3.5.2 People change communities

Here is the exam questions pack for this topic. Read the information below and have a go at the questions. The mark scheme is posted here too:

Ecosystems and communities exam questions

Ecosystems and communities exam questions MS

In this topic we were introduced to a lot of key terminology. It’s really important to be able to use these words in their correct contrext. What, for instance, is the difference between and ecosystem and an environment, a species and a population or a niche and a habitat?

Make sure you can define these terms and use them correctly. Here’s a link I think you might find useful.

Here I should really upload a picture of the wonderful model ecosystem complete with string labels that you made and I will do as soon as I get a minute to take a decent picture of it.

We looked at some interesting examples of how humans have introduced species into an ecosystem either purposely, or unwittingly, with devastating consequences. One interesting (though almost certainly apoctyphal) story is on the St Stephen’s Island Wren which was a species of bird found (reputedly) only on St Stephen’s Island off the coast of New Zealand.

The island had a lighthouse on it and the lighthouse had a lighthouse keeper who in turn had a cat, Tiddles. Turns out that Tiddles was one hungry cat and he caused the eradication of the wren through his voracious appetite!

This is an extreme example but the introduction of the grey squirrel into Britain as pets around about 100 years ago provides a more typical example. The squirrels escaped captivity or where released into the wild in small numbers only to go on to displace the red squirrel from its’ ranges throughout the British isles.


The article above begs an interesting question – is it worth it or is it even ethical to preserve species like the red squirrel that have been displaced by a more successful competitor? The cost of maintaining suitable red squirrel friendly habitats in the UK must run into the millions of pounds per year. Is it worth the cost?

Exam focus: make sure that you can explain that ecosystems are a delicate balance of interactions between populations, communities and the physical environment. Alien species disrupt this balance, often in unpredicatable ways. The key learning point from this topic is that populations in a community depend on each other.



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