Chapter: 08. Adaptation
Learning Outcomes
Children will be able to:
define adaptation and habitat recall the names of plants and animals, and their adaptations studied in earlier classes record the adaptations shown by plants and animals living in desert/ aquatic conditions prepare a list of plants and animals occurring in different habitats with their common names and adaptations
HABITAT
The place where an organism, i.e., plant or animal lives is called its habitat or natural habitat. Different kinds of plants grow naturally in different areas. Animals also tend to select their most favourable areas and prefer to live there.
Examples of Habitats:
Aquatic habitat: Fish and ducks live in water, as do water hyacinth, water chestnut, and lotus plants. Terrestrial habitat: Lions, tigers, deer, and elephants are found in forests, while cows and buffaloes can be seen around us. Aerial habitat: Sparrows, crows, butterflies, and mosquitoes fly in the air. Arboreal habitat: Squirrels and monkeys prefer to live on trees. Desert habitat: Cactus grows in deserts, and camels are most comfortable in deserts. Why Organisms need a Habitat
An organism’s natural habitat provides everything it needs to survive, such as:
shelter
To animals, it also provides: a safe place to keep eggs and young ones protected. a place to hide from predators. an escape from danger by blending with the surroundings. Features of a Habitat
A habitat has the following two main components:
Abiotic or Physical Components: These are the physical features of the habitat. They include air, water (humidity), temperature, light, soil, rock, etc. Biotic or Living Components: Plants, animals, and microbes are the living components of a habitat.
Types of Habitats
Broadly, three types of habitats can be identified: aquatic, terrestrial, and aerial habitats.
1. Aquatic Habitat
Aquatic habitat includes all waterbodies where life can exist.
Freshwater habitats: Rivers, streams, lakes, and ponds. Marine habitats: Brackish water, estuaries, bays, seas, and oceans. Plants living in water or aquatic habitat are called hydrophytes. They are either fixed, submerged, or floating and have adapted accordingly. Aquatic animals are adapted for swimming or floating.
2. Terrestrial Habitat
Based on the topography (surface features) of land, terrestrial habitat may be:
Forest and grassland habitats Land plants which need a moderate amount of water are called mesophytes. Plants growing in deserts are called xerophytes. Examples include cacti, succulents, babool, and acacia. Desert animals include camels, desert foxes, kangaroo rats, and lizards.
3. Aerial Habitat
Aerial habitat is occupied by insects, birds, and bats, which have wings to fly. They are called aerial creatures. Activity 1: To study a pond habitat
Aim: To study a pond habitat. Procedure: A teacher arranges for a trip to a nearby pond. Students observe the animals and plants in the pond water and on the land nearby. They make a list of plants and animals seen there. Students study the main features of water animals like fish and frog, and water plants like Hydrilla and water hyacinth, drawing diagrams and summarizing observations.
ADAPTATIONS
The process of change or adjustment by which an organism becomes better suited to its environment is called adaptation. Adaptation also refers to the ability of living things to adjust to different conditions within their environment. The special features that enable plants and animals to be successful in a particular environment are called adaptive features or adaptive traits.
To survive and reproduce, all living organisms need to adapt to their environment. Adaptations do not appear suddenly in a day or two; they take thousands of years. Organisms that fail to adapt to their environmental changes perish. This means only those organisms survive that are adapted to changes in their environment. Darwin gave the concept of “Struggle for existence” and “Survival of the fittest.” Adaptations are responsible for the diversity of organisms.
Know Your Scientist: Charles Robert Darwin
Charles Robert Darwin (1809-1882) was an English naturalist, geologist, and biologist. He is famous for his Theory of Evolution by Natural Selection, which was published in the book Origin of Species in 1859. He is credited for providing insight into the diversity of life on Earth and the origin and adaptations seen in living organisms. He defined evolution as ‘descent with modifications’ and ‘survival of the fittest’.
Aquatic Adaptations
Since life originated in the ocean, and early forms were aquatic, today we still find the maximum variety of aquatic plants and animals occupying this habitat. Let us discuss adaptations in aquatic plants and animals.
Adaptations in Aquatic Plants
Aquatic plants have special adaptations that help them to survive in water. They are grouped into floating, submerged, and fixed aquatic plants.
Adaptations in Floating Aquatic Plants
Size and Buoyancy: Small-sized, very light, and spongy. Air Spaces: Have air-filled spaces between their cells, which help them float in water. Roots: Do not reach the soil on the waterbed and float freely on the surface of water, hence called free-floating plants. Leaves: Have a waxy coating to prevent rotting in water. Examples: Water lettuce (Pistia), duckweed, and water hyacinth (Eichhornia). Water hyacinth (Eichhornia): A floating aquatic flowering plant. Its roots are poorly developed and free-floating to provide buoyancy. The petiole is bulbous, and the leaf-blade is thick and spongy.
Fig. 8.1 Free-floating aquatic plants
Fig. 8.2 Water hyacinth Adaptations in Submerged Aquatic Plants
Growth: Grow completely underwater. Leaves: Long and tapered, offering the least resistance to flowing water. Stomata: Have no stomata. Gas exchange for breathing and photosynthesis takes place through the surface of the plant body. Gas Exchange: Use carbon dioxide dissolved in water for photosynthesis and release oxygen into water. Examples: Vallisneria (tape grass) and Hydrilla. Vallisneria: Roots are poorly developed. Leaves are long and ribbon-like, arising in clusters and swaying with water current. Used in aquariums. Hydrilla: Has a long, slender, and branching stem. Leaves are strap-like and pointed with claw-like serrations along the margin, arranged in whorls.
Fig. 8.3 Floating, submerged and fixed aquatic plants
Vallisneria Hydrilla
Fig. 8.4 Submerged aquatic plants Adaptations in Fixed Aquatic Plants
Stems: Hollow and lightweight stems help them float. Leaves: Broad and have a waxy coating to prevent rotting in water. Stomata: Present only on the upper surface of the leaves. Roots: Long roots, rooted to the soil on the waterbed, with the rest of their part floating on the surface of water. Therefore, also called fixed-floating plants. Examples: Water lily and Lotus. Water lily (Nilofar): A fixed-floating plant. Roots fix the plant to the bottom of the pond or lake. Stem is short and buried in the mud. Leaves are large, notched, and float on the water surface, coated with wax. Petiole is very long and filled with air. Lotus (Nelumbo): Also a fixed-floating plant, similar to water lily except its leaves are circular and without a notch.
Water lily
Fig. 8.5 Fixed-floating aquatic plants Adaptations in Aquatic Animals
Actively swimming animals include fishes, frogs, crocodiles, whales, and seals. Their body is adapted for swimming.
Adaptations in Fish
Fishes are adapted for aquatic mode of life with the following adaptations:
Streamlined Body Shape: Body is spindle-shaped or boat-shaped, tapering at both ends. This shape offers least resistance while swimming. Head and body are compressed, and snout is subconical. Paired fins: Two pairs - one pair of pectoral fins and one pair of pelvic fins. Median fins: Three in number - caudal fin, dorsal fin, and anal fin. (i) Caudal fin and tail: Push the body forward, function like a rudder, and help in changing direction during swimming. (ii) Pectoral fins: Act as balancers. (iii) Dorsal fin: Acts as a stabilizer. Scales: Entire body surface is covered with scales and slime, protecting the body from decay in water.
Fig. 8.6 A fish showing aquatic adaptations Air bladder: Some fish have an air-filled bladder, providing buoyancy. By increasing or decreasing the volume of gas, the fish can rise or sink. Gills: Fish have gills for gas exchange, located behind the head in the opercular chamber. Gills are formed of gill filaments and a network of blood capillaries. As water flows through the opercular chamber and passes over the gills, oxygen from water enters the gill filaments, and CO2 comes out into the water.
Fig. 8.7 Gills in a fish Lateral-line system: Fishes possess sense organs in the lateral line that can detect changes in the pressure of water currents.
Desert Adaptations
Desert climate is dry and hot in the daytime but is cold at night. There is excessive shortage of water in the desert. Because of this, both plants and animals are scarce and specially modified to survive in such adverse environmental conditions, called xeric climate.
Adaptations in Desert Plants
Plants growing in deserts are called xerophytes, and their adaptations are xeric adaptations. Since desert plants live in an extremely dry environment, they show adaptations to conserve and store water and to prevent loss of water.
Root: Desert plants have long roots to obtain water from deeper layers of soil. Stem: It is spongy and succulent, adapted to store water. Stem takes over the function of leaves, becoming green for photosynthesis. Stem has a thick and waxy coating to prevent loss of water by evaporation. Leaves: The leaves in desert plants are reduced to spines to prevent loss of water from the surface. Spines also protect the plant against herbivores. Examples: Different types of cacti and some bushes like kikar or babool. Desert Adaptations in Opuntia
It is the most common cactus.
Stem: Flat, spongy, and succulent to store water, and becomes green to carry out photosynthesis. Leaves: Reduced to spines to prevent water loss. Waxy coating: On stem reduces water loss. Roots: Long roots reach deep into the ground to obtain water.
Fig. 8.8 Opuntia Desert Adaptations in Kikar (Babool) Tree
Bark: Reddish-brown or blackish and rough to prevent evaporation of water. Leaves: Light green, and the leaf blade is divided into leaflets. Branches: Bear long and strong thorns.
Fig. 8.9 Kikar (babool) tree
Adaptations in Desert Animals
Desert animals have to protect themselves from the scorching heat and need to conserve water. Therefore, they have the following adaptations:
Heat Avoidance: To avoid heat, most desert animals remain inactive inside their burrows during daytime. They come out only at night-time. Such animals that are active at night are called nocturnal. The skin of desert animals is without sweat glands. Desert animals excrete concentrated urine. Examples: Camels, kangaroo rats, coyotes, cottontail rabbits, rattlesnakes, white-tailed antelopes, squirrels, barn owls, etc. Desert Adaptations in Camel
Camel is so well-adapted to desert conditions that it is called the “ship of the desert.” It shows the following adaptations to desert conditions:
Padded Feet: Limbs have large pads, which help it walk on hot and slippery sand without sinking. Hump for Storing Fat: Has a hump that stores food in the form of fat. Therefore, a camel can survive without food for long. Storage of Water: A camel drinks a large quantity of water (up to 40 litres at one time) and stores it in the water cells of the stomach wall. Flaps on Nostrils: Nostrils have flaps that close during a duststorm.
Fig. 8.10 A camel showing adaptations to desert conditions Long Eyelashes: Eyes have long eyelashes, which protect eyes from dust and sand during a duststorm. Heat Tolerance: A camel can adjust its body temperature according to the surrounding air. Absence of Sweat Glands: Skin is without sweat glands to prevent loss of water by perspiration.
Mountain Adaptations
Climate of mountain habitat is very harsh with features like:
Very high winds and wind pressure Thin atmosphere with low concentration of carbon dioxide and oxygen High amount of ultraviolet (UV) radiation Thin rocky soil that is poor in nutrients Scarcity of food especially during long chilly winter Therefore, mountain plants and animals are adapted to protect themselves against cold and snow.
Adaptations in Mountain Plants
Shape: Usually tall and straight trees, having cone-shaped appearance, hence called conifers. Conical shape: Helps them bear harsh wind and prevents them from being knocked down. Reproductive structures: Bear cones instead of flowers. Evergreen: To maximize photosynthesis. Leaves: Have a waxy coating and are needle-like to prevent water loss and help snow to slide down. Branches: Droop downward to shed off excess snow. Examples: Pine, Deodar, Fir, Juniper, etc. Adaptations in Pine Tree
Evergreen: Can photosynthesise whenever there is sufficient light. Cone-shaped: With flexible branches directed downward to cope with heavy snowfall. Leaves: Needle-shaped for protection against snow. Trunk: Has thick bark to protect against the cold. Cones: Bears cones (not flowers) that protect seeds during harsh winter.
Fig. 8.11 A pine tree and a twig with needles and cones Adaptations in Fir Tree
Evergreen: Tall evergreen tree. Trunk: Covered with thick bark to protect it against drought, extreme cold, and excessive heat from jungle fire. Leaves: Needle-shaped and have wax-covered bands of stomata. Color: Leaves are mostly dull-coloured. Cones: Cylindrical and produce winged seeds.
Fig. 8.12 A fir tree
Adaptations in Mountain Animals
Fur: Have thick and fluffy fur on the whole body, including feet and toes. Hooves: Strong hooves for running on rocky slopes and jumping from rock to rock. Diet: Eat mountain grasses, mosses, and lichens. Blood: Mountain air is thin and has low oxygen content. Therefore, mammals here have more red blood corpuscles to provide sufficient oxygen to the body. Hibernation: Some animals hibernate (go for long winter sleep) to conserve energy for winter. Examples: Sheep, mountain goat, bear, snow leopard, mountain lion, antelope, musk deer, and Himalayan wild yak.
Fig. 8.13 Mountain animals Mountain Adaptations in Mountain Goat
Woolly Coat: Two layers of woolly coat protect them against chilly winter and high-speed winds. Camouflage: White woolly coat helps them protect from predators by blending with their white snowy surroundings. Hoofs: Cloven or cleft hoofs in their feet are divided into two toes, helping them climb steep, rocky slopes. Feet Pads: Tips of their feet have small pad-like structures, helping them move on mountain surface without slipping. Muscles: Strong shoulder and neck muscles help them propel up steep slopes.
Aerial Adaptations
Birds, bats, and insects are true aerial creatures. Birds are the masters of aerial life.
Adaptations for Flight in Birds: Aerial Adaptations in Pigeon
Various aerial adaptations in birds are as follows:
Wings: Forelimbs are modified into wings, which are powerful organs of flight. Body Shape: Birds have a streamlined body (head pointed in front, narrow tail at the end). Such a shape minimizes resistance against air during flight. Tail: Tail feathers help the tail act as a balancing and steering organ, helping change direction during flight. Tail acts as a rudder and as a brake to check speed. Feathers: Body of birds is covered with feathers. They keep the body warm and light. Feathers on the forelimbs help in flying, and on the tail help in steering and as a rudder. Flight Muscles: The breast muscles are much enlarged and control the movement of wings during flight. Air Sacs: Extensions of the lungs, providing additional air to the lungs and hence more oxygen. Pneumatic Bones: Bones in birds are hollow and have air cavities, making the body light for flight. Bones are fused to form a rigid but light frame for the attachment of flight muscles. Beak: Jaws are modified into a toothless horny beak. This reduces body weight. Beak substitutes for hands for picking up things.
Fig. 8.14 Aerial adaptations in birds Activity 2: To study aerial modifications in birds
Aim: To study aerial modifications in birds. Procedure: Watch birds in your neighbourhood. Note their body structure and correlate them to aerial life. Aerial Adaptations in Plant Seeds
No plants are aerial. It is only the seeds and fruits of certain plants that are dispersed to distant places by air. For dispersal by air, seeds of plants show the following characteristics:
Size and Weight: Seeds are small, dry, and light in weight (e.g., grasses, orchids). Appendages: Seeds of some plants have silky hair or wings so that they can be easily carried away by the wind. Hairy seeds: Madar, Oak, Dandelion, and Cotton. Winged seeds: Maple and Drumstick. They act as parachutes and help seeds float in the air for long distances. 
Self Study
Charles Robert Darwin (1809-1882) was an English naturalist, geologist, and biologist. He is famous for his Theory of Evolution by Natural Selection, which was published in the book Origin of Species in 1859. He is credited for providing insight into the diversity of life on Earth and the origin and adaptations seen in living organisms. He defined evolution as ‘descent with modifications’ and ‘survival of the fittest’.
Fig. 8.1 Free-floating aquatic plants
Fig. 8.2 Water hyacinth
Fig. 8.3 Floating, submerged and fixed aquatic plants
Vallisneria Hydrilla
Fig. 8.4 Submerged aquatic plants
Water lily
Fig. 8.5 Fixed-floating aquatic plants
