Ecological Adaptations – Adaptation and Habitats in Plants and Animals

The Biology Topics of ecology involve studying the relationships between living organisms and their environment.

Adaptation of Plants and Animals to their Habitat – Introduction, Types & Importance

Adaptation is a quality of the organism (morphological, physiological, behavioural) that enables the organism to survive and reproduce in its habitats. Adaptations allow organisms to live in different types of habitats.

Types of Adaptation

Adaptations are of two types Phenotypic and Genotypic.

1. Phenotypic Adaptations
These are favourable changes in morphology and physiology that develop in response to changes in environmental conditions. They disappear when the environmental conditions become normal.

• Phenotypic plasticity: The ability of a genetically similar population to undergo phenotypic changes in response to variations in the environment, is called phenotypic plasticity.
• Ecads or ecophenes The phenotype variants formed in a population (homogeneous genetic stock) due to changes in environment are called ecads or ecophenes.

Variations appear in erectness, size of internodes, size and b number of leaves, etc. Euphorbia hirta growing in open land is prostrate and profusely branched. The same plant is small-leaved, compact, and cushioned when grows in the footpath.

2. Genotypic Adaptations
These are genetically adapted local populations that evolve from a species having a wide range of distribution. The different ecotypes of a species are morphologically, physiologically, and developmentally adapted under different habitats and environmental conditions. Although ecotypes differ genetically, they are interfertile. This is clear from the occurrence of intermediate forms in the transition regions between two ecotypes. The intermediate forms are called ecocline.

Plant Adaptations: Introduction and Ecological Classification of Plants

A. Adaptation to Light Regime

1. Heliophytes:
Plants growing in bright light, are called Heliophytes or Sun plants. Sun plants are adapted to higher temperature optima for photosynthesis.

The rate of respiration is also high. The important characteristics of heliophytes are

• Shorter and thicker internodes.
• Smaller and thicker leaves.
• Thick cuticle, often sunken stomata.
• Leaves are pale green in colour with shining surfaces or hairy growth.
• Palisade parenchyma is well developed.
• Here leaf orientation is erect.
• Cells are smaller with smaller intercellular spaces.
• Mechanical and conducting tissues are more developed.
• The Root system is extensive. There is a good amount of flowering and fruiting.
• In the case of sun plants the Rubisco activity and the quantity of soluble protein content is high.

2. Sciophytes:
Sciophytes grow well under shade. They are adapted to the low intensity of light. They have low photosynthetic, respiratory, and metabolic activities. Perfect shade plants are ferns and several herbs growing on the forest floor under the canopy of trees and shrubs. Important characteristics of shade plants are

• Stems are soft, and slender with large internodes.
• Leaves are thin and large.
• Leaves have a bright green colour.
• Leaf cells tire large. Here leaf orientation is horizontal.
• The cuticle is thin.
• Stomata are not sunken.
• Palisade parenchyma is less developed.
• Mechanical and conducting tissues are less developed.
• In the case of shade plants, the Rubisco activity and the quantity of soluble protein content are slightly slower.
• Roots are fewer and smaller.
• Vegetative growth is more as compared to flowering and fruiting.

Difference between Sun and Shade Plants:

Sun Plants	Shade Plants
1. These plants have thicker stems with shorter internodes.	1. These plants have narrower stems with longer internodes.
2. In these plants, leaf cells are smaller with smaller chloroplasts.	2. In these plants, leaf cells are larger with broader chloroplast.
3. Here the epidermis is thick-walled with a thicker cuticle.	3. Here the epidermis is thin-walled with a thinner cuticle.
4. In these plants, osmotic pressure is higher.	4. In these plants, osmotic pressure is lower.
5. Here palisade parenchyma is well developed.	5. Here palisade parenchyma is less developed.

B. Adaptation in Aquatic Plants (Hydrophytes)

Hydrophytes are plants adapted for growing in water, water-logged soil, or on substrata with an abundance of water. Hydrophytes are of four types-

• Submerged hydrophytes: The plants live inside the water, either attached to the substratum or suspended in water, e.g., Hydrilla, Vallisneria.
• Floating hydrophytes: They float freely on the surface of the water and have no contact with the bottom, e.g., Lemna, Wolffia, Eichhornia, Pistia, Trapa, Azolla, Salvinia, etc.
• Rooted hydrophytes with floating leaves: These have roots fixed in mud but the leaves float on the surface of water, e.g., Nelumbo, Nymphaea, Victoria, etc.
• Emergent hydrophytes: In these plants, the root is fixed in the soil and the stem remains partly or completely exposed to air, e.g., Ranunculus, Scirpus, Sagittaria, etc.

Morphological Adaptations:

• Roots are poorly developed.
• Root hairs are absent or poorly developed,
• A root cap is absent in hydrophytes, although some floating hydrophytes have root pockets or root sheaths in place of the root cap. They function as balancers (Pistia, Lemna).
• The stem is soft, flexible, and spongy.
• A large amount of mucilage is present on submerged leaves, their function is to prevent decay underwater.
• The submerged leaves are either long ribbon-like (Vallisneria) or finely segmented (Utricularia). These give little resistance to the water waves.
• The floating leaves are generally large, broad, and thick with a waxy coating on their upper surface.
• Multiplication by vegetative means, flowers, and seeds are poorly developed.

Anatomical Adaptations:

• Plants possess aerenchyma containing air cavities. Gases in air cavities serve for photosynthetic and respiratory functions. Gases also give buoyancy to the plants.
• The epidermis in submerged parts is without a cuticle, here it is meant for the absorption of water and nutrients.
• Mechanical tissue is reduced.
• The conducting tissue (xylem) is reduced.
• Roots are absent or poorly developed.
• Stomata are either absent or present on the upper surface of leaves.
• Mesophyll tissue is not differentiated into palisade and spongy parenchyma.
• Chlorophyll is present in almost all parts of plants.

Physiological Adaptation:

• The hydrophytes have low osmotic pressure.
• The submerged parts secret mucilage to protect the plants against friction, desiccation, and decaying effects.
• The uptake of minerals and gaseous exchange takes place through the general surface.
• The rate of transpiration is low, most of the hydrophytes possess hydathodes to excrete water.

C. Adaptation in Xerophytes

The plants that grow in dry or xeric conditions or where the availability of water is negligible, are known as xerophytes.
1. Ephemeral or Drought Escapers:
These plants complete their life cycle in a very short period only during rains. They live only for a period of 4-6 weeks, e.g., Tribulus terrestris, Solanum xanthocarpum.

2. Annuals or Drought Evaders:
The plants live for about 3 or 4 months, a few weeks longer than the rains. The size remains small, leaves have thick waxy, hairy coating with or without prickles to reduce transpiration, e.g., Echinops echinatus, Solanum surattense.

3. Succulents or Drought Resisting:
These xerophytes store water in their roots, stems, or leaves for drought periods. Succulents are stored in stems (Opuntia, Cacti), leaves (Aloe, Agave), and roots (Asparagus sp.).

4. Nonsucculents or Drought Enduring:
These are true xerophytes that actually endure drought conditions. They suffer from both external and internal dryness, e.g., Acacia, Ziziphus, Calotropis, etc.

Morphological Adaptations:

• The root system is extensively developed with abundant root hairs. Roots may go upto 30 meters deep in search of water.
• The stem is stunted, hard, and woody with thick bark.
• In some cases stem is modified into a flattened leaf-like structure, called phylloclade, e.g., Opuntia.
• Leaves are generally small and may be leathery or slender and hard. Sometimes leaves are modified into spines to reduce water loss.
• In some plants, petiole is modified into leaf leaf-like structure, called phyllode, e.g., Acacia, Parkinsonia.
• Leaf surfaces are shining and glazed so as to reflect light.
• In some plants, like Asparagus, and Ruscus, axillary branches are modified into leaf-like structures called cladode.

Anatomical Adaptations:

• The epidermal cells are covered by a thick layer of cuticle in all xerophytes. The epidermis may have lignification and deposition of wax in addition to cutin.
• Stomata are generally present on the lower surface of the leaf and are sunken, hairs are often present in the stomatal pits.
• The leaves of many grasses possess larger motor cells which help in the rolling of leaves so as to reduce transpiration, e.g., Poa, Agropyron.
• Mesophyll cells are differentiated into palisade and spongy parenchyma.
• Latex, gum, and resin are found in many xerophytic plants. It helps in retaining water.
• Vascular tissue is well-developed in xerophytes.
• Mechanical tissue is very well developed.
• Secondary growth in dicots is very common. Cork cambium is also well developed to form an outer bark, which cuts the rate of transpiration.

Physiological Adaptation:

• Many grasses possess the C4 pathway of photosynthesis. They use less water to achieve higher rates of photosynthesis, particularly at higher temperatures.
• True xerophytes usually possess heat shock proteins, called chaperones, which provide them with physiological adaptations to higher temperatures.
• Many xerophytes accumulate proline (an amino acid) in the cells to maintain osmotic and water potential in their leaves.
• In many of the succulents, stomata remain closed during the daytime (photoactive stomata) and perform the CAM pathway of photosynthesis.
• The osmotic pressure of cells is maintained high and the rate of transpiration is reduced.

Drought Avoiding Plants:
The life cycle of these plants is very short and these ephemerals complete their life cycle before summer comes, e.g., Argemone.

D. Adaptation in Halophytes

The plants which are adapted to grow in saline habitats are called halophytes. The saline habitats have high concentrations of salts in soil or water. They occur in tidal marshes and coastal dunes, mangroves, and saline soils.

Mangrove Plants:
Halophytes that grow in marshy conditions of tropical deltas and along ocean edges, e.g., Rhizophora, Avicennia, etc. Sundarban is an ideal example of a mangrove forest. The important adaptations of halophytes are as follows.

• Plants produce a large number of stilt roots from the main stem and the branches.
• Many plants produce pneumatophores or respiratory roots in large numbers all around the trunk of the tree. Pneumatophores develop from underground roots and project beyond the water level in the air. They are provided with numerous pores, known as pneumatodes through which the exchange of gases for respiration takes place.
• Some mangrove plants possess salt-secreting glands over their leaves, e.g., Avicennia.
• Mangrove plants do not disperse their mature seed. Seeds germinate inside the fruits while the latter are attached to the plant. A sufficiently grown seedling falls down in the swamp in such a way that epicotyl remains above the level of muddy soil, e.g., Rhizophora, Avicennia. This type of germination is called Viviparous germination.
• The epidermis is thick-walled and strongly cutinized. The mesophyll is almost devoid of intercellular spaces and the palisade tissue is the main chlorenchyma (Sonneratia). Mucilage cells also occur. Stomata are sunken.
• Mangrove plants have high concentrations of organic solutes like proline and sorbitol. They are meant to raise osmotic concentration.

Mesophytes:
These are land plants that grow under average conditions of temperature and moisture. They are supposed to be intermediate between hydrophytes and xerophytes.

• In mesophytes, the root system is well developed with the tap root and its branches in dicotyledones and a cluster of fibrous roots in monocotyledones. Root hairs are abundant for the absorption of water from the soil.
• The stem is solid, erect, and normally branched. All the different kinds of tissue, particularly the mechanical and conducting tissues, have reached their full development in mesophytes.
• The leaves and branches are provided with a cuticle. Stomata are relatively uniform in structure and the guard cells show a maximum capacity for movement.

Different Adaptation of Plants:

Adaptated Plant Groups Name	Example
1. Hydrophyte (Aquatic adaptation)	Nelumbo sp., Nymphaea sp.
2. Xerophyte (Desert adaptation)	Calotropis sp., Opuntia sp.
3. Halophyte	Sagittaria sp.
4. Mesophyte	Mango, Jackfruit
5. Oxylophyte	Oxalis sp.
6. Psychrophyte	Rhododendron
7. Lithophyte	Utricularia
8. Psammophyte	Okenia hypogaea

Types of Animal Adaptation with Examples

Like plants, animals also adapt to different environmental conditions to survive and flourish. Animals have also developed a number of techniques in their bodies to meet the challenges of the environment in which they live. Animals have adaptations to

• Particular feeding habits like carnivory and herbivory.
• Protection from predators.
• Camouflage for easy predation.
• Structural and behavioural adaptation to attract mate.
• Physiological and behavioural adaptation to environmental variations and stress conditions, e.g., migration, hibernation, aestivation, etc.

1. Migration

It is a two-way movement of an animal group to other places for food, climate, and other reasons. Migration is of three types – daily, seasonal, and periodic. The distance may be short or long. Long-distance migration is observed on Arctic Terns. They nest close to the North Pole in summer, fly south to Antarctica in autumn, and return North Pole again in each spring. Short-distance migration is observed in whales. Migration occurs in locusts when their number increases beyond the feeding capacity of the homeland. Large populations migrate in search of food in various directions.

2. Camouflage

Some animals have the capacity to blend with the surroundings or background. It is called camouflage. It is a common adaptation in animals to remain unnoticed for protection or aggression, e.g., many insects, reptiles, and mammals. It is difficult to distinguish leaf-like grasshoppers or Praying Mantis from the surrounding foliage. Similarly, stick insects, leaf insects and dead leaf butterflies can not be noticed unless and until they show movement. Desert animals like lizards, camels, and lions are sand coloured and hardly visible against their background unless they move. The chameleon can change its colour according to its background. Camouflage is protective of animals that are preyed upon by others. It is advantageous in predation for predators like Preying Mantis as they remain unnoticed till the prey comes within their striking range.

3. Mimicry

The phenomenon of producing similarities with nonliving objects by which a living animal or plant species may conceal itself in the surroundings or obtain protection from enemies is known as mimicry. Mimicry may be achieved either by altering the physical appearance or by changing behaviour. The living form which undergoes mimicry is known as mimetic and the object with which similarity is established is known as model.

Classification of Mimicry:
Mimicry may be categorized into three types namely, Protective mimicry, Aggressive mimicry, and Conscious mimicry.

1. Protective Mimicry:
To get protection from the predator animals, the mimicry shown by the animals is known as protective mimicry. This may again be of two types concealing mimicry and warning mimicry.

(a) Concealing mimicry:
Sometimes the animals try to conceal themselves in the surroundings so as to evade getting noticed by the enemies. In this case, the mimetic organism develops a similarity with an inanimate object either in physical appearance or in colour and because of this, it becomes difficult to locate the mimetic animal.
Examples:

• Cryptolithode (a white-coloured crab) takes the shape of pebbles in the seashore and therefore they are difficult to be recognized.
• A type of butterfly named Papilio machaon produces a pupa that when sticks to a tree branch appears green. Again when it attaches to the tree trunk or stone it becomes grey in colour.
• The structure of the body and colour of the butterfly Kallima paralekta becomes such that it appears to be a dry leaf.
• The larva of the geometric moth, Selenia tetralunaria when remains attached to the branch of the tree appears to be a twig.
• The body shape and colour of the insect Phyllium appear like a fungus-infected green leaf.
• The body structure of a stick insect is like that of a dry twig of a plant.
• Arisaema is known as the Snake plant. In this plant, the exterior part of the inflorescence looks like a greenish-violet colour with the appearance of a cobra snake.

(b) Warning mimicry:
With the help of this mimicry, an animal may get protection from an enemy. In this case mimetic animal is usually non-poisonous, and this animal may take the shape of the model organism which is harmful or poisonous. In this case, both the body shape and colour of the organism may be altered. As a result of this, the enemies take the mimetic animal as harmful or poisonous. The Batesian and Mullerian mimicry are the two different types of warning mimicry.
Examples:

• When an animal species is comparatively unprotected but appears as edible they may mimic one protected and unpalatable organism, the mimicry is termed as Batesian mimicry. The mimicry of butterfly Pieris mimics tasteless Helicornius and gets protection from the predator animal.
• In the case of Mullerian mimicry, two or more unpalatable species of animal mimic each other. The Ctenuchid moth shows Mullerian mimicry by mimicking a type of wasp. In this case mimetic animals and models both get privilege.

Besides Batesian and Mullerian mimicry, there are certain examples of other warning mimicry.

• Some non-poisonous coral snakes of the family Colubridae take the colour of the snakes of the poisonous Elaphidae family.
• Some spiders live together with ants and take the colour ants.
• Sesia crabroniformis, a type of moth mimics the dreaded wasp, Vespa crabro.

2. Aggressive mimicry:
Usually, the predator animals for capturing the prey exhibit this type of mimicry. The mimicry in this case helps the mimetic animal in attack instead of defence. The mimicry of this type is termed as aggressive mimicry. Aggressive mimicry may be of two types such as concealling mimicry and alluring mimicry.

• Concealing mimicry: In this case, the predator animal remains in ‘such a disguise that the prey cannot recognize in the environment. As a result, the prey may easily be. caught by the predator animal. e.g., some spiders take the colour and shape of the flower when it remains within the flower. This helps the spider to conceal itself in the environment.
• Alluring mimicry: In this case, the predator animal remains in such a disguise that the prey becomes attracted to it. The American horned toad Ceratophrys sits quietly and rotates one finger over the head. Because of this the prey animals become attracted and go towards the toad. The deep sea angler fish, Lophius for capturing prey may exhibit alluring mimicry.

3. Conscious mimicry:
Some animals pretend as dead when they realize the possibility of any danger. Such mimicry is known as conscious mimicry. American opossum, Didelphis, stays like a dead animal when it senses any danger.

4. Colouration

In the living world, there is the existence of various colours. Like mimicry, animals may achieve adaptation through colouration also. However, in many cases, the animals may get protection through colouration. Colouration may be divisible into two types namely concealing coloration and warning colouration.

• Concealing colouration: With the help of such colouration the animals may conceal themselves within the surroundings in such a way that it becomes difficult to find them. If mimicry is associated with colouration, it gets special adaptation in nature.
• Warning colouration: The colouration, in this case, protects the animal in such a manner that the predator animal gets frightened to attack the prey. Batesian and Mullerian mimicry exhibit this type of mimicry. Dark spots on the wings of some moths confuse the predators and they get protection from this.

Natural Selection Vs. Mimicry and Colouration:
Mimicry and colouration confer the organism’s adaption either in an individual manner or jointly. Therefore, the variations developed due to colouration and mimicry may give fitness to living organisms. Hence, the animals get natural selection by way of their colouration or mimicry.

5. Echolocation

Bats are nocturnal flying mammals that do not employ eyesight for the location of their path, food, place of rest, etc. They produce high-frequency sound which produces echoes after striking various objects on the principle of sonar. Echoes are analyzed by the bats to know their path. Echolocation is also used by other animals, e.g., whales.

6. Adaptation to Excessive Cold (Cold Hardening)

Animals have also developed adaptations to extreme cold conditions. Animals of colder areas possess thick fur and sub-cutaneous fat, they help in the conservation of heat. During excessive cold, they may undergo hibernation. However, sea animals can not undergo hibernation. Sessile animals can not migrate. Certain sessile animals, such as barnacles and mollusks which live in very cold intertidal zones or northern shores, several insects and spiders resist the effect of cold by a process, known as cold hardening. Such animals are called freeze-tolerant animals. They possess ice-nucleating proteins, which induce ice formation in the extracellular spaces at very low sub-zero temperatures.

Some animals can tolerate environmental temperatures below 0°C by accumulating glycerol or antifreeze proteins that lower the freezing point of their body fluids. Such animals are called freeze-avoiding animals. The fishes in the Antarctica region remain active in cold seawater due to the presence of antifreeze compounds.

7. Adaptation to Water Scarcity

The animals, which live in dry or xeric habitats, are called xerocoles. The xerocoles are of two types drought evaders and drought resistants.

• Drought evaders: The drought-evading xerocoles adopt either a short annual life cycle or undergo aestivation or some other dormant state during the dry season. The eggs and pupae of many insects (ants, bees, butterflies) and eggs of some invertebrates may remain dormant for several months during the dry season. In dry habitats, the birds breed and make nests during the rainy season, when there is abundant food.
• Drought resistants: These xerocoles can carry out their normal function throughout the year. They are able to resist aridity and heat through morphophysiological adaptations or by modifying their feeding activity patterns.

Some animals avoid heat by adopting nocturnal habits and remaining underground during the daytime. Kangaroo and desert rats seldom drink water. They possess thick coats to minimize evaporative desiccation. 90% of their water requirement is met from metabolic water while 10% is obtained from food. Loss of water is minimized by producing nearly solid urine and feces.

Camel has a number of adjustments to desert conditions economical in water consumption, tolerance to fluctuations of temperature, and no sweating till body temperature rises to 55°-66°C. The animal produces dry feces and concentrated urine. During periods of non-availability of water the animal stores urea and does not produce urine. When water is available, a camel can rehydrate itself quickly by drinking a large quantity of water, some 80 liters in 10 minutes.

8. Behavioural Adaptations in Desert Lizards

Desert lizards lack the physiological ability that mammals have to deal with high temperatures. They keep their body temperature fairly constant by behavioural means. They enjoy the sun and absorb heat when their body temperature drops below the comfort zone, but move into shade when the surrounding temperature starts increasing. Some species are capable of burrowing into the soil to hide and escape from too much heat. Therefore, not only desert lizards but almost all reptiles are called cold-blooded animals, as they cannot maintain a constant inner temperature. So, behavioral adaptation helps them to do so.

Different Adaptations with their Characteristic Features and Examples: