BJU Ecology - Unit 2: Community Ecology+ (Final Exam)

community

formed by all of the populations that occupy the same habitat at the same time

• physical features (ex: south-facing slope)

• chemical features (ex: salt levels in water)

• physical features (ex: temperature)

• the species found in it

what is a habitat (what is it characterized by)?

different species within a community that have a very similar function(s) (ex: multiple species who eat vegetation — insect-eating bird guild)

what is a guild?

• Interaction between climate and topography

• the kinds and amount of food and other resources influence which species can live there

• individuals within a population have adaptive traits that allow for survival and reproductive success, and allows them to exploit resources

• within a community that there are many types of intra- and interspecific interactions

• population densities and history of N over time, along with arrivals and disappearances of species which leads to acute temporal change

What are five factors that shape the structure of a community?

Dictates the habitat’s temp, rainfall, soil types which in turn dictates what kind of plants are in the area and eventually animals

how do interactions between climate and topography affect the community structure?

• pattern of population sizes

• feeding (trophic) levels

• number of species in an area

Together the five factors that shape the structure of a community (climate/topography, kinds and # of resources, adaptations, interactions, and pop. density) influence overall…?

• Primary producers (base): makes up bulk weight of organisms in community. Anything photosynthetic.

• Primary consumers: made up of herbivores (eats primary producers)

• Secondary consumers: predators; mostly carnivores, what eats primary consumers.

• Tertiary consumers: predators of predators; eat primary and secondary consumers

Know the trophic levels (pyramid) and their functions from base to top.

• Ecological: Specific function of a species within the habitat (the position it holds). The sum of activities performed by the species. The sum is designed to help the species survive and reproduce.

• Fundamental: refers to the set of resources a population can theoretically/potentially use under ideal conditions

• Realized: The actual amount of biotic and abiotic resources an organism uses due to circumstances such as predation, competition, environmental constrictions. More constrained and is the actual area an organism uses.

What is the difference between realized and fundamental, and ecological niche?

True

T/F When two species have the exact ecological niches, there is intense competition and something has to be done to lower intensity.

the sum total of the organism’s use of the biotic and abiotic resources in the habitat.

What is a niche

neutral relationship

0/0

+/0

commensalism

mutualism

+/+

true

T/F In many cases the Fundamental niche is the same as the realized niche, but not normally

predation/parasitism/parasitoidism

+/-

competition

-/-

competition

Which type of interspecific interaction has the greatest impact on shaping community structure?

Ammensalism (elephant walking and unknowingly stepping on ants)

-/0

competitive exclusion principle

If 2 species cannot coexist and 1 is either driven away or a micro-extinction, then what principle will prevail?

resource partitioning

how can 2 species with the same needs occupy what appears to be the same niche?

symbiosis

A term used to describe an ecological relationship between two different species that live together or have direct contact with each other, and can include relationships based on commensalism, mutualism, and/or parasitism.

interspecific competition

a term used to describe competition between two different species

One species might so out-compete the other that the one might become extinct within the population.

Why does competition typically reduce 1 or both species?

competition

a term used to describe an interaction (such as when a territorial dispute occurs) between two individuals of the same species

If successful = resource partitioning

If unsuccessful = competitive exclusion principle

If competition is fierce, then to reduce conflict to reduce niche overlap. If this is successful what happens? If unsuccessful?

Pub. 1958: pop. ecology of some warblers of a NE coniferous forest which showed resource partitioning where groups of different species of warblers were found different strata and formed a feeding guild.

What does MacArthur’s warbler study

niche overlap

the portion of the niche’s resources that are shared by 2 or more species

character displacement

What is another way to reduce competition besides resource positioning?

• Allopatry: no overlap, no competition between A and B

• Sympatry: overlap A and B which leads to the potential for intense competition and certain phenotypes become pronounced.

What is the difference between allopatry and sympatry when it comes to character displacement?

• Resource Partitioning: This is the process by which coexisting species divide and specialize in the use of resources, allowing them to coexist by utilizing different parts of the same resource or occupying different niches within the ecosystem. It promotes species diversity and reduces direct competition, enabling multiple species to thrive in the same habitat.

• Competitive Exclusion Principle: This principle states that two species competing for the same limited resources cannot coexist indefinitely in the same habitat. One species will always outcompete the other, leading to the local extinction or displacement of the weaker competitor. This principle emerged from the work of Russian biologist Georgii Gause in the 1930s.

• Character Displacement: This is an evolutionary adaptation in a heritable trait, caused by resource partitioning. It occurs when the trait to use the resource adapts over generations to a distinctly new character state, such as a smaller or larger beak better matched to the available seed food supply

What is the difference between resource partitioning, competitive exclusion principle, and character displacement

Coevolution (reciprocal evolution)

Prey adaptations and predator adaptations are often related in a relationship called…?

the sensory world by which the animal uses to perceive the world around them

What is an umwelt?

• Passive (hiding)

• Active (escape)

• Aposematic coloration (bright colors that warn the predator that it is toxic)(can be somewhat passive)

• Cryptic coloration (camouflage) (can be placed under a passive adaptation).

What are the four prey adaptations?

• Batesian mimicry: harmless mimic and harmful model

• Mullerian mimicry: two are harmful species resembling each other and are near each other. Both benefit (doesn’t really have a model/mimic)

What is the difference between Mullerian and Batesian mimicry

cryptic coloration

a passive defense whereby an organism uses camouflage to avoid predator detection

aposematic coloration

Animals with effective chemical defensives (e.g. poison dart frog) are often brilliantly colored, a warning or advertisement color to predators known as?

coevolution

Reciprocal evolutionary adaptations of two interacting species, whereby a change in one species acts as a selective force/pressure on another species, in which counteradaptation in turn acts as a selective force on the other species is called

• Predation involves one organism (the predator) capturing and consuming another (the prey), which can significantly influence population dynamics and community structure by affecting prey availability and competition for resources.

• Competition occurs when multiple organisms vie for the same limited resources, which can lead to negative impacts on all involved, ultimately affecting the overall health of the community.

which two types of biological interaction (e.g. predation, competition, etc.) do you feel (as well as most biologists) are most important in structuring communities and why?

Food chain

Transfer of food energy from a plant, to an herbivore, to a predator, and to another predator (each representing a "link"), is called a

10%

How much “energy", in percent, is actually transferred from one link to another according to the energy hypothesis?

energetic hypothesis

The _____ hypothesis suggests that the length of a food chain is limited by the inefficiency of energy transfer along the chain, and if this hypothesis is correct, food chains should be longer in habitats of higher photosynthetic productivity, a prediction that can be tested.

• Stenophagous = feeding specialists; consume specific food

• Euryphagous = general feeders; leads to more complex food webs

Two types of feeders in food webs

true

T/F There are no true communities with just stenophagous feeders

• Group species into broad categories (trophic levels)

• Do it by the species

The two are often done as a hybrid

What are two ways to draw a food web?

food chains

Required to make food webs

• energetic hypothesis

• dynamic stability hypothesis

(both influence F.C.)

What two hypotheses explain why the length of a food chain is limited?

suggests that the length of a F.C. is limited by amount of potential energy at each trophic level. It is most widely accepted and if this hypothesis is true, then food chains should be longer in habitats that have greater biomasses of plant matter

What is the energetic hypothesis?

States that long chains are less stable than short chains. Fluctuates impact biomass at lower trophic levels which magnifies impacts at higher trophic levels which potentially leads to extinction of top predator.

In variable environments (extreme climatic change), top predators are going to have adaptations to withstand environment shocks (great reduction of food available)

The longer the FC, the slower the recovery rate from environmental shocks (for top predators)

What is the dynamic stability hypothesis?

FC length is shorter due to constant environmental shocks

How can an unpredictable climate effect a FC length?

If the energetic hypothesis is true, then the tree hole with higher leaf litter (more biomass) will have longer FC than holes with low leaf litter.

How do the energetic hypothesis and tree hole community theory fit together?

• species which exert a powerful control on a community based on sheer number (biomass)

• Typically exerts control over how other species grow in the area

• Based on biomass or abundance (density)

What is a dominant species?

• some exploit limited resources

• more efficient ways to use resources

Why do some species become dominant?

species that are not common in the community, but still exert a strong control over community structure

What is a keystone species?

community structure

what populations coexist in the same area

• Removal experiments

• Dr. Robert Paine — worked with genus Pisaster (sea star) in rocky, intertidal regions. He looked at the interactiosn/relationship between Pisaster and Mytilus (mussels). After counting total population, he removed Pisaster and found Mytilus expanded in population size which led to the subsequent extinction of other invertebrates, algae, plankton, etc. in tide pools. There were not many Pisaster in the pool starting off, but even the removal of the 2-4 Pisaster results in the eventual extinction of the whole tidal pool.

• Similar experiment with sea otters and sea urchins which food on kelp: when otters are abundant, sea urchins are lower and when rare, sea urchins are higher which leads to less kelp which leads to less biomass which leads to eventual extinction

What is used to determine if a species is a keystone species and how important a species is?

• Type I: as prey pop. density increases (x-axis), the number of prey consumed (y-axis) evenly increases

• Type II: as prey pop density increases (x-axis), the number of prey consumed (y-axis) increases, just not as fast as the density (x-axis).

• Type III: as prey pop density increases (x-axis), the number of prey consumed (y-axis) remains relatively low until it suddenly increases exponentially due to the development of search image in predators and the predators switching the prey preference.

What are the 3 general patterns of functional responses that emerge with predator-prey interactions (predation)

1. number of predators depends on prey pop. density (the reproductive rates in prey and predator along with predators limiting prey)

2. number of prey depend on predators (increase prey mortality as predators increase)

What are the assumptions of a Lotka-Volterra Model?

as prey increases, predator increases, and as predator increases, prey decreases. (Pred and prey are tightly coupled)

What does the Lotka-Volterra Model state?

horizontal line; m = 1/0

dn pred / dt = 0 (pop. growth rate = 0)

(x-axis = pop size of pred; y-axis = pop size of prey)

What line represents the trends of predators densities?

vertical line; m = 0/1

dn prey /dt = 0 (pop growth rate = 0)

(x-axis = pop size of pred; y-axis = pop size of prey)

What line represents the trends of prey population densities?

Remove predators; fence off area; and add different food amounts (this method is hardly ever used since it’s so impractical)

How can one know if it is a Lotka-Volterra situation? (is the population size of prey depend on pred or just vegetation?)

a. pred decrease; prey increase

b. pred increase; prey increase

c. pred increase; prey decrease

d. pred decrease; prey decrease

What counter-clockwise movement of interactions between pred. and prey. pop. densities is often seen when combining trends of pred and prey densities?

• primary: start with habitat with no soil

• secondary: disturbed area with soil

What are the two types of succession and what is their primary difference?

• habitat with no soil is formed

• early colonizers (pioneer species — small, rapid life cycles, adapted to areas with high sunlight and winds, along with nutrient poor soil)(e.g. lichens, small plants, mosses)

• Once small layer of soil is formed from pioneer species, species richness increases in habitat

How is a primary succession habitat started?

• one species creates conditions for their own replacement

• most often seen in primary succession models

• systems tend to move towards a climax community

• inhibition model/hypothesis: early species compete with other early species

• Facilitation model: how early species are replaced (only for primary succession)

What is autogenic environmental change

• disturbed area with soil

• typically not starting with just lichen since there is already soil which typically has a seedbank and/or organisms in it.

• inhibition model/hypothesis: early colonizers compete against any species that can replace it. The sequence of succession depends on who gets there first over who is already there. the first species makes the site less suitable for both early and later colonizers while making the site more suitable for itself

• tolerance model / climax pattern model/hypothesis: sequence of who gets there and establishes themselves is predictable based on several factors: topography, climate, soil type, rainfall, wind, and temperature

Secondary succession model

a complex network of interconnecting and overlapping food chains showing feeding relationships within a community

what is a food web?

dominant species

A type of “species” in a community that has the highest abundance or highest biomass.

A type of “species” in a community that has the highest abundance or highest biomass.

a type of “species” in a community that is not especially abundant, but exerts strong control on community structure (Robert Paine developed this concept using removal experiments of Pisaster sea star and their effects on Mytilus populations).

Type II

When looking at the three functional responses of prey population density (x-axis) to the number of prey consumed by a predator (y-axis), what type of curve shows that consumption of prey by each predator increases, but not as fast as increases in prey density?

Type III

When looking at predator-prey interactions, what type of functional response (‘type’) shows that a predator response is lowest when prey density is at its lowest level or occurs often when predators switch to alternative prey or when they develop a search image for that prey item, so as to give a curve that is slow in the beginning, and later giving rise to a steep curve.

dt/dN​=rN−aNP

where:

• N = prey population

• r = intrinsic growth rate of the prey

• P = predator population

• a = predation rate coefficient

Which Lotka and Volterra Model equation represents population growth equation for the prey population?

dt/dP​=baNP−mP

where:

• P = predator population

• N = prey population

• b = efficiency with which consumed prey are converted into predator births

• a = predation rate coefficient

• m = predator mortality rate

Which Lotka and volterra model equation represents population growth equation for the predatory population?

dN/dt = rN

What equation in the Lotka and Volterra Models represents exponential growth?

aNP or β

Which symbol in the Lotka and Volterra Models represents the prey consumed?

increase

In the absence of predators, the prey population will:

pioneer

opportunistic colonizers of vacant or vacated habitats, are called _____ species

carnivores

carnivores that consumer herbivores are generally called

climax

the persistent species composition (like a beech-maple forest community whereby succession almost always succeeds to this type of forest community) that remains stabilized is called a ______ community.

secondary succession

A form of sequential change that starts with soil, and that usually starts off with a disturbed area such as a plot of land that goes fallow (uncut, unmowed, or agricultural field that has bare soil).

species richness and species evenness

what makes up biodiversity?

species richness

refers to the number of species

species evenness

the proportion of each species relative to the whole

1. Distance effect: islands far away from a source of colonizers will have lower biodiversity.

2. Area effect: larger islands will have more habitat and therefore more diversity

3. Immigration and emigration effect: small islands that are farther away from source of colonizers have fewer immigrants and higher extinction rates due to lower effective population size (suff. genetic var.; Ne)

   1. Doesn’t refer to migration patterns since it’s assumed they are not leaving a permanent effect since it is typically moving through an area and not staying

What three effects influence island patterns?

y-axis = rate of immi/extinct; x-axis = number of species

1. immigration and extinction rates: as immigration decreases, extinction increases (makes an x)

2. effect of island size/area: as immi, decreases, extinction increases with large island trends are shifted towards the right (the number of species at equilibrium will be larger on large islands compared to small islands due to larger habitat diversity and niches)(makes two x’s)

3. Effect of distance from mainland: as immig decreases, extinction increases and as distinct increases, the number of species decreases at the same point compared to an island closer (two lines downwards for immigration with imm/near being higher than immi/far and a line for extinct going upward)

Know how to draw graphs pertaining to the three effects of island patterns

conservation biology

goal-oriented science to devise mechanisms to counter the biodiversity crisis

• 1.5-3+ million species

• 30-80 million species left to be discovered due to the advancement of molecular genetics

How many discovered species are there, and how many species are left to be “discovered”?

tropics

Where is the highest biodiversity found?

50%

____% of land mass has been altered by human activity and used over 50% of accessible fresh water. Marine = ??? %

we are losing much of the “undiscovered” species at an alarming rate

What is the major concern that conservation biology is focused on?

true, but current extinction rate is very high and only increasing

T/F Extinction is a natural phenomenon

Because the species hasn’t been “discovered” yet

Why is it difficult to come up with actual extinction rates?

1. loss of genetic diversity

2. Loss of species diversity

3. loss of ecosystem diversity

What 3 levels of challenges that impact biodiversity (3 components of biodiversity crisis)

• small-population approach

• declining population approach

What are the two main approaches to conservation?

Studies the processes that can cause small populations to become extinct. It’s the “smallness” that finally drives the population to extinction.

• at the core of the idea is the extinction vortex: over time, as the pop. density reaches it K, the density decreases, which leads the population to be prone to increase inbreeding and become more vulnerable genetic drift, which after the threshold for genetic vortex is reached, the vortex starts.

What is the small-population approach to conservation?

1. genetic variation

2. genetic drift

3. loss of adaptiveness

What are the key factors driving extinction vortexes?

minimum viable population size

Makes a prediction of a population’s chance of survival; usually expressed as probability of survival

calculate the effective population size (Ne)

How is the minimum viable population size determined?

• requires researcher(s) to determine Ne which will be based on the breeding potential and long-term survival of the population.

• Use formula that incorporates the sex ratio of breeding individuals into the estimate of Ne

How is a meaningful estimate of Ne established?

Ne = (4 Nf(Nm))/ (Nf + Nm)

Nf = # of fem. that successfully bred

Nm = # of males that successfully bred

Formula for Ne?