Edexcel A2 Biology Unit 4(6BIO4) 13/06/11 - OFFICIAL THREAD !

How does the entomologist use insects to find the time of a death?can anyone explain it to me in a clear and conise way so that I NEVER forget.
This is what I already know.
They collect the eggs,maggots and pupa from a death body.And they find the time when it hatched on the body?
How do they use this then to find the time of the death

It's not just collecting eggs, maggots, pupae and adults. Entomologists have knowledge about which species invade dead bodies and they know WHEN adults invade corpses. Some species will invade a dead body as soon as it dies and some will do so for hours after. Knowledge of how long it takes for invasion helps entomologist to determine when the eggs were laid.

Additionally, these entomologists also have knowledge of the life cycle of these invading insects and they know how long each cycle lasts. So if they see a certain stage (egg, maggots, pupa, whatever) on a body, they can deduce how long it took to get to that stage.

So it all just has to do with patterns of invading and lengths of life cycles.

EDIT: Here's an example.

Suppose Fly X invades a dead body 2 days after death and you know the following about the life cycle of Fly X

Eggs are laid
Larvae develop after 1 day
Pupae develop after larvae reach a maturity of 1 day
Pupae require 2 days to mature into adult Fly X.

Suppose an entomologist finds pupae on a dead body, what can he conclude? Well, it would have taken 2 days for Fly X to arrive and lay eggs, 1 day for larvae to develop from eggs and another day for pupae to develop. Pupae take 2 days to mature, so the youngest pupa can be under 2 days (I guess you can assess whether the pupae are "old/young" based on appearance).

So time of death could have been a minimum of 4 days and a maximum of 5/just under 6 days ago based just on this evidence.

U need to pay to download it?
what is it?
is it a CGP revision guide?

Thanks for the link - I already have this book as a hard copy but I have found it useful for more 'in depth' explainations so would recommend it to others

Thanks for this

basically am stuck on genetics part. If a gene codes for a specific polypeptide chain how can you have different alleles which are the same gene because different alelles have different polypeptide chains( they usually have one amino acid thats different) and that would therefore make them different genes

Is it that the differences are so small, i.e. one amino acid difference still makes it the same polypeptide chain?

very confused
any ideas or explanation would be helpful?basically am stuck on genetics part. If a gene codes for a specific polypeptide chain how can you have different alleles which are the same gene because different alelles have different polypeptide chains( they usually have one amino acid thats different) and that would therefore make them different genes

Is it that the differences are so small, i.e. one amino acid difference still makes it the same polypeptide chain?

very confused
any ideas or explanation would be helpful?

Thanks!
hey umm have yu got a link for fyzx?
Lol i noe this is not a fyzx thread, but if yu have plz post!

Yeah will post it on the unit 5 thread. Thanks again, the book looks really good.

hellow poeple does anyone no where i can get handouts/questions based on 6bio5??oh please poeple if you knoew let me no cuz i im sick from pastpapers they are not helpfull,most of them contain questions that is not in the sylabus at al.

hellow poeple does anyone no where i can get handouts/questions based on 6bio5??oh please poeple if you knoew let me no cuz i im sick from pastpapers they are not helpfull,most of them contain questions that is not in the sylabus at al.