1.10 Niche and Competition

Niche and
Competition

Open Ended

Distinguish among parasitism, mutualism, and commensalism. Provide an example for each.

KWBAT Use data to analyze how competition influences niche-partitioning in an ecological community.

Agenda

1. Do Now

2. Niche and Competition
3. Community Structure

4. EXIT Ticket

Niche (neesh)

A species' niche is its ecological role or "way of life," which is defined by the
full set of conditions, resources, and interactions it needs (or can make use
of)

Each species fits into an ecological community in its own special way and
has its own tolerable ranges for many environmental factors. For example,
a fish species' niche might be defined partly by ranges of salinity (saltiness),
pH (acidity), and temperature it can tolerate, as well as the types of food it
can eat.

Predict what happens IF two
species have the same niche?

USE 2 of the following vocabulary words in your response:

Competition

increase

Limited resources

decrease

Ecosystem
Extinction
Evolve

If two species have the same niche then,______________

Open Ended

If two species have the same niche then,______________

IMPORTANT!

As we'll see, two organisms with exactly the same niche
can't survive in the same habitat (because they compete
for exactly the same resources, so one will drive the
other to extinction). However, species whose niches only
partly overlap may be able to coexist. Also, over long
periods of time, they may evolve to make use of more
different, or less overlapping, sets of resources.

Competitive Exclusion Principle

The competitive exclusion principle tells us that
two species can't have exactly the same
niche in a habitat and stably coexist because
they would compete for precisely the same
resources.

Here are 2 types of microorganisms. (Graph
1 and Graph 2).

What do you notice is occurring in Graph 3?

Open Ended

What do you notice is occurring in Graph 3?

When grown individually in the lab, both species thrive. But when they
are grown in the same test tube (habitat) with a fixed amount of
nutrients, both grow more poorly and P. aurelia eventually outcompetes
P. caudatum for food, leading to P. caudatum's extinction.

HOW CAN
NATURE AVOID
COMPETITIVE
EXCLUSION?

● Competitive exclusion

can be avoid because….

● Competitive exclusion

can be avoid since…

Resource Partitioning
Competitive exclusion may be avoided if one or both
of the competing species evolves to use a different
resource, occupy a different area of the habitat, or
feed during a different time of day. The result of this
kind of evolution is that two similar species use largely
non-overlapping resources and thus have different
niche.

Resource partitioning, helps the species coexist
because there is less direct competition between
them.

How are
these
lizards
able to
coexist?

Keywords to
use:
Habitat
Vegetation
Sunlight
Moisture

Open Ended

How are these lizards able to coexist?

Community Structure

Key points:

● A community's structure can be described by its species

richness, which is the number of species present, and
species diversity, which is a measure of both species
richness and species evenness (relative numbers).

● Community structure is influenced by many factors,

including abiotic factors, species interactions, level of
disturbance, and chance events.

● Some species, such as foundation species and keystone

species, play particularly important roles in determining
their communities' structure.

Community Structure

Community structure is essentially the composition of
a community, including the number of species in
that community and their relative numbers.

It can also be interpreted more broadly, to include all of
the patterns of interaction between these different
species

^2

2

Species
Diversity

How do we measure community

structure?

Species
Richness

Species richness is the number of
different species in a particular
community. If we found
30 species in one community, and
300 species in another, the second
community would have much
higher species richness than the
first.

Species diversity is a measure of
community complexity. It is a
function of both the number of
different species in the
community (species richness) and
their relative abundances
(species evenness). Larger
numbers of species and more
even abundances of species lead
to higher species diversity

What factors shape community
structure?

The structure of a community is the result of many
interacting factors, both abiotic (non-living) and biotic
(living organism-related).

List 5 factors that can shape
(influence) community structure?

Open Ended

List 5 factors that can shape (influence) community structure?

● The climate patterns of the

community's location.

● The geography of the community's

location.

● The heterogeneity (patchiness) of the

environment

● The frequency of disturbances, or

disruptive events.

● Interactions between organisms.

Foundation and Keystone Species

Foundation

Species

A foundation species plays a unique,
essential role in creating and defining a
community. Often, foundation species act
by modifying the environment so that it can
support the other organisms that form the
community.

Keystone
Species

A keystone species is a species that has a
disproportionately large effect on
community structure relative to its biomass
or abundance. Keystone species differ from
foundation species in two main ways: they
are more likely to belong to higher trophic
levels (to be top predators), and they act in
more diverse ways than foundation species,
which tend to modify their environment

Key Points (Niche and Competition):

• In interspecies competition, two species use the same limited resource.

• Competition has a negative affect on both of the species (-/-
  interaction).

• A species' niche is basically its ecological role, which is defined by the set of conditions, resources, and interactions it needs (or can make use of)

• The competitive exclusion principle says that two species can't coexist if they occupy exactly the same niche (competing for identical resources).

• Two species whose niches overlap may evolve by natural selection to
  have more distinct niches, resulting in resource partitioning.

EXIT TICKET

1. Explain how interspecific competition may lead to

resource partitioning.

Criteria for Success
2pt- Define interspecific competition
2 pts- Define resource partitioning
2pts- Explain the relationship between both