Intro Bio II Exam 3 Ecology Review

Direct effect deals with the direct impact of one individual on another when not mediated or transmitted through a third individual. These can include which of the following?

• Competition

• Predation

• Parasitism

• Mutalism

• Commensalism

Describe how an increase in a limiting nutrient can lead to a fish dying.

• Increasing a limiting nutrient can lead to biomagnification, which will lead to changes in the ecosystem

• Increasing a limiting nutrient can lead to eutrophication which can lead to algae blooms which will lead to DO being used up and fish dying due to poor oxygenation

• Increasing a limiting nutrient allows for the keystone species to change, thus affecting the ecosystem the fish lives in

Answer explanation

Eutrophication: Occurs when a body of water receives large inputs of nutrients, stimulating excessive primary production. This increased phytoplankton growth results in an increase decomposition which can lead to hypoxia in the water

An invasive predator would likely sit at the ____ (top / bottom) of the food chain and ____ (would / would not) be a keystone species. As it ____ (grows / shrinks) in number, it would eliminate the keystone species (in all likelihood), throwing the ecosystem out of balance

The following is an example of what?

You witnessed _____ when you added alewife, because the addition of a secondary consumer changed the abundance of a primary producer. 

• Competitive Dominance

• A Trophic Cascade

• Biomagnification

• Eutrophication

Answer explanation

A trophic cascade occurs when the abundance of individuals at one trophic level affects the abundance of individuals several trophic levels removed from them

Biomagnification (seeing ____ (more / less) of a toxin higher in a system) takes time to develop as each link in the chain has to build up a lot of toxins. Organisms further ____ (up / down) the food chain have more toxin in them as they live ____ (shorter / longer) and consume ____ (less / more).

In ____ ____ (top down / bottom up), keystone predators regulate and keep in check the rest of the ecosystem, allowing everything to stay in balance. ____ ____ (top down / bottom up) discusses how nutrient availability also regulates the extent to which life can grow

Describe nitrogen fixation

• Transforming oxygen into nitrogen

• Bonding nitrogen to a single carbon

• Converting nitrogen gas into ammonia

• Combining nitrogen with sulfur

Eutrophication is characterized by ____ (small / large) populations of ____ (primary / secondary) producers and ____ (high / low) levels of dissolved oxygen

In competitive dominance hierarchies, arrows point from ____ (stronger / weaker) species to ____ (stronger / weaker) species (competitively speaking).

Food web arrows indicate what?

• Energy flow

• Competition

• Food sources

• Dominance hierarchies