BIOL 4120: Principles of Ecology
Lecture 7: Animal adaptations to
the Environment
Dafeng Hui
Office: Harned Hall 320
Phone: 963-5777
Email: dhui@tnstate.edu
Topics
7.1 Animals have various ways to acquire energy and nutrients
7.2 Animals have various nutritional needs
7.3 Animal require oxygen to release energy contained in food
7.4 Regulation of internal conditions involves homeostasis and
feedback
7.5 Animals have different methods of maintaining their body
temperatures
7.6 Poikilotherms depend on environmental temperatures
7.7 Homeotherms escape the thermal restraints of the environment
7.8 Endothermy and Ectothermy involve trade-offs
7.9 Heterotherms take on characteristics of ectotherms and
endotherms
7.10 Torpor helps some animals conserve energy
7.11 Some animals use unique physiological means for thermal
balance
7.12 Maintenance of water balance
7.13 Biological clocks influence animal activity
Chapter 7 Animal Adaptations to the
Environment
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Animals are heterotrophs and derive their energy
and most nutrients from consuming organic
compounds contained in other plants and animals
Key processes common to all animals
• Acquire and digest food
• Absorb oxygen
• Maintain body temperature and water balance
• Adapt to light and temperature variations
Animals encounter different constraints in aquatic
versus terrestrial environments
7.1 Animals have various ways of
acquiring energy and nutrients

Energy sources for plants and animals
Three Feeding Methods of Heterotrophs:
•
•
•
•
Herbivores: Feed on plants.
Carnivores: Feed on animal flesh.
Omnivores: Feed on both plants and animals
Detritivores: Feed on non-living organic matter
(earthworm, dung beetle).
Animals have various ways of
acquiring energy and nutrients

Mouthparts
reflect how
organisms obtain
their food.

Herbivores
• Grazers (cattle, dear, sheep, grasshopper)
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Leafy material (Ruminants chew the cud; Non ruminants
are less efficient)
High in cellulose and some lignin (C:N ratio)
• Use specialized microorganisms in gut to help digest the
difficult carbohydrate molecules in ruman or cecum or
redigestion (Fermentation)
• Microorganisms produce proteins, lipids etc
• Browsers

Woody material (Termites)
• High in lignin and cellulose
• Use specialized microorganisms in gut to help digest the
difficult carbohydrate molecules
• Microorganisms produce proteins, lipids etc
• Granivores (birds)

Seeds
• Crop with specialized enzymes
• Gizzard for grinding
• Frugivores (monkey etc.)
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Fruit

Carnivores
• First level feed directly on herbivores
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No cellulose
Rapid digestion and easy assimilation
Hunting is energy consuming
• Second level feed on first level carnivores

Omnivores
• Food eating habits vary with season, life cycle
and their sizes

Fox
• Preferential carnivore
 Insects, small mammals and birds
 but eats berries, fruit, grass

Bear
• Preferential herbivore
 Buds, leaves, berries, fruit, etc
 Supplemented by insects, fish and small to medium
mammals

Red Fox is an
example of
an omnivore
7.2 Animals have various nutritional
needs
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Animals need amino acids and specific minerals such as sodium,
calcium, magnesium, etc
High quality and quantity of plants are very important to animal
survival
Herbivores show certain preference on high N plants (Taste and
odor)
Deficiency in minerals influences distribution, behavior, and
physiology of animals
Sodium can be hard to obtain and can be a problem
• Kangaroos, Rabbits in Australia

Overgrazing of sodium rich plants can cause population collapse (plants died)
• Elephants
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See preference for sodium rich water hole in Wankie National Park,
Zimbabwe
Dear: eating mineral-rich soil in spring
High potassium in spring vegetation may cause calcium,
magnesium deficiency in goats, cattle and sheep (influence
hormone balance)
Nutrient conditions influence growth and reproduction.

Deer need lots
of calcium,
phosphorus and
protein to grow
antlers, which
are needed for
reproductive
success
• Deficiency
results in
stunted antlers
7.3 Animals require oxygen

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Energy from organic compounds in the food they
eat
Release energy primarily through aerobic
respiration
O2 is required (could be an issue for aquatic
animals)
Methods to acquire O2
•
•
•
•
•
Body surface: insects, tracheal tubes
Lungs: mammals, birds, reptiles
Lung and air sacs: birds
Lungs: whales and sharks
Gills: Fish
Respiration systems
Animals need to use aerobic
respiration

Therefore need to have
excellent oxygen uptake
system

Small animals
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•
Diffusion
•
Diffusion and spiracles
•
•
Vascularised skin
Simple lungs
•
Lungs
•
•
Lungs
Anterior and posterior air sacs
•
Gills
•
•
Lungs
Special haemoglobin oxygen storage
systems
Insects
Amphibians
Mammals
Birds
Fish
Aquatic mammals
O2 countercurrent exchange
BIOL 4120: Principles of Ecology
Lecture 7: Animal adaptations to
the Environment
Dafeng Hui
Office: Harned Hall 320
Phone: 963-5777
Email: dhui@tnstate.edu
7.4 Regulation of internal conditions
involves homeostasis and feedback
Homeostasis: The maintenance of a
relatively constant internal environment in
a varying external environment.
Homeostasis depends on negative feedback
Negative feedback: when a system
deviates from the normal or desired state,
mechanisms function to restore the
system back to that state.
Example: room temperature setting
Homeostasis

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
To stay alive, animals
need to keep their body
within certain limits
• Temperature
• Water balance
• pH
• Salt balance
Feedback systems to
help to keep within
specific limits
Outside limits –
• Dehydration
• Heat shock
• Salt imbalance
• Death
Negative feedback (thermoregulation)
Animals exchange energy with their surrounding
environment

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Body structure influences
the T exchange
Temperature (Tb, Ts, Ta)
Tb<->Ts conduction
• Boundary layer (a thin layer
of air surround the body)
• Core temperature Tb
• Surface temperature Ts
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Ears
Fingers
Toes
Ts<->Ta: conduction,
convection, radiation,
evaporation
Insulation (air, body
covering) influences energy
exchanges
7.5 Animals have different methods of
maintaining their body temperatures
Three groups of animals
 Endothermy resulting in homeothermy
• Use of internal heat source (metabolically)
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Mammals and birds
Maintain a fairly constant temperature (warm-blooded)
Ectothermy resulting in poikilothermy
• Use of external heat sources

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
Reptiles, amphibians, fish, insects and invertebrates
Results in a variable body temperature (cold-blooded)
Heterotherm
• Uses both endothermy and ectothermy


Bats, bees and hummingbirds
Depends on environmental situations and metabolic needs.
7.6 Poikilotherms depend on
environmental temperatures
• As the temperature
increases, so does the
metabolic rate
• Therefore these animals
are more active during the
day
• Every 10oC doubles
metabolic rate
• Naturally low metabolic
rate and high conductivity
• Activities also control
temperature
• Upper and lower limits vary


Lizards and snakes have a
5oC
Amphibians have a 10oC
Operative T range: range of body T at which poikilotherms can carry out
their daily activities (next slide).


During the day, the snake
can maintain a fairly
constant temperature by
adjusting it’s environment
(bask in sun to raise T,
seek shade to cool,
submerge in water etc)
During the night, it has
few options
• Temperature drops 1015 degrees
• Become torpid (slow
moving)
• Restricted by
environment
• Limited to Maximum
size due to need for
surface area to gather
heat
• No minimum size

Poikilotherms in water
• No insulation
• Match of body temperature to water temperature
• Water temperature normally only changes slowly
with season
• Poikilotherms can adjust slowly to a wide range
of temperatures than land poikilotherms
(acclimation)
• Stressed by rapid temperature changes
7.7 Homeotherms escape the thermal
restraints of the environment
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Homeotherms can escape the thermal
restraints of the environments, thus can
exploit a wide range of thermal
environments
But needs energy to maintain relative
constant T
Therefore homeotherms use large amounts
of glucose etc to maintain temperature
(aerobic respiration)
O2 is consumed during respiration
Rate of O2 consumption is used to measure
metabolic rate
Resting metabolic rate and ambient
temperature
Thermoneutral zone:
a range of
environmental
temperatures within
which the metabolic
rates are minimal.
Critical T: lower and
upper critical T
Homeotherms can escape the thermal
constraints of the environments
Ways to keep body warm:
1. Insulation to reduce the convection: fur, feather, or body
fat
Mammals: fur, change fur in the winter
Fur can keep body heat in and the heat out
Birds: feather
Insects: a dense fur-like coat (moths, bees)
2. When insulation fails: shivering (a form of involuntary
muscular activity that increase heat production.
3. Small mammals: burn brown fat (bats) without shivering.
Ways to keep body Cool:
1. birds and mammals: evaporation of moisture from skin
2. mammals: sweat glands (horse, human), panting
3. birds: gular fluttering
7.8 Endothermy and Ectothermy involve
trade-offs
New
Scientist,
2009
7.8 Endothermy and Ectothermy involve
trade-offs
Endotherms can survive in large range of T,
why not all animals are endotherms?
Endotherms
Activity: under all environments
Energy: high
Food:
most for respiration, less
to growth
Limits on size:
limit on minimum size
Ectotherms
limited to environmental T
low
less for respiration
more to growth
limit on maximum size
Limited in size
Warm-blooded animals: body
mass (volume) produce
heat, lost through surface
area, the ratio of surface to
volume is key factor too.
• Small animals have
larger ratio and greater
relative heat loss to
environment, require
higher mass-specific
metabolic rate to
maintain and consume
more food energy per
unit body weight.
• Too small
 Need too much
energy to keep
temperature stable
Cold-blooded animals absorb heat through
 2 gm limit
surface, thus the surface area to volume is
 Shrew (Solex spp)
also a key factor. Large animals limited to
eats own body
weight in food every
warm areas.
day to maintain
temperature
Metabolic rate and body mass
7.9 Heterotherms take on characteristics
of ectotherms and endotherms
Temporal heterotherms: species that sometimes
regulate their body T and sometimes they do not.
Insects, bats, bees, hummingbirds
Adult insects can be ectothermic and endothermic:
T limits on flight: 30oC for take off, and no
more than 40oC for flight
Need warm-up to take off: ectothermic
Flight: burn energy, endothermic
7.10 Torpor helps some animals
conserve energy

Torpor
• Small homeothemic animals
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Become heterothermic
Body temperature drops to ambient at night
Inactive
• Bats, Some mice, kangaroos
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Hibernation
• Many poikilotherms and some mammals have winter torpor to
save energy
• Selective advantage when resources are few
• Mammals
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Heart rate, respiration fall
Temperature drops to ambient
Groundhogs, chipmonks
Not bears
•
•
•
•
•
No temperature change
Just long sleep with no eating, drinking, defecating or urinating
Females give birth and feed young in this period
Can wake up easily
Do not visit a bear cave in winter!
7.11 Some animals use unique physiological
means for thermal balance
Storing body heat:
Camel, oryx and some gazelles
Body T change from 34oc to 41oC for camel (morning to
afternoon)
Reduce need for evaporative cooling and save water and energy
Supercooling:
many ectothermic animals of temperate and Arctic regions
When the body T below freezing points without actually freezing
The presence of certain solute (glycerol) in the body lower the
freezing points
Wood frog, grey tree frog, spring peeper
Countercurrent heat exchange:
to conserve heat in a cold environment and to cool vital part of
body during heat stress.

Countcurrent heat exchange happens in
homeotherms (porpoise, whale) as well as in certain
poikilotherms (tuna, mackerel shark)
To
preserve
heat in
cold
water,
and get
ride of
heat in
warm
water
To cool
brain,
reduce T
by 2-3oC
7.12 Maintenance of water balance

Terrestrial
• Input

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Drinking
Eating
Produced by metabolism (respiration)
• Output – Need to control in extreme
environments

Urine
• Concentrated to avoid water loss
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Feces
Evaporation
• No sweat glands in some mammals

Breathing
What happens to ungulates in a hot
dry climate like Africa
No pants, no
sweating to save
water, store heat in
body (T up to 46oC
at daytime, release
heat at night 36oC)
Countcurrent heat
exchange to lower
head T
Eat at nighttime,
more water in plants
Respiration to
produce water
Maintenance of water balance

Aquatic
• Freshwater (hyperosmotic, high salt in
body)
• Prevent excess uptake of water

Remove excess water
• Retain salt in special cells (gills)
• Large amounts of very dilute urine
• Saltwater (hypoosmotic, low salt in body)

If salt concentration is higher than in body,
dehydrate
• Ion pumps, gill (fish)
• Kidneys (eliminate salts, marine mammals)
• Salt secreting glands in birds
Buoyancy aids aquatic organisms to stay
afloat

Gas or swim bladder (most fish)
• 5-10% body volume

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Lungs in air-breathing animals
Replace heavy chemical ions in the
body fluids with lighter ones
• Squid (ammonium ions to replace sodium
ions)
• Shark, mackerels, bluefish: store lipids
(less dense than seawater)
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Aquatic animals
need to move up
and down in water
Buoyancy aids
Shark
• Large fatty
liver
• Must swim to
not sink
Fish
• Gas bladder
• Used to move
up and down
Seal
• Blubber
• Can float on
surface with
air in lungs
7.13 Biological clocks influence animal
activity
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Daily and seasonal light and dark
cycles
Critical daylengths trigger seasonal
responses
Activity rhythms of intertidal
organisms follow tidal cycles
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Animals react to changing light through internal
biological clocks
Internal Biological Clocks have adaptive value
• Used to change behavior: feeding, food storage,
reproduction, migration.
 Daily (Circadian rhythm): sleep, metabolic rate,
temperature
Predators must match their feeding activity with
prey.
Seasonal: food storage, migration
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Seasonal
Changes for
male deer
Only needed
during mating
season
Can be
damaged and
need
replacing
Critical daylengths trigger seasonal responses
Squirrels start activity when the day starts, regardless
of the season
Daylengths influence organisms activity

Critical daylength
• Duration of light or dark reaches a certain proportion of the
24-hour day, it inhibits or promotes a photoperiodic response.
• Normally 10-14 hours
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Day-neutral organisms: not controlled by daylength
Short-day organisms: reproduction (or other activity) is
stimulated by daylength shorter than critical daylength
Long-day organisms: ~longer~
Diapause: a stage of arrested growth over winter in insects
of the temperate regions controlled by photoperiod.
• Requirement: 12-13 hours of light
• A quarter-hour difference can determine diapause or not
Activity rhythms of intertidal
organisms follow tidal cycles

Crabs from a tidal estuary
retain timed activities in a
fixed environment
• Color change (day and night)
• Activity (tides)
• Two clocks
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Tidal
Solar
The END
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Circadian (24 hr) rhythm
is very important to
most living organisms
Timing measures
• Light
• Temperature
• Moisture

Temperate zone
• Light cycle

Arctic and subarctic
zones
• Temperature

Tropical and subtropical
zones
• Moisture
Water Movement in Aquatic
Environment
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Isomotic (isotonic): Body fluids and
external fluid are at the same
concentration.
Hypoosmotic (hypotonic): Body fluids
are at a lower concentration of salt
than the external environment.
Hyperosmotic (hypertonic): Body
fluids are at a higher salt
concentration than the external
environment. (freshwater)
Fig. 5.4
Digestive systems are
different for these
different type of
animals
Stomach
Caecum:
Intestine
Colon