Maintaining a Balance
Topic 5: Temperature Regulation in Animals
Biology in Focus, HSC Course
Glenda Childrawi, Margaret Robson and Stephanie Hollis
DOT POINT
 Identify the broad range of temperatures over which life is
found compared with the narrow limits for individual species
 Compare responses of named Australian ectothermic and
endothermic organisms to changes in the ambient
temperature and explain how these responses assist
temperature regulation.
Temperature Tolerance
Temperature is one of the many limiting factors that can
determine the presence of life on Earth. For example, tissue
temperatures greater than 42C are lethal to most organisms as
important enzymes begin to denature.
janellekeith.blogspot.com
Temperature Tolerance
Extreme temperatures (above
100C ) denature not only
proteins, but also nucleic acids.
This destruction of DNA results
in cell death. Its therefore not
surprising that habitats that
offer temperature conditions
that are fairly stable are highly
sought after and result in much
competition.
jennifermarohasy.com
Temperature Tolerance
Most living things live at temperatures between 10 and 35C.
Active growth in most plants occurs between 5 and 40C. Some
species of plants and animals have moved and adapted to occupy
niches where temperatures fall outside the optimal range of
temperatures over which life can be found.
kirabell.blogspot.com
Range of Temperatures
The diverse array of living organisms on Earth are found across a
broad range of temperatures. There are living creatures that can
survive as low as -70C or as high as 56C. Some bacteria can
even survive at temperatures of 350C near deep ocean vents.
guardian.co.uk
Range of Temperatures
There is an enormous variation
in temperatures over the Earth.
The average variation in
environmental temperature is
more prominent on land (-89 to
60C). This vast range of
temperatures found on Earth
has been beneficial in allowing
diversity of niches for species.
sciencedude.blog.ocregister.com
Range of Temperatures
Much like enzymes, individual species have an optimal range of
temperatures at which they can function. For each living species,
this is a fairly narrow range. The temperature range in which a
species can survive is called its tolerance range. It’s usually
only a few degrees outside of the range at which it is
comfortable.
2lanehighway.blogspot.com
Temperature Regulation
The terms ectotherms and endotherms relate to the ability of an
animal to regulate its body temperature. ‘Therm’ relates to
temperature, ‘ecto’ means outside and ‘endo’ means inside.
outback-australia-travel-secrets.com
Temperature Regulation
Ectotherms depend on an
external source (the
environment) for heat energy.
Fish, amphibians, reptiles and
most invertebrates fall into this
category.
Endotherms rely on internal
sources for energy such as
metabolic activity. Birds and
mammals are all endothermic.
heathernicolezilla.tumblr.com
Ectotherms
The body temperature of
ectotherms fluctuates over a
small range of temperatures. It
is influenced by the ambient
temperature (temperature of
the environment) and the
organism has only a limited
ability to control its body
temperature.
chapterfortyfour.webnode.com
Ectotherms
In nature, these organisms adapt their behaviour to regulate their
body temperature and so if it is measured in the wild , their body
does not show as wide a range of fluctuation. Scientists can do
this using a radio telemetry device.
edgeofexistence.org
Ectotherms
Brown snakes are found across
most of Australia, inhabiting a
range of habitats from open
grasslands to desert scrub, but not
in rainforest areas.
en.wikipedia.org
Ectotherms
Brown snakes are usually diurnal (awake during the day). If the
ambient temperature rises beyond the brown snake’s tolerance
level, it will seek shelter in the shade during the day and become
active in the later part of the day when it is cooler, or even at
night.
oceanwideimages.com
Ectotherms
If the ambient temperature drops
below the optimum range,
brown snakes bask in the sunlight
to gain additional heat. In very
cool weather, the snake becomes
less active, slowing down its
metabolism and uses fat reserves.
If the cold period is prolonged,
the snake will hibernate in a
sheltered spot.
hvbackyard.blogspot.com
Endotherms
Under laboratory conditions and in nature, the body temperature
of an endothermic organism tends to remain stable despite
variation in the ambient temperature. An endothermic organism
has the ability to control its body temperature and maintain it at a
stable level within a very narrow range.
animammal.blogspot.com
Endotherms
In low ambient temperatures, the main source of heat in the body
of endotherms is that generated as a result of the metabolic
activity of their cells, particularly the muscle and liver cells. The
size of the animals body also plays a significant role.
gdargaud.net
Endotherms
Some endotherms have special heat-producing tissue called
brown fat, which can be quickly metabolised in cold conditions.
The common bentwing bat produces brown fat in late summer
and through autumn when food is abundant. In the cold winter
months, the brown fat is metabolised and used to increase body
temperature, allowing these bats to fly after periods of
hibernation.
leichhardt.nsw.gov.au
Endotherms
If the ambient temperature is high, endotherms have a
physiological cooling mechanism as well. The rate of heat loss
from the body can be adjusted by altering the flow of blood near
the surface.
altonphysio.blogspot.com
Endotherms
Evaporative cooling such as sweating, panting or licking saliva
onto the body surface is a common cooling mechanism.
Evaporative cooling brings with it the risk of water loss. Animals
that live in hot, dry climates have to develop mechanisms for
cooling that do not allow too great a loss of water.
huffingtonpost.com
Endotherms
Endotherms also show adaptations in their behaviour to help
regulate their body temperature. Body temperature in humans is
approximately 37C and that of birds is 40C (these may fluctuate
within about 1.5C).
ausemade.com.au
Endotherms
The fairy penguin is found along the southern Australian coastline
and in Tasmania and New Zealand. It is the smallest of all
penguins and lives in burrows in coastal sand dunes, not in the ice
and snow like most penguins.
news.com.au
Endotherms
Fairy penguins have feathers that provide an insulating layer.
These feathers trap a layer of air close to the skin which reduces
the amount of heat lost. This layer of air can be altered
depending on the ambient temperature.
scarletwonderland.com
Activity/Homework
-Students are to complete:
 1.5.1 Adaptions and Responses to Temperature Activity and
DOT Point 1.11