Download 3.1 Section Objectives – page 65

SNAKE
JUDE LAW
COYOTE
COW
BIRD
BEETLE
GRASS
BERRIES
• If grass were no longer cut on a lawn, what
would it look like in a year?
• Five years?
• In 90 years?
Ecologists can predict the changes that will take
place over time in an area….like evolution of an
environment
Succession: Changes over Time
• Ecologists refer to the natural changes and species
replacements that take place in an ecosystem over
time as succession.
• Succession occurs in stages.
• At each stage, different species of plants and animals
may be present.
Succession: Changes over Time
• As succession progresses, new organisms move in.
• Others may die out or move out.
There are two types of succession—
• primary
• secondary.
• The colonization of organisms in a completely
barren land is called primary succession.
• Primary succession takes place on land where there
are no living organisms.
PRIMARY SUCCESSION
• The first species to take hold in an area like
this are called pioneer species.
PRIMARY SUCCESSION
• As these first organisms die, more soil builds- and it
has more and more nutrients in it.
Exposed rock
Primary succession
• As soil builds, bigger plants will grow, bringing in
herbivores and eventually carnivores
SECONDARY SUCCESSION
• Secondary succession is the sequence of changes
that takes place after an existing community is
severely disrupted in some way.
• Secondary succession, however, occurs in areas that
still have land containing nutrients in the soil.- Not
completely starting from scratch, like primary.
Succession: Changes over Time
SECONDARY SUCCESSION
• Because soil already
exists, secondary
succession takes less
time than primary
succession to become a
rich ecosystem again.
• In an evolving ecosystem, populations will
continue to grow until they reach their carrying
capacity.
• This is the maximum amount of organisms that
can survive in an ecosystem
– It is determined by the amount of resources available,
such as:
• Habitat
• Water
• Food
No population can live beyond the
environment’s carrying capacity for
very long.
● The “J” shape shows growth at a constant rate (exponential growth).
● When the “J” becomes an “S” shape…it means the population has reached
carrying capacity.