Adaptation is defined as the possession of the characteristics or traits or behaviour or structure or features that evolved over a period of time which enable an organism to survive and reproduce in response to changes in the environment or habitat. In other words, adaptation is the change in structure, function and behaviour of an organism in order to adjust or survive in its environment.
It is expected that every organism must adapt to its environment in order to survive. Plants and animals possess certain features which enable them to adapt to either aquatic or terrestrial habitats.
a) Adaptation of Animals to Aquatic Habitat
- Possession of streamlined body for easy movement in water, e.g. Tilapia fish and toad.
- Possession of fins for movement as in the case of fish and webbed toes as in toad.
- Possession of gills for gaseous exchange in fish and tadpoles.
- Possession of swim bladder for the purpose of buoyancy in water, e.g. Tilapia fish.
- Possession of tail for swimming, e.g. tadpoles.
- Possession of sticky undersurface for attachment to surfaces of objects, e.g. snails and flatworms.
- Possession of suckers or hairs for attachment to vegetation so as to avoid being swept away by water current, e.g. leeches.
b) Adaptation of Animals to Terrestrial Habitat
- Possession of powerful limbs for movement, e.g. mammals.
- Possession of lungs for gaseous exchange, e.g. mammals, birds, reptiles and amphibians.
- Possession of sweat glands for excretion and cooling, e.g. mammals.
- Possession of hairs as in mammals and that of feathers as in birds for body temperature regulation.
- Possession of skin as in mammals and cuticle by insects to protect and prevent drying up and injury.
c) Adaptation of Animals to Aboreal Habitat
- Possession of wings for flight, e.g. birds.
- Possession of hollow bones to make them light, e.g. birds.
- Possession of bright colour as well as camouflage, e.g. chameleon.
- Possession of powerful limbs, claws and tails for climbing and piercing, e.g. birds, monkeys and baboons.
- Possession of streamlined body for easy flight, e.g. birds.
- Possession of strong muscles and tendon to ease flight, e.g. birds.
- Feeding mainly on grains to provide energy required for flight, e.g. birds.
a) Adaptation of Plants to Aquatic Habitat
- Possession of waxy cuticles on leaves to prevent wetting, e.g. water lettuce
- Possession of long stem and flower stalk to expose the flowers and leaves, e.g. water lily.
- Possession of adventitious roots, e.g. water lettuce.
- Possession of air floats in the leaves and stems for buoyancy, e.g. water hyacinth.
- Possession of breathing roots for gaseous exchange, e.g. white mangrove.
- Possession of air spaces in the tissues for buoyancy, e.g. water lettuce.
Note: Plants that can live successfully in water are called hydrophytes.
b) Adaptation of Plants to Terrestrial Habitat
- Possession of extensive root system for anchorage and water absorption, e.g. mahogany.
- Possession of thick barks on the stems to protect internal tissues.
- Possession of numerous leaves to enhance better photosynthesis.
- Possession of succulent stems by desert plants to enable them store excess water.
- Possession of tiny and scanty leaves by desert plants to reduce water loss through transpiration.
- Possession of thick, waxy cuticles on leaves to prevent water loss through transpiration.
Note: Plants which can survive in extremely dry places are called xerophytes while plants that can survive in places which are not too dry or too wet are called mesophytes.
Special Adaptation of Some Organisms
a) Adaptation of Tilapia Fish for Movement
The Tilapia fish possesses certain features which adapt it for movement in water. These adaptive features are:
- Possession of fins for movement in water.
- Presence of streamlined body for easy movement.
- Possession of lateral line system for detection of vibration in water.
- Possession of powerful tail which is used for propelling the fish forward.
- The direction of the fins and scales backward to aid easy movement through water.
- Possession of large eyes without eyelids which enables it to see predators and preys easily.
- Possession of swim bladder which aids its buoyancy in water.
- The silvery-white colour of the body below and black above prevent it from being seen by enemies.
b) Adaptation of Birds for Flight
The birds possess certain features which adapt them to live in the air. These adaptive features are:
- Possession of light body weight to ease flight.
- Possession of feathers.
- Possession of wings for flight.
- Streamlined shape of the body to ease flight.
- Presence of hollow and light bones to make flight easy.
- Possession of oil gland which serves as water proof against wetness of feathers.
c) Adaptation of Chameleon
Chameleon and reptiles possess some features which enable them to live successfully in the forest. These adaptive features are:
- Possession of long, sticky tongue used for capturing preys.
- Possession of claws on its feet used for holding objects on which it walks.
- Possession of long tail which is also used for holding objects on which it walks.
- Ability to change the colour of the body in order to hide from its predators or enemies.
- Possession of powerful eyes which enable it to see preys and predators easily.
d) Adaptation of Endoparasites
Endoparasites like tapeworm possess certain features which enable them to adapt to the alimentary tract of human. These adaptive features are:
Adaptation of tapeworm Taenia solium to its habitat in the gut of human
- Tapeworm possesses hooks on the scolex for attachment to gut wall.
- It possesses suckers for attachment to gut wall.
- It has a ribbon-like, flat or tape-like body to fit into the gut of host.
- It has a fast rate of proliferation of proglottides to ensure survival of the organisms or ensure perpetuation of the species.
- Large surface area of its body allows absorption of food from the gut.
- It is a hermaphrodite and this allows successful sexual reproduction.
- The surface of its body is thin and permeable and allows rapid absorption of food.
- The wall of its body is resistant to digestion by host digestive enzymes.
- Mature proglottides loaded with eggs are detached and expelled with faeces of the host for dispersal.
e) Adaptation of Toad or Frog for Food, Protection and Movement
i) For Food
- It possesses special olfactory organ in the head for smelling/perceiving the odour of its food.
- It has the ability to draw eyes in so that they make bulges in the root of the mouth which help to prevent their prey from escaping and help in swallowing.
- The tongue is attached at the front of the mouth which can be rapidly extended to capture/trap prey.
- The tongue is long and sticky to help hold the prey.
- The tongue which is long helps in catching prey.
ii) For Protection
- The skin is slimy with mucous gland which makes the animal difficult to be caught by predators.
- Slimy fluid keeps the skin moist and prevents the skin from drying up.
- Toad has poison glands on the skin which is poisonous and distasteful to the predators.
- Brownish colour or cryptic colouration helps to blend with the colour of the surroundings and this prevents them from being noticed by enemies and predators.
- The colour can be altered to match the type of background.
iii) For Movement
- A toad has long hind limb with powerful muscles which enable it to hop or jump efficiently away from predators on land.
- Absence of tail facilitates hopping or jumping movement.
- Webbed hind limb can be used as paddle for efficient swimming in water.
- The stout and short nature of fore limb absorbs shock on landing and for propping up the front end of the body on landing after a jump or hop.
- It possesses streamlined body for easy movement and swimming.
Adaptation of Hydrophytes and Xerophytes
- Some hydrophytes lack/ have reduced roots/root hairs/root caps.
- Do not need firm anchorage in water/wetland.
- Presence of large air space parenchyma in roots/ leaves; provide support for bouyancy.
- Presence of hairs on the leaves; to prevent blockage of the stomata.
- Stomata pores occur only at the upper epidermis of the leaves to aid transpiration/loss of water;
- Numerous adventitious roots and root hairs; aid the absorption of water/mineral salts.
- Small size of the plant; for buoyancy/floating in water.
- Waxy upper surface of the leaf; to prevent clogging of the leaf by water;
- Long petiole/leaf stalk to support/ expose the broad lamina for photosynthesis.
- Long flower stalk/pedicel; to expose flower for pollination/ pollinating agents.
- Presence of breathing roots/ pneumatophores; for breathing/gaseous exchange.
- Possession of thick succulent leaves/stem; for storing water;
- Reduction of leaves to spines; to reduce water loss/rate of transpiration;
- Thick waxy cuticle on epidermis; to reduce water-loss/transpiration;
- Possession of long tap root system; to obtain water from great depth of soil;
- Presence of sunken stomata; to reduce water loss;
- Reduced number of stomata; to prevent excessive water loss;
- Possession of multiple epidermal layers; for water conservation/to reduce water loss.