This MCQ module is based on: Autotrophs, Heterotrophs and Insectivorous Plants
TOPIC 36 OF 46
Autotrophs, Heterotrophs and Insectivorous Plants
🎓 Class 7
Science
CBSE
Theory
Ch 10 — Life Processes in Plants
⏱ ~14 min
🌐 Language: [gtranslate]
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A Surprise at the Botanical Garden
On a school trip to the botanical garden in Shillong, Arjun and his classmates stopped in front of a glass case. Inside were plants with jug-shaped leaves and leaves that looked like pink clamshells. The guide whispered, "Watch carefully — these plants eat insects." A small fly landed on one of the clamshells and in a blink the leaf snapped shut. The class gasped. Arjun asked, "But aren't plants supposed to make their own food? Why do these plants need insects?"
Think first: Green plants can make their own food from CO\u2082, water and sunlight. Yet some plants still trap insects. What missing ingredient might these plants be hunting for? (Hint: think about what healthy soil provides that air and water cannot.)
10.7 Not All Plants Feed the Same Way
In Part 1, we met autotrophs (plants that cook their own food) and heterotrophs (organisms that eat ready-made food). Nature, however, has several in-between arrangements. Some plants are partly autotrophic and partly heterotrophic; others cannot photosynthesise at all and must steal food from another living plant.
| Type | Food strategy | Example |
|---|---|---|
| Autotrophic | Makes own food by photosynthesis | Mango, paddy, hibiscus |
| Insectivorous | Photosynthesises but also traps insects for nitrogen | Venus fly trap, pitcher plant |
| Parasitic | Lives on another living plant and takes its food | Cuscuta (amarbel) |
| Saprophytic | Feeds on dead and decaying matter | Mushrooms, bread mould |
| Symbiotic | Two organisms live together, each helping the other | Lichens (fungus + alga) |
10.8 Insectivorous Plants — Green, Yet Hungry for Insects
Insectivorous plants are green, so they do photosynthesise. But the soils they grow in — often marshy or water-logged — are poor in nitrogen. Nitrogen is needed to build proteins, so these plants supplement their diet by catching insects and digesting them. They are therefore partial heterotrophs.
The Venus Fly Trap
The Venus fly trap has pairs of leaves hinged like a book. Along the edges are stiff bristles that mesh together like teeth. Inside each lobe are tiny sensitive hairs. When an insect touches two hairs in quick succession, the two halves of the leaf snap shut within a second. The plant then releases digestive juices that break down the insect and absorbs the soft, nutrient-rich liquid.
The Pitcher Plant
In a pitcher plant, one part of the leaf has grown into a deep jug with a lid. The rim is slippery and often brightly coloured with sweet-smelling nectar. An insect that lands to drink the nectar slips down the inner wall and falls into a pool of digestive fluid at the bottom. The lid prevents rainwater from diluting the trap, and downward-pointing hairs stop the insect from climbing out.
Remember: Although insectivorous plants catch insects, their main food is still glucose from photosynthesis. The insects supply minerals — especially nitrogen — that the soil cannot provide.
10.9 Parasitic Plants — Thieves among the Leaves
A parasitic plant takes food from a living host plant. The common example in Indian fields is Cuscuta (amarbel) — a yellow-orange, thread-like vine that twines around shrubs and small trees. Cuscuta has no chlorophyll, so it cannot photosynthesise. It develops peg-like roots called haustoria that push into the host's stem and suck out food and water.
10.10 Saprophytes — The Recyclers
Walk through a damp forest floor and you will see mushrooms, toadstools and white fuzzy bread mould. These are fungi — they are saprophytes. Fungi have no chlorophyll. They secrete digestive juices onto dead leaves, fallen logs or old rotis and absorb the dissolved food.
Saprophytes are important because they recycle the minerals locked in dead bodies back into the soil, where plants can pick them up again.
10.11 Symbiosis — Partners for Life
Sometimes two very different organisms live so closely together that both benefit. This partnership is called symbiosis.
Lichens — An Alga and a Fungus Together
A lichen is a crusty grey-green patch that grows on tree bark, old walls and rocks. Inside, two organisms live together:
- An alga carries out photosynthesis and makes food.
- A fungus provides shelter, water and minerals, and holds the partnership to the rock.
Each supplies what the other cannot make on its own. Lichens are so close a partnership that biologists treat them as a single organism.
Activity 10.2 — Observe a Fly Trap in Action (Demonstration) L2 Understand
You need: a photograph or short video clip of a Venus fly trap closing on a fly (ask your teacher to show it on a classroom tablet or projector).
- Watch the clip twice. On the first viewing, count how many seconds pass between the fly touching the leaf and the trap closing.
- On the second viewing, note where the trigger hairs are located on the leaf.
- Discuss in pairs: What would happen if a falling raindrop touched only ONE hair? Why is the two-touch design useful for the plant?
Predict: Would a Venus fly trap eventually die if its soil had plenty of nitrogen-rich fertiliser and no insects were available? Give a reason.
No — the plant would survive. Insects are an extra source of nitrogen. If the soil already supplies enough nitrogen-rich minerals, the Venus fly trap can live by photosynthesis alone, just like any other green plant. The two-touch trigger design prevents the plant from wasting energy closing for every raindrop or falling leaf — only a moving insect is likely to brush two hairs within seconds.
Key idea: Plants are classified by how they feed, not by how they look. A plant may be green and still be a partial heterotroph; a plant may be leafless and still be alive as a parasite.
Competency-Based Questions
Arjun's uncle grows roses in his garden. One morning he notices orange thread-like vines climbing all over a healthy rose bush, and the rose leaves are starting to wilt. He tells Arjun, "We have to remove these quickly or we will lose the rose bush."
1. The orange vine on the rose bush is most likely: L2
(b) Cuscuta (amarbel) — a leafless, yellow-orange parasitic vine that twines around garden plants and sucks their sap.
2. Why do insectivorous plants catch insects even though they have green leaves? L3
They grow in swampy or boggy soils that are very poor in nitrogen. They can photosynthesise for glucose, but to make proteins they need nitrogen. Catching and digesting insects supplies this extra nitrogen.
3. True or False: A fungus is an autotroph. L1
False. Fungi lack chlorophyll. They are saprophytes — they feed on dead and decaying matter.
4. In a lichen, what does each partner give the other? L2
The alga has chlorophyll and makes food for both partners through photosynthesis. The fungus gives the alga shelter, minerals and water, and anchors the pair to the rock or bark.
5. Fill in the blank: A plant that lives on a living host plant and draws food from it is called a __________ plant. L1
parasitic
Assertion–Reason Questions
Choose: (A) Both true, R explains A. (B) Both true, R does not explain A. (C) A true, R false. (D) A false, R true.
A: A pitcher plant is a partial heterotroph.
R: It has green parts that photosynthesise, but also digests insects to obtain minerals.
(A) — both statements are true and R explains A correctly.
A: Cuscuta has yellow stems instead of green ones.
R: Cuscuta contains no chlorophyll and does not need to carry out photosynthesis.
(A) — both correct. Because Cuscuta steals food from its host, it does not need chlorophyll, so its stems are not green.
A: Lichens are an example of parasitism.
R: In a lichen, one partner harms the other.
(D) — A is false; lichens are an example of symbiosis, not parasitism. R is true in the sense that parasitism involves one partner harming the other, but this does not apply to lichens.
Frequently Asked Questions — Autotrophs, Heterotrophs and Insectivorous Plants
What does the topic 'Autotrophs, Heterotrophs and Insectivorous Plants' cover in Class 7 Science?
The topic 'Autotrophs, Heterotrophs and Insectivorous Plants' is part of NCERT Class 7 Science Chapter 10 — Life Processes in Plants. It covers the key ideas of autotrophs, heterotrophs, saprophytes, parasites, insectivorous plants, Venus flytrap, pitcher plant, explained through everyday examples, labelled diagrams and hands-on activities drawn from the NCERT Curiosity textbook. Students learn not just definitions but also the reasoning behind each concept so they can answer competency-based questions and assertion–reason items. The lesson helps Class 7 students build a strong base for higher classes by linking each idea to real observations at home, school and in nature, and by preparing them for CBSE school assessments and Olympiads.
Why is 'Autotrophs, Heterotrophs and Insectivorous Plants' important for Class 7 NCERT Science?
'Autotrophs, Heterotrophs and Insectivorous Plants' is important because it builds core scientific thinking that Class 7 students will use throughout middle and secondary school. NCERT Chapter 10 — Life Processes in Plants — introduces autotrophs and related ideas that appear again in Class 8, 9 and 10 Science. Mastering this subtopic helps students read labels and safety signs, understand news about science and technology, and perform better in CBSE school exams. The chapter also encourages curiosity and evidence-based thinking — skills that support the National Education Policy (NEP) 2020 focus on conceptual understanding and competency-based learning.
What are the key concepts students should remember from Autotrophs, Heterotrophs and Insectivorous Plants?
The key concepts in 'Autotrophs, Heterotrophs and Insectivorous Plants' for Class 7 Science are: autotrophs, heterotrophs, saprophytes, parasites, insectivorous plants, Venus flytrap, pitcher plant. Students should be able to define each term in their own words, give at least one everyday example, and explain how the concept connects to other chapters in NCERT Class 7 Science. For example, linking the idea to daily life — in the kitchen, classroom or outdoors — makes revision easier. Writing short notes, drawing labelled diagrams and solving the NCERT in-text and exercise questions for Chapter 10 will help students retain these concepts for unit tests and the annual CBSE examination.
How is Autotrophs, Heterotrophs and Insectivorous Plants taught using activities in NCERT Curiosity Class 7?
NCERT Curiosity Class 7 Science teaches 'Autotrophs, Heterotrophs and Insectivorous Plants' using an inquiry-based approach with Predict–Observe–Explain activities. Students are asked to make a guess first, then perform a simple experiment with safe, easily available materials, and finally explain what they observed. This matches the NEP 2020 focus on learning by doing. For Chapter 10 — Life Processes in Plants — the textbook includes hands-on tasks, labelled diagrams and questions that build Bloom's Taxonomy skills from Remember (L1) to Create (L6). Teachers use these activities, along with competency-based questions (CBQs) and assertion–reason items, to check real understanding rather than rote memorisation.
What real-life examples of autotrophs can Class 7 students observe at home?
Class 7 students can observe autotrophs at home in many simple ways linked to 'Autotrophs, Heterotrophs and Insectivorous Plants'. Kitchens, school bags, playgrounds and the night sky are full of examples that connect to NCERT Chapter 10 — Life Processes in Plants. For instance, students can check labels on food and cleaning products, watch changes while cooking, or observe the Sun and Moon across a week. Keeping a small science diary — noting the date, what was observed and a quick sketch — turns everyday life into a science lab. These real-life connections make concepts stick and prepare students well for competency-based questions in CBSE Class 7 Science.
How does 'Autotrophs, Heterotrophs and Insectivorous Plants' connect to other chapters of Class 7 Science?
'Autotrophs, Heterotrophs and Insectivorous Plants' connects to many other chapters in NCERT Class 7 Science Curiosity. The ideas of autotrophs appear again when students study related topics like heat, light, changes, life processes and Earth-Sun-Moon. For example, understanding this subtopic helps in building mental models for later chapters and for Class 8, 9 and 10 Science. Teachers often use cross-chapter questions in CBSE examinations to test whether students can apply what they learned in Chapter 10 — Life Processes in Plants — to new situations. This integrated approach matches the NEP 2020 and NCF 2023 focus on holistic, competency-based learning.
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