Chapter 16-18.3 Flashcards
the group of species that occupy a given area, interacting directly or indirectly
community
It refers to a subset of the species, such as a plant, bird (avian),
small mammal, or fish community.
Community
It suggests relatedness or similarity among the members in their taxonomy, response to the environment, or use of resources.
Community
Two features of the community structure that the rank-abundance diagram illustrate
species richness
species evenness
count of number of species occurring within the community
Species richness
the equitability in the distribution of individuals among the species
species evenness
What defines the biological structure of the community?
species composition
the species ranking based on relative abundance, ranked from the most to least abundance (x-axis)
rank abundance
the simplest quantitative measure of community structure
species richness
Mathematical indices which consider both the number and relative abundance of species within the community
species diversity
one of the simplest and most widely used indices of species diversity
Simpson’s diversity index
when a single or few species predominate within a community; often defined as the most numerically abundant
dominants
a species that has a disproportionate impact on the community relative to its abundance
keystone species
function in a unique and significant manner, and their effect on the community is disproportionate to their numerical abundance
Keystone species
describe species interactions
food webs
abstract representation of feeding relationships within a community
food chain
a descriptive diagram—a series of arrows, each pointing from one species to another, representing the flow of food energy from prey (the consumed) to predator (the consumer)
food chain
the arrows from the consumed to the consumer
links (link or linkage)
feed on no other species but are fed on by others
basal species
feed on other species and they are prey of other species
intermediate species
not subject to predators; they prey on intermediate and basal species
top predators
It provide a useful tool for analyzing the
structure of communities and a number of measures have been developed to quantify food web structure.
food web
Organisms that derive energy from consuming plant and animal tissue
heterotrophs or secondary producers
division of heterotrophs (trophic levels)
herbivores
carnivores
omnivores
groups of species that exploit a common resource in a similar fashion
guilds
commonly used to define a group of species based on their common response to the environment, life history characteristics, or role within the community
functional type
What defines the form and structures of terrestrial communities?
vegetation
Characteristics of Communities
biological structure: species composition
physical structure: abiotic and biotic factors
What defines aquatic communities?
features of abiotic environment (such as water depth, flow rate, salinity)
vertical stratification of forest
emergent
canopy
understory
ground cover
forest floor
vertical structure of the vegetation in savanna communities
herbaceous layer
woody plant layer
two distinct vertical layers recognized based on light penetration through the water column
photic layer
aphotic layer
spatial change in community structure
zonation
changes in the physical and biological structures of communities as one moves across the landscape
zonation
likened associations to organisms, with each species representing an interacting, integrated component of the whole
organismic concept of communities
development of the community through time
succession
states that the relationship among coexisting species (species within a community) is a result of similarities in their requirements and tolerances, not to strong interactions or common evolutionary history
individualistic or continuum concept
the goal is to return a community or ecosystem to a close approximation of its condition before disturbance by applying ecological principles
restoration ecology
involves a continuum of approaches ranging from reintroducing species and restoring habitats to attempting to reestablish whole communities
restoration ecology
group of plant and animal species that inhabit a given area
community
an expression of the species’ ecological niche
community structure
result of differences in species’ tolerance and interactions along environmental gradient
zonation
one species may be influenced by interaction with many different species is not limited to competition
diffuse interactions
occur when one species does not interact with a second species directly but instead influences a third species that does indirectly interact with the second
indirect interaction
occurs when two species that do not compete with each other for limited resources affect each other indirectly by being prey for the same predator
apparent competition
functional grouping of species based on sharing similar functions within the community or exploiting the same resource (e.g., grazing herbivores, pollinators, cavity-nesting birds)
guilds
The structure of food chains suggests that the
productivity and abundance of populations at any given trophic level are controlled (limited) by the productivity and
abundance of populations in the trophic level below them
bottom-up control
occurs when predator populations control the
abundance of prey species
top-down control
type of top-down control which occurs when a predator in a food web suppresses the abundance of their
prey (intermediate species) such that it increases the abundance of the next lower trophic level (basal species) on which the intermediate species feeds
trophic cascade
results when individuals compete in proportion
to their size, so that larger plants cause a large decrease in the
growth of smaller plants, and small plants cause a small (but proportionate to their size) decrease in the growth of larger
plants
symmetric competition
larger plants have a
disproportionate advantage in competition for light by shading smaller ones, resulting in initial size differences being
compounded over time
asymmetric
temporal change in community structure
succession
the gradual and seemingly directional change in community
structure through time from field to forest
succession
usually characterized
by high growth rates, smaller size, high degree of dispersal, and high rates of per capita population growth
early successional species or pioneer species
generally have lower rates of dispersal
and colonization, slower per capita growth rates, and are larger and longer-lived
late successional species
two different types of succession
primary succession
secondary succession
occurs on a site
previously unoccupied by a community—a newly exposed surface such as the cement blocks in a rocky intertidal environment
primary succession
occurs on previously occupied sites (previously existing communities) after disturbance
secondary succession
defined as any process that results in the
removal (either partial or complete) of the existing community
disturbance
series of sites within an area that are at different
stages of succession (seral stages)
chronosequence
includes attributes such as the number of species, the relative abundance of species, and the kinds of species comprising a community
community structure
a group of organisms that all make their living in a similar way
guild
a discrete, punctuated
killing, displacement, or damaging of one or more individuals (or colonies) that directly or indirectly creates an opportunity for new individuals (or colonies) to become established
disturbance
any relatively discrete event in time that disrupts ecosystem, community or population structure and changes resources, substrate availability, or the physical environment
disturbance
predicts that intermediate levels of disturbance promote higher levels of diversity
intermediate disturbance hypothesis
one of several distributions that
give a reasonable match to the relative abundance of species
lognormal distribution
point on a continuum of vegetation through time, it is often recognizable as a distinct community
seral stage
