UCM Ecology Exam 2

Chapters 4-7

centerpiece of ecology

theory of evolution by natural selection

evolution

change over time in the allele frequencies in a population

adaptation

characteristics that improves an organisms ability to survive or reproduce

chromosomes

tightly coiled DNA

gene

DNA segments that code for proteins / traits

alleles

different forms of a gene

EX] AA, aa, Aa

natural selection

process in which individuals with certain characteristics tend to survive and reproduce at a higher rate

• acts on an organism’s phenotype

lamarck

• transformism

• “inheritance of acquired characteristics”

transformism

• complex organisms have developed gradually over geologic time from simpler ones

• individuals passed on changes acquired during their lifetimes

  • EX] giraffe long necks, the more they stretch to reach leaves the longer their necks get, then pass the long necks onto offspring

malthus

• “an essay on the principle of population”

  • human pop was growing very fast but the food supply was not, he asked what would happen and when

  • essay inspired Darwin’s thoughts on competition for resources and what advantages would help people survive and reproduce

hutton

• theory of uniformitarianism = geological processes are slow

  • EX] erosion, sedimentation

• + Lyell

Darwin

• evolution by natural selection

• descent with modification in “the origin of species”

wallace

• “father of biogeography”

• theory of evolution through natural selection (Darwin had more evidence)

mendel

• “father of modern genetics”

darwin’s observations

• The distinction between species and varieties of species were sometimes unclear

•  Fossil animals are now extinct but similar to living species

• Geographic variation and species replacement

• Gradients of change in species among islands, but also within islands

• breeders can select desirable characters

natural selection summary

• offspring appear, behave, and function like their parents

• cartoon exists and is heritable

• more offspring are produced than the environment can support

• some individuals have a higher chance of surviving and therefore reproducing

ALL due to their traits

descent with modification

• populations accumulate differences over time

• eventually can lead to macroevolution

macroevolution

results in new species

• differ from ancestors (modification)

• share characteristics with ancestors (descent)

age of earth

4.55 billion years

mechanisms of evolution

1. natural selection

2. mutations

3. gene flow

4. genetic drift

fitness

genetic contribution of an organism of future generations

types of natural selection

• stabilizing selection

• directional selection

• disruptive selection

• artificial selection

stabilizing selection

intermediate phenotypic trait is favored over the extremes

EX] middle sized owls

directional selection

favors one extreme

EX] cheetah/gazelle speed

disruptive selection

two extreme phenotypes are favored over the intermediate trait

EX] bird beak size

artificial selection

natural selection by humans

EX] selective harvesting (hunting bigger animals), antibiotic resistance

mutations

different alleles are formed by mutations, can provide new genes

• ultimate source of genetic variation

  • central to evolutionary process

  • recombination rearranges existing variation

• rare events

gene flow

movements of alleles (dispersal)

• makes populations more similar to each other

• can introduce new alleles into a population

genetic drift

chance events (random)

• most influential in small populations / short times

fixation

allele reaches 100% frequency (not necessarily uncommon)

impacts of genetic drift

• allele frequencies fixation (or lost)

• reduces genetic variation in population

• can increase frequency of bad alleles

• increase differences between populations

founder effect

few individuals start a new, isolated population

• their alleles will become a significant fraction

• genetic drift example

bottleneck effect

population is drastically reduced in size

• the surviving individuals constitute a random genetic sample of the original population

• genetic drift example

all four types of adaptations can have a negative and positive effect except for….

natural selection

harmful effects of low genetic diversity

• random loss of genetic variation

• inbreeding (mating between close relatives)

allele effects in small populations

• population growth rate decreases as the population density decreases

• individual fitness lower at low population sizes

• loss of genetic diversity = lower reproductive success

  • difficulty finding mates

extinction vortex

• positive feedback system

• small populations tend to get even smaller

phenotypic variation is due to …

genes AND environment

examples of environmental effects on phenotypes

• temp can determine turtle sex

• pH can determine flower color

• season can determine rabbits coat color

phenotypic plasticity

variation in form due to the environment

ecotypes

locally adapted and genetically distinctive populations

evolutionary significant unit

populations that exhibit a high level of genetic differentiation may need to be managed as separate units

sexual selection

organisms ability to obtain or successfully copulate with a mate (males and females may differ in morphology and behavior)

• characters that help organs obtain mates

  • little value/could be disadvantageous

morphology differences

• sexual dimorphism

• size

• color

• structures

• behavior (territorial, secretive, etc)

intersexual selection

usually female choosing male (mate choice)

intersexual selection

male-male competition (aggressive behaviors)

why the differences in male-female mating strategies?

• females usually have greater investment in reproduction = choosy

• males usually have a higher reproductive potential = aggressive, competitive

  • more mates = higher level of aggression

• variation in reproductive success greater for males than females

runaway theory

if females prefer a trait that trait and preference is passed on

handicap principle

traits displayed by males in good condition ONLY = honest indicators of male condition

evolutionary arms race

a change in the traits of one species act as a selection pressure on the other species

• drives directional selection

the red queen hypothesis

“now here you see it takes all the running you can do to keep in the same place)

coevolution

reciprocity

• species A evolves because of species B and species B evolves because of species A

biological species concept

• individual can interbreed (exchange alleles)

• produce fertile offspring

  • hybrids are not their own species because they are sterile

• reproductively isolated

how do we classify asexual reproducing organisms

• morphology

• ecology

• DNA (chemical)

scientific names

binomial name - Latin - italicized

• 1st word = genus

  • capitalized

• 2nd word = species

  • never capitalized

EX] Puma concolor

taxonomy

classifying and naming organisms

• taxon / taxa

systematics

evolutionary relationships of organisms

• degree of divergence

cladistics

• Developing phylogenetic trees/cladograms

• Uses ancestral and derived characters (not similarities)

• Timing

Taxonomic Hierarchy

• domain

• kingdom

• phylum

• class

• order

• family

• genus

• species

phylogenies

• branching

• length of branches

homologous structures

similarities due to shared ancestry

analogous structures

similar structures on unrelated species

• convergent evolution

  • adaptations to deal with a common environment

macroevolution

• fossil record is rich with transitional forms

  • small changes accumulate

how do species form

1. allopatric speciation

2. symmetric speciaiton

allopatric speciation

populations become isolated (geographic speciation)

sympatric speciation

inhabit same geographic region but become two different species

isolating mechanisms of reproduction

1. prezygotic

2. postzygotic

interbreeding in populations

• if populations DO interbreed, they cannot diverge

• if populations DO NOT interbreed, each can develop different adaptations

• preventing mixing of genes = critical part of formation of new species

prezygotic mechanisms

• geographical isolation

  • EX] located in different places

• ecological isolation

  • EX] different habitats but can be in the same location

• temporal isolation

  • EX] different breeding seasons

• behavioral isolation

  • EX] courtship differences (songs, dances, gifts)

• mechanical isolation

  • EX] ?

• prevention of gamete fusion

incomplete reproductive isolation

• ongoing hybridization

• fuzzy species boundaries

possible outcomes of hybridization

1. fusion

   • become one species

2. continue hybridization

   • stable zone

3. reinforcement

   • very different species

species concept

several species that are difficult to separate

subspecies

consistent geographic variation

evolutionary significant units (ESU)

• looking at genetic difference in populations than can be significant for present and future generations

• could be an entire species

• a species may have several ESUs

temperature with evolution

ecologically important environmental factor

• organisms have evolved to regulate body temperature

microclimate

scale of a few kilometers, meters or cm

• space matters, scale related to organism

macroclimate

large scale - climate diagrams

microclimate factos

• altitude

• aspect

• color of ground

• vegetation

• boulders/burrows

• aquatic temperatures

microclimate altitude

temp higher at lower elevations

microclimate aspect

northern aspect in shade (cooler, wetter)

VS

southern aspect in sun (warmer, drier)

• moss on the north side of a tree

  • cooler, more moisture

microclimate color of ground

albedo

• light surfaces reflect sun (high albedo) vice versa

arid and semiarid areas = more bare ground due to absorption vs reflection

microclimate vegetation

plants provide shade

microclimate boulders and burrows

soil is a good insulator, under soil is more cooler and humid

microclimate aquatic temperatures

resistant to change because of its specific heat (capacity to absorb heat), water stabilizes temperature

• 3000 times higher than air

ectotherms

external sources of energy

endotherms

internal sources of energy

thermal neutral zone

range of temps when metabcoil rate does not change

lower than thermal neutral zone

increase metabolic rate, metabolize energy stores, shiver

higher than thermal neutral zone

increased heart rate, increased blood flow to skin, sweat

why is regulating body temperature so important?

rates of chemical reactions are very specific

evolutionary tradeoffs

no species can thrive under all conditions due to energy limitations

principle of allocation

as a population adapts to a set of conditions, its fitness under other conditions is reduced (evolutionary tradeoffs)

adaptation vs acclimation

adaptation = long-term, genetic response of a population

acclimation = short-term, a type of adaptation

BOTh reduce/minimize stress, both require tradeoffs

psychrophilic

cold loving

• high altitudes, deep water

thermophilic

heat loving

• hot springs, temps up to 110C

heat budget

Hs = Hm +- Hcd +- Hcv +- Hr = He

metabolic heat

always a heat gain

conduction

direct physical contact

• heat flow from warmer object to colder object