Download Adaptations to Terrestrial and Aquatic

Plants evolved root, vascular systems and stomates to
obtain water and nutrients, and pump them through their
bodies
Adaptations to Terrestrial and Aquatic Environments
•Some adaptations of plants for life on land
•Osmotic adaptations of fish for marine life
•Adaptations of animals to desert environments
•Physical adaptations required for large size
•Biochemical adaptations to extreme environments
•Homeostasis and how is it achieved?
•Microorganisms live in water and
depend on diffusion to bring
nutrients to their cells—limited to
a few µm
Water vapour diffuses from stomates
Water evaporates from mesophyll cells
Tension pulls water out into the leaf veins
•Plants pump water over
considerable distances and
transport nutrients to leaves
through their vascular system
•This pump is driven mainly by
transpiration pull
And up the xylem vessels in the stem
•Water is evaporated at the leaf
surface which creates negative
pressure pulling water up through
the plant
And up the root
Water moves into the
root—osmosis and into the xylem
When nutrients or water are scarce plants grow more roots and
less shoots
Plants control water loss
•Waxy leaf cuticle
•Stomates on the underside—regulate
evaporation
Spines and hairs help desert
plants deal with heat and
drought
•still boundary layer that
traps moisture and reduces
evaporation
water and/or soil nutrients
scarce –more allocation to
root development
Water and soil nutrients
plentiful—larger shoots, more growth
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Plants have difficulty trapping CO2 without losing water
Most plants and algae employ the C3
mode of CO2 uptake, which is not
very water efficient
Oleander has its stomates situated within hairy pits on the leafs
under surface
RuBP has a low affinity for CO2
but the spongy mesophyll allows free air
flow—high water loss
Many plants adapted to arid conditions eg. grasses use the C4 mechanism
CAM plants are even more water efficient than C4 metabolism
•PEP-carboxylase has
much higher affinity for
CO2 than RuBPcarboxylase
•Stomates open at night
only when transpiration
is low
•OAA is formed and
stored within cell
vacuoles.
•Stomates closed and
mesophyll tightly
packed to reduce air
circulation keeps CO2
levels in the leaf low but
conserves water.
•Photosynthesis can be
highly efficient without
water loss
Desert plants/succulents
Eg Crassulaceae
CAM means
Crassulacean Acid metabolism
•During the day
stomates close and
OAA is recycled to
release CO2 to the
Calvin-Benson cycle
•Day and night
enzymes have different
T-optima
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marine fish also live in ‘dry’ environment
Tigriopsis is a tiny copepod crustacean that lives in splash pools
and experiences dramatic fluctuations in salt concentration
Water and salt
balance is a
critical problem
for fish
Marine fish live in water more concentrated than their body tissues. They must drink to take on
water and excrete salts.
Freshwater fish live in a dilute medium and tend to take on water through their gills, and produce
dilute urine. They need to take up salts by active uptake.
Tigriopsis responds to high salt stress by producing large quantities of amino acids that make
its blood more concentrated—requires energy
It responds to these changes with rapid changes in blood
chemistry and metabolic rate.
Adaptations for life in hot environments
The scarcity of water in the desert
make evaporative cooling very costly
Sharp
increase in
metabolic
rate, as amino
acids are
metabolized
In response to a sudden dilution of their environment, they metabolized the amino acids.
Reduce activity, or go underground
during the day and be more active at
night when it is cool
Many desert plants orient their leaves
away from direct sunlight, and others
shed their leaves and become dormant
during hot and dry periods.
The kangaroo rat has both physiological and behavioural
adaptations for desert environments
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Large animals have evolved muscular pumps to circulate
fluids and nutrients around their bodies
CO2 released
into lung and
exhaled
CO2 carried
away in blood
Insects pump O2 to their body tissues using a tracheal system
Hemoglobin
in RBC
binds O2
The tracheal system
opens to the outside
through spiracles
O2 released
to tissues
Gas exchange and ion exchange occurs across the surface of
the gills in fishes and other aquatic animals
Trachea divide into
tracheoles which divide into
finer air capillaries
Counter-currents can also be useful for retention—eg heat
Arrows
indicate
direction of
heat transfer
Filaments and folds
increase surface area
O2 rich water
O2 diffuses
from water
into blood
Blood flow
is counter
current to
water flow
Heat is shunted directly from artery to vein in the leg
bypassing the foot and allowing its temperature to drop to
conserve body heat
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Acetylcholinesterase Isozymes in rainbow trout
Halophilic bacteria can adapt to high salt concentrations by
producing enzymes with high salinity optima.
Winter adapted
trout, T-opt is 2C
Summer adapted
trout, T-opt is 17C
Temperature adaptation in cold-blooded animals often
involves changing enzymes as temperature changes
Comparison of salinity optima for respiratory enzymes in a
halophilic and halophobic bacteria
Homeostasis/regulation often occurs through negative feedback systems
A thermostat
is a typical
negative
feedback
system
Maintaining a constant internal temperature warmer than the external
environment is costly—the bigger the gradient the bigger the cost
What do
we mean
by the
term
positive
feedback?
This West-Indian
hummingbird, conserves
metabolic energy by
setting its thermostat
down at night
Set-point 40C
Set-point 20C
Negative feedback—if T is too high heater switched off, if too low heater switched on. The
feedback is considered negative because the response is opposite to the deviation.
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