Download NOTES ECOLOGY - Pascack Valley Regional High School District

NOTES ECOLOGY
SPECIES INTERACTION &
COMMUNITY DISTURBANCE
I. Populations in Communities INTERACT
A. Competition: struggle for resources
between living things
1. Example:
a. Interspecific competition: competition
between species that depend on the
same limited resource
2. Competitive exclusion is when 2 species are
so similar in their requirements that the same
resource limits both populations’ growth. One
species may succeed OVER the other one and
take away all the resource.
3.
Niche: unique living arrangement of an
organism defined by its habitat, food sources,
time of day it is most active, and other factors
a. Example: 2 similar lizards, one eats
on tall shrubs, other low shrubs, * if niches
are similar, may see competitive exclusion *
B. Predation
1.
2.
One organism eats another
Predator --> the hunter
a. Fast and strong
b. Good senses- hearing, sight, smell
c. Camouflage
d. Sharp teeth, claws
3. The Prey --> the food
a. Good eyesight,
hearing, smell
b. Camouflage
c. Fast, agile, some are
poisonous or has
spikes
C.
Symbiotic Relationships
1. A close interaction between species in which
one of the species lives in or on the other
2. Parasitism: + - one organism benefits
(parasite) the other is harmed (host)
a. Intestinal worms and animals
3. Mutualism: + + both organisms benefit from
each other
a. E.coli and people; tube worms and
bacteria
4. Commensalism: + 0 Only one organism benefits
while the other is NOT harmed, or helped- rare
a. Spider crab using seaweed to cover itself to
hide from danger
Parasitism
Mutualism
Commensalism
II. Disturbances are Common in
Communities
A.
Disturbances to communities
1. Fires, volcanoes, floods, storms, droughts
2. Effects can be positive
i. Shipwreck- can be new habitat
ii. Forest fires- some
plants sprout
B.
1.
Ecological Succession
Primary succession: process by which a community
arises in a virtually lifeless area with no soil
ex: bare rock, “start from scratch”
i. bacteria, lichens --> moss --> “pioneer organism”
ii. Grasses --> shrubs --> trees
2. Secondary succession: when disturbance
damages existing community but leaves the
soil in tact
Ex. When a farmer ploughs down
field to dirt, then abandons it
CLIMAX COMMUNITY
When an ecosystem has reached a stage where
it doesn’t change very much and the community
is fairly stable.
This is the final step in Ecological Succession,
although many communities never make it to thi
step before another disturbance comes to start
the process over.
Human Activity and Species Diversity
Human Disturbances can have a negative or positive
effect on the community-- in most cases it is negative.
Examples are:
Clearing of land-- this can be done by making farms, clear
cutting for lumber, building roads, buildings or parking
lots.
Introduced species-- Species that are moved into an area
that they do not normally grow either intentionally or
unintentionally. Some of these species do not make it in
their new environment but others take over the native
(indigenous) species and strip the native species of their
resources.