IX - Community Processes: Species Interactions & Succession Flashcards
Niche
role that an organism plays in an ecosystem.
Niche can also be defined by
range of conditions & resources within
which an organism can live
Conditions
many physical attributes of the
environment, though not consumed, that influence
biological processes & population growth
Conditions examples
temperature, salinity, acidity
Resources
substances or parts of the environment used
by an organism & consumed or otherwise made
unavailable to other organisms
Resources examples
food, water, &
nesting sites for animals; water, nutrients, & solar
radiation for plants
Niche is not the same as
Habitat
Habitat
Actual place an organism lives
fundamental niche
the full range of conditions & resources that an organism could theoretically use in the absence of competition with other species.
realized niche
the portion of the fundamental niche that an organism actually occupies; actual range of conditions & resources that an organism uses.
Nich overlap between species leads to
Competition
Competition causes organisms to not be able to
occupy the full fundamental niche
Generalists
Broad niches
Specialists
Narrow niches
Examples of generalists
cockroaches,
coyotes, dandelions, humans
Examples of specialists
spotted owls, which require old–growth forests in the Pacific Northwest; giant pandas, which eat primarily bamboo in bamboo forests of China
Generalists may have advantage when
environmental conditions change
Specialists may have advantage when
environmental conditions remain constants
Native species
species that normally live
& thrive in a particular ecosystem
Nonnative/exotic species
originate in other
ecosystems; may enter an ecosystem
by migration or by deliberate or
accidental introduction by humans
Example of nonative species
"killer bees", wild bees from Africa were imported to Brazil to increase honey production, but instead displaced native bees, decreased honey production, spread, & posed threat because of aggressive behavior
Indicator species
species that
serve as early warnings that a
community or ecosystem is being
damaged
Examples of indicator species
Decline of migratory songbirds in North America indicates loss & fragmentation of habitat in mesoAmerica & South America Presence of trout in mountain streams is an indicator of good water quality Presence of spotted owls is indicator of healthy old– growth forest.
Keystone species
species that play a
critical role in an ecosystem
Keystone species examples
Sea otter -> prevent sea urchins from depleting kelp beds
dung beetles -? remove, bury, & recycle animal waste
Beavers -> build dams & create habitat for other species
Major types of biotic interactions includes
Interspecific competition
Predation
Symbiosis
interspecific competition
when
two or more species use the same
limited resource (food, space, etc.)
and adversely affect each other
interspecific competition example
fire ants and native species
of ants in North America; fire ants
are better competitors & sharply reduce populations of up to
90% of native species.
predation
members of one
species (predator) feed on another
species (prey)
predation example
lion feeding on gazelle
Symbiosis
a long–lasting
relationship in which species live
together in intimate association
Types of symbiosis
parasitism
mutualism
commensalism
Parasitism
one organism
(parasite) lives on part of another organism
Parasitism example
flea living on a dog
Mutualism
two species interacting in a
way that benefits both
Mutualism example
flowering plants and
insects
Commensalism
one organism benefits from
another, but neither helps nor harm that other organism
Commensalism example
epiphyte growing on a tree (epiphyte benefits & tree not effected, unless there are many epiphytes
Lichens and mycorrhizae has a
symbiotic relationship
Types of interspecific competition includes
interference competition
exploitation competition
interference competition
one species limits another
species’ access to a resource
Interference competition example
hummingbirds defending
feeding territories
exploitation competition
competing species both have
access to a limited resource,
but one exploits the resource
more quickly or efficiently
Principle of competitive exclusion
In a classic experiment
(1934), Gause showed
that two species with
identical niches cannot coexist indefinitely.
Examples of competitive exclusion
Paramecium aurelia outcompetes Paramecium caudatum
Resource partitioning
Species with similar resource requirements can coexist because they use limited resources at different times, in different ways, or in different places.
Resource partitioning example
Five species of insect–eating
warblers are able to coexist
in spruce forest of Maine.
Character displacement
Over many years coexisting species with similar niches tend to evolve physical & behavioral adaptations to minimize competition.
Character displacement example
on islands where they co– occur, species of Darwin's finch have evolved different bill sizes & eat different size prey.
Succession
gradual & fairly predictable change in
species composition with time
What are the possibilities of succession?
Some species colonize & become more abundant;
Other species decline or even disappear
Two kinds of succession
Primary succession
Secondary succession
Primary succession
gradual establishment of biotic communities in an area where no life existed before
Secondary succession
gradual
reestablishment of biotic communities in an area where a biotic community was previously present
Primary succession example
Primary succession over several hundred years on bare rock exposed by a retreating glacier on Isle Royal in northern Lake Superior.
Primary succession occurs with
Time in lifeless areas
Primary succession examples include
succession newly formed islands &
succession after the retreat of a glacier
Primary succession progression
Lichens & mosses first colonize bare rock
Small herbs & shrubs colonize
Tree species colonize
Pioneer species
first species to colonize
Primary succession in a newly created pond
Bare bottom Submerged vegetation Emerging vegetation Temporary pond & prairie Wetland red maple forest & swamp
Successional changes in animal community accompany
Successional changes in plant community
Early successional species
Raddit Quail Ringneck pheasant Dove Bobolink Pocket gopher
Mid Successional specie
Elk moose deer Ruffled grouse snowshoe hare Bluebird
Late successional species
Turkey
Martin
Hammond’s flycatcher
Gray squirrel
Wilderness species
Grizzly bear Wolf Caribou Bighorn sheep California condor Great horned owl
Both primary & secondary succession
Are driven by three mechanisms
Three mechanisms
facilitation
inhibition
tolerance
facilitation
a process by which an earlier successional species makes
the environment suitable for later
successional species
facilitation example
legumes
fixing nitrogen can enable later
successional species
inhibition
a process whereby one
species hinders the establishment &
growth of other species
Inhibition example
shade
of late successional trees inhibits
the growth of early successional
trees;
tolerance
a process whereby later
successional species are unaffected
by earlier successional species.
During succession
species diversity & stratification tend to increase, while growth rates & primary productivity tend to decrease.
Plant size during early & late succession
Early - small
Late - large
Species diversity during early & late succession
Early - Low
Late - High
Trophic structure during early & late succession
Early - mostly producers
Late - mixture of producers, consumers, & decomposers
Ecological niches during early & late succession
Early -few, more generalized
Late -many, more specialized
community organization during early & late succession
Early - low
Late - high
Biomass during early & late succession
Early - Low
Late - high
Net primary productivity during early & late succession
Early - High
Late - Low
Food web during early & late succession
Early - Simple
Late - Complex
Efficiency for nutrient cycling during early & late succession
Early - Low
Late - high
Efficiency of energy use during early & late succession
Early - low
Late - high
Disturbance
discrete event
that disrupts an ecosystem or
community
examples of natural
disturbance
fires, hurricanes,
tornadoes, droughts, & floods
examples of human–caused disturbance
deforestation,
overgrazing, plowing
What is the role of disturbance in succession?
disturbance initiates
secondary succession by eliminating part or all of the existing community, & by
changing conditions &
releasing resources
Secondary succession occurs where the
natural
community of organisms has been disturbed, removed,
or destroyed
Secondary succession example
“old field succession” in eastern North
America, where agricultural fields go through
succession from herbaceous plants, to shrubs & early
successional trees, to mid–successional forest, to
oak–hickory forest;
according to the classic view, succession proceeds
until an area is occupied by a climax community,
however recent views recognize that succession is
influenced by
variability & chaotic events such that a
single climax is not predictable.
In the species equilibrium model of island biogeography (developed by Robert MacArthur & Edward O. Wilson) the number of species on an island is determined by t
he
balance between
immigration &
extinction.
Small islands are
expected to have
lower immigration rates & higher extinction rates, & hence less species than large islands.
Far islands are
expected to
have
lower immigration rates, & hence less species than near islands
large habitat patches tend to have
more species
habitat patches that are near larger intact habitat
areas tend to have
more species
Stability has three aspects
Inertia
Constancy
Resilience
inertia (or persistence)
the ability of a system to resist
being disturbed or altered;
constancy
the ability of a living system to maintain a
certain size or state
resilience
the ability of a living system to recover after a disturbance
Signs of poor health or stressed ecosystems
- decrease in primary productivity;
- increased nutrient losses;
- decline or extinction of indicator species;
- increased populations of pests or disease organisms;
- decline in species diversity;
- presence of contaminants.
