Review questions for test 2
EBIO 2040

What temporal changes in population sizes are commonly observed in nature?  What are some of the underlying causes for these changes?

Why are small populations more prone to extinction than large ones?


What are "Alee effects?"

What are the major life history events in an organisms life that influence its fitness?

Organisms can allocate their resources (energy, nutrients) to what basic functions?  How might allocation to these functions change over the lifetime of the organism?

What biotic and abiotic environmental factors influence life history strategies of an organism?

In an evolutionary context, what is the ultimate “goal” of life history strategies?

What pattern of survivorship in a population (i.e. pattern of mortality in a cohort over its lifetime) would select for early reproductive maturity?

What is the term for an organism that reproduces once and then dies?  What is the term for an organism that reproduces repeatedly over its lifetime?

Why should an organism delay allocation to reproduction until later in its life?

If competition is high and disturbances rare, would you expect plants to produce many small seeds, or a few, large seeds?  Why?

Under what kind of environmental conditions would a high amount of parental investment into care for offspring be beneficial?  What are the costs for the parent?

What are the life history traits associated with r selection?  In what kind of environments would r-selected traits be favored?

What are the life history traits associated with K selection?  In what kind of environments would K-selected traits be favored?

What is intraspecific competition?  Does it enhance, or inhibit population growth?

What is a “limiting resource?”  Can two species that have different limiting resources compete with each other?

What are some common limiting resources for microorganisms?  plants (low and high productive habitats)?  herbivores?  carnivores?

Define “R*.”  How is this concept used to predict competitive ability?

Define “exploitation competition.”  How does it differ from “interference competition?”  Can plants use interference to compete with a neighbor?

If two species have the same niche, and one species is a superior competitor, what will happen?  What is the name for the ecological principle describing this phenomenon?

How can the effect of the physical environment on resource acquisition influence the outcome of competition? 

How can evolutionary change lead to coexistence among species that potentially compete?

Why are leaves the preferred food source for terrestrial herbivores?

What are the potential benefits to herbivores (particularly insects) to being specialists on just a few plant species?

How can plants defend themselves against herbivores?

What type of consumer:
* kills and consumes their prey?
* lives in close association with its host while consuming it (but don’t necessarily kill it)?
* lays its eggs on hosts (usually other insects), allowing its young then consume and kill the host?

Can predator-prey interactions cause population cycling?

Describe the assumptions of the Lotka-Volterra equations for predator and prey population growth.  What predications does the model make about population cycling in predator and prey populations? 

What factors contribute to limiting the degree to which predators drive prey populations to extinction?

What determines benefit (i.e. net energy gain) of different prey species?

Are there tradeoffs for prey to being physically defended against predators?  If so, what are some potential tradeoffs?

What is meant by “crypsis?” "mimicry?"

How can chemical defense of prey work effectively- i.e. how can they help predators learn not to eat them?

What are some hunting strategies used by predators that help increase their efficiency at capturing prey?

What is a “pathogen?”

Approximately what percentage of organisms on Earth are parasites?

What are the relative merits and disadvantages for parasites to living inside vs. outside a host?

What is a plant “gall,” and how does it help to protect against parasites/herbivores?  Is there a similar structure in insects to fight off parasitoids?

How do “phytoalexins” help to fight off attacks by parasites in plants?

Why would a disease outbreak with a frequency shorter than the lifetime of a vertebrate host cause less mortality than one with a frequency longer than the lifetime of the host?

Evolutionary responses in parasites sometime lead to lower mortality in host populations.  Why would this occur?

How can parasites affect the outcome of competition between 2 species?

What is meant by brood parasitism?

Define mutualism and commensalism.  Are mutualisms rare, or common?

If interacting with another species results in the investment of energy or resources, how can the relationship be a mutualism?

What is a trophic mutualism?... a habitat mutualism?  … a service mutualism?

What is a “mycorrhizae?”

Approximately how many angiosperms (flowering plants) have mycorrhizae?  how many gymnosperms?

Why do many herbivores benefit from having a mutualism with protists, bacteria, and/or fungi?

Lichens are a mutualism between what types of organisms?  What functions do each partner perform?

What is meant by an “obligate mutualism?”

Can a mutualism ever switch over to a parasitism?  Is there evidence of mechanisms to limit the potential for one partner to cheat on the other?

A group of interacting species that occur together at the same place and time is called what?

What criteria might be used for deciding how to define what species occur in a community?

What are the 2 components of ecological diversity?

What is the Shannon-Wiener index, and what does it estimate?

What is “biodiversity?”

How is dominance of species in a community estimated?

What is a “keystone” species?

How can species interactions be indirect?  Is a trophic facilitation an indirect interaction?

What are the main filters that determine whether a species becomes a member of a community?

Approximately what percentage of foreign species vectored by humans becomes established?  What percentage of these established species becomes a nuisance species?

What is meant by “non-equilibrium” theory in the context of diversity and species co-existence?

What is the primary mechanism under equilibrium conditions that leads to species coexistence?

How can predators and herbivores partition their food resources?  Can plants partition resources among species?

What is a disturbance?  How does the frequency of a disturbance influence diversity, and by what mechanisms?

What is the “insurance hypothesis” in the context of species diversity?  What ecosystem services may be enhanced by increasing diversity?

How does the “redundancy hypothesis/ rivet hypothesis” predict the relationship between diversity and community function, i.e. as diversity increases or decreases, how does the rate of function change?

True or false, communities don’t change at all in the absence of disturbances?

The impact of the disturbance on a community is determined  by what 3 major factors?

What is the general relationship between the intensity of a disturbance and its frequency?

What determines the frequency of fire in terrestrial communities?

What are the 3 general categories of fire intensity?

What strategies have been used by ecologists to study succession, given that it may take 100’s of years?

Early conceptual models of succession emphasized what biological interaction as most important?

Why would life history traits be important to succession?  Why is the “path” of succession associated with life history traits?  What trade-offs in life history traits would change over the course of succession?

What are the major differences between primary and secondary succession?

What are “ecosystem services?”