• A biological community is a collection of populations of different species living close enough to interact with one another For example, a pond = insects, fish, algae, animals, plants, frogs all live close enough to interact

• Three types of community interactions:–Competition–Predation–Symbiosis

mutualismcommensalismparasitism

Community InteractionsCommunity Interactions

• Competition for resources like, water, nutrients, light, food, territory

• Occurs due to a limited number of resources• No two species can occupy the same niche in the same habitat

at the same time competing for the same resources

Competition

Competition for Food

Competition for Space

Competition for sunlight

Predation• Predation is when an organism captures and feeds

on another organism.• Predator = “the hunter” and Prey = “the hunted”

Lynx hunting the snowshoe hare

Bigger fish eating smaller fish

Beetle eating an earthworm

Symbiosis

• Symbiosis- any relationship where two species live closely together.

• Three types:– Mutualism (+/+) both organisms benefit– Commensalism (+/Ø) one benefits, other unaffected– Parasitism (+/-) one benefits, other harmed

Mutualism (+/+)Mutualism: both species benefit from a 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

Symbiotic Commensalism (+/ø)• Commensalism – One member of a symbiotic 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 nutrient-rich 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

Symbiotic Parasitism (+/-)• Parasitism- a relationship where 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

Keystone SpeciesKeystone 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 rolein stabilizing population sizes in the community

Keystone Species

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.

Pacific Northwest

Intertidal Zone

Habitat: a place where an organism livesHabitat: a place where an organism lives

• Habitats include both biotic and abiotic factors like shelter, water, food and space.

• Examples:forestdesertpondtidal poollarge intestineneighborhood street

Niche: an individual’s ecological roleNiche: 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 environ-mental conditions, like sunlight, temperature, and food.

HABITAT vs NICHEHABITAT vs NICHE

FLOWERS

FRUIT

HOLES

EXIT TICKET

1) What is a community?2) Name the 3 types of community interactions.3) Name the 3 types of symbiosis.4) How do mutualism, commensalism, and parasitism

differ?5) What is a Keystone species?