4.2 Niches and Community Interactions Define niche. Describe the role competition plays in shaping communities. Describe the role predation and herbivory play in shaping communities. Identify the the three types of symbiotic relationships in nature.

What is a niche? The place in the ecosystem where an organism lives is called its habitat. Ex: An earthworm’s habitat is moist soil. Ex: A penguin’s habitat is the frozen tundra of the arctic. Habitats are determined by both the abiotic and biotic factors an organism requires to survive.

What is a niche? A niche is the role an organism plays in the ecosystem. It consists of all the physical and biological conditions in which a species lives and the way the species obtains what it needs to survive and reproduce. This includes: the organism’s feeding habits. where it lives in the ecosystem. its reproductive behavior. what it contributes to its surroundings.

What is a niche? An organism’s niche must contain all of the resources an organism needs to survive. A resource is any necessity of life: For plants, resources can include sunlight, water, and soil nutrients. For animals, resources can include nesting space, shelter, types of food, and places to feed.

For example, in a freshwater pond community, a carp (type of fish) eats decaying material from around the bases of underwater plants. In the same community a snail scrapes algae from the leaves and stems of the same plants. Both organisms live in the same pond habitat, but they occupy different niches because one eats decaying material from around the bases of underwater plants and the other scrapes algae from the leaves and stems of the same plants.

Describe the role competition plays in shaping communities. Competition occurs when organisms try to use the same limited resources, (food, space, water). Direct competition between species often results in one species dying out. (Winner/Loser) This is the basis of the competitive exclusion principle. This principle states that no two species can occupy the same niche in exactly the same habitat at the same time.

Describe the role competition plays in shaping communities. Competition helps determine the number and type of species in a community. 2 types of competition to be aware of: Intraspecific: competition between members of the same species. Interspecific: competition between members of different species.

Describe the role predation and herbivory play in shaping communities. Predator-prey and herbivore-plant interactions help shape communities. Predation occurs when one organism (predator) captures and eats another (prey).

Describe the role predation and herbivory play in shaping communities. Herbivory is an interaction that occurs when an animal (herbivore) feeds on producers (such as plants). Ex: very dense populations of white-tailed deer are eliminating their favorite food plants from many places across the United States.

Identify the three types of symbiotic relationships in nature Symbiosis – when 2 species live closely together in one of three ways: Mutualism: + + Commensalism: + 0 Parasitism: + -

Mutualism + + Both species benefit from the relationship. Ex: nitrogen-fixing bacteria, a type of bacteria that live in the root nodules of legumes (peas and clover). The bacteria make nitrogen compounds used by the plants. The plants supply moisture and organic nutrients to the bacteria. In this way, both organisms benefit. Clown fish/sea anemone

Commensalism + 0 2 organisms of different species living in a relationship that is beneficial to one and the other is not affected. Ex: Sharks and the remora fish.

Parasitism + - One organism (parasite) benefits and the other organism (the host) is harmed. Athlete’s foot fungus in humans Digestive tract tapeworms.