OCR Biology chapter 1 specification answrers

Hay guys! I answered the A2 OCR biology spec for chapter 1.

I hope this gives you ideas on how to possibly answer the questions. please feel free to correct me if am wrong in what I've written :P

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  • Created by: VEZ
  • Created on: 18-09-12 19:24
Preview of OCR Biology chapter 1 specification answrers

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Chapter 1
Outline the need for communication systems within
multicellular organisms, with reference to the need to respond
to changes in the internal and external environment and to
coordinate the activities of different organs. (A2.1)
As an organism grows and develops more cells it becomes more
difficult for the innermost cells/tissues to gain nutrients and
dispose of waste, this results in the development of a series of
internal systems, which all need to regulated within a specific
range. This "range" is essential to the cellular activities (such as
metabolic processes) as they tend to require enzyme's which will
denature once the conditions fluxuate too far from the constant.
Changes in both the internal and external environments can lead
to these fluxuations in; pH, temperature and the toxins present.
Inorder for these changes to be reversed and regulated they must
be monitored, for which a communication system must be in place.
This "system" must cover the whole body, enable cells to
communicate, detect and respond to changes and allow long term
and short term responses. In most organisms these are the Nervous
and Hormonal communication systems.
State that cells need to communicate with each other by a
process called cell signaling. (A2.1)
Cell signaling is the term used to describe a communication system
within a multicellular organism, it refers to the response of one cell
to changes in either the external or internal environment which will
induce another response from a different cell until the change is
either reversed or increased (negative or positive feedback).

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State that neuronal and hormonal systems are examples of cell
signalling. (A2.1)
There are two major forms of cell signalling, these are the hormonal
and nueronal systems. The hormonal system is one specific to
longer term responses due to the release of specific chemicals into
the blood stream which will target cells with the specific receptor
site, although this can be used for faster responses as well.…read more

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Describe the physiological and behavioural responses that maintain a
constant core body temperature in ectotherms
and endotherms, with reference to peripheral temperature receptors,
the hypothalamus muscles.…read more

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When hot, the hairs lie flat, providing little insulation, meaning heat can be
through convection and radiation.
When cold, hairs raise to trap a layer of air, insulating the skin and reducing
loss.…read more


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