Structural adaptations are special modification of structures which help organisms to survive better in their various environment. Some examples of structural adaptations are describe below.

Structural Adaptation for Obtaining Food

(a) By Toad

The toad possesses special olfactory organ in the head for perceiving the odour of its food.
It has the ability to draw eyes in so that they make bulges in the roof of the mouth which helps to prevent their prey from escaping or help in swallowing.
The tongue is attached to the front of the mouth which can easily be extended to capture or trap the prey.
The tongue is long and sticky to help hold the prey.
The tongue is long to help catch the prey.

(b) By Bird

Birds have structural adaptation (beaks) and feet which enable them to obtain food.

Carnivorous birds such as eagles have powerful, sharp, curved beaks for killing and tearing the flesh of their prey which include small birds, e.g. chicks, rats, toads and lizards.
They have sharp, strong, curved claws for catching, gripping and killing the prey.
Grain eating birds like the domestic fowls have short horny beaks for pecking at the grains. They also possess short, blunt and strong claws on their toes for scratching the soil.
The filter-feeding birds such as the water duck have beaks with serrated edges for sieving out food form water into the mouth. They also have webbed feet for swimming in the water.
Insect eaters, such as the wood peckers have long, slender, pointed beaks for picking insects from cracks and holes in the barks of trees.
Nectar-sucking birds, such as the humming bird and sunbird, have long-hollow beaks with tubular tongues for sucking nectar from flowers.
Fish eaters, such as the king fisher and heron, have long pointed beaks for killing and picking fish from the water and long feet for wading in the water.
Seed eaters such as the parrots have strong, short and hooked beaks for cracking hard seeds. Weaver birds on the other hand have short, strong and conical beaks for picking up small seeds.

(c) By Insects

Insects have structural adaptation for obtaining food in different ways based on the type of mouth parts.

Biting and chewing mouth parts: These are found in cockroaches, grasshoppers, termites,locusts, etc. they posses strong mandible and maxillae (mouth parts) which enable them to bite and chew plant parts.
Piercing and sucking mouth parts: These are found in aphids, mosquitoes, cotton stainers, mealy bugs, and capsids or mirids. These insects possess strong mouth parts called proboscis which enable them to pierce through the skin and suck blood, e.g. mosquitoes, while others use the proboscis to pierce through plants and suck liquid materials from plant tissues.
Sucking mouth parts: These are mainly found in butterflies and bees. They also possess long, coiled proboscis which enable them to suck nectars from the flowers of plants. Houseflies equally are sucking insects but they only suck liquid food using their mouth parts.
Boring mouthparts: These are found mainly in weevils and their larvae. They bore into plant parts and stored products and destroy the tissues as they feed on them.

(d) By insectivorous Plants

These are plants that feed on insects. They have special structural adaptive features for obtaining food.

1) Utriculata species: The utriculata species or bladderworts which live in ponds and slow-flowing streams are capable of catching insects and other small organisms by means of their bladders. Each bladder has sensitive hairs near a trap door which is normally closed. When an insect touches the sensitive hairs, the trap door suddenly opens inwards. Water carries the insect into the bladder as the trap door closes, and the insect is digested inside the bladder.

2) Drosera species: The drosera species or sundew has leaves which bear tentacles that secrete a clear, shiny and sticky liquid. This liquid attract insects. When an insect rests on the leaf, the leaf curls. As the insect struggles, it stimulates the tentacles which bend over and entangle it. Glands between the tentacles secrete enzymes which digest the insect. The products of digestion are later absorbed into the plants.

Structural adaptation for Protection and Defence

Some animals have structural adaptive features which enable them to protect and defend themselves against their enemies. Examples of such animals are:

Snakes: The snakes attack their enemies or defend themselves by biting and injecting their venom into the victim. They can also attack their enemies by spitting venom into their eyes.
Bees and wasps: Bees and wasps have stings for attacking their enemies or persons who intrude into their nests.
Birds: Birds have wings with strong muscles which enable them to fly away from predators.
Praying mantis: The praying mantis has sharp spines on the first pairs of legs which it uses to attack and kill insects on which it feeds. It also uses these legs to defend itself.
Scorpions: The scorpions use stings to attack their prey or defend themselves.

Adaptation for Protection by Toad

The toads produce distasteful or foul smelling chemicals which make their predators keep away from them.
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 which helps it to blend with the colour of the surrounding and this prevents them from being noticed by enemies or predators.
The colour can be altered to match the type of background.

Adaptation for Movement by Toad

A toad has long hind limb with powerful muscles which enable it to hop/jump effectively away from predators on land.
Its absence of tail facilitates hopping and jumping movement.
Webbed hind limbs can be used as paddle for efficient swimming in water.
The stout or short nature of its fore limbs absorb shock on landing and for propping up the front end of the body on landing after a jump/ hop.
It has streamlined body for easy movement and swimming.

Structural Adaptation to Attract Mates

Animals and plants possess special adaptive features which enable them to attract their mates for the purpose of reproduction. Examples of organisms and their structural adaptations to attract mates include.

Agama lizard: The adult male Agama lizard is brightly colourd. The male lizard displays itself under the sun, to attract female lizards for mating.
Toad: The males have nuptial pads on their thumbs with which they hold the females firmly during mating.
Birds: Male domestic fowls and peacocks are brightly coloured with beautiful feathers. The males make special feather displays to attract mating partners.
Flowering plants: The bright colouration of flowers attract insects which pollinate the flowers.

Adaptation of tapeworm to the gut of man

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.

Structural Adaptation to Regulate Body Temperature

Mammals and birds are known to regulate their body temperatures so that their respective body temperatures remain more or less constant. Constant body temperature is necessary for normal functioning of organs and tissues in the body.

Based on their ability to regulate their body temperature, vertebrates are grouped into two namely,

1) Homeothermic animals: Homeothermic animals have constant body temperature. In other words, the body temperature does not change with the temperature of the environment. Examples are found in mammals and birds.

2) Poikilothermic animals: Poikilothermic animals do not have constant body temperature; the body temperature changes with the temperature of the environment. Examples are found in fishes, amphibians and reptiles.

Structural adaptation of some animals to regulate body temperature are discussed below:

Adaptation by Mammals

1) The hair enclose a layer of still air around the body. This layer of air acts as an insulator which reduces heat loss from the body. The layer of air also reduces the rate at which sweat evaporate from the body. The slower the rate of sweat evaporation from the body, the slower the rate of heat loss from the body.

When the weather is cold, the hairs stand almost erect and enclose a thicker layer of air. When its is warm, the hairs stand at an angle and enclose a thinner layer of air. The hairs regulate the thickness of the layer of air above the skin and hence the rate of heat loss from the body.

2) The fat layer under the skin is a poor conductor of heart, and this reduces heat loss from the body.

3) The sweat glands in the skin make it possible for sweat to be produced. Evaporation of the sweat from the skin brings about heat loss.

4) The skin also has a large surface area for heat loss through radiation

Adaptation by Birds

Feather on the skin enclose air which forms an insulator around the bird. This insulator reduces heat loss form the body.
The subcutaneous fat in the bird forms layer of insulation which reduces heat loss from the body.
Regular flight by birds help to generate heat which keep the body temperature fairly constant.

Structural Adaptation for Water Conservation

Some plants and animals have adaptive features which enable them to conserve water. Plants which do not have access to sufficient water are called xerophytes.

Adaptation by Plants

Plants have well developed root systems which provide large surface area for water absorption.
They posses chlorophillous stems which photosynthesize.
Some plants have swollen stems or leaves that act as storage organs.
Some plants have thick or waxy cuticles which reduce the rate of transpiration.
Most plant have thick bark or cork which resist temperature or transpiration.
Some plants have sunken stomata to reduce transpiration rate.
There is reduced number of stomata to reduce transpiration rate.
Some plants have small or needle-like leaves to reduce transpiration.
Some plants have drought resistant protoplasm which can tolerate high loss of water without being damaged.
Some plants have surface roots to enable them absorb maximum moisture.
Some plants possess rolling or folding leaves which reduce transpiration.

Adaptation by Animals

Some animals, e.g. Agama lizard, snakes, etc possess scales on the skin which reduce water loss from the body.
Some animals like land snail possess shell which helps them to reduce evaporation of water from the body.
Some animals like cockroach and grasshopper possess exoskeleton made of chitin which help them to reduce water loss from the body.
Some animals like pigeon possess feather on the skin which help them to reduce water evaporation from the skin.
Other animals like sheep and cattle have hairs on their skin which help them to reduce water loss form the skin.