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Biology 154: Animal Form and Function R85,00
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  3. Stellenbosch University (SUN)
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Biology 154: Animal Form and Function

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A 78 page summary (lecture notes) of all information covered in the lectures of Biology 154 in Semester Two, Term Four on Animal Form and Function. This summary contains extra definitions, explanations and diagrams. Tables and bullet points are used to aid memorisation. Leave a 5 star rating if you...

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  • October 4, 2020
  • 78
  • 2020/2021
  • Class notes
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FORM AND FUNCTION OF ANIMALS


Lecture One: Homeostasis (1)


Elephants and Their Elephants use their ears for releasing body heat as they do not
Methods Thermoregulation have sweat glands - except in their toes.

How They Do This
● The large surface area serves as a heat radiator.
● When in hot weather, the blood supply increases in the
ear.
● By flapping their ears, convection and cooling speeds
up.

Morphology
● A high surface areas to volume ratio occurs due to the
folds in the skin.
● This allows for more space for heat
expansion/evaporation.
● Elephants cool down by increasing blood flow to these
highly vascularised skin patches where heat is lost.

Physiology
● Air travels over the thin skin of the ear and this cools
the web of vessels in the ears before it returns back into
the main body.
● Elephants face the wind and spread their ears to
increase this.

Surface Area vs Volume
Sa
V
Surface Area​: Amount of area exposed at the surface.

An animal's body shape and size is constrained due to its
surface area to volume ratio.
- Endothermic animals cannot be too big or too small.

As a cell gets larger = the surface area to volume ratio gets
smaller.

Materials are exchanged at the surface and are used to supply
the cells that make up the volume. Therefore, an organism’s
surface area must be large compared to its volume for effective

, exchange.

A single cell organism (amoeba) = diffusion is effective.
But if an organism is too large then diffusion cannot accurately
occur.




Image: https://www.youtube.com/watch?v=CYaADg5NfEw&app=desktop

In this diagram, we can see that cube 1 will provide more
substances to the nucleus via diffusion compared to cube 3.

The Importance of Shape The body’s surface is the main site for heat exchange with the
environment.

Heat Conservation Adaptation
These reduce surface area volume ratios.
● Round body shapes.
● Small ears.
● Shorter limbs

Heat Loss Adaptation
These increase surface area to volume ratios.
● Elongated bodies.
● Longer limbs.
● Large thin ears.

Endotherms
● Endotherms use internally generated heat (via
metabolic processes usually) to maintain body
temperature.
● Their body temperature generally stays steady.
(Constant, internal body temperature).

The Smallest Endotherms Smallest Terrestrial Endotherms = ​shrews​ and ​hummingbirds
that are both about 2grams in weight.

, They have a ​high surface area to volume ratio​.

Metabolism
● Since they are endotherms, their metabolism must work
very hard to maintain body temperatures.
● To feed their metabolism they eat hourly (else they
would starve to death).

Torpor​: the state of slowed body functions (reduced
metabolism) used to conserve energy and heat during cold
evenings.

Energy Budgets
Energy budgets (daily) are difficult to maintain as body size
decreases.

Hummingbirds eat 2-3 times their body weight each day to fuel
their metabolisms. During ​torpor​, they consume up to 50 times
less energy and become hypothermic. Torpor is an
evolutionary strategy used to preserve their metabolism/energy
budgets.

The Two Levels of Biological processes are a result of natural selection.
Explanation of Biological
Phenomena Proximate (Mechanistic) Explanations = ​How it works.

Ultimate (Evolutionary) Explanations =​ ​Why it works like
that.

Basal Metabolic Rate & All living organisms depend on complex chemical reactions
Body Size that are temperature reliant.

Life is SUSTAINED by the regulating of body temperature.

Example of Temperature
Regulation




This mechanism is called a ​Negative Feedback Loop​.
- This brings about the concept of ​HOMEOSTASIS​.

, Homeostasis Homeostasis​: This is the ability of organisms to regulate the
condition of their internal environment within narrow limits. Life
is ONLY possible within physiological limits.

Maintaining a relative constancy of the internal (fluid)
environment.

Fluid Meaning
● Internal environment refers to the extracellular fluid =
interstitial fluid + plasma.

Stable Environments Homeostasis maintains optimal conditions for enzyme action
and cell functions throughout the body.

It is vital for cell survival since each cell makes up part of a
body system which maintains the internal environment shared
by all cells.

Three Mechanisms for 1. Physiology
Homeostasis 2. Morphology
3. Behaviour

Example Many homeostatic responses are regulated by the ​nervous
system and endocrine system​ working
together/independently.

Example:
1. Increased muscle activity results in increased CO2
levels.
2. Chemoreceptors (nerve cells) sensitive to CO2 send
impulses to the brain to increase heart and breathing
rate.
3. Simultaneously, the endocrine system responds by
secreting epinephrine which increases the heart rate.

This results in more O2 entering the body system and travelling
to the muscle and CO2 is removed.

Requirement for The 3 Requirements for Homeostasis
Homeostasis
1. Sensors/Receptors
These monitor the condition.

2. Control Centers (integrators)
These integrate the incoming information and compare
it to the set point and determine the reaction.

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