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F214 Unit 1 Module 1 Communication & Homeostasis
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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.
State that cells need to communicate with each other by a
process called
cell signalling.
State that neuronal and hormonal systems are examples of cell
signalling.
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What internal conditions do cells need?
Suitable temperature Suitable pH
Sufficient water for solutions to be produced
Minimal toxins
Low levels of inhibitors
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Unicellular Organisms Responses
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Multicellular Response
Multicellular organisms are more efficient. Why? In order to
respond what do they need to be able to which unicellular life
does not?
A communication system which
Covers the whole organism
Allows intercellular communication
Enables specific communication Enables rapid communication
Encompasses short and long term responses
How does the communication system in school work? What kinds
of
message does it need to carry? What is the timeframe?
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Cell Signalling
Cell A releases chemical, Cell B responds upon detection
Neuronal System
Hormonal System
Compare & contrast
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Define the terms negative feedback, positive feedback and
homeostasis.
Explain the principles of homeostasis in terms of receptors,
effectors and
negative feedback.
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Homeostasis
...is the maintenance of the internal environment in a constant
statedespite external fluctuations
Which conditions do humans maintain using homeostatic
mechanisms?
Body temperature
Blood glucose Salt levels
Water potential of blood
Blood pressure
CO2 concentration
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Negative feedback
STIMULUS -> RECEPTOR -> CELL SIGNALLING -> EFFECTOR
-> RESPONSE
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Negative Feedback
Choose any one of the internal conditions maintained within
humanswhich we have listed already.
Draw and annotate the negative feedback loop
Include all of the organs/tissues involved in the operation and
explain
the roles of each
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Positive feedback
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Menu for Today
1 - Definitions please; Stimulus, response, negative feedback,
positive feedback,
homeostasis write them without ref to book
2 - Questions p.7 by discussion
3 - Individual Stretch and Challenge tasks DISCUSS when
complete
4 - Understanding Biology p.488 onwards Write a summary of the
key points relating to the development of
control systems within increasingly complex organisms for
completion by Thursday in a form which can be shared
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Sharing our work on Development of Control Systems
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Maintaininga Steady Body Temperature
Most organisms benefit from keeping their core temperature at a
steady
level why?
Enzymes
Globular nature
Lock & Key
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Describe the physiological and behavioural responses that
maintain a
constant core body temperature in ectotherms.
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Ec
totherms
Ectotherms are those organisms which were once referred to as
cold-
blooded. DONTdo this as its not accurate!
Some examples of ectotherms might be.....?
Advantages of being an ectotherm might be...?
Less food for respiration and so less feeding needed
More energy devoted to growth >
Disadvantages?
Long periods of inactivity due to climate
Need to pre-warm in mornings>
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Chlamydosaurus kingii
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Ec
totherm Behaviours
Exposure to Sun butterflies in the morning
Orientate toward Sun
Orientate away from Sun
Remain below ground
Increase breathing rate to evaporate water
Form swarms or groups bees do this
Alter body shape some lizards do this
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Ec
totherms - task
Find a networked computer!
Find one or two good examples of ectotherms which display some
of these
behaviours
Track down some information about those organisms and their
behaviour
Turn what you have into a couple of powerpoint slides
Bring it back with 15 minutes to spare (or email to
[email protected])
Share what youve got!
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Ec
totherms (Recap)
List the behaviours typical of ectotherms and state how each
serves its
purpose
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Describe the physiological and behavioural responses that
maintain a
constant core body temperature in endotherms, with reference to
peripheraltemperature receptors, the hypothalamus and effectors in
skin and muscles.
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Endotherms
Maintain body temperature through use of internal heating
system
Harness exergonic reactions (what is exergonic? what is the
opposite?)
Respiration is an example of such a reaction
Endotherms regulate temperature by increasing rate of this in
liver cells
Unlike ectotherms they therefore use some food energy for
heating
Endotherms can also use behavioural mechanisms
Which behavioural mechanisms do you use?
http://www.youtube.com/watch?v=CfBadEGTwyI
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(a) Vasodilaton; (b) vasoconstriction
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Endotherms (cont...)
Advantages/Disadvantages of endothermy?
Advantages include;
Can live in cooler climates
Can be more active at night/in winter Are not so influenced by
external conditions
Like taking your environment with you
Disadvantages include:
Energy goes to heating instead of other things, e.g. Growth
Need to find more food
Food supply most limited in winter, when heating is most
important >
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Endotherms (cont...)
Task;
Use books, other than the course text this time, to list and
explain the
physiological and behavioural mechanisms used by endotherms
>
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Endotherms Temperature Control
The HYPOTHALAMUS is the key
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Endotherms Temperature Control
The hypothalamus monitors blood temperature
Follows a system of negative feedback, as discussed in previous
lessons >
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Controlling body temperature by negative feedback
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Endotherms Temperature Control
The hypothalamus monitors blood temperature
The bodies extremities also contain temperature sensors and
these can
provide a kind of early warning system for the hypothalamus
>
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Summary Tasks
1 Questions from p.11 of course text
2 Track down and answer any relevant questions you can find in
older
texts (Understanding Biology p.507 q.2b, 4, 6, 7
3 Make a slideshow which allows you to compare and contrast, for
a
Zoo audience made up of members of the public, the behavioural
and
physiological mechanisms used by ectotherms and endotherms to
maintain
a suitable body temperature. For display Thursday final 15
minutes.
