but it not unique to members of that group

polytomy

internal node of a cladogram with more than two intermediate descdendents

reversal

character reverts back from a derived state back to the ancestral state over many generations

root

ancestral lineage of tree

Adaptation

the process by which a species becomes better suited to its environment through evolutionary changes.

Alleles

alternative forms of a gene that arise by mutation and are found at the same place on a chromosome.

Apomorphy

a derived trait or characteristic shared by a group of organisms that distinguishes them from others.

Continuous variation

refers to a range of small differences in a given trait among individuals of a population, often resulting from the combined effects of multiple genes.

Disruptive selection

is a type of natural selection that favors individuals at both extremes of a phenotypic range, leading to increased variation within a population.

Ecological isolation

occurs when two populations are prevented from interbreeding due to differences in their ecological niches or habitats, even when they coexist in the same area.

Founder effect

refers to the reduced genetic diversity that occurs when a small number of individuals from a larger population establish a new population, potentially leading to increased prevalence of certain genetic traits.

Genetic load

refers to the reduced biological fitness of a population due to the presence of deleterious alleles. It represents the burden on the population caused by the accumulation of harmful genetic variations.

Monophyletic Group

a group of organisms that are descended from a common ancestor and include all its descendants.