Thursday, January 20, 2011

Adaptation - Group 4

1. To deal with salt,
-all mangrove trees exclude some salt at the root level
-all can tolerate more salt in their tissues than "normal" plants (1/10 as salty as sea water)
-some salt is stored in old leaves which are later shed.

To deal with the low oxygen levels in the soil,
-they develop aerial or air-breathing roots (take in above ground air) .


2. Plants are put into categories according to there adaptation to water availability.
  • Hydrophytic- adapted to aquatic or semi-aquatic conditions. A classic example is Potamogetum, a genus of pond weeds where the stems have large air species in order to raise the leaves as near to the surface of the water as possible. Rice is semi-aquatic.
  • Mesophytic- Middle water conditions, typical temperate terrestrial conditions.
  • Xerophytic- adapted to conditions of low water availability. This includes plants from a variety of conditions, including sand dunes, high alpine habitats and equatorial deserts. Sorghum is a xerophytic plant.

Mesophytic plants are not especially adapted to low water/high temperatures. If water is lost (by transpiration) faster than it is lost then wilting results. The cells become flaccid. The stomata close as a result of the guard cells becoming flaccid. This helps to prevent further water loss. As the leaves fold up as the plant wilts it also helps to remove some of the leaf surfaces from the direct effects of the sun.
Transpiration itself helps to keep plants cool by the evaporation of water, in a similar way to the way sweating helps to cool down the skin of mammals.
Most mesophytic plants maintain a temperature slightly higher than the air temperature if the air temperature is below 25*C and lower than the air temperature if it rises above 30*C.

3. How do polar bears survive in regions where temperatures are constantly freezing?
  • Their thick fur keeps Polar Bears warm in frigid air and water.
  • Their skin is black and allows increased heat absorption from the sun’s rays to keep them warm.
  • When on smooth and slippery ice, their paws have pads that are adapted to increase traction on the ice to prevent slipping.
  • Their claws are curved to enable them to dig into the ice.
  • They have smaller ears and tails than other species in order to reduce heat loss.
  • They have flat layers that helps to insulate heat.

4. How do deep-sea anglerfish locate its prey in darkness?
  • The females has a piece of dorsal spine that protrudes above their mouths like a fishing pole tipped with a lure of luminous flesh.
  • These built-in rod attracts prey close enough to be caught and eaten. The big mouths and pliable bodies of the Angler fish can swallow prey up to twice their own size.
  • The male, which is smaller than the female, has no need for such an adaptation. It continually seeks for a female and over time, evolved into a permanent parasitic mate.
  • The male young is a free-swimming male angler. When it encounters a female, he latches onto her using his sharp teeth.
  • Over time, the male will physically fuse with the female, connecting to her skin and bloodstream and losing his eyes and all his internal organs except the testes. A female will carry six or more males on her body.


5a) Freshwater fish cannot survive in saltwater as:
  • Difference in water content: The ionic composition of the 2 types of waters are different.
  • Difference in physiology: Freshwater fish maintain the physiological mechanisms that permit them to concentrate salts within their bodies in a salt-deficient environment.
  • Freshwater fish also concentrate salts to compensate for their low salinity environment. They produce very dilute, copious urine
  • Should a salt water fish be put in an environment like freshwater, without salt, their existing mechanism would remove too much salt and they would lose too much salt and will die.

Saltwater fish cannot survive in freshwater as:
  • Marine fish excrete excess salts in a hypertonic environment.
  • They use a special mechanism to rid their plasma of excess salt, which builds up when they drink seawater.
  • Freshwater fish does not need such a mechanism and thus, does not posses such a mechanism. Their bodies will be full of excess salt and the freshwater fish will die.

5b)  -pH of seawater is around 7.3
-pH of freshwater is around 5.8-7.0
-Freshwater is stable and easy to maintain if you are keeping a freshwater aquarium. Saltwater can have different salinity levels, so it is unstable. Fishes living in saltwater could die due to unstable salinity levels.


Done by:
Preston, Yu Chong, Rayner, Hardy, Benjamin, Christopher

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