Question

3.19 describe the three types of symbiosis. give an example of each. 3.20 what is the difference between primary and secondary succession? 3.21 what three characteristics do ecologists use to describe populations? 3.22 what kind of graph is shown below? when would this type of growth typically occur?

Explanation:

3.19

Mutualism is a symbiotic relationship where both organisms benefit. For example, bees and flowers - bees get nectar and flowers get pollinated. Commensalism is when one organism benefits and the other is neither helped nor harmed. An example is barnacles on whales - barnacles get a place to live and whales are unaffected. Parasitism is when one organism (parasite) benefits at the expense of the other (host). Tapeworms in the human intestine are an example.

Primary succession occurs in an area where there was no previous community, like on newly formed volcanic islands. It starts with pioneer species like lichens. Secondary succession occurs in an area where a community previously existed but was disturbed, like after a forest fire. Soil is already present in secondary succession, which allows for a faster - growing community.

Ecologists use population size (the number of individuals in a population), population density (number of individuals per unit area or volume), and population distribution (how individuals are spread out in the area) to describe populations.

Answer:

Mutualism: Bees and flowers. Commensalism: Barnacles on whales. Parasitism: Tapeworms in human intestine.

3.20