Ecology Exam 3

Biodiversity hotspots

areas with lots of species and diversity

island size

a geographic pattern of diversity, species richness increases logarithmicaly, w/ increase in land mass size

island

any kind of isolated habitat

latitude

a geographic pattern of diversity, species richness decreases linearly with an increase in latitude

ex. there are many lizards in areas near the equator, but only 2 in michigan, you lose species richness as you travel north

ecotone

a geographic pattern, a transition zone between 2 different types of habitat species richness, increases with convergence of different types of ecosystems

ex. estuary

equilibrium theory of island biogeography

proposed by Macarthur and Wilson, proposes that all islands reach an equilibrium of species richness, can be applied to other ecosystems. Can help explain S of islands of different sizes and distances from mainland.

S

equilibrium number of species, amount an island can support balanced by extinction and immigration

is the carrying capacity for the community

(draw an isocline graph for S)

an isocline graph

graphs 2 things at once

if there are no species on an island, the extinction rate is

0

land bridge

a type of island, forms when sea level rises or from other changes, isolating the island from the mainland

• begins with species richness of mainland, loses the richness over time since the island is smaller (came from a bigger habitat and got divided up)

(draw a graph)

relaxation fauna

species that remain isolated on the new island, they are the ones that don’t die out and remain when S is reached

oceanic

type of island, there wasn’t one before and it appears, typically forms from volcanic activity

• begins with 0 richness, gains it over time

• ex. Hawian islands

(draw graph)

islands closer or farther from mainland will have a higher S

closer, there is a higher immigration rate due to shorter traveling distance

(draw graph)

• farther islands will catch up eventually in immigration, however never in population size because they have the same rate of extinction as the closer islands. Therefore farther islands always have a lower S

• however farther islands usually have more unique species

bigger or smaller island will have a higher S?

bigger, species are more likely to encounter a big island than a small island, and a bigger island can support more species than a smaller one

(draw a graph)

Significance of mangroves

mangrove trees are kinds of islands, provide a land habitat in the middle of a body or water that many insects live on. Scientists killed all the species on a mangrove and essentially made it into an oceanic island. Species richness over time then came back up, similar to what it was before scientists killed the species.

• shows almost any isolated habitat follows island biogeography theory

fragmented habitats

a habitat that was once large and continuous but now is broken into smaller, more isolated patches. Roads and national parks create them, as well as natural disasters and environmental obstacles. They are concerning for endangered animals especially, as the habitat decreases in S as it becomes fragmented and access to resources decreases

one way to bring fragmented habitats together

to make land bridges over roads, expands habitat and resource access, as well as helps preserve gene flow and diversity

ecological niche

specific role of a species in an ecosystem

includes all physical, chemical, and biological components needed for that species’ survival

physical resources

abiotic components that must be assimilated for survival, including O2, CO2, water, light (for photosynthesizers), nutrients, and minerals

physical factors

abiotic parameters that affect where an organism can live including temp, pH, salinity, and light

draw a graph of a single species with no competition for prey size vs. individuals eaten

looks like a bell shaped curve

niche width

quantifies the variance in resource use. The more adaptable the species, the broader the niche. Specialists have less width, generalists have more

specialist

can live in few habitats, eat few types of food, tolerate a narrow range of environmental conditions, K selected

generalists

can live in many habitats, eat many types of food, tolerate a wide range of environmental conditions, R selected

Hutchinsonian niche

quantifies the level of resources and factors that a species needs for survival, you can plot several resources and factors in multi-dimensional space.

• Can plot multiple single factor niches so they become multi factor niches

• can measure for example prey size eaten, oxygen content of water lived in, water salinity lived in. Turns the graph into a 3d box

niche multidimensional hypervolume

plots of multiple resources and factors and the range within which a species is found

• has unlimited dimensions

• shows Hutchinsonian niche, quantifying ecological niches

• used in ecology to see if conditions are appropriate to be able to reintroduce endangered species to a habitat, or see why they are endangered in the first place

niche separation

distance between mean resource curves for 2 species. There is sometimes overlap and sometimes not, the curves may intercept or not

niche overlap

area of resource curves that overlap, the overlap is where competition occurs

competition

occurs when 2+ niches overlap in 2+ species, leads to a decrease in population of at least 1 species’ population because there are less resources available , is a kind of interaction

• even if there is plenty of food, they can fight over it, creating competition

preemptive competition

competition for specific space where resources can be obtained

• not the same as territoriality

  • ex. plants want to be in the best sunlight spot, compete but not necessarily intentional

interference competition

once species limits anothers access to a resource even if its abundant

• can have to do w/ territoriality

• ex. bears picking the best spot on the river to catch salmon

• lions and hyenas hating eachother and not wanting to share territory

• butterflies fight over abundant nectar sources

• some trees poison the ground so others cannot grow there

allelopathy

producing chemicals to interfere with another plant’s ability to grow

exploitation competition

once species uses more of a limited resource, leading to the detriment of the other species

• 1st species is usually better at exploiting

3 competition types

interference, preemptive, exploitation

competition isocline

predicts the result of competition between 2 species, works best with exploitation competition where there is a clear competition and resource, but there are multiple kinds: competitive exclusion, weak competition/stable equilibrium, and unstable equilibrium

(draw graphs of each)

6 elements of a competition isocline

• N₁ pop size of species 1

• N₂ pop size of species 2

• a₁₂ effect on species 1 by 2

• a₂₁ effect on species 2 by 1

• K₁ carrying capacity of species 1

• K₂ carrying capacity of species 2

competitive exclusion isocline

if there is a larger difference in population between the two species, there will be less competition. Always eventually ends with the species with the larger K outcompeting the other. If the dominant species is at its K, the other species population is at zero. Therefore K is the amount it takes to bring species 2 to zero

• species 1 is better at exploiting resources

draw graph

competitive exclusion

local extinction or near extinction of a species due to interspecific competition

• species with a higher K, better exploitation, etc. will outperform others

• the species with the highest isocline is the “winner”

weak competition/stable equilibrium isocline

no species will die out, competition is less intense. Will always over time acheive an equilibrium in which there are steady populations for both species, and their Ks are similar. Alpha values are smaller than other forms.

• can lead to character displacement over evolutionary time

• competition still has an effect but not exclusion.

Character displacement

natural selection essentially, separation of 2 species in morphology or behavior as a result of competition. Occurs over evolutionary time, an overlap will evtually separate. Occurs all the time in the tropics and other table environments

ex. wildabeest, zebra, and giraffess have the ability to eat all the same plants, but eat different ones at different heights, showing stable equilibrium

ex. parasites

ex. warblers eating at different tree heights

draw graph

unstable equilibrium isocline

K’s are roughly equal, but are above alpha values. It is possible for one species to be driven no population, but also possible for equilibirum to be acheived depending on the initial population sizes. Competition is fairly intense.

unstable equilibrium

occurs when the result of competition depends on initial population sizes. Alpha values are large, bigger than K. Can lead to either competitive exlcusion or character displacement

• unequal population sizes leads to competitive exclusion

explain how the population of asian tiger and native mosquitoes relate to isoclines

the asian mosquitoes were brought to the US in a tire shipment, which held a lot of water. Native mosquitoes can control the asian populations through competition. In wilderness and trees, the two populations show an unstable equilibrium isocline. In tires, however, competitive exclusion occurs and the asian mosquitoes outcompete.

producer

made food with photosynthesis, are autotrophs

ex. plants, algae, some bacteria

consumer

also known as a predator or heterotroph, obtain food from eating living organisms

• everything but producers

primary consumers

eat producers, are herbivores

secondary consumers

eat primary consumers, are carnivores

ex. praying mantis, whale

tertiary consumer

eat secondary consumers

omnivore

eat producers and consumers

parasite

an organism that feeds on another while it is living, or inhabits the host organism

• the host is rarely killed

  • also known as micropredators

parasitoid

larvae of an organism parasitizes their host, but never the adults

• frequently kills the host

• only in flies and wasps

detrivore

eat waste products from other organisms like dung and cast off body parts

• heterotrophic

• ex. dung beetle (NOT vultures)

decomposers

not detrivores,breaks down organic matter into simpler compounds

• recycles nutrients and minerals back into soil and water

• ex. some fungi and bacteria

prey defense mechanisms

urtication, camoflauge, escape, and chemical sequestration

urtication

irritating predators by physical structures on the body that poke you

• ex. porcupine

chemical sequestration

when an organism stores toxic chemicals

• tobacco, milkweed (butterflies consume it and can become toxic)

Aposematic coloring

coloration to warn that something is toxic, usually red or yellow

• ex. poison arrow frogs: consume toxic insects, become toxic to predators

• poison dart frogs, toxic to the touch. Red and yellow

optimal foraging theory

organisms will obtain the max amount of energy under a given set of foraging conditions

• finding a balance between calories and time

• want the most calories

• how much can you eat vs. how hard you have to work

• includes energy maximizers and time maximizers

• ex. wolves could eat mice, but a moose has many more calories, but also requires more energy to catch

energy maximizer

species that make receiving the most energy per meal their priority, want the most food they can eat

• snakes, angler fish

time maximizer

species that make spending the least amount of time catching a meal their priority

• grazing species like rabits or cows

different respinses to prey increase

functional response, numerical response, combined responsefu

functional response

each individual predator consumes more prey individuals, leads to healthier individuals of the predator population, when there is more food to eat, individuals will eat more

numerical response

predators increase in numbers, overall predator population consumes more prey, not individuals

• breeding more, not eating more, causes an overall increase in population

  • strongest functional response has the lowest numerical response

combined response (to prey increase)

if predators eat or breed more, the % of predation increases

• predation is density dependant up to a certain point, because you can only eat so much

• prey can always outbreed predators

  • ex. all wildabeest give birth at the same time, lions have tons of food, but they can only eat so much (can’t eat everything)

• competition in a trophic guild can lead to stable equilibrium which can then lead to charatcer displacement

ecological guild

group of ecologically similar organisms, they compete if they are in the same environment. Can be in a guild even if they are not in the same envrionment

allopatric

indiviauls of 2 species not living within the same community

• no competition

  • ex. deer and moose (moose go crazy from deer brainworm)

sympatric

2 species living in the same community

• ex. Lake Malawi: 250 sympatric species of cichlids, has 10 distinct trophic guilds, leading to many super specific niches and a complex environment

community equilibrium theory

every species and combination of species has a limit to their population size (equilibrium) within an ecosystem

• competition and predation are main community structuring forces

interspecific competition

component of community equilibrium theory, species within trophic guilds competing for scarce resources structure communities

• draw back to fundamental nice: Hutchinsonian niche for species in absence of competition

• but with competition: realized niche and character displacement→subset of fundamental niche actually utilized by species

  • competition decreases realized niche

predation

other component of equilibrium theory, predators consume prey and its corresponding effects structure communities

• if you remove starfish from shore, muscles wipe out all species in the area

• removing a predator can do more than impact population of prey

keystone species

a predator that affects an ecoystem to a far greater degree than their biomass would suggest

• removal can effect many seemingly unrelated species

• ex. kangaroos, rats, starfish, beaver, wolves

  • NOT termintes, have a lot of biomass

trophic cascade

removal of a keystone species causing changes to multiple trophic levels

ex. when elk populations increase, they eat more vegetation, causing loss of trees for songbirds and beavers

community nonequilibrium theory

species and combinations of species are rarely at equilibrium, de-emphesizes K

• communities are far more dependent on abiotic, density indep. effects for their structure

• abiotic extrinsic view

• richness, diversity, and complexity increases in favorable environmental conditions

• will suffer under disturbances like floods, droughts, fire, a