Transcript Ecology Lecture 6 Ralph Kirby Adaptation of Animals to their environment The environments on Earth vary greatly.

Ecology
Lecture 6
Ralph Kirby
Adaptation of Animals to their
environment
The environments on Earth
vary greatly. See earlier
lectures
Therefore animals (and all
other living organisms)
need to adapt to fit their
environment
|Obtaining nutrients is
probably one of the most
important
– Input into system is the
plants
– Plants consumed by
herbivores
– Herbivore animals eaten
by carnivores
– Omnivores use both
sources but may have a
preferred one
Herbivores
– Grazers (Ruminants)
Leafy material
Ruminants chew the cud
Non ruminants are less efficient
Coprophagy
– High in cellulose and some lignin
– Use specialized microorganisms in gut to help digest the difficult
carbohydrate molecules in ruman or cecum or redigestion
– 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
Seeds
– Crop with specialized enzymes
– Gizzard for grinding
– Frugivores
Fruit
Carnivores
– First level feed directly on herbivores
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 size
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
Animals need
– Essential amino acids
(14)
– Other amino acids
– Minerals
Herbivores need high
nitrogen help
microorganisms in
the digestion of
cellulose and lignin
However, season is
very important
Herbivores get more
high nitrogen food in
Spring and therefore
they reproduce at
that time
Availability is very
important for a
carnivore or
omnivore
Minerals
Animals need specific minerals such as sodium,
magnesium, etc
Sodium can be hard to obtain and can be a
problem
– Kangaroos
– Rabbits in Australia
Overgrazing of sodium rich plants can cause population
collapse
– Elephants
See preference for sodium rich water hole in Wankie National
Park, Zimbabwe
High potassium can cause magnesium
deficiency in goats, cattle and sheep
Deer need lots of
calcium,
phosphorus and
protein to grow
antlers, which are
needed for
reproductive
success
– Deficiency results
in stunted antlers
Animals need to use
aerobic respiration
Therefore need to have
excellent oxygen uptake
system
Small animals
– Diffusion
Insects
– Diffusion and spiracles
Amphibians
– Vascularised skin
– Simple lungs
Mammals
– Lungs
Birds
– Lungs
– Anterior and posterior
air sacs
Fish
– Gills
Aquatic mammals
– Lungs
– Special haemoglobin
oxygen storage
systems
Homeostasis
To stay alive, animals
need to keep their
body within certain
limits
–
–
–
–
Temperature
Water balance
pH
Salt balance
Fedback systems to
help to keep within
specific limits
Outside limits – death
– Dehydration
– Heat shock
– Salt imbalance
Temperature
–
–
–
–
Insulation
Boundary layer
Core temeprature
Surface temeprature
Ears
Fingers
Toes
Animals have different methods of
maintaining their body temperatures
Endothermy resulting in homeothermy
– Use of internal heat source
Mammals and birds
Dinosaurs?
Ectothermy resulting in poikilothermy
– Use of external heat sources
Reptiles, amphibians, fish, insects and invertebrates
Dinosaurs?
Heterothermy
– Uses both endothermy and ectothermy
Bats, bees and hummingbirds
Dinosaurs?
Poikilotherms on Land
– 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
Hibernation
During the day, the
snake can maintain a
fairly constant
temperature by adjusting
it’s environment
During the night, it has
few options
– Temperature drops 10-15
degrees
– Become torpid (slow
moving)
– Restricted by environment
– 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
– Adjust over wider range than land poikilotherms
– Stressed by rapid temperature changes
– Smaller change than reptiles over much longer period
Note that homeotherms are not restricted by their environment
– Move at same rate in tropics and at poles
Homeothermy needs energy
Therfore homeotherms use
large amounts of glucose
etc to maintain temperature
Need insulation in cold
Need cooling mechanisms
in heat
Faster
Move for longer periods
Stronger
More environments
But limited in size
– Too big?
Core temperature build up
Dinosaurs?
– Too small
Need to much energy to
keep temperature stable
2 gm limit
Solex spp eats own body
weight in food every day
to maintain temperature
Insects can be ectotherm and endotherm
– Ectotherm for take off (30oC)
– Endotherm for flight (not more than 44oC)
Torpor
– Small homeothemic animals
Become heterothermic
Body temperature drops to ambient at night
Inactive
– Bats, Some mice, kangaroos
Hibernation
– Many poikilotherms and some mammals have winter torpor to save
energy
– Selective advantage when resources are few
– Mammals
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!
Homeotherms and some poikilotherms use insulation to minimize temperature
changes
–
–
–
–
–
–
–
Fur and fat in mammals
Feathers in birds, note water repellant feathers in water birds
Blubber in aquatic mammals such as seals
Water repellant fur in polar bears
Can also work in hot environment, see camels
Shivering in emergency
Burn highly vascular brown fat to produce heat, see groundhogs and human babies
Terrestrial poikilotherms use microenvironments to change their temperature
– Basking of reptiles followed by cooling in shade can give a fairly stable temperature
during the day
– Changing shape to increase or decrease convection and radiation
– Note that basking can increase water loss
Cooling in birds, mammals and
some insects uses evaporation
– Only certain mammals have
sweat glands
Horses and man.
Dogs pant
Pigs wallow
Camels can store body
heat
– 34oC in morning
– 41oC by late afternoon
Counter current flow
can also be used to
reduce temperature
– Porpoise
– Gazelle
Controlling water balance
Aquatic
– Freshwater
Prevent excess uptake of water
Remove excess water
– Retain salt in special cells
– Large amounts of very dilute urine
– Saltwater
If salt concentration very similar to cells
– Limited problems
If salt concentration is higher
– Ion pumps
– Kidneys
– Salt secreting glands in birds
Terrestrial
– Input
Drinking
Eating
Produced by metabolism
– Output – Need to control in extreme environments
Urine
– Concentrated to avoid water loss
Feces
Evaporation
– No sweat glands in some mammals
Breathing
What happens to ungulates in a hot
dry climate like Africa
Biological
clocks have
adaptive value
– Used to
change
behavior
Daily
Seasonally
Mammals use
melatonin to
maintain
biological clock
– Produce by
pineal gland at
night
– Used to get
over jetlag
Seasonal
Changes for
male deer
Only needed
during mating
season
Can be
damaged and
need replacing
Melatonin
linked
Seasonal changes for squirrels
When will you find food at different times of the year?
Melatonin linked
Note also Seasonal Affected Disorder (SAD) in humans
– Why you have a very high suicide rate in Norway, Sweden and Finland
Crabs from a tidal estuary
retain timed activities in a fixed
environment
– Color change
– Activity
– Two clocks
Tidal
Solar
Redunancy is probably present in
most organisms
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