"So, naturalists observe, a flea has smaller fleas that on him prey; and these have smaller still to bite ’em; and so proceed ad infinitum."

- Jonathan Swift

Biotic-Biotic Community Relationships

I. SYMBIOSISII. COMPETITION

III. PREDATOR/PREY

Symbiosis – when organisms of two species live closely together for a long time.

Word root: Greek for “living together”

3 Types of Symbiosis

1) Parasitism – one species benefits, the other is harmed. (+, - )

Ex. human and tapeworm

2) Commensalism – one species benefits, the other is not affected. ( +, 0 )

Ex. badger and burrowing owl

3) Mutualism – both species benefit ( +, + )

Ex. squirrel and oak

Practice with symbiosisWhat kind of symbiosis is shown in these examples?

Parasitism (+,−) Mutualism (+, +)

Commensalism (+,0)

1) The sphinx moth gets food from a honeysuckle flower. Pollen that sticks to the moth will pollinate the next flower.

2) Several small remora ride

a larger predatory shark

and may eat some of the

waste from the larger fish.

What kind of symbiosis is shown in these examples?Parasitism (+,−) Mutualism (+, +)

Commensalism (+,0)

3) The tick attaches itself to warm-blooded animals and uses the blood as a food supply.

4) Small mites feed on the body moisture of the long-horned beetle of South America.

5) Small scorpion-like animals sit on the long-horned beetle and eat mites.

What kind of symbiosis is shown in these examples?Parasitism (+,−) Mutualism (+, +)

Commensalism (+,0)

6) A plover is a bird that

eats small parasites off

the scales and teeth of

a crocodile.

7) Many families own a dog. What kind of symbiosis is this?

Parasite-Related Vocabulary

host

vector

Example: Malaria is a disease that

infects humans that is transmitted by a mosquito bite. The mosquito is the vector and the human is the host.

- The organism that has the parasite.

- The organism that carries a parasite and spreads it to the host organism.

II. Competition

- when two organisms compete for the same resources in a community.

RESOURCES: what organisms need for survival and successful rearing of young.

examples: food, habitat, nesting sites or materials, mates, light, water

Types of competition

1) Interspecific – between members of two different speciesEx. Owls and foxes live in the same

community and both eat rodents

2) Intraspecific – between members of the same species

Ex. All members compete for exact same food, habitat, etc.

III. Predator/prey relationships

One species has adaptations for hunting, the other for avoidance.

Some + for prey species: When predators eliminate sick or old prey • controls over-population • controls spread of disease • less competition.

Biotic-biotic relationships drive evolution.

• Predator and prey species co-evolve adaptations to best capture/escape each other.

• Evolution also favors organisms with traits that make them best at competing for limited resources.

Example: Wolves that hunt best together as a pack are more likely to survive and pass on their traits.