Exam 4 Flashcards
(12 cards)
Explain the four main types of species interactions, and identify the nomenclature of +/0/-
Commensalism (+/0): One species benefits and the other is unaffected.
Competition (-/-): Both species compete against each other, which takes energy from other resources.
Consumption (+/-): One organism eats another; herbivory, predation, and parasitism.
Mutualism (+/+): Both species benefit.
Explain niche.
An ecological niche is the range of resources that a species can use and the range of conditions it can tolerate.
Contrast species richness and species evenness.
Richness: The distinct number of species in a region.
Evenness: The relative abundance of different species in a region.
Interpret and draw a food web (what is at the bottom—what is at the top?).
Predators are at the top and prey are at the bottom. Arrows point to the predator, who consumes the organism.
Contrast bottom-up and top-down effects in a food web.
Bottom-Up: The nutrients, sunlight, or water determines the abundance of primary producers who are at the bottom of the food web.
Top-Down: The presence or absence of consumers from the top of the food web that may change the species composition in the community.
Define and explain the role of a keystone species.
They may have a greater impact on the community structure that their abundance would suggest.
Explain primary vs. secondary succession—articulate the differences between the two.
Succession is the recovery of the community following a severe disturbance.
Primary succession is when a disturbance removes the soil and organisms in a community (glaciers, volcanoes, floods).
Secondary succession is when a disturbance removes all or some of the organisms but the soil is intact (hurricanes, fires).
Distinguish between r- and K-selected species, and relate them to succession.
R-selected species maximize their reproductive rate. They have high fecundity and low survivorship. These species appear early in succession.
K-selected species live at the carrying capacity and invest more energy in fewer offspring. They have low fecundity and high survivorship. These species appear later in succession when the habitat has stabilized.
Distinguish between NPP and GPP.
Net Primary Productivity: the energy that primary producers invest in building biomass (the weight of organic material)
Gross Primary Productivity: the total chemical energy produced in the given area and time (not useful bc some is lost as heat/cellular respiration)
Explain energy transfer between trophic levels—how does productivity decline at higher trophic levels? Explain the pyramid of productivity.
Energy dissipates at each level. 90% of energy is lost at each trophic level. Only 10% of energy is transferred to the next level.
Explain biomagnification, and provide an example.
It is the increasing concentration of toxic substances in organisms at higher trophic levels. This occurs because the biomass decreases up a level, but the toxin does not, so its concentration increases.
