2.5-2.6 natural disruptions in ecosystem & adaptations

natural disruption

abiotic/biotic event that brings mortality to organism & changes to spatial patterning in ecosystems they inhabit

ecological consequences

_____ _____ of disruption are dependent on intensity/frequency of disruption

examples of natural disruption

drought, wildfire, disease, tsunamis, hurricanes, volcanic eruptions, climate change, earthquakes, meteor strikes, continental drift/plate tectonics

K-T extinction event

> ¾ all plant/animal species became extinct → adaptive radiation of mammals

mount pinatubo eruption

caused average temperature of earth to decrease by 0.5 degrees

global warming

sea level rising/ retreating shorelines

indian ocean tsunami

loss of fisheries, farmland

loss of habitat

decreases biodiversity

local extinctions

local natural species go extinct in original habitats

background extinctions

loss of species at low rate of extinction

1-5 species for every million species on earth

mass extinctions

significant rise in extinction rate (25-75%)

usually due to some catastrophic event

5 mass extinctions in geology time

time scale

some earth process can occur in different scales of time

periodic

predictable events

old faithful geyser, migration events, planetary orbits, tides

episodic

groups of events that happen occasionally

hurricane season, el nino, pollen release

random

no true observable pattern

meteor impacts

earth’s climate

_____ ______ has changed over time - warm periods, cool periods (ice ages)

changes in temperature affect biodiversity

ice age

sea levels fall as oceans retreat due to glacial formation

warming periods: oceans rise as glaciers melt

repeated action can change surface of continents which can cause habitat change

land becomes exposed from melting ice, new species move into area

plate tectonics/continental drift

cause major changes in habitats over geologic time

movement of continents has allowed species to move, adapt to new environments, and form new species through natural selection

led to extinctions/evolutions of new species

evolution

change in genetic composition of population over time

microevolution

evolution below species level, small genetic changes

macroevolution

evolution that gives rise to new species, genera, families, classes, or phyla

large scale, long term evolutionary changes

artificial selection

humans determine which individuals breed, with a preconceived set of traits in mind

produced numerous breeds of livestock/pets

most modern agricultural crops → result of many years of careful breeding

produce unintended results such as herbicide resistance

natural selection

environment determines which individuals survive and reproduce

only offspring with fittest genotypes will pass on their genes to next generation

key ideas of theory of evolution

• individuals produce an excess of offspring

• not all offspring can survive

• individuals differ in their traits

• differences in traits can be passed on from parents to offspring

• differences in traits are associated with differences in ability to survive and reproduce

fitness

individual’s ability to survive and reproduce

adaptation

trait that improves individual’s fitness

5 random evolution processes

• mutation

• gene flow

• genetic drift

• bottleneck effect

• founder effect

mutation

random change in genetic code produced by mistake in copying process

more mutations → evolution

some scientists argue sickle cell anemia help resist malaria/lactose originated with a mutation

evolution by mutation

mutation can arise in population → increase in frequency over time

gene flow

individuals move from one population to another and thereby alter the genetic composition of both populations

• alters the frequency of alleles in population

can bring genetic variation to population that lacks it

high gene flow

in population that experiences natural/artificial selection ___ ___ ____ from outside can prevent population from responding to selection

evolution by gene flow

low genetic variation = lots of defects, introduce new species→ decline in defects

genetic drift

change in genetic composition of population over time as result of random mating

alters genetic composition of SMALL populations

evolution by genetic drift

small population: some less-common genotypes can be lost through random mating → genetic composition change over time

large population: less difficult for less-common genotypes to be lost → genetic composition stays same

bottleneck effect

reduction in genetic diversity of population caused by reduction in size (due to catastrophe → fire/hurricane)

species are less able to adapt to future environmental changes

reduced genetic variation

reduced population numbers =

disease/low fertility

low genetic variation can cause increased risk of _____ / __ ____

population decline/extinction

resulting low diversity can lead to _____ ______ /_______e

extinction

death of last member of species

evolution by bottleneck effect

population experiences drastic decrease in size, some genotypes will be lost, genetic composition of survivors will be different from original group

founder effect

change in genetic composition of population as result of descending from small # of colonizing individuals

evolution by founder effect

few individuals from mainland colonize island, genotypes on island only represent subset of genotypes present in mainland population

*some genotypes not present in new population

speciation

evolution of new species

allopatric speciation

speciation that occurs with GEOGRAPHIC isolation

finch species

common example of allopatric speciation, led to large variety of ____ _____ in galapagos islands which descended from 1 species that colonized islands from south america mainland

geographic isolation

physical separation of group of individuals from others of same species

reproductive isolation

result of 2 populations within species evolving separately to point that they can no longer interbreed/ produce viable offspring

sympatric speciation

evolution of one species into two, without geographic isolation

POLYPLOIDY