All animals need to respond to changes in there environment and co-ordinate the activity of various organs in their bodies , the cellular activity in the body is dependent on enzymes, the tissues of the body are a collection of specialised cells and the organs of the body is a collection of tissues, thus the activity of the organs is dependent on the activity of enzyme’s and these enzymes can only work efficiently under certain set conditions, so for the enzymes to work efficiently and correctly the body must be able to control its temperature, pH and ensure its body remains free of toxins, despite any environmental variations. To do this the body has a number of receptors who’s functions are to detect a stimulus (a change in their environment) once a change has been detected the receptor will communicate with an effector and this will respond via negative feedback, in order to reverse the any change to the animal the stimulus has brought about
image1 horned lizard basking
ectothermic animals will tend to live (in the natural
state) in environment where the temperatures are very constant and warm, and not
in environment where the temperatures will vary greatly this is because the
cold environment will limit the animals ability to perform physiological
activities. If an Ectotherm begins to get cold their behaviour, responses,
and movement will become sluggish , to rectify this the animals will move to a
sunny area orientate their bodies to face the sun, enabling more heat to be
absorbed quickly, and bask (sit in sun) until a more favourable temperature is
reached. If they become too hot they will find a shaded or retreat to a cool
underground area where they will remain until the environmental temperature
cools. There ectotherm’s also have physical responses to temperature, either an
increase in it or a decrease in it, for example the horned lizard, bearded
dragon, all the snake species, and many others, have the ability to alter the
surface area of the body by expanding or contacting its rib cage. The snakes
body is effectively a long rib cage so they will flatten out all the way along
(see image 1). In the case of the invertebrates the locust will increase its
breathing when hot thus increasing evaporation or water to aid in cooling.
image 2 entering cool water
The Endotherms have a much different set of responses to control
temperature, as their blood becomes warm the hypothalamus in their brain, will
send out a signal to reverse the changes in their blood (getting too hot or too
cold). Additionally the endotherms have peripheral temperature restores, and
they monitor the temperature of the extremities of the animals (hands, feet,
tail, ears, ect) the information the receptors detect gets fed back to the
thermoregulatory centre (the hypothalamus) and this then initiates the behavioural
mechanisms the individual animal has for controlling and maintaining body
temperature for example moving in to the shade or entering cool water (see image2).
There are other physiological things the endotherms do to
maintain body temperature, vasoconstriction is one of them. If the animals becomes
too cold there arterioles in the dermis (skin), will constrict, preventing less
blood to flow to the surface of the skin thus less heat will be lost through
radiation. Additionally endotherms can release less sweat (liquid) at the
surface of the skin and the hairs of the body will stand upright via the erector
pili muscle contracting thus trapping more air for insulation. Furthermore thyroxin
and adrenaline will be released increasing the rate of reparation thus
generating more heat and finally the endotherms have the ability to shiver,
which increases muscle contractions, and again increasing respiration and
generating more heat, they can also simply move in to the sun light and as the ectotherm’s
do orientate their bodies to face the sun exposing more of the surface area to
the heat the sun’s rays generate and absorb the heat that way alternately if
the temperature in extremely cold the endotherm will roll up in a ball as small
as the animals can get, reducing the surface area exposed to the cold environment
thus reducing the amount of heat lost.
Conversely if the endotherm is too hot the arterioles in
the dermis (skin) vasodilate (dilate) meaning more blood is pushed in to the capillaries
near to the surface of the skin thus radiating more heat from its skin, the
sweat glands on the skin of the animals will release water from the body, the
water on the skin will evaporate using the heat from the blood supply the
latent heat of vaporisation. However it must be mentioned that the canine
species only have sweat gland on the
pads of their feet and on their noses (which is why it is wet this also keep
the nose functioning properly,they will
lose heat via panting or behavioural mechanisms swimming, going underground or
in to shade)(Carol S. Foil, 2006-2015). The endotherm will
reduce its metabolism which in turn reduces heat generated via respiration and
the erector pili muscles will relax so the hairs lie flat thus no air can be
trapped, they can reduce their movements (staying still) and increase their
surface area, orientate themselves so that the least amount of their body is
exposed to the sun or simply move in to the shade (http://www.thestudentroom.co.uk/attachment.php?attachmentid=100885&d=1304796816,
n.d.)