Community Interactions
• A biological community is a collection of populations of
different species that interact with each other
a pond = insects,
fish, algae,
animals, plants,
frogs all live close
enough to interact
COMMUNITY
INTERACTIONS
PREDATION
COMPETITION
SYMBIOSIS
COMPETITION
• when different species require the same
resources to survive and reproduce
Competition for Food
Competition for Space
Competition for sunlight
PREDATION
• when one species captures and
consumes another for energy
• Predator: “the hunter”
• Prey: “the hunted”
SYMBIOSIS
• the process of living together
TOGETHER
PROCESS
SYMBIOSIS
MUTUALISM
PARASITISM
COMMENSALISM
MUTUALISM (+/+)
Mutualism: both species benefit from the relationship
Cleaner birds and crocodiles:
Birds eat decaying meat stuck
between crocodile teeth
Clown fish and anemones:
Clown fish chases away fish that
like to eat anemones while the
clown fish are protected from
predator fish by the stinging
tentacles of the anemone
Lichens (fungus/algae):
the fungi provides structure and
protection for the algae and also
obtains water and mineral;
algae makes food for the fungi
through photosynthesis
COMMENSALISM (+/ø)
• Commensalism – one species of the relationship benefits
and the other is neither helped nor harmed
Triggerfish creates feeding
opportunities for smaller fish
by moving large rocks too big
for them to shift themselves.
As the whales travel, the
barnacles gain access to nutrientrich waters, while the whale neither
benefits nor is harmed by its riders
Bugs (non parasitic) living on large
herbivores like water buffalo.
Birds cleaning non-parasitic bugs
off of the water buffalo
PARASITISM (+/-)
• Parasitism- one organism (parasite) depends
on another (host) for nourishment or other
benefit.
• Some species live within the host
Ticks are parasites that feed on
the blood of their hosts often
carrying diseases
Tapeworm eggs are usually eaten
in contaminated meat and then
mature in the animal’s intestines
CUCKOO BIRD
WARBLER BIRD
PREDATION
HOW
Mr. Kim & Chicken Wings
Mr. Kim hunts out and destroys chicken wings for energy
COMMENSALISM
HOW
Mr. Kim & his dogs
Mr. Kim drops food while he eats (0) and the dogs pick up
the scraps (+)
PARASITISM
HOW
Mr. Kim & his wife
Mr. Kim loses money (-) while bae gets food & jewelry (+)
Keystone Species
• A keystone species is a species that plays a
critical role in maintaining the structure of an
ecological community
• Removing the keystone species, the food web
can be adversely affected
• “Holds the community
together”
• Plays an important role
in stabilizing population
sizes in the community
Keystone
Species
Pacific
Northwest
Intertidal Zone
Removing the Pisaster starfish caused a loss of diversity in the intertidal
zone of the Pacific Northwest. Being a top predator, Pisaster kept lesser
organisms in the food chain within stable limits. When removed, these
populations flourished and crowded out other species. Within ten years,
seven species disappeared from the community = biodiversity loss.
Habitat: a place where an organism lives
• Habitats include both biotic and abiotic
factors like shelter, water, food and space.
• Examples:
forest
desert
pond
tidal pool
large intestine
neighborhood street
Niche: an individual’s ecological role
• A niche describes the way of life of a species. Each
species is thought to have a separate, unique niche in
a habitat
• A niche includes its place in a food web
– Are they a food source for others? Top carnivore?
• A niche includes how the
organism lives, eats,
reproduces
• How they uses environmental conditions, like
sunlight, temperature,
and food.
HABITAT vs NICHE
FLOWERS
EXIT TICKET
1)
2)
3)
4)
What is a community?
Name the 3 types of community interactions.
Name the 3 types of symbiosis.
How do mutualism, commensalism, and parasitism
differ?
5) What is a Keystone species?