To survive, plants and animals must adapt to the extreme conditions of their habitats. Extreme dry or cold conditions represent some of the harshest climates with the greatest challenges that either may face. They must balance their needs for growth and reproduction with the availability of resources and energy.
If dry and cold conditions prevail, a plant may slow its rate of photosynthesis. Photosynthesis describes the process by which plants make food, using water and carbon dioxide from the environment in a chemical reaction fuelled by the sun. A plant may close the stomata or pores on its leaves to conserve water if water becomes a limiting factor. Likewise, an animal may decrease its activity level to conserve energy that will keep it warm.
Plants and animals respond to dry and cold conditions through modification of their physical structure. Plants of tundra regions, for example, tend to grow low to the ground to focus their energy on reproduction rather than growth during the short growing season. Many plants may be dark-coloured to maximise absorption of heat. Likewise, animals of these environments are short-legged to conserve heat. These animals also have warm winter coats. Some bird species such as the ptarmigan have two sets of feathers, accomplishing the same purpose.
Plants and animals will enter periods of dormancy or hibernation if dry and cold conditions persist. Arctic animals such as the grizzly bear hibernate over the coldest winter months so they can avoid the harsh challenges of continuing to find food and keep warm. Plants go dormant during the winter when the amount of sunlight decreases. Without adequate sunlight, they cannot make food or energy.
Energy conservation is vital in extreme weather conditions. Plants and animals optimise their energy needs by slowing their growth. Growth requires energy. By slowing its rate, plants and animals require less energy. Animals of these regions also reproduce less frequently than animals that don't face the same environmental challenges. Likewise, tundra plants are primarily perennials, with many conserving additional energy by reproducing through tillers rather than seeds.
Other Animal Adaptations
Animals of dry and cold regions have a distinct advantage over plants in that they can leave an area during the winter. Many species of waterfowl and sea birds migrate during the winter to find food and other resources in less harsh environments. Some animals, such as the Arctic hare and ermine, use the snow to their advantage by changing the colour of their coat to white to blend in with their surroundings. This camouflage helps protect them from predators and allows them to conserve energy.