Download Ecosystems and Communities

Ecosystems and Communities
Chapter 4
What shapes an ecosystem?
Biotic and Abiotic Factors
 Biotic Factors  living things
that affect an organism
–biotic factors affecting bullfrog:
plants it eats, birds that might eat
it, other species that compete for
food or space
What shapes an ecosystem?
Factors  physical, or
nonliving factors that affect
organisms
Abiotic
–bullfrog affected by availability of
water and temperature of air
Habitat
includes both biotic and
abiotic factors
Biotic and Abiotic Factors
Abiotic Factors
Biotic Factors
ECOSYSTEM
Niche
 An organism’s niche includes:
 Place
in food web
 Range of temperatures organism needs to
survive
 Type of food it eats
 How it obtains food
 Other species that use it as food
 Physical conditions necessary for survival
 When and how it reproduces
Niche
 Two species cannot share the same
niche in the same habitat.
 Different species can occupy similar
niches.
 Ex
- three species of warblers live in the
same spruce trees but feed at different
elevations and in different part of the trees
Warbler Niches
Cape May Warbler
Feeds at the tips of branches
near the top of the tree
Bay-Breasted Warbler
Feeds in the middle
part of the tree
Spruce tree
Community Interactions
 Competition  same or different
species attempt to use an
ecological resource in the same
place at the same time
 resource
= necessity of life (water,
nutrients, light, food, space)
Community Interactions
 Competitive Exclusion Principle - no two
species can occupy the same niche in
the same habitat at the same time
 Direct competition in nature often
results in winner and loser – losing
organism fails to survive
Community Interactions
 Predation - one organism captures and feeds
on another organism
 Predator – the one killing and eating
 Prey – the food
 Studies show that predation can actually
help maintain diversity. Gray wolves were
killed out in many parts of North America.
What happened to deer and herbivore
populations? What happened to many
plant species in North American
ecosystems?
Community Interactions
Mimicry – a harmless species resembles a poisonous or
distasteful species.
Example: Batesian mimicry – a palatable or harmless
species mimics the an unpalatable or harmful model.
Community Interactions
 Müllerian mimicry - two or more unpalatable
species resemble each other.
Community Interactions
 Camouflage or cryptic coloration – a passive defense
that makes potential prey difficult to spot against its
background.
Aposematic coloration –
warning coloration; seen in
animals with effective chemical
defenses.
Symbiosis
 When two species live close together.
 Three types:
– one is harmed (host), one
benefits (parasite)
 Mutualism – both benefit
 Commensalism – one is neutral, one
benefits
 Parasitism
Parasitism examples:
Right: Wheat rust is a
parasitic fungus
Above: Fleas, ticks, mosquitos and tapeworms
are parasites too!
Mutualism examples:
Above: the butterfly
and the flowers –
The butterfly gets
the nectar (food)
and the flowers get
pollinated.
Below: the Oxpecker and the
zebra - the oxpecker eats ticks
and flys away with a warning
scream when danger is near.
So the oxpecker gets food and
the zebra stays safe and
doesn’t have ticks.
Commensalism examples:
Below: Barnacles on whales –
they don’t effect the whale
but the barnacles are sessile
(the don’t move on their own)
and they need to travel
through water to get their food.
Above: Sea anemones and
clownfish – the sea anemones
have nematocysts that sting most
organisms but the clownfish is not
affected by the stings so the
clownfish hide in the anemone so
predators can’t get to them.
Ecological Succession
 Ecosystem constantly changing
due to natural and human
disturbances
 older organisms die out and new
organisms move in, causing
further changes in the community
Ecological Succession
 Primary succession – occurs in areas
where no life exists
– new rock created by volcano, rock
exposed when glaciers melt
 Ex
Pioneer species
– first to
populate new
land
Usually lichens (algae
and fungus) that can
break up rock to begin
soil formation
Succession changes the composition of species
found in a community at a specific time by removing
some of them or changing the resources available
Ecological Succession
 Secondary Succession – occurs when
community is destroyed or altered but
soil is still there.
Ex – Fire and
clear cutting
regrows to
mature, stable
community
called climax
community.
Forest Fire Regrowth