Ch. 21: Fish Communities and Ecosystems

Assemblage

a subset of the larger community, possibly species that utilize an area in a similar manner or have similar ancestral linkages

Community

all the assemblages living together in a given area

Ecosystem

the biotic community and abiotic environment with which a community interacts

If a researcher is studying only the group of benthic-dwelling fishes that utilize the same rocky substrate within a specific reef, which ecological term best describes this specific subset?

Guild

In the hierarchy of ecological organization, which sequence correctly orders the concepts from the most specific subset to the most inclusive system?

Assemblage → community → ecosystem

In a coral reef study, a team measures the nutrient cycling rates between the reef structure, the water chemistry, and the entire biological population. This study is operating at which level?

Ecosystem

True or False: A guild and an assemblage can be the same thing depending on the environment.

False

Which of the following scenarios best represents the transition from a 'community' level of study to an 'ecosystem' level of study in a freshwater stream?

A. Analyzing how seasonal changes in water temperature and dissolved oxygen affect the survival of the resident fish and insect populations

B. Observing the predatory interactions between smallmouth bass and the various minnow species living in the stream

C. Counting the total number of different fish species found within a 100-meter stretch of the stream

D. Comparing the genetic diversity of a single trout species across different sections of the same river system

A. Analyzing how seasonal changes in water temperature and dissolved oxygen affect the survival of the resident fish and insect populations

Guild

functional group that emphasizes ecological > taxonomic similarities

Fish communities often segregate along ______ dimensions.

vertical

An ontogenetic habitat shift could reflect…

a body size constraint related to the current speed at which an individual can hold position without expending too much energy or using too much oxygen

Stochastic VS Deterministic processes

Stochastic - independent of biological interactions; includes weather events

Deterministic - dependent or a function of biological interactions, including competition, predation, and symbioses; often depends on density and the ecological niches of the species

Direct VS Indirect predation

Direct - immediate mortality or delayed mortality due to injury

Indirect - habitat shifts caused by a predator’s presence

True or False: Predation can affect gene frequencies in populations through the evolution of antipredator adaptations.

True

Why must the ecological similarities (niche similarities) be considered along with the taxonomic similarities when understanding a fish community? 

Just because species are closely related (via taxonomy) doesn't mean that they fill the same ecological roles. In the same vein, species that are NOT closely related might fill very similar roles or function in very similar ways. 

Taxonomy tells us what they are. Ecology/niche tells us what they do.