Maarg Manthan · Topic 3.4

Adaptation in Plants and Animals: Examples

Environment & Ecology › Population Ecology and Species Interactions · Topic 3.4

An adaptation is a feature of structure, physiology or behaviour that helps an organism to survive and reproduce in its environment, and which has been shaped by natural selection over generations. Adaptations are of three kinds: morphological, such as spines, fur and fins; physiological, such as concentrating urine or producing antifreeze; and behavioural, such as migration, hibernation or burrowing. Plants of dry regions, called xerophytes, have thick cuticles, sunken stomata, reduced leaves and succulent stems; water plants, hydrophytes, have air-filled tissue, aerenchyma, and floating leaves; salt-loving plants, halophytes, such as mangroves, have breathing roots called pneumatophores. Animals show adaptations such as the kangaroo rat's use of metabolic water in deserts, the thick blubber of seals in polar seas, and the streamlined body and gills of fish.

5 min read · UPSC Prelims · Environment & Ecology · Population Ecology and Species Interactions

At a Glance

Dry-land plants Xerophytes
Water plants Hydrophytes
Salt plants Halophytes
Types Structural, physiological, behavioural
Desert rodent Kangaroo rat
Exam link UPSC Prelims, Environment & Ecology: Population Ecology and Species Interactions

Where Does It Fit?

This topic follows the account of the tiger and lion census. It describes how organisms fit their environment, which leads to the next topic on homeostasis. Previous topic: Methodology of Tiger Census and Lion Census. Next topic: Homeostasis.

How Do Plants Adapt?

Group	Adaptations and examples
Xerophytes	Plants of dry places. Thick waxy cuticle, sunken stomata, reduced or spiny leaves, deep or spreading roots, water-storing stems. Examples: cactus, Opuntia, Euphorbia, Acacia. Many use CAM photosynthesis, opening stomata at night
Hydrophytes	Water plants. Air-filled aerenchyma for buoyancy, thin cuticle, floating leaves, little root system. Examples: water lily, lotus, Hydrilla, water hyacinth
Mesophytes	Plants of moderate conditions with broad leaves and normal roots, such as most crops
Halophytes	Salt-tolerant plants. Mangroves have pneumatophores (breathing roots), prop roots, salt-excreting glands and viviparous seeds that germinate on the tree. Examples: Rhizophora, Avicennia
Epiphytes	Grow on other plants. Velamen roots absorb moisture from air. Examples: orchids, ferns
Insectivorous plants	Get nitrogen from trapped insects in poor soil. Examples: pitcher plant, sundew, Venus flytrap, bladderwort
Mountain plants	Cushion forms, small leaves and hairy covering to resist cold and wind

How Do Animals Adapt?

Desert animals: camel stores fat in the hump and can drink huge amounts and tolerate water loss; kangaroo rat gets water from metabolism and has concentrated urine; reptiles have scales and are active at night
Polar animals: thick fur, blubber and countercurrent heat exchange in limbs; white colour; Bergmann’s and Allen’s rules; polar bear, seal, penguin
Aquatic animals: streamlined body, fins, gills, swim bladder, webbed feet and waterproof feathers
Arboreal animals: prehensile tail, grasping hands, such as monkeys
Fossorial animals: burrowing animals with strong forelimbs and small eyes, like moles
High-altitude animals: more red blood cells and haemoglobin with high oxygen affinity, as in the yak and snow leopard
Behavioural adaptations: migration, hibernation, aestivation, nocturnal habits, group living
Camouflage and mimicry: colouring to blend or imitate harmful species, like the viceroy butterfly mimicking the monarch

What Else Should You Remember?

Natural selection: the process proposed by Darwin and Wallace that produces adaptations
Acclimatisation versus adaptation: acclimatisation is a temporary change within a lifetime, while adaptation is inherited
Convergent evolution: unrelated species developing similar traits, like wings of birds and bats
Adaptive radiation: one ancestor giving rise to many forms, like Darwin’s finches
Cactus spines: modified leaves that cut water loss and protect
Photosynthesis in stem: cactus stems do the work of leaves
Mangrove viviparity: seedlings sprout while on the tree, so they can root in mud when they fall
Sundarbans: tigers there swim and tolerate salt water
Lotus: leaves have a waxy surface that repels water
Camel: oval red blood cells, thick eyelashes and broad padded feet
Penguin: huddling to save heat
Fish scales: slime and scales reduce friction
Bat echolocation: a sensory adaptation for night
Seasonal coat change: Arctic fox and ptarmigan change colour
Bird beak variety: beaks suit food type
Pollination syndromes: flowers adapted to bees, birds, bats or wind
Seed dispersal: hooks, wings, fleshy fruits and floats
Drought deciduous: trees dropping leaves in dry season
Link: maintaining internal balance is in Homeostasis
Link to tolerance: see Range of Tolerance and Maximum Range
Caution: adaptation is not purposeful, it results from selection of random variation
Water storage in baobab: trunk stores water in dry Africa and Australia
Leaf modifications: needle leaves of conifers shed snow and cut water loss
Root adaptations: tap roots reach deep water while stilt roots support mangroves
Insect adaptations: social insects, mimicry and metamorphosis help survival
Adaptation to fire: thick bark and resprouting in savanna trees
Human adaptation: high-altitude people like Sherpas and Tibetans have genetic traits for low oxygen
Limits of adaptation: too rapid change can exceed the speed of adaptation, leading to extinction

Why Does It Matter for the Exam?

Plant groups: xerophyte, hydrophyte, halophyte
Mangrove roots: pneumatophores
Desert animals: camel, kangaroo rat
Current affairs link: mangrove conservation
Common errors: calling acclimatisation an adaptation or CAM plants day openers

As an analytical point, adaptation means that species are fitted to their present climate, so rapid climate change can leave them behind. Species with narrow adaptations, such as mountain plants and polar animals, are at greatest risk.

Why Is This Topic Important?

Types Three
Plants Xero, hydro, halo
Animals Desert, polar

What Came Next?

The next topic covers homeostasis. Next topic: Homeostasis.

Key People and Terms

Xerophyte Dry-place plant
Hydrophyte Water plant
Halophyte Salt-tolerant plant
Pneumatophore Breathing root
Aerenchyma Air-filled tissue
Viviparity Seed germinating on parent

Exam Corner

Points to Remember

Mangrove roots: pneumatophores.
Cactus stem is photosynthetic; spines are leaves.
Kangaroo rat uses metabolic water.
Aerenchyma gives buoyancy.
CAM stomata open at night.

Do Not Confuse With

Adaptation and acclimatisation Inherited versus temporary
Xerophyte and halophyte Dry versus salty habitat
Convergent and adaptive radiation Similar traits from different ancestors versus many forms from one

Memory Hook

Dry cactus saves water, water lily floats, mangrove breathes through roots.

Mains Angle

Questions ask for examples of adaptation. These points help.

Types Three
Plants Habitat traits
Animals Extreme zones

A Question You May Face

An original practice question, not a past paper question.

“Explain the morphological, physiological and behavioural adaptations of plants and animals with examples from different habitats.”

How to Answer

Define Adaptation.
Plants Xero, hydro, halo.
Animals Desert, polar.
Process Selection.

GS Relevance

Prelims: adaptations of desert, aquatic, mangrove, polar plants and animals with examples. GS Paper 3: ecology.

Frequently Asked Questions

What is an adaptation?

An adaptation is a heritable feature of an organism's body, function or behaviour that improves its chances of survival and reproduction in its environment. It arises by natural selection over many generations, and it may be morphological, physiological or behavioural, such as spines in cactus, concentrated urine in desert rats or migration in birds.

What are the adaptations of xerophytes?

Xerophytes, plants of dry habitats, reduce water loss through thick waxy cuticles, sunken stomata, reduced or spiny leaves and hairs. They store water in fleshy stems or leaves, have deep or widespread roots and often open stomata at night using CAM photosynthesis. Examples are cactus, Opuntia and Euphorbia.

What are pneumatophores?

Pneumatophores are special breathing roots that grow upward from the muddy soil in mangrove plants such as Avicennia and Rhizophora. They have pores through which air enters the roots, which allows them to respire in waterlogged, oxygen-poor and salty soils.

How does the kangaroo rat survive in deserts?

The kangaroo rat of North American deserts survives without drinking water by getting water from the metabolism of dry seeds, producing very concentrated urine, having nasal passages that recover moisture, and staying in cool burrows during the day. It is a classic example of a physiological and behavioural adaptation.

What is the difference between adaptation and acclimatisation?

Adaptation is a hereditary change that evolves over generations through natural selection and is permanent in the population. Acclimatisation is a temporary, reversible adjustment of an individual's body to a changed environment within its lifetime, such as increased red blood cells in a person who moves to high altitude.

PYQ Practice — Statement Analysis

1 Pneumatophores are found in mangrove plants.

True

As breathing roots.

2 Hydrophytes have well developed cuticle and no aerenchyma.

False

They have aerenchyma.

3 Adaptations are inherited features.