Adaptations in Organisms

Adaptations are special features that allow a plant or animal to live in a particular place or habitat.

The living things adapt themselves so that they can:

  • successfully compete for food
  • defend themselves from attack by other organisms
  • find favourable conditions to reproduce
  • respond efficiently to the change in environment

Aquatic Adaptations in Plants

Aquatic plants are called hydrophytes (hydro: water; phyte: plant). For a life in water:

  • Hydrophytes have reduced root system as water is easily available.
  • Floating leaves have stomata only on their upper surface while the submerged ones have no stomata at all.
  • The leaves are thin and narrow. For example Hydrilla, or long, flat, ribbon shaped for example Vallisneria. These adaptations protect the plant body from any damage due to water currents.
  • The stem may be long, slender and spongy, to prevent them from getting carried away by water current. for example, lotus.
  • Flat leaves on surface plants are for floatation. The broad upper surface is coated with wax which acts as water repellant. For example: lotus, water lily.

Examples: water lily, Hydrilla, Vallisneria, Pistia, water hyacinth (Eichhornia).

Aquatic Adaptations in Animals

The animals that live in water show the following characteristics:

  1. Streamlined body (pointed at both ends) that reduces friction when the animal moves through the water.
  2. Smooth, almost hairless body helps aquatic mammals move through the water with little friction.
  3. Webbed feet in ducks, (formed from thin skin between the toes), work like paddles for swimming.
  4. Flattened tail that serve as oar.
  5. Fins of fish help to swim, steer and maintain balance. A whale has flippers for swimming.
  6. Long legs and necks in cranes keep the bodies of wading birds out of the water. The long neck helps the birds to reach the water, or below it, for food.
  7. Blubber of whale, a thick layer of fat or oil stored between the skin and muscles of the body, provides insulation.
  8. Eyes are positioned on top of the head which allows animals to hide in water and still detect predators or prey above the water.
  9. Transparent eyelids cover the eyes water of animals swimming underwater.
  10. Nostrils positioned near the top of the head allow animals to come to the surface to breathe in air. Nostrils close when the animal goes under the water. For example, whales, dolphins.
  11. Some fish have swim bladder which is filled with air to help maintain buoyancy.
  12. Fish and aquatic invertebrates like prawns have gills for respiration.

Terrestrial Adaptations in Plants

Terrestrial plants include mesophytes (meso: moderate) and xerophytes (xero: scarce water).

Mesophytic Adaptations

Mesophytes are terrestrial plants which are adapted to neither a particularly dry nor particularly wet environment. Mesophytes include the majority of terrestrial plants which have the following adaptations:

  • Mesophytes generally require a continuous water supply and have large, thin and broad leaves with a large number of stomata on the undersides of leaves.
  • The roots of mesophytes are well developed, branched and provided with a root cap.
  • The shoot system is well organised.

Xerophytic Adaptations

Xerophytes are desert plants, well adapted to high temperature and water shortages. They are adapted to store and conserve water. The adaptations that xerophytes may exhibit are:

  • Succulent leaves and stems to store water. for example, cacti.
  • They have few or no leaves which reduce transpiration.
  • Many desert trees and shrubs have thorns for protection from enemies.
  • Fewer stomata to reduce water loss.
  • Deep widespread root system caters to maximum water uptake.

Adaptations in Desert Animals

  • Most of the desert animals avoid being out in the sun during the day. Many desert mammals, reptiles, and amphibians live in burrows to escape the intense desert heat. They come out during the night when the temperatures are low.
  • Due to constant exposure to high temperatures, desert animals need to maintain their body temperatures at an optimum level for which some of them have developed long body parts that provide greater body surface to dissipate heat.
  • These animals have scaly skin, resistant to drying.
  • Camels have a hump to store fat.
  • A camel can drink very large amounts of water in one day or survive for a relatively long time without drinking any water. They can excrete concentrated urine when there is water scarcities and thus reduce loss of water.
  • Desert animals like reptiles have minimised loss of water by excreting urine in the form of insoluble uric acid. This ensures very little wastage of water.

Adaptations to survive in extreme cold and scarcity of water

  • The animals which live in cold climates (like polar bear) have very thick fur over the body to trap air and insulate it.
  • They also have a layer of stored fat under the skin to give additional insulation.
  • The body shape and size of many cold climate mammals is well adapted to the cold climate. They are round and bulky with short legs, ears and tail. These adaptations help to conserve heat.
  • Penguins have a thick layer of densely packed feathers to reduce heat loss. Its flippers and legs are also adapted to reduce heat loss.

Aerial Adaptations in Animals

Aerial animals include a small number of animals that are able to fly in air. These animals come to the trees or land or water for safety or shelter. These are called arboreal animals (which dwell on trees). They may walk or run on land or glide in air for a short while to land on the tree or ground. Flying squirrel, flying lizard, tree frogs, lemurs and monkeys belong to this group.

True aerial animals are birds and bats. These animals exhibit adaptations to balance themselves and stay in air, soaring or flying. These adaptations include:

  • Streamlined body to steer through the air.
  • Wings: Forelimbs are modified into wings to help them to fly.
  • Birds have wings that are covered with feathers which trap air to keep the body warm and help the bird to fly. Bats have an extension of the skin between fingers of forelimb which help them to fly.
  • Bones: Bones are hollow to make them light.
  • Flight muscles: Very strong flight muscles are attached from the body to the wings.