Ecology Chapter 10

What are the six different interactions between different species?

1) competition

2) predation

3) herbivory

4) parasitism

5) disease

6) mutualism

What are the two different types of competition?

1) resource competition - occurs when a number of organisms utilize a common resource that is in short supply

2) interference competition - occurs when the organisms seeking a resource harm one another in the process, even if the resource is not in short supply

What is scramble competition?

all individuals are equally affected, no winners or losers

What is contest competition?

some individuals acquire resources at the expense of other individuals

What are some aspects of the process of competition?

animals need not see or hear their competitors, many or most of the organisms that an animal sees or hears will not be its competitors, competition in plants usually occurs among individuals rooted in position and therefore differs from competition among mobile animals

What do the two sets of equations in the Lotka-Volterra equations apply to?

predation-prey interactions and non predatory situations involving competition for food or space

What are the three possible outcomes when two species are put together?

1) both species coexist

2) species 1 becomes extinct

3) species 2 becomes extinct

What is the problem Tilman had with the Lotka-Volterra equations?

only describes competition by its results (according to changes in the population sizes of the two competing species)

What is Tilman's mathematical model of competition based on?

resource use (two resources)

What is the difference of the final predictions of Lotka-Volterra versus Tilman's model?

Tilman's model can be extended to make community-level predictions about species diversity and succession; and emphasizes mechanism

What three important ideas have come from these mathematical models of two competing species?

1) competition can lead to one species winning and the second species going extinct

2) some competitive interactions can lead to coexistence

3) we can understand competitive interactions only by knowing the resources involved and the mechanisms by which species compete

What is a niche?

animal's place in the biotic environment, its relations to food and enemies; the role of an animal in its community

What is the competitive exclusion principle?

complete competitors cannot coexist; two species with similar ecology cannot live together in the same place; if no differentiation between niches, one species will eliminate or exclude the other

True or false: the fundamental niche is an abstract concept.

True

What are some situations where competitive exclusion would not be expected to occur?

unstable environments that never reach equilibrium and are occupied by colonizing species; environments in which species do not compete for resources; fluctuating environments that revers the direction of competition before extinction is possible

What is the most common way plant ecologists study the effect of one plant species on a competing species?

the use of replacement series (an array of plots with different combinations of the two species)

For the effect size equation, a _______ result means that competition is reducing the density or biomass of the species and a _______ effect implies facilitation, a higher density or biomass under conditions of interaction.

positive, negative

True or false: we should assume that competition in natural populations is always occurring.

False

What are the criteria for establishing occurrence of interspecific competition? (1 is weakest and 6 is convincing evidence in natural populations)

1) observed checkerboard patterns of distribution consisted with predictions

2) species overlap in resource use

3) intraspecific competition occurs

4) resource use by one species reduces availability to another species

5) one or more species is negatively affected

6) alternative process hypotheses are not consistent with patterns

What are the classifications of interactions?

Competition: both species harmed

Predation: one harmed, one benefits

Mutualism: both benefit

What are proximate effects?

the use or defense of a resource by one individual that reduces the availability of that resource to other individuals

What are ultimate effects?

results of proximate effects that are a decrease in contribution of individuals in future generations (reduction in fitness)

What are resources (in terms of competition)?

something that is consumed by the organism; abundance is reduced by consumption; used for growth, maintenance, or reproduction; reduction in resources reduces population growth; important when they are limited

In order for their to be competition, the common resource must be _____.

limited

Intraspecific competition is ____ species, while interspecific competition is ____ species.

within, between

What are the two methods of competition?

exploitative - consumption of a shared resource

interference - direct, aggressive interactions used to defend resource

Competition between species is often _____. So one species is dominant.

asymmetrical

What does the effects of competition depend on?

population density

What is the Lokta-Volterra equation based on? (know the equation)

the logistic curve of population growth between two species

What is the conversion factor in the Lotka-Volterra equation?

expresses species 1 in unit of species 2

What is Tillman's model of competition between species based off of?

resource limits and resource consumption rates

When will a species compete?

If their niches overlap

What is a fundamental niche?

all the environmental factors relevant to a species survival and reproduction; it is an abstract concept because it requires the absence of other organisms

What is a realized niche?

the actual set of factors observed in the presence of competition (competition limits a species from filling the fundamental niche

What is an example of competitive exclusion discussed in class?

Gause's Paramecium - when grown together aurelia takes over

Birch's grain beetle - blue declines in low temp but dominates in high temp

What is a way that ecologically similar species can coexist?

resource partitioning (species specialize on different resources)

What are some characteristics of resource partitioning?

reduces resource overlap which reduces intensity of competition; produced by natural selection; "ghost of competition past"

What is an example of resource partitioning discussed in class?

Terns on Christmas island (differences in diet and beak shape)

What are some examples of competitive exclusion/release discussed in class?

rodents

two species of surfperch (like discussion example)

How is competition an evolutionary force?

it reduces individual fitness because natural selection will favor traits that reduce competition (example: Galapagos finches)

What is character displacement?

evolution towards niche divergence because of competition

What are some examples of apparent competition?

indirect interaction via a shared enemy and indirect interaction via other species on the same trophic level