Transcript 3.1 Communities

3.1
Communities
Communities

Remember: a communities are
interacting populations of different
species
Communities

Why do certain populations live in certain
communities?
Polar bears only live in cold
 Catfish can live in warmer water than trout


Abiotic and biotic conditions make life
suitable for some organisms, not others
Communities

Limiting factors affect an organisms
ability to survive

For example, food,
temperature, predators
Communities

Range of tolerance is the ability of an
organism to withstand changes in the
environment

Organisms thrive under optimum conditions
and don’t do as well when conditions change
Succession in Communities
Over time change can happen, one
community is replaced by another
 If a lawn is not cut, the grass gets taller
and it becomes a meadow. Later shrubs
and trees begin to grow into a forest

Succession in Communities
Succession is orderly, natural changes
and species replacements
 Succession occurs in stages, each stage
creates conditions suitable for the next

Succession in Communities

Primary succession is the colonization
of new sites that don’t even have soil


Lava flows, avalanches
The first species to grow there are called
pioneer species. When they die,
decomposition forms soil

lichen
Succession in Communities

Primary Succession
Succession in Communities
As conditions become suitable, new
organisms move in
 Climax community is a stable, mature
community

Succession in Communities

Secondary succession is the sequence
of community changes after disturbance
by natural disaster or human action

Soil already there,
just needs rebuilding
Succession in Communities

Secondary succession