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 Biology 1BI0

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 Food tests and the energy in food Diffusion, osmosis and active transport Osmosis in potatoes and percentage change in mass

Cells and Control

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Genetics

Topic overview Asexual and sexual reproduction Meiosis and the formation of gametes DNA structure, genes and the genome Extracting DNA from fruit Mendel's work and the inheritance of blood groups Alleles, genotype and phenotype Monohybrid crosses and sex determination Probability and ratios from genetic crosses Causes of variation: genes and environment The Human Genome Project Genetic variation and the effects of mutation

Natural Selection and Genetic Modification

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Health, Disease and the Development of Medicines

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Plant Structures and Their Functions

Topic overview Photosynthesis as an endothermic reaction Limiting factors in photosynthesis Light intensity and the rate of photosynthesis Root hair cells, xylem and phloem Transpiration and translocation Leaf structure for photosynthesis and gas exchange Factors affecting the rate of transpiration Plant adaptations to extreme environments Plant hormones, phototropism and gravitropism

Animal Coordination, Control and Homeostasis

Topic overview Hormones, endocrine glands and homeostasis The menstrual cycle and its hormones Hormonal and barrier contraception Homeostasis and thermoregulation Controlling blood glucose, and type 1 diabetes Type 2 diabetes and body mass The urinary system and the production of urea The nephron, filtration and selective reabsorption Treating kidney failure: dialysis and transplants

Exchange and Transport in Animals

Topic overview Why multicellular organisms need exchange surfaces Alveoli and gas exchange Rate of diffusion and Fick's law The blood and its components Arteries, veins and capillaries The heart and the circulatory system Cellular respiration as an exothermic reaction Aerobic and anaerobic respiration compared Investigating the rate of respiration Cardiac output, stroke volume and heart rate

Ecosystems and Material Cycles

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 Energy transfer between trophic levels Human impact on ecosystems and biodiversity Food security The carbon cycle The water and nitrogen cycles Factors affecting the rate of decomposition Calculating the rate of decay

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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Key Concepts in Biology

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ANitrates cause an algal bloom that blocks the light.

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