Symbiotic Relationships

Question 1

Symbiosis

Answer 1

Is a close association between different species

Question 2

3 types of symbiosis

Answer 2

1. Mutualism (both species benefit)
2. Parasitism (one benefits, other is harmed)
3. Commensalism (neither are harmed, but one benefits)

Question 3

Escherichia coli and humans

Answer 3

Harmless strains of eschericia coli (E. coli), a bacterium, are found in the colon as part of the normal gut flora.

In this relationship:

• bacteria benefit by obtaining glucose and nutrients from the undigested food remains in the colon
• humans benefit by: gaining vitamin K2 (needed to form the enzyme thrombin) AND protection against the growth of pathogenic bacteria within the gut

Question 4

Nitrogen-fixing bacteria and plants

Answer 4

Nitrogen fixing is necessary to convert atmospheric nitrogen into forms that living organisms can use. Occurs between nitrogen fixing bacteria (Rhizobium) that live in root nodules of legumes

In this relationship:

• Rhizobium benefit by gaining glucose and other nutrients as well as a favourable habitat
• the plant benefits by gaining nitrates, used to make amino acids which form proteins

Question 5

Mycorrhizal fungi and plant roots

Answer 5

Approximately 70-80% of plants have mycorrhizal. These fungi infect the roots and send out root-like structures called hyphae.

In this relationship:

• mycorrhizal provides the plant with:
  1. An increased adaptive surface
  2. Protection against pests
• the plant provides the fungus with glucose