Polar bears have adapted to survive in regions with extremely low temperatures with some physical and behavioural adaptations.
For example, they have a thick layer of blubber to minimise heat loss and keep warm in cold regions. Also, they have black skin underneath their white fur, to absorb radiation from sunlight to gain heat, while still being camouflaged with their surroundings which helps them hunt.
They also have a behavioural adaption to dig burrows under the snow to shelter from harsh blizzards to prevent being killed by the low temperatures.
5. Why can’t a saltwater fish survive in freshwater aquarium? What are the differences in pH between seawater and freshwater ponds?
A saltwater fish has higher concentrations of mineral salts in the body than the fresh water, so the fresh water enters the cells of the fish through osmosis, and is at risk of having its cell membranes burst due to excess water gained. Freshwater fish are able to survive because they can excrete excess water through their kidneys.
A freshwater fish is unable to live in saltwater as it is unable to excrete salt, which will accumulate and kill the fish. Saltwater fish are able to survive as they are able to excrete excess salt.
The pH levels are normally neutral, but sometimes freshwater bodies are polluted by acid rain leading to slightly acidic water. Also, seawater can be slightly acidic, but sometimes slightly alkaline due to the dissolved calcium carbonate from shells of some of the saltwater organisms such as planktons and molluscs.