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Class 7 Science Chapter 1 Nutrition in Plants — Formulas & Key Points

CBSE Class 7 Science Chapter 1 Nutrition in Plants lays the foundation for understanding how plants make their own food and how different organisms obtain nutrients. This formula sheet brings together every definition, process equation, mode of nutrition, and key term from the NCERT textbook in a structured, exam-ready format. Use it for quick revision before tests or as a reference while solving NCERT exercise questions.

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Key takeaways

✓Photosynthesis equation: 6CO₂ + 12H₂O → C₆H₁₂O₆ + 6O₂ + 6H₂O in the presence of sunlight and chlorophyll.
✓Autotrophic nutrition means organisms synthesise their own food; heterotrophic nutrition means organisms depend on others for food.
✓Saprotrophs feed on dead and decaying matter; parasites obtain nutrition from living hosts without killing them immediately.
✓Symbiosis is a mutually beneficial relationship, such as lichens (algae + fungi) or legume-rhizobium associations.
✓Stomata are tiny pores on leaves that regulate gas exchange and transpiration during photosynthesis.
✓Chlorophyll, the green pigment in chloroplasts, is essential for trapping light energy required for photosynthesis.
✓Insectivorous plants like pitcher plant and Venus flytrap obtain nitrogen from trapped insects in nitrogen-deficient soils.

Core Definitions and Nutrition Modes

Understanding the terminology of nutrition is the first step. Nutrition is the process by which an organism takes in food and utilises it for growth, maintenance and repair. The two broad categories are autotrophic and heterotrophic. Autotrophs (like green plants, algae and some bacteria) synthesise their own food using simple inorganic substances. Heterotrophs (animals, fungi, most bacteria) depend on autotrophs or other organisms for food. The chapter distinguishes three heterotrophic sub-types: saprotrophic (feeding on dead organic matter), parasitic (deriving nutrition from a living host), and holozoic (ingesting solid food and digesting it internally, typical of animals).

Nutrition: Process of intake and utilisation of nutrients for energy, growth and repair.
Autotrophic nutrition: Self-synthesis of food from CO₂, water and minerals using sunlight (photosynthesis) or chemical energy (chemosynthesis).
Heterotrophic nutrition: Dependence on other organisms for ready-made organic food.
Saprotrophic nutrition: Feeding on dead and decaying organic matter (e.g. fungi, many bacteria).
Parasitic nutrition: Obtaining nutrients from a living host, often harming it (e.g. Cuscuta, ticks).
Holozoic nutrition: Ingestion of complex food, internal digestion, absorption and egestion (animals).

The Photosynthesis Equation — Formula Table

Photosynthesis is the central chemical process by which green plants convert light energy into chemical energy stored in glucose. The overall balanced equation is critical for exams and conceptual clarity. The process occurs in two stages: light reactions (in thylakoids, producing ATP and NADPH and releasing O₂) and dark reactions or Calvin cycle (in stroma, fixing CO₂ into glucose). The equation below represents the net summary. Chlorophyll acts as the catalyst and sunlight as the energy source. Water is split (photolysis) to release oxygen, and carbon dioxide is reduced to form glucose. This single equation encapsulates the entire chapter and must be memorised verbatim, including the number of molecules and the role of chlorophyll and sunlight.

Key Terms and Definitions

This section lists every important term from the NCERT Class 7 Science Chapter 1 in alphabetical order with precise definitions. Mastering these definitions is essential for MCQs, fill-in-the-blanks and short-answer questions. Many board exam questions directly test the meaning of chlorophyll, stomata, symbiosis, host, parasite, saprotroph and insectivorous plants. Each term is defined using NCERT language to match mark-scheme expectations. Use flashcards or the CBSETUTOR.ai photo-upload feature to quiz yourself on these definitions daily. Chlorophyll is the green pigment found in chloroplasts that absorbs light energy for photosynthesis. Stomata are tiny pores on the epidermis of leaves, surrounded by guard cells, regulating gas exchange (CO₂ in, O₂ out) and transpiration. Xylem transports water and minerals from roots to leaves. Phloem transports prepared food (glucose, sucrose) from leaves to other parts. A parasite is an organism that lives on or inside another organism (the host) and derives nutrition from it, often harming the host. Saprotrophs are organisms that obtain nutrients by decomposing dead and decaying organic matter. Symbiosis is a close association between two different species in which both benefit (mutualism). Insectivorous plants are plants that trap and digest insects to supplement nitrogen, typically in nitrogen-poor soils. Lichens are composite organisms formed by symbiotic association of algae (which photosynthesise) and fungi (which provide shelter and moisture). Rhizobium bacteria live in root nodules of leguminous plants, fixing atmospheric nitrogen in exchange for shelter and food.

Chlorophyll: Green pigment in chloroplasts that absorbs light energy for photosynthesis.
Stomata: Tiny pores on leaf surface, bordered by guard cells, allowing gas exchange.
Guard cells: Specialised cells surrounding stomata that control opening and closing.
Xylem: Vascular tissue transporting water and minerals from roots upward.
Phloem: Vascular tissue transporting synthesised food from leaves to all parts.
Host: The organism from which a parasite derives nutrition.
Parasite: Organism living on/in a host, deriving food, often harming the host (e.g. Cuscuta).
Saprotroph: Organism feeding on dead organic matter (e.g. mushrooms, moulds).
Symbiosis: Mutually beneficial relationship between two species (e.g. lichen, legume-rhizobium).
Insectivorous plants: Plants that trap and digest insects for nitrogen (e.g. pitcher plant, Venus flytrap, sundew).
Lichen: Symbiotic association of algae and fungi.
Rhizobium: Nitrogen-fixing bacteria in root nodules of legumes.

Types of Heterotrophic Nutrition — Comparison Table

Heterotrophic nutrition is subdivided based on the source and method of obtaining food. The NCERT textbook introduces three main types in this chapter: saprotrophic, parasitic and symbiotic (though symbiosis often benefits both partners, the heterotrophic partner still depends on the autotrophic one). Understanding the differences is crucial for diagram-based questions and definitions. Saprotrophs secrete digestive enzymes onto dead matter, break it down externally, and absorb the nutrients (extracellular digestion). Examples include fungi (mushrooms, bread mould), many bacteria and some protists. Parasites attach to or penetrate a living host, absorbing nutrients directly, often causing disease or weakening the host. Cuscuta (dodder) is a classic plant parasite with no chlorophyll, twining around host stems. Ticks, lice, tapeworms and Plasmodium (malaria) are animal parasites. Symbiotic nutrition involves a close, prolonged association where both organisms benefit. Lichens are a textbook example: algae photosynthesise and share food with fungi; fungi provide moisture, minerals and protection. Legume plants host Rhizobium bacteria in root nodules: bacteria fix atmospheric nitrogen into ammonia for the plant; the plant supplies carbohydrates to bacteria. This interdependence is called mutualism and is a subset of symbiosis.

Memory Tricks and Mnemonics

Remembering the photosynthesis equation, modes of nutrition and key terms becomes easier with mnemonics and visual associations. For the photosynthesis equation, use 'Six Carbon Dioxide Twelve Water Sunlight Chlorophyll Give One Glucose Six Oxygen Six Water' to recall 6CO₂ + 12H₂O → C₆H₁₂O₆ + 6O₂ + 6H₂O. To remember the two stages of photosynthesis, think 'Light Reactions Light Up, Dark Reactions Do Carbon' (Light reactions need light, produce ATP and O₂; dark reactions fix carbon in the Calvin cycle). For modes of nutrition, use the acronym 'AHS' for Autotrophic, Heterotrophic, Symbiotic, or 'SAP' for Saprotrophic, Autotrophic, Parasitic to cover the main categories. For remembering that stomata open during day and close at night, picture 'Stomata are Solar-powered doors'. To recall that xylem carries water up and phloem carries food, use 'Xylem = X-tremely high (upward), Phloem = Food flow'. For insectivorous plants, remember 'Pitcher Plants Pour Nitrogen' to associate them with nitrogen-poor soils. For Cuscuta, the parasite plant, think 'Cuscuta Clings and Cheats' (no chlorophyll, depends entirely on host). For lichen symbiosis, 'Algae and Fungi Are Friends Forever' reminds you both benefit. These tricks save time in exams and reduce silly mistakes.

Photosynthesis equation: 'Six Carbon Dioxide Twelve Water Sunlight Chlorophyll Give One Glucose Six Oxygen Six Water'.
Light vs Dark reactions: 'Light Reactions Light Up, Dark Reactions Do Carbon'.
Modes of nutrition: 'AHS' for Autotrophic, Heterotrophic, Symbiotic.
Xylem and Phloem: 'Xylem = X-tremely high (water up), Phloem = Food flow (sugars around)'.
Stomata function: 'Stomata are Solar-powered doors' (open in sunlight, close in dark).
Insectivorous plants: 'Pitcher Plants Pour Nitrogen' (supplement nitrogen from insects).
Cuscuta parasite: 'Cuscuta Clings and Cheats' (no chlorophyll, lives off host).
Lichen symbiosis: 'Algae and Fungi Are Friends Forever' (both benefit).

Common Mistakes — Signs, Units and Notation

Students often lose marks due to notation errors, incorrect chemical formulae or confusing terms. In the photosynthesis equation, always write the arrow as → (not =) because it is a reaction, not an algebraic equation. Write chlorophyll and sunlight above the arrow or mention 'in the presence of chlorophyll' in words. Do not write 'CO2' without subscript; the correct notation is CO₂ with subscript 2. Similarly, use O₂, H₂O, C₆H₁₂O₆ with proper subscripts. Do not confuse glucose (C₆H₁₂O₆) with starch (a polymer of glucose). Plants store glucose as starch, but the photosynthesis equation produces glucose. Another common error is writing 'chloroplast' when the question asks for 'chlorophyll' (chloroplast is the organelle; chlorophyll is the pigment inside it). Do not mix up xylem and phloem: xylem transports water and minerals upward; phloem transports food in all directions. Stomata is plural; the singular is stoma. Write 'guard cells' not 'guard cell' because there are two per stoma. When describing parasites, do not say they 'kill the host immediately' — that would make them predators or pathogens; parasites usually keep the host alive to continue feeding. For symbiosis, ensure you state that both organisms benefit; one-sided benefit is commensalism or parasitism, not symbiosis. In diagrams, label chloroplasts, stomata, guard cells and veins (xylem/phloem) clearly. Spelling errors like 'photosynthisis' or 'nutrician' cost marks in descriptive answers.

Always use subscript notation: CO₂, H₂O, O₂, C₆H₁₂O₆ (not CO2, H2O, etc.).
Write chlorophyll and sunlight as conditions (above arrow or in words), not as reactants.
Use → for reactions, not = (chemical process, not equation).
Chlorophyll (pigment) vs chloroplast (organelle) — do not confuse.
Xylem = water up; Phloem = food around (do not swap functions).
Stomata (plural), stoma (singular); guard cells (always plural, two per stoma).
Parasites harm but do not immediately kill the host (unlike predators).
Symbiosis means mutual benefit; one-sided benefit is not symbiosis.
Spell correctly: photosynthesis, nutrition, chlorophyll, saprotroph.

Solved Mini-Examples Applying Key Concepts

Applying the formulas and definitions to sample questions helps consolidate understanding. These three worked examples mirror the style of NCERT exercise questions and CBSE term exams. Example 1 tests the photosynthesis equation and the role of chlorophyll. Example 2 tests classification of organisms by nutrition mode. Example 3 tests understanding of symbiosis and insectivorous plants. Work through each step to see how definitions translate into exam answers.

Important Constants, Values and Facts

While Chapter 1 Nutrition in Plants is more concept-driven than numerical, certain facts and values recur in exam questions and must be memorised. Chlorophyll absorbs mainly red and blue wavelengths of light and reflects green, which is why plants appear green. The chemical formula of glucose produced during photosynthesis is C₆H₁₂O₆. Oxygen (O₂) is released as a by-product; this is the oxygen we breathe. Stomata are typically more numerous on the lower surface of leaves (to reduce water loss). Each stoma is surrounded by two guard cells that swell to open the pore and shrink to close it. Cuscuta (dodder) is a parasitic plant that completely lacks chlorophyll and appears yellow or orange. Rhizobium bacteria in legume root nodules can convert atmospheric nitrogen (N₂) into ammonia (NH₃), a form plants can use. Insectivorous plants include pitcher plant (Nepenthes), Venus flytrap (Dionaea) and sundew (Drosera). These facts often appear in match-the-following, true/false and one-mark definition questions. Knowing them precisely ensures you do not lose easy marks. CBSETUTOR.ai's 24×7 AI tutor can quiz you on these facts interactively using photo uploads of your notebook or textbook diagrams, helping reinforce memory at a flat ₹999/month for all classes 6–12, with a 3-day free trial to explore the platform.

Glucose formula: C₆H₁₂O₆ (product of photosynthesis).
Oxygen: By-product of photosynthesis, released through stomata.
Chlorophyll absorbs red and blue light, reflects green (why plants look green).
Stomata: More abundant on lower leaf surface (reduce water loss).
Guard cells: Two per stoma, control opening and closing by turgor pressure.
Cuscuta: Parasitic plant, no chlorophyll, appears yellow/orange.
Rhizobium: Nitrogen-fixing bacteria in legume root nodules, convert N₂ to NH₃.
Insectivorous plants: Pitcher plant, Venus flytrap, sundew (trap insects for nitrogen).
Lichen: Symbiotic association of algae (autotrophic) and fungi (provide shelter).
Photosynthesis site: Chloroplasts in mesophyll cells of leaves.

One-Glance Last-Minute Revision Box

Use this checklist the night before your exam or during quick revision sessions. It distils the entire chapter into bullet points that you can scan in 5 minutes. Photosynthesis: 6CO₂ + 12H₂O + light → C₆H₁₂O₆ + 6O₂ + 6H₂O (chlorophyll needed). Autotrophic nutrition: Self-synthesis of food (green plants, algae). Heterotrophic nutrition: Dependence on others (animals, fungi, bacteria). Saprotrophic: Feed on dead matter (mushrooms, moulds). Parasitic: Feed on living host (Cuscuta, ticks). Symbiotic: Mutual benefit (lichen, legume-Rhizobium). Chlorophyll: Green pigment in chloroplasts, absorbs light energy. Stomata: Tiny pores for gas exchange, surrounded by guard cells. Xylem: Transports water and minerals upward. Phloem: Transports food. Insectivorous plants: Trap insects for nitrogen (pitcher plant, Venus flytrap). Cuscuta: Parasite, no chlorophyll. Rhizobium: Nitrogen-fixing bacteria in legume roots. Lichen: Algae + fungi symbiosis. Guard cells: Control stomatal opening. Products of photosynthesis: Glucose (stored as starch) + O₂. Raw materials: CO₂, H₂O, sunlight, chlorophyll. Keep this box handy on a sticky note or screenshot on your phone for quick review during morning revision or between exam papers. Pair it with solved NCERT questions and previous year papers for complete preparation. CBSETUTOR.ai offers instant doubt clearing by uploading a photo of any diagram or question — try the 3-day free trial.

Photosynthesis equation: 6CO₂ + 12H₂O + light → C₆H₁₂O₆ + 6O₂ + 6H₂O (chlorophyll required).
Autotrophic: Self-food synthesis (plants, algae).
Heterotrophic: Depend on others (animals, fungi, bacteria).
Saprotrophic: Dead matter (mushrooms, moulds).
Parasitic: Living host (Cuscuta, ticks, lice).
Symbiotic: Mutual benefit (lichen, legume-Rhizobium).
Chlorophyll: Green pigment, light absorption, in chloroplasts.
Stomata: Gas exchange pores, two guard cells each, mostly on lower leaf surface.
Xylem: Water and minerals up; Phloem: Food distribution.
Insectivorous: Pitcher plant, Venus flytrap, sundew — trap insects for nitrogen.
Cuscuta: Parasite, no chlorophyll, yellow/orange.
Rhizobium: N₂ → NH₃ in legume root nodules.
Lichen: Algae (food) + Fungi (shelter).
Products: Glucose (starch) + O₂. Raw materials: CO₂, H₂O, light, chlorophyll.

How CBSETUTOR.ai Helps Master Nutrition in Plants

Revising formulas and definitions is only half the battle; applying them to diagrams, filling gaps in understanding and solving variety questions is where students often struggle. CBSETUTOR.ai provides a 24×7 AI tutor accessible on your phone or computer. Simply photograph any NCERT diagram — a leaf cross-section, stomata, lichen structure, Cuscuta attachment — and ask the AI to label it, explain it or generate practice questions. The tutor breaks down complex processes like the light and dark reactions of photosynthesis into step-by-step explanations in simple language. It also offers instant answers to doubts like 'Why do guard cells swell?' or 'How does Rhizobium help legumes?' without waiting for the next class or tuition session. At a flat ₹999 per month for every subject in classes 6 to 12, it replaces expensive coaching for Chapter 1 and beyond. Parents appreciate the transparency: one price, no hidden fees, and a 3-day free trial so your child can explore the AI tutor risk-free. Whether your child is in a metro with packed coaching schedules or a Tier-2 city with limited resources, CBSETUTOR.ai levels the playing field with on-demand, high-quality doubt resolution and revision support. Try uploading a page from your NCERT textbook today and see how the AI tutor responds — it is like having a personal science teacher available round the clock.

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Step-by-step breakdowns of photosynthesis, modes of nutrition, symbiosis.
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Frequently asked questions

What is the exact chemical equation for photosynthesis in Class 7?+

The balanced equation is 6CO₂ + 12H₂O + light energy → C₆H₁₂O₆ + 6O₂ + 6H₂O, in the presence of chlorophyll. A simplified version often taught is 6CO₂ + 6H₂O + light → C₆H₁₂O₆ + 6O₂, assuming net water consumption.

What is the difference between autotrophic and heterotrophic nutrition?+

Autotrophic nutrition means the organism synthesises its own food from simple inorganic substances (CO₂, water) using light or chemical energy (e.g. green plants). Heterotrophic nutrition means the organism depends on other organisms for ready-made organic food (e.g. animals, fungi).

What are saprotrophs and give two examples?+

Saprotrophs are organisms that obtain nutrition by feeding on dead and decaying organic matter. They secrete enzymes to break down the matter externally and absorb the nutrients. Examples: mushrooms (fungi) and many bacteria.

Why is Cuscuta called a parasite?+

Cuscuta (dodder) is called a parasite because it has no chlorophyll and cannot photosynthesise. It twines around a host plant, penetrates its stem and absorbs water, minerals and ready-made food, harming the host without killing it immediately.

What is symbiosis? Give one example from Chapter 1.+

Symbiosis is a close, long-term association between two different species in which both organisms benefit (mutualism). Example: Lichen is a symbiotic association of algae (which photosynthesise and provide food) and fungi (which provide moisture, minerals and shelter).

What is the function of stomata in leaves?+

Stomata are tiny pores on the leaf surface (mainly on the lower epidermis) that allow gas exchange: carbon dioxide enters for photosynthesis and oxygen exits. They also regulate water loss through transpiration and are controlled by guard cells.

How do insectivorous plants obtain nutrition?+

Insectivorous plants like pitcher plant, Venus flytrap and sundew can photosynthesise but grow in nitrogen-poor soils. They trap and digest insects to obtain nitrogen and other minerals needed for proteins and growth, supplementing their autotrophic nutrition.

What is the role of Rhizobium bacteria in legume plants?+

Rhizobium bacteria live in root nodules of leguminous plants (like peas, beans) and convert atmospheric nitrogen (N₂) into ammonia (NH₃), which the plant uses to make proteins. In return, the plant provides carbohydrates and shelter to the bacteria — a symbiotic relationship.

Do I need to memorise chemical formulas for Class 7 Science Chapter 1?+

Yes, you should memorise the photosynthesis equation (6CO₂ + 12H₂O → C₆H₁₂O₆ + 6O₂ + 6H₂O) and the molecular formula of glucose (C₆H₁₂O₆). Write them with correct subscripts and always mention chlorophyll and sunlight as conditions.

How can CBSETUTOR.ai help me prepare for Chapter 1 Nutrition in Plants?+

CBSETUTOR.ai offers a 24×7 AI tutor you can access via photo upload. Snap any diagram, definition or question from your NCERT textbook and get instant explanations, labelled diagrams and practice questions. It costs just ₹999/month for all subjects in classes 6–12, with a 3-day free trial.

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