1. 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?

2. Plants evolved root, vascular systems and stomates to obtain water and nutrients, and pump them through their bodies
Microorganisms live in water and depend on diffusion to feed and cleanse their cells—limited to a few mm
Plants pump water s and transport nutrients to leaves through their vascular system
transpiration pull is the main pump
Evaporation at the leaf ‘sucks’ water up through the plant
Water vapour diffuses from stomates
Water evaporates from mesophyll cells
Tension pulls water into the leaf veins
And up the xylem vessels in the stem
And up the root
Water moves into the root—osmosis and into the xylem

3. When nutrients or water are scarce plants adapt:
grow more roots and less shoots
water and/or soil nutrients scarce –more allocation to root development
Water and soil nutrients plentiful—larger shoots, more growth

4. 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

5. Oleander has its stomates situated within hairy pits on the leafs under surface

6. Plants have difficulty trapping CO2 without losing water
Most plants and algae employ the C3 mode of CO2 uptake—stomates must remain open for hours--not very water efficient
RUBISCO has a low affinity for CO2
but the spongy mesophyll allows free air flow—maximize CO2 capture but high water loss

7. Many plants adapted to arid conditions eg. grasses use the C4 mechanism
PEP-carboxylase has much higher affinity for CO2 than RUBISCO
Stomates mostly closed and mesophyll tightly packed to reduce air circulation keeps CO2 levels in the leaf low and conserves water.
Photosynthesis can be highly efficient without water loss, but only occurs in the bundle sheath.

8. CAM plants are even more water efficient than C4 metabolism
Stomates open at night only when transpiration is low
OAA is formed and stored within cell vacuoles.
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
Desert plants/succulents
Eg Crassulaceae
CAM means
Crassulacean Acid metabolism

9. marine fish also live in ‘dry’ environment
Water and salt balance is a critical problem for fish
Marine fish live in water more concentrated than their body tissues
—tend to lose water and must drink to offset water loss.
Freshwater fish live in a dilute medium –tend to take on water & lose salts through gills
—produce dilute urine and take up salts by active uptake.

10. Tigriopsis is a tiny copepod crustacean that lives in splash pools and experiences dramatic fluctuations in salt concentration
It responds to these changes with rapid changes in blood chemistry and metabolic rate.

11. Tigriopsis responds to high salt stress by producing large quantities of amino acids that make its blood more concentrated—requires energy
Sharp increase in metabolic rate, as amino acids are metabolized
In response to a sudden dilution of their environment, they metabolized the amino acids.

12. Adaptations for life in hot environments
The scarcity of water in the desert make evaporative cooling very costly
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

13. Large animals have evolved muscular pumps to circulate fluids and nutrients around their bodies
CO2 released into lung and exhaled
Hemoglobin in RBC binds O2
O2 released to tissues
CO2 carried away in blood

14. Insects pump O2 to their body tissues using a tracheal system
The tracheal system opens to the outside through spiracles
Trachea divide into tracheoles which divide into finer air capillaries

15. Gas exchange and ion exchange occurs across the surface of the gills in fishes and other aquatic animals
Filaments and folds increase surface area
O2 diffuses from water into blood
Blood flow is counter current to water flow
O2 rich water

16. Counter-currents can also be useful for retention—eg heat
Arrows indicate direction of heat transfer
Heat is shunted directly from artery to vein in the leg bypassing the foot and allowing its temperature to drop to conserve body heat

17. Halophilic bacteria can adapt to high salt concentrations by producing enzymes with high salinity optima.
Comparison of salinity optima for respiratory enzymes in a halophilic and halophobic bacteria

18. Acetylcholinesterase Isozymes in rainbow trout
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

19. Homeostasis/regulation often occurs through negative feedback systems
A thermostat is a typical negative feedback system
What do we mean by the term positive feedback?
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.

20. Maintaining a constant internal temperature warmer than the external environment is costly—the bigger the gradient the bigger the cost
This West-Indian hummingbird, conserves metabolic energy by setting its thermostat down at night
Set-point 40C
Set-point 20C