Parasitism is a relationship in which one organism lives on or in a host, taking what it needs and harming the host.

Mutualism is a relationship in which both of the organisms involved gain a benefit.

Describe how a tapeworm lives at the expense of its host.

It attaches to the host's gut wall and absorbs digested food, so the host takes in less nourishment.

Explain why a flea is described as a parasite.

It feeds on its host's blood, gaining food while causing the host irritation and possible infection.

Describe how an oxpecker bird and a buffalo both benefit from living together.

The bird eats ticks and other parasites from the buffalo's skin, so it gains food and the buffalo loses its parasites.

Edexcel GCSE Combined Science Biology 1SC0

Key Concepts in Biology

Topic overview Eukaryotic and prokaryotic cells Specialised cells and their adaptations Microscopes and magnification calculations Size, scale and units in cell biology Enzyme action and denaturation Factors affecting enzyme activity Enzymes in synthesis and digestion, and rate calculations Diffusion, osmosis and active transport Osmosis in potatoes and percentage change in mass

Cells and Control

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Genetics

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Natural Selection and Genetic Modification

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Plant Structures and Their Functions

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Animal Coordination, Control and Homeostasis

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Topic overview Levels of organisation and interdependence Abiotic and biotic factors in a community Parasitism and mutualism Sampling with quadrats and transects Estimating population size from field data Human impact on ecosystems and biodiversity The carbon cycle The water and nitrogen cycles

Ecosystems and Material Cycles

Parasitism and mutualism

3 things to know
Paper 2

Overview

Parasitism and mutualism, with tapeworms, fleas and mistletoe as parasites, and oxpeckers and buffalo, cleaner fish, nitrogen-fixing bacteria in pea plants, and chemosynthetic bacteria in deep-sea tube worms as mutualistic partners.

What you need to know

Answer each one before you reveal it.

Your recallNot started

Key term

What is parasitism?

Key term

What is mutualism?

Key term

Mistletoe grows attached to the branches of a tree. Explain why this is parasitism.

Questions from this subtopic

Each one with the model answer underneath.

1
What is parasitism?
Model answer
Parasitism is a relationship in which one organism lives on or in a host, taking what it needs and harming the host.
2
What is mutualism?
Model answer
Mutualism is a relationship in which both of the organisms involved gain a benefit.
3
Describe how a tapeworm lives at the expense of its host.
Model answer
It attaches to the host's gut wall and absorbs digested food, so the host takes in less nourishment.
4
Explain why a flea is described as a parasite.
Model answer
It feeds on its host's blood, gaining food while causing the host irritation and possible infection.
5
Mistletoe grows attached to the branches of a tree. Explain why this is parasitism.
Model answer
Mistletoe takes water and mineral ions from the tree, so the mistletoe gains while the tree is deprived.
6
Describe how an oxpecker bird and a buffalo both benefit from living together.
Model answer
The bird eats ticks and other parasites from the buffalo's skin, so it gains food and the buffalo loses its parasites.

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