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									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   Camels can store body
some insects uses evaporation   heat
– Only certain mammals have     – 34oC in morning
  sweat glands                  – 41oC by late afternoon
     Horses and man.
                                Counter current flow
     Dogs pant
     Pigs wallow
                                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

								
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