16.3 Types of Interactions

List predators that are also prey.

Limiting Factors A resource that is so scarce that it limits the size of a population. Example: food becomes a limiting factor when a population becomes too large for the amount of food available.

How is a population of organisms affected by a limiting factor? Populations of organisms cannot grow without limit because limiting factors will restrict their population size.

Carrying capacity The largest population that an environment can support. Example: When plants produce a large crop the primary consumers grow, but when the plants decrease the consumers will decrease.

Interactions Among Organisms Three main relationships through which species and individuals affect each other. Competitive relationships Predator and prey relationships Symbiotic relationships

Competition Happens when two or more individuals or populations try to use the same resource. High during winter season due to lack of plant growth.

How is the elk population affected by winter? The elk population decreases during the winter because there are fewer plants for them to eat.

Predators and Prey Prey – the organism that is eaten Predator – the organism that eats the prey. Example: when a bird eats a worm. Worm=prey, bird=predator

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Prey Adaptations Animals run away from predators. Prairie dogs run to underground burrows. Small fishes swim in groups (schools).

Camouflage Blending into the background. Rabbits freeze so that their natural color can blend in.

Camouflage

Defensive Chemicals Animals defend themselves with chemicals. Skunk spray predators. Hooded pitohui – a deadly toxin in the skin of the poison arrow frog and a bird.

Warning Coloration Animals with chemical defense must be able to warn predators by warning colors. Black, white, read, yellow and orange.

Warning Coloration

Symbiosis A close, long-term association between two or more species. Three groups: mutualism, comensalism, and parasitism.

Symbiosis

Mutualism A symbiotic relationship in which both organisms benefit. Bees get pollen from the flower and it also transfers pollen to a new flower.

Commensalism A symbiotic relationship in which one organism benefits and the other is unaffected. Remoras (small fish) ride on a shark and feed on scraps of food left by sharks.

Parasitism A symbiotic relationship in which one organism benefits while the other is harmed. Parasite- organism that benefits from this relationship. Host – organism that is harmed in this relationship.

What does a parasite get from its host? A parasite gets nutrition and a place to live from its host.

Review Questions Briefly describe an example of a predator-prey relationship. Be sure to identify the predator and the prey. A bird (predator) eats a worm (prey)

Explain the probable relationship between the giant Rafflesia flower, which smells like rotting meat, and the carrion flies that buzz around it. The relationship between the flower and the flies is probably a mutualistic relationship where bother the flower and the flies benefit.

Predict what might happen to a wolf population during spring. During the spring, when the plants flourish, the elk population can increase because more food is available to them. An increase in elk population would also allow the wolf population to increase.

Explain the relationship between the carrying capacity and limiting factors. The carrying capacity of an environment is determined by the limiting factors of that environment.