Parasitism and mutualism

Question 1

interdependence

Answer 1

where the survival of one species is closely linked with another species

Question 2

parasite

Answer 2

an organism that feeds on a host organism, harming the host but benefiting the parasite

Question 3

examples of animal parasitic relationships (3)

Answer 3

flea - other animals, including humans, are the host
-they feed by sucking the animal’s blood after piercing its skin

head louse - humans
-head lice feed by sucking blood after piercing the skin on the head

tapeworm - animals including humans
-lives in the intestines and absorbs nutrients from the digested food in the intestine

Question 4

example of a plant parasitic relationship

Answer 4

mistletoe - trees such as apple are the host

mistletoe grows roots into the tree to absorb water and nutrients from the host

Question 5

mutualism

Answer 5

when two organisms live closely together in a way that benefits them both

Question 6

examples of animal mutualistic relationships (2)

Answer 6

oxpecker and herbivore (e.g. deer)

• the oxpecker is a bird that eats skin parasites, so benefits by getting food
• the herbivore benefits from the loss of skin parasites

larger fish (e.g. shark) and cleaner fish

• the larger fish benefits from loss of dead skin and parasites
• the cleaner fish benefit by getting food

Question 7

example of plant mutualistic relationship

Answer 7

nitrogen-fixing bacteria and legume plants

• the bacteria in root nodules are protected from the environment and get food from the plant
• the legume plant gets nitrogen compounds for healthy growth from the bacteria

Question 8

A tapeworm is a parasite that lives in the intestines of mammals. Explain why it is classed as a parasite [3]

Answer 8

the tapeworm depends on the host for its food supply

it absorbs digested food from the host’s intestines, so it benefits from the relationship

the host is harmed because it is losing some of the nutrients in the food it eats

Question 9

Define the term parasite [1]

Answer 9

a parasite is an organism that feeds on and causes harm to a host organism while living on or in the host

Question 10

Explain what is meant by mutualism [1]

Answer 10

when two organisms both benefit from a close relationship

Question 11

Explain how the relationship between nitrogen-fixing bacteria and legumes is mutualistic [2]

Answer 11

the bacteria benefit from getting food from the plant and protection from the environment

the plant benefits from getting nitrogen compounds which it needs to make proteins for healthy growth