Adaptation and plant adaptations
A raincoat suits the rainy season and a sweater suits winter. Plants and animals too have "dresses" in their bodies that suit the place where they live. Nobody gets them in a day; they come over a very long time.
Adaptation (अनुकूलन) is a gradual change in body parts or behaviour that helps an organism to adjust to its surroundings.
In the figure : In the figure aquatic plants have a floating leaf (A), a hollow stem with air spaces (B) and short fibrous roots (C).
Rule 1: Aquatic plants — They have a waxy layer, hollow stems with air spaces, short fibrous roots, and thin ribbon-like leaves in fast water.
- Easy : Hollow stem with air spaces helps the plant to float.
- Medium : Thin ribbon-like leaves bend with fast water without tearing.
- Exam-type : Waxy layer keeps water out of the plant surface.
In the figure : In the figure of a desert plant the leaves become thorns (A), the fleshy green stem (B) stores water and makes food, and the deep roots (C) reach water.
Rule 2: Desert plants — They have no leaves or needle-like leaves or thorns, a fleshy green stem that stores water and makes food, deep roots and a waxy layer.
- Easy : Thorns reduce loss of water.
- Medium : Deep roots reach water far below the sand.
- Exam-type : The green stem makes food since there are almost no leaves.
In the figure : In the figure, in snowy regions the conical shape of conifers like the deodar and pine (P) lets snow slide off; snow would pile up on a round crown (Q).
Rule 3: Other regions — Snowy regions have conical conifers (deodar, pine) with sloping branches and thick bark. Forests have tall trees and climbers with tendrils. Grasslands have fibrous roots that stop soil erosion.
- Easy : Sloping branches let snow slide off.
- Medium : Tendrils help climbers to rise towards sunlight in thick forests.
- Exam-type : Fibrous roots of grass hold soil together.
Adaptation is slow and takes a long time. It is not a sudden change.
Thinking an organism changes its body when it moves to a new place. Adaptations come over many generations.
Memory clue: Water – Wax and Waterproof; Desert – Deep roots and Dry thorns; Snow – Slope.
Spot the difference
| Habitat | Plant feature | Use |
|---|---|---|
| Water | Hollow stem, waxy layer | Floats, stays dry |
| Desert | Thorns, fleshy stem, deep roots | Saves water |
| Snowy region | Conical shape, thick bark | Snow slides off |
Practice questions
- 1What is adaptation?
- 2Why do aquatic plants have hollow stems?
- 3What are thorns of a desert plant modified from?
- 4Name two conifers of snowy regions.
- 5What do tendrils help a climber to do?
- 6How do grasslands benefit from fibrous roots?
- 7Why is the stem of a desert plant fleshy and green?
- 8A tree has a round crown with spreading flat branches. Explain why it is less suitable for a snowy region.
Show answers (try them yourself first)
- 1A gradual change in body parts or behaviour that suits the surroundings.
- 2The air spaces help them to float.
- 3Leaves
- 4Deodar and pine.
- 5Climb up and reach sunlight.
- 6They stop soil erosion.
- 7Fleshy to store water; green to make food as leaves are absent.
- 8Snow would pile up on its branches and may break them; a conical shape lets snow slide off.
Adaptations for food in plants
A mosquito sucks blood and an ant takes sugar from a cake, but a plant that sucks food from another plant or catches insects is stranger still. Some plants find food in unusual ways.
A parasitic plant (परजीवी वनस्पती) gets food from another plant (the host). An insectivorous plant (कीटकभक्षी वनस्पती) eats insects.
In the figure : In the figure dodder (cuscuta) is a leafless parasite (B) whose haustorial roots (C) suck water and food from the host plant (A).
Rule 1: Parasitic and saprotrophic — Dodder (cuscuta) is a leafless parasite with haustorial roots. Fungi have no chlorophyll and absorb food from starchy foodstuffs.
- Easy : Dodder has no leaves and gets food from its host.
- Medium : Bread mould (a fungus) grows on stale bread and absorbs food from it.
- Exam-type : Dodder cannot make its own food because it has no leaves and no chlorophyll for food making.
In the figure : In the figure the pitcher plant grows in nitrogen-poor soil: an insect (C) falls into its jar (B) under the lid (A) and is digested for nitrogen.
Rule 2: Insectivorous plants — Drosera, Venus flytrap and pitcher plant grow in nitrogen-poor soil, so they catch and digest insects for nitrogen.
- Easy : Pitcher plant: insect falls into the jar.
- Medium : They still make food by photosynthesis; the insects give nitrogen.
- Exam-type : Because the soil lacks nitrogen, eating insects is their adaptation.
Parasite = takes food from a host. Insectivorous plant = eats insects for nitrogen.
Thinking insectivorous plants get all their food from insects. They make food too; insects give nitrogen.
Memory clue: Pitcher = Pot that traps; Dodder = Drinks from the host.
Spot the difference
| Plant | How it gets food |
|---|---|
| Dodder | Haustorial roots suck food from the host |
| Fungi | Absorb food from starchy foodstuffs |
| Pitcher plant, Drosera | Catch and digest insects |
Practice questions
- 1What is a parasitic plant?
- 2Name a leafless parasitic plant.
- 3How do fungi get their food?
- 4Name two insectivorous plants.
- 5Why do insectivorous plants eat insects?
- 6What are haustorial roots?
- 7A plant has no leaves and is found winding on a tree, with roots entering the tree. Name the type and say how it feeds.
- 8Riya says a pitcher plant is an animal because it eats insects. Correct her.
Show answers (try them yourself first)
- 1A plant that gets food from another plant.
- 2Dodder (cuscuta)
- 3By absorbing it from starchy foodstuffs; they have no chlorophyll.
- 4Pitcher plant and Venus flytrap (or Drosera).
- 5Their soil is poor in nitrogen.
- 6Roots of a parasite that suck water and food from the host.
- 7Parasite (like dodder); it takes food from the host tree through haustorial roots.
- 8It is a plant; it makes food by photosynthesis and uses insects only for nitrogen.
Adaptations in animals
A fish does not need a swimming class and a cheetah does not need running shoes. Their bodies are already made for swimming and running. A pigeon's eyes on its sides, and a tiger's eyes in front, have reasons too.
Animals show adaptations according to the place where they live (aquatic, desert, snowy) and the way they feed (carnivore eats flesh, herbivore eats plants).
In the figure : In the figure a fish has a tail fin and other fins (A) to swim and balance, gills (B) to breathe, an air bladder (C) to float, and scales (D).
Rule 1: Aquatic animals — Fish have scales, fins, a spindle-shaped body, gills and an air bladder. Frogs and ducks have webbed toes; frogs breathe through skin and lungs.
- Easy : Fins help a fish to swim and balance.
- Medium : Spindle shape cuts through water easily.
- Exam-type : A frog uses webbed toes to swim and its skin and lungs to breathe.
In the figure : In the figure a carnivore (P) has its eyes in front, so it can judge the distance of its prey. A herbivore (Q) has its eyes on the sides, a wide-angle view to watch for predators.
Rule 2: Carnivores and herbivores — Carnivores have strong legs, claws, sharp canines, padded paws and eyes in front. Herbivores have eyes on the sides, long legs with hooves, mobile ears and strong teeth.
- Easy : Eyes in front: a tiger judges the distance of prey.
- Medium : Eyes on the sides: a deer sees a wide area and spots a predator.
- Exam-type : Mobile ears of a herbivore help to catch sounds of danger from any direction.
Rule 3: Desert and snowy animals — Desert animals have thick skin, long legs with cushioned soles, folds of skin on nostrils, long eyelashes and burrows. Snowy-region animals have a white body and long thick hair.
- Easy : Camel: cushioned soles do not sink in sand.
- Medium : Long eyelashes and nostril folds keep sand out.
- Exam-type : White colour hides animals in snow; thick hair keeps them warm.
Eyes in front = hunter. Eyes on the sides = hunted.
Thinking every animal with claws is a carnivore. Check the whole set: canines, eyes in front and padded paws.
Memory clue: Front eyes = Find prey; Side eyes = Scan for enemies.
Spot the difference
| Type | Features |
|---|---|
| Aquatic (fish) | Scales, fins, gills, air bladder |
| Carnivore | Claws, sharp canines, eyes in front |
| Herbivore | Eyes on sides, hooves, mobile ears |
| Desert / snowy | Thick skin, cushioned soles / white body, long hair |
Practice questions
- 1Name two adaptations of fish for swimming.
- 2What is the use of the air bladder of a fish?
- 3How does a frog breathe?
- 4Where are the eyes of a carnivore?
- 5Why does a herbivore have eyes on the sides?
- 6Name two desert adaptations of animals.
- 7Why are animals in snowy regions white and covered with long thick hair?
- 8An animal has hooves, long legs, side eyes and mobile ears. Say its type, and explain two of its features.
Show answers (try them yourself first)
- 1Fins and spindle-shaped body.
- 2It helps the fish to float.
- 3Through skin and lungs.
- 4In front of the face.
- 5To get a wide view and watch for predators.
- 6Thick skin and long eyelashes (also burrows).
- 7White hides them in snow; thick hair keeps them warm.
- 8Herbivore; side eyes give a wide view and long legs with hooves help it run from predators.
Camouflage, aerial animals and Darwin
A green insect sitting on a green leaf is hard to see, while the same insect on a red flower is easy to spot. The hawk that cannot see it goes hungry, so the hidden insect lives on.
Camouflage (छद्मावरण) is a body colour or pattern that blends with the surroundings. Natural selection (नैसर्गिक निवड) is the process in which the organisms best suited to their surroundings survive and pass on their features.
In the figure : In the figure a bat flies with the help of the patagium (A), a thin fold of skin between its forelegs and hind legs.
Rule 1: Aerial animals — Birds have a spindle-shaped body, hollow bones, feathers and wings. Insects have a light body and two pairs of wings. Bats fly with the patagium. Reptiles like lizards have scaly skin and clawed toes.
- Easy : Hollow bones make a bird light.
- Medium : A bat flies with a skin fold, not feathers.
- Exam-type : An insect with two pairs of wings and a light body flies easily.
In the figure : In the figure of camouflage the green grasshopper blends with the green leaf (P) but is easy to see on the red flower (Q).
Rule 2: Camouflage — Body colours that blend with the surroundings hide an animal from enemies or from its prey.
- Easy : A green grasshopper on a green leaf is hidden.
- Medium : The same grasshopper on a red flower is easy to see.
- Exam-type : Camouflage helps both hunters and the hunted.
In the figure : In the figure of natural selection (an example) the beetles that are hard to see on the leaf survive and pass on their colour, so green beetles become more common.
Rule 3: Darwin and natural selection — Darwin explained the survival of the fittest and natural selection. Those best suited to the surroundings survive and pass on their features.
- Easy : Hard-to-see beetles survive.
- Medium : Survivors pass on their colour to their young.
- Exam-type : Over many generations, green beetles become more common.
Camouflage hides; natural selection explains who survives.
Thinking an animal changes colour on purpose to survive. Those with a suitable colour survive over generations.
Memory clue: Darwin = Different survive, the Fittest Win.
Spot the difference
| Animal | Adaptation for flying |
|---|---|
| Bird | Spindle body, hollow bones, feathers, wings |
| Insect | Light body, two pairs of wings |
| Bat | Patagium (skin fold) |
Practice questions
- 1What is camouflage?
- 2Why are bird bones hollow?
- 3What is the patagium?
- 4Name two features of insects for flight.
- 5Who gave the idea of natural selection?
- 6Why is a green grasshopper safe on a green leaf?
- 7In a place with green leaves, brown and green beetles live. Birds eat more of the beetles that are easy to see. Which colour will become more common and why?
- 8Sameer says the beetles became green because they wanted to hide. Correct him.
Show answers (try them yourself first)
- 1A body colour or pattern that blends with the surroundings.
- 2To make the body light for flying.
- 3A thin fold of skin of a bat between its fore and hind legs.
- 4Light body and two pairs of wings.
- 5Charles Darwin
- 6It blends with the leaf, so enemies cannot see it.
- 7Green; green beetles survive and pass on their colour.
- 8Beetles with a suitable colour survived and passed it on over generations; it was not a wish.
Classification and binomial nomenclature
A school library arranges books by subject, then shelf, then row. A librarian finds a book fast because of this order. Scientists too sort millions of living things into groups so that they can study them easily.
Classification (वर्गीकरण) is grouping organisms by their similarities and differences. Binomial nomenclature (द्विनाम पद्धती) gives each organism a two-part scientific name, genus + species, as proposed by Carl Linnaeus.
In the figure : In the figure the hierarchy of classification goes from the biggest group to the smallest: Kingdom, Phylum, Class, Order, Family, Genus, Species.
Rule 1: Hierarchy — Organisms are grouped in order: Kingdom, Phylum, Class, Order, Family, Genus, Species. Each step down has fewer organisms with more in common.
- Easy : Kingdom is the biggest group.
- Medium : Species is the smallest group.
- Exam-type : Members of a species can reproduce among themselves to form new individuals like themselves.
In the figure : In the figure of Carl Linnaeus's binomial nomenclature the scientific name has two parts, the genus (A) and the species (B), as in Bos taurus, the cow.
Rule 2: Scientific names — Examples: Canis lupus familiaris (dog), Bos taurus (cow), Hibiscus rosa-sinensis (hibiscus), Sorghum bicolor (jowar). The first word is the genus; the second is the species.
- Easy : Bos taurus: genus Bos, species taurus.
- Medium : Sorghum bicolor is the scientific name of jowar.
- Exam-type : The same scientific name is understood by scientists in every country, unlike local names.
Hierarchy from big to small: Kingdom → Species. Scientific name = Genus + species.
Thinking a scientific name can be written in any way. It has two parts: genus then species.
Memory clue: King Philip Came Over For Good Soup – Kingdom, Phylum, Class, Order, Family, Genus, Species.
Spot the difference
| Level | Meaning |
|---|---|
| Kingdom | Biggest group |
| Genus | First part of the scientific name |
| Species | Second part; smallest group |
Practice questions
- 1What is classification?
- 2Write the hierarchy of classification.
- 3Which is the biggest group?
- 4Who proposed binomial nomenclature?
- 5Name the two parts of a scientific name.
- 6Give the scientific name of the cow.
- 7In Sorghum bicolor, which word is the genus and which the species?
- 8Why do scientists use scientific names instead of local names?
Show answers (try them yourself first)
- 1Grouping organisms by similarities and differences.
- 2Kingdom, Phylum, Class, Order, Family, Genus, Species.
- 3Kingdom
- 4Carl Linnaeus
- 5Genus and species.
- 6Bos taurus
- 7Sorghum is the genus; bicolor is the species.
- 8The same name is understood by scientists in every country.
Quick revision
- Adaptation = gradual change that suits surroundings. It is not sudden.
- Plants: aquatic, desert, snowy, forest, grassland; parasitic and insectivorous plants.
- Animals: aquatic, carnivore, herbivore, desert, snowy, aerial, reptile; camouflage.
- Classification hierarchy; binomial name = genus + species (Linnaeus).