One organism (the predator) kills and eats another (the prey).

What is intraspecific competition?

Competition between members of the same species.

What is interspecific competition?

Competition between members of different species.

A relationship in which both organisms benefit.

Give an example of mutualism involving a plant.

Nitrogen-fixing bacteria in bean root nodules, or mycorrhiza on tree roots.

What is commensalism?

A relationship in which one organism benefits and the other is neither helped nor harmed.

A relationship in which the parasite benefits and the host is harmed.

Why does a tapeworm cause weight loss?

It absorbs digested food in the host's gut, so the host gets fewer nutrients.

Is a head louse an endoparasite or an ectoparasite?

An ectoparasite: it lives on the outside of its host.

The Plasmodium parasite, which lives in the blood.

An organism that carries a parasite from one host to another.

Give two ways to control the spread of malaria.

Insecticide-treated bed nets and draining the standing water where mosquitoes breed.

How do mycorrhizal fungi benefit a tree?

They help it take in water and mineral ions; the tree gives them sugars.

Relationships between organismsIB MYP Biology: Flashcards

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What is predation?

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What is predation?: One organism (the predator) kills and eats another (the prey).
What is intraspecific competition?: Competition between members of the same species.
What is interspecific competition?: Competition between members of different species.
What is mutualism?: A relationship in which both organisms benefit.
Give an example of mutualism involving a plant.: Nitrogen-fixing bacteria in bean root nodules, or mycorrhiza on tree roots.
What is commensalism?: A relationship in which one organism benefits and the other is neither helped nor harmed.
What is parasitism?: A relationship in which the parasite benefits and the host is harmed.
Why does a tapeworm cause weight loss?: It absorbs digested food in the host's gut, so the host gets fewer nutrients.
Is a head louse an endoparasite or an ectoparasite?: An ectoparasite: it lives on the outside of its host.
What causes malaria?: The Plasmodium parasite, which lives in the blood.
What is a vector?: An organism that carries a parasite from one host to another.
Which organism is the vector for malaria?: The female Anopheles mosquito.
Give two ways to control the spread of malaria.: Insecticide-treated bed nets and draining the standing water where mosquitoes breed.
How do mycorrhizal fungi benefit a tree?: They help it take in water and mineral ions; the tree gives them sugars.

Exam questions on Relationships between organisms

A farmer in Kenya grows beans. The roots of the bean plants have small swellings called nodules that contain nitrogen-fixing bacteria. The bacteria change nitrogen gas from the air into nitrogen compounds that the plant can use. The plant supplies the bacteria with sugars and a protected place to live.
Explain how each organism benefits from this relationship.2 marks
A man in Buenos Aires becomes ill after eating undercooked beef. A tapeworm is found living in his small intestine. The tapeworm has hooks and suckers on its head and absorbs digested food from the man's gut. The man loses weight even though he is eating normally.
Explain why the man loses weight even though he is eating normally.2 marks
A school nurse in Muscat compares two treatments for head lice. For each treatment, 50 live lice are placed on a clean sample of hair and the treatment is applied. As a control, 50 lice are placed on a hair sample treated with water only. After 30 minutes the nurse counts the lice that have stopped moving. For shampoo A, 47 lice had stopped moving. For shampoo B, 29 had. With water only, 2 had.
Process the results to find the percentage of lice that stopped moving with each treatment, and state which treatment was most effective.3 marks

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Written by the Exaim team, led by Shaun Daswani (Head of Upper Secondary, Improve ME Institute; MSc Financial Mathematics, Imperial College London; BSc, UCL) and Jason Daswani (operational lead, Improve ME Institute; LSE).