Succession

[jsmith613]

http://www.kscience.co.uk/resources/ks5 ... ession.rtf

I am struggling with question 3
(here is the mark scheme but it makes little sense)
http://www.kscience.co.uk/resources/ks5 ... ion_ms.rtf

I understand a and b

When it comes to question ci) and cii) I am not entirely sure what they way
I for sure don't understand what they want for 3cii)

Here is my intepretation of 3ci)
Succession would be interrupted by farming practice which leads to a loss of habitat;
many insects depend on colonising plant species; which destroyed by farming;
farmers often decide which crops to grow; but these plants are not suitable for insects; therefore insects have nowhere to lay eggs and will have no or little food for young;

Many of these insects seen as pests; pesticides may be used by farmers to destroy insects

Could someone tell me if my intepretation of 3ci) is correct. COULD SOMEONE PLEASE HELP ME WITH 3cii)

[sciencemaniac]

what exactly is 3ci?

[jsmith613]

(c) The graph shows the number of species from three insect groups which are thought to be extinct or close to extinction in three different habitats in the UK.

(i) Farming often produces temporary areas of bare soil on which colonisation may start, but these data show that many species of insect associated with the type of community that develops in this habitat are endangered. Suggest why.

(ii) Suggest explanations for the differences between the data for live trees and dead trees.

[jsmith613]

Here is the exact marking guide for 3cii)

a lot of species on dead trees endangered cf live trees;
there are fewer dead trees (than previously);
reason for dead trees being removed;
a lot of beetles on dead trees endangered cf live trees;
dead trees a habitat for more species, so more affected;
by loss of dead trees;
butterflies do not feed on dead trees;
so not affected.



How is it relevant to quesion 3cii)

[jsmith613]

surely the graph is asking for EXPLANATIONS for the different NOT EXPLANATIONS for what could happen if trees went?

[canalon]

As far as I can see, the test is not really good as there are a lot of implicit prior knowledge that I am not sure you (can) have:
But for 3cii what they want is for you to compare the number of extinct (or almost) on dead trees to the number of live trees. There are a lot for the dead tress, and much less for the live ones. Why? well because there are much less dead trees now since they are usually removed quickly as they are a problem for forest owners. (explain why) And that removal causes those species dependent of dead trees to disappear. On the other hand, the loss of live trees is much less marked, and it affects minimally species living from them. The exception are butterflies that are feeding on leaves, not off the wood itself (unlike beetles), and hence are not affected by the disappearance of dead trees.

[jsmith613]

oooh
thanks so much 4 this!