NCERT Solutions for CBSE Class 7 Science Chapter 1: Nutrition in Plants

CBSE Class 7 Science Chapter 1 Nutrition in Plants is organized into seven core sections in the NCERT textbook. The chapter begins by distinguishing between autotrophic and heterotrophic nutrition, then dives into photosynthesis—the process by which plants make food. Students learn the raw materials (carbon dioxide, water, sunlight), the site of photosynthesis (leaves, chloroplasts), and the products (glucose, oxygen). The chapter then explores how nutrients are replenished in soil, introduces saprotrophic nutrition (fungi and bacteria feeding on dead matter), and explains parasitic plants like dodder (Cuscuta). The final sections cover symbiosis, including mutualism (e.g., legume-bacteria nitrogen fixation) and the role of insectivorous plants like pitcher plant and Venus flytrap. Each NCERT intext question and end-of-chapter exercise is designed to test conceptual clarity, not rote memory. Questions range from 1-mark definitions to 5-mark explanations with diagrams. The chapter carries approximately 8–10 marks in the Class 7 annual exam, and concepts reappear in Class 10 Life Processes chapter, making thorough understanding now a long-term investment.

Autotrophic nutrition is the hallmark of green plants. The term 'auto' means self and 'troph' means nourishment—plants nourish themselves without depending on other organisms. This is achieved through photosynthesis: plants absorb carbon dioxide from air via stomata, draw water from soil through roots, and capture sunlight energy using chlorophyll (the green pigment in leaves). These raw materials undergo a chemical reaction to produce glucose (stored as starch) and release oxygen as a byproduct. Autotrophs are called producers because they form the base of every food chain. A single mango tree, for instance, produces kilograms of glucose daily during peak summer, fueling its own growth and providing food for herbivores. The CBSE Class 7 Science Chapter 1 Nutrition in Plants syllabus emphasizes this concept because it explains why forests are called 'lungs of the Earth'—they release oxygen—and why deforestation reduces food availability for all life forms. In exams, expect 2-mark questions asking students to define autotrophic nutrition and 3-mark questions requiring examples and the photosynthesis equation in word form.

Photosynthesis is the central reaction in CBSE Class 7 Science Chapter 1 Nutrition in Plants. The word equation is: Carbon dioxide + Water + Light energy → Glucose + Oxygen. Alternatively, using chemical symbols: 6 CO₂ + 6 H₂O + Light energy → C₆H₁₂O₆ + 6 O₂. This equation tells us six molecules of carbon dioxide and six molecules of water, in the presence of light energy absorbed by chlorophyll, yield one molecule of glucose and six molecules of oxygen. Photosynthesis occurs in two stages. The light-dependent reactions happen in the thylakoid membranes inside chloroplasts, where light energy splits water molecules (photolysis), releasing oxygen and capturing energy. The light-independent reactions (Calvin cycle) occur in the stroma, where captured energy is used to fix carbon dioxide into glucose. Students must memorize the word equation for 2-mark questions and be able to label a diagram showing chloroplast, stomata, and the flow of gases. Understanding that oxygen is a byproduct—not the main product—is crucial; glucose is the food the plant needs, while oxygen benefits aerobic organisms like us.

Chlorophyll and stomata are two structures students must master for CBSE Class 7 Science Chapter 1 Nutrition in Plants. Chlorophyll is a green pigment located in chloroplasts, primarily in leaf cells. It absorbs light energy (mainly red and blue wavelengths) and converts it into chemical energy, initiating the photosynthesis reaction. Without chlorophyll, a plant cannot perform photosynthesis—this is why variegated leaves with white patches (lacking chlorophyll) do not contribute to food production in those regions. Stomata (singular: stoma) are tiny pores on the leaf surface, mostly on the underside, surrounded by two guard cells. These pores open during the day to allow carbon dioxide in and oxygen out, and close at night or during water stress to prevent water loss. The exchange of gases (CO₂ in, O₂ out) is essential for photosynthesis. In exams, students are often asked to draw and label a stoma, explain its function, or describe what happens if stomata are blocked (photosynthesis stops, plant starves). Understanding that stomata also release water vapor (transpiration) connects this chapter to later chapters on transportation in plants.

Heterotrophic nutrition is the mode by which organisms obtain ready-made organic food from other living or dead organisms. The term 'hetero' means other, indicating dependence on others for nutrition. All animals (humans, cows, lions, insects), fungi (mushrooms, yeast), and most bacteria are heterotrophs. Heterotrophic nutrition is categorized into three main types covered in CBSE Class 7 Science Chapter 1 Nutrition in Plants: holozoic (ingesting solid food, e.g., humans eating rice), saprotrophic (feeding on dead decaying matter, e.g., fungi on fallen logs), and parasitic (living on or in a host and deriving nutrition at the host's expense, e.g., tapeworms in intestines). Heterotrophs play critical roles: herbivores transfer plant energy to carnivores, decomposers recycle nutrients, and parasites, though harmful, regulate host populations. The NCERT textbook contrasts heterotrophs with autotrophs to show the interdependence of life—every heterotroph ultimately depends on autotrophs for food energy captured from the sun. Exam questions often ask students to classify organisms as autotrophs or heterotrophs, or to explain with examples the different types of heterotrophic nutrition.

Saprotrophic nutrition is a special type of heterotrophic nutrition where organisms feed on dead and decaying organic matter. Saprotrophs (also called saprophytes or decomposers) include most fungi (bread mold, mushrooms) and many bacteria. They do not have a mouth or digestive system like animals. Instead, they secrete powerful digestive enzymes onto the dead matter (fallen leaves, dead animals, rotting fruit), breaking complex organic molecules into simpler substances externally. They then absorb these simpler nutrients through their body surface. CBSE Class 7 Science Chapter 1 Nutrition in Plants dedicates a section to saprotrophs because they are essential for nutrient cycling. Without decomposers, dead organisms would pile up, and the soil would lose essential minerals like nitrogen, phosphorus, and potassium—nutrients that plants need to grow. In forest ecosystems, fungi decompose leaf litter and return nitrogen to the soil; in compost pits, bacteria and fungi decompose kitchen waste into rich humus. Exam questions may ask students to explain the role of saprotrophs in an ecosystem or to give examples and describe their mode of nutrition.

Parasitic nutrition is a mode of heterotrophic nutrition where one organism (the parasite) lives on or inside another living organism (the host), deriving nutrition at the host's expense without providing any benefit in return. Parasites harm the host by absorbing nutrients, weakening it, and sometimes transmitting diseases. CBSE Class 7 Science Chapter 1 Nutrition in Plants introduces two key examples: Cuscuta (dodder), a parasitic plant, and ticks or lice as animal parasites. Cuscuta has no roots in soil and no green leaves; it wraps around a host plant's stem and penetrates it with specialized structures called haustoria, sucking the host's sap. The host plant becomes weak, its growth stunted, and it may eventually die. In animals, parasites like tapeworms live in the intestine, absorbing digested food from the host, leading to malnutrition. Mosquitoes are ectoparasites (external) that suck blood, while tapeworms are endoparasites (internal). Understanding parasitism is important because it explains crop damage (Cuscuta on tomato, sugarcane) and human diseases (malaria, tapeworm infection). Exam questions often ask students to differentiate parasites from predators (predators kill and eat prey immediately; parasites keep the host alive to feed on it over time).

Symbiosis means 'living together' and refers to a close, long-term interaction between two different species. CBSE Class 7 Science Chapter 1 Nutrition in Plants covers three types of symbiotic relationships: mutualism, commensalism, and parasitism. In mutualism, both organisms benefit. Classic examples include lichens (fungus + alga living together: fungus provides structure and water, alga makes food via photosynthesis) and the relationship between legume plants (peas, beans) and nitrogen-fixing bacteria (Rhizobium) in root nodules. The bacteria convert atmospheric nitrogen into ammonia (a form plants can use), and the plant supplies the bacteria with carbohydrates. In commensalism, one organism benefits and the other is neither helped nor harmed—e.g., a bird building a nest in a tree. In parasitism, one organism benefits and the other is harmed (covered earlier). Symbiotic relationships show that nature is not only about competition; cooperation is equally important for survival. Exam questions ask students to define symbiosis, give examples of mutualism, and explain the roles of each partner in a symbiotic relationship.

A critical concept in CBSE Class 7 Science Chapter 1 Nutrition in Plants is how soil nutrients are replenished. Plants absorb minerals (nitrogen, phosphorus, potassium) from soil through their roots. Over time, continuous farming depletes these nutrients, making soil infertile. Nature replenishes soil nutrients through decomposers—bacteria and fungi that break down dead plants, fallen leaves, animal waste, and carcasses. During decomposition, complex organic molecules (proteins, cellulose, fats) are broken into simpler inorganic forms (nitrates, phosphates) that plant roots can absorb again. This completes the nutrient cycle. Farmers also add organic manure (compost, cow dung) or chemical fertilizers to restore soil fertility. The chapter explains that leguminous plants (peas, beans, pulses) improve soil nitrogen because Rhizobium bacteria in their root nodules fix atmospheric nitrogen. Crop rotation (growing legumes alternately with cereals) is a traditional farming practice that naturally enriches soil. Understanding nutrient cycles connects this chapter to environmental science and explains why monoculture farming leads to soil degradation. Exam questions may ask students to describe how decomposers help replenish soil nutrients or explain the advantage of growing legumes.

While not heavily emphasized in CBSE Class 7 Science Chapter 1 Nutrition in Plants, insectivorous (carnivorous) plants like pitcher plant (Nepenthes), Venus flytrap, and sundew are fascinating examples. These plants are autotrophs—they perform photosynthesis—but they also trap and digest insects to obtain nitrogen and other minerals absent in the nutrient-poor soils (bogs, marshes) where they grow. The pitcher plant has modified leaves shaped like a pitcher filled with digestive fluid. Insects attracted by nectar fall in, drown, and are digested by enzymes; the plant absorbs the nutrients. Venus flytrap has hinged leaves that snap shut when triggered by insect movement. These plants supplement their nutrition but still rely on photosynthesis for carbohydrates. Exam questions are rare on this topic at Class 7 level, but if asked, students should explain that insectivorous plants are partial heterotrophs—they perform photosynthesis but also consume insects for minerals. This dual mode of nutrition helps them survive in nitrogen-deficient environments.

Scoring well in CBSE Class 7 Science Chapter 1 Nutrition in Plants requires understanding question patterns and answer structuring. The chapter typically yields 8–10 marks in annual exams through a mix of 1-mark (MCQ, fill-in-the-blank, match-the-following), 2-mark (short definitions, one-sentence explanations), 3-mark (explain with example, differentiate between two concepts), and 5-mark (describe a process with diagram, explain with multiple examples) questions. For 2-mark questions like 'Define autotrophic nutrition,' write a two-sentence answer: definition + one example. For 3-mark questions like 'How do plants obtain raw materials for photosynthesis?', structure your answer in three parts: CO₂ from air via stomata, water from soil via roots, sunlight absorbed by chlorophyll. For 5-mark questions like 'Describe the process of photosynthesis,' include the word equation, list raw materials and products, mention the site (chloroplast), role of chlorophyll, and draw a labeled diagram of a leaf cross-section showing stomata and chloroplasts. Always use NCERT terminology (e.g., 'haustoria' for Cuscuta's sucking roots, 'stomata' not 'pores'). Underline keywords like autotroph, heterotroph, saprotroph, parasite, symbiosis. Diagrams should be labeled neatly with pencil and scale. Practice previous years' CBSE question papers to identify recurring question types.

Students often lose marks in CBSE Class 7 Science Chapter 1 Nutrition in Plants due to conceptual confusion and poor answer structuring. One common mistake is writing 'plants eat food from soil'—plants absorb water and minerals from soil but make their own food (glucose) in leaves via photosynthesis. Another error is confusing stomata (pores for gas exchange) with chloroplasts (organelles containing chlorophyll). Students also mix up parasite and predator: a predator kills its prey immediately and eats it, while a parasite keeps the host alive to feed over a long period. Writing 'Cuscuta has roots' is incorrect—Cuscuta has haustoria (specialized sucking structures), not roots. In symbiosis questions, students often describe only one organism's benefit and forget to mention the other. For instance, in mutualism between bees and flowers, students write 'bee gets nectar' but omit 'flower gets pollinated.' In photosynthesis equations, writing 'plants take in oxygen' is wrong—plants take in carbon dioxide and release oxygen during photosynthesis (the reverse happens during respiration at night). Another frequent error is stating 'stomata are always open'—stomata open during day for photosynthesis and close at night or during drought to conserve water. Finally, students must use NCERT terminology: write 'saprotroph' or 'saprotroph,' not 'scavenger' (scavengers eat dead animals but do not decompose them chemically).

Parents and students often struggle with CBSE Class 7 Science Chapter 1 Nutrition in Plants because the chapter introduces several new concepts—photosynthesis equation, types of heterotrophic nutrition, symbiosis—that require both memorization and conceptual clarity. This is where CBSETUTOR.ai becomes invaluable. CBSETUTOR.ai is a 24×7 AI tutor that has ingested every NCERT textbook for Classes 6–12, including the complete Class 7 Science book. Students can upload a photo of any NCERT exercise question (or any school worksheet), and the AI provides a step-by-step solution aligned with CBSE marking scheme expectations. For example, if a student is confused about the difference between a parasite and a saprotroph, they can ask CBSETUTOR.ai, and within seconds receive a clear comparison with examples (Cuscuta vs. mushroom). The AI explains concepts using simple language, offers worked examples, and even generates practice questions similar to those in CBSE exams. Parents love CBSETUTOR.ai because it costs just ₹999/month flat for Classes 6–12 (one price for all classes, no hidden fees), comes with a 3-day free trial (no credit card required), and gives children instant homework help—no more waiting for tuition class the next day or googling unreliable answers. Whether a student needs help at 6 AM before school or 10 PM during exam prep, CBSETUTOR.ai is available round-the-clock, ensuring no concept in CBSE Class 7 Science Chapter 1 Nutrition in Plants remains unclear.