Biology ADAPTATIONS

KEY TOPICS

`star` Adaptations
`star` Adaptations in Desert Organisms
`star` Adaptations in Colder Areas
`star` Adaptations in Extreme Habitats
`star` Adaptations in Desert Lizard

ADAPTATIONS

● While considering the various alternatives available to `color{violet}("organisms for coping with extremes")` in their `color{violet}("environment")`, we have seen that some are able to respond through certain `color{violet}("physiological adjustments")` while others do so behaviourally (migrating temporarily to a less stressful habitat).

● These responses are also actually, their `color{violet}("adaptations")`.

● So, an `color{violet}("adaptation")` is any attribute of the `color{violet}("organism (morphological, physiological, behavioural)")` that enables the `color{violet}("organism")` to `color{violet}("survive")` and reproduce in its `color{violet}("habitat.")`

● `color{violet}("Many adaptations")` have evolved over a `color{violet}("long evolutionary time")` and are genetically fixed.

ADAPTATION IN DESERTS ORGANISMS

● In the absence of an `color{violet}("external source of water,")` the `color{violet}("kangaroo rat in North American deserts")` is capable of meeting all its `color{violet}("water requirements")` through its `color{violet}("internal fat oxidation (in which water is a by product).")`

● It also has the ability to concentrate its urine so that `color{violet}("minimal volume of water")` is used to remove `color{violet}("excretory products.")`

● `color{violet}("Many desert plants")` have a thick cuticle on their `color{violet}("leaf surfaces")` and have their `color{violet}("stomata")` arranged in `color{violet}("deep pits")` to minimise water loss through `color{violet}("transpiration.")`

● They also have a special `color{violet}("photosynthetic pathway (CAM)")` that enables their `color{violet}("stomata")` to remain closed during day time.

● Some `color{violet}("desert plants like Opuntia,")` have no leaves – they are reduced to spines–and the `color{violet}("photosynthetic function")` is taken over by the `color{violet}("flattened stems.")`

ADAPTATION IN COLDER AREAS