Overview
"Life processes" refer to the essential activities that keep animals alive. These include nutrition, respiration, circulation, excretion, movement, and response. In Class 7 NCERT context these topics are presented with simple examples and diagrams — from single-celled organisms to complex animals including insects, fish, birds and mammals. Understanding the purpose of each process, where it happens, and how it varies between animal groups is the most important learning outcome for CBSE board-style questions.
Key Terms (learn these)
- Nutrition: Heterotrophic, autotrophic (briefly), ingestion, digestion, absorption.
- Respiration: Aerobic, anaerobic, gills, lungs, trachea.
- Circulation: Blood, hemoglobin, single/double circulation (basic idea), heart.
- Excretion: Kidney, nephridia (in simple animals), ammonotelic/ureotelic patterns (simple explanation).
- Locomotion: Appendages, muscles, wings, fins, jointed legs.
Nutrition in Animals
Animals cannot make their own food (they are heterotrophs). Nutrition starts with ingestion (taking in food), followed by digestion (breaking food into small usable molecules), absorption (taking digested food into the body), and egestion (removal of undigested material).
Different animals show adaptations for different diets:
- Herbivores (e.g., cows) have flat teeth for grinding and often a longer gut for digesting cellulose with the help of microbes.
- Carnivores (e.g., lions) have sharp teeth and shorter guts because meat is easier to digest.
- Omnivores (e.g., humans) have mixed dentition and an intermediate gut length.
Example — Human Digestive System (simple steps)
- Mouth: Mechanical breakdown (teeth) + saliva (enzyme).
- Oesophagus: Food moves by peristalsis.
- Stomach: Acid and enzymes continue digestion.
- Small intestine: Major digestion & absorption (villi increase surface area).
- Large intestine: Water absorption and egestion.
Respiration
Respiration releases energy from food. The common types discussed are aerobic respiration (requires oxygen) and anaerobic respiration (no oxygen). In animals, organs for gas exchange differ:
- Gills — in fishes; thin, feathery structures with a large surface area to exchange oxygen and carbon dioxide with water.
- Tracheal system — in insects; network of tiny tubes (tracheae) that carry air directly to tissues.
- Lungs — in mammals, birds and many reptiles; internal organs where oxygen enters blood and carbon dioxide leaves.
Key idea: Surface area and thin membranes make gas exchange efficient. Always link the structure (gills/trachea/lungs) with its function in answers.
Circulation
Circulation means transport of materials — oxygen, nutrients, hormones, and waste — inside the body. Simple animals may not need a circulatory system (diffusion is enough), while complex animals use blood or haemolymph.
- Open circulatory system: In insects, blood (haemolymph) flows into body cavities and bathes organs directly.
- Closed circulatory system: In fishes, amphibians, reptiles, birds and mammals, blood flows in vessels. The heart pumps blood through arteries, capillaries and veins.
Briefly explain the heart’s role: it pumps blood; blood carries oxygen from lungs/gills to tissues and returns carbon dioxide to be expelled. For CBSE, draw a simple labelled heart and write short bullets about its function.
Excretion
Excretion is the removal of metabolic wastes. In animals, major excretory organs include kidneys (in mammals), nephridia (in some worms), and malpighian tubules (in insects). Explain the role of kidneys: filtration of blood, selective reabsorption and formation of urine. Mention why excretion is important — to maintain internal balance (homeostasis).
Movement and Locomotion
Animals move using muscles, joints, limbs, fins or wings. Relate form to function: birds have hollow bones and wings for flight; fish have streamlined bodies and fins for swimming. Insects have jointed legs and an exoskeleton that supports muscle attachment.
Simple Nervous Response
Animals respond to changes in their environment (stimuli) using sense organs and effectors. Explain the flow: stimulus → receptor → coordination (brain/ ganglia) → effector (muscle/gland). Give one clear example — touching a hot object causes immediate withdrawal due to reflex action.
Comparative Summary — How Life Processes Differ
For quick revision, memorise a table comparing major processes across simple and complex animals. Focus on these contrasts:
- Nutrition: Amoeba (cell surface digestion) vs Human (organ system).
- Respiration: Earthworm (skin) vs Fish (gills) vs Human (lungs).
- Circulation: Insects (open) vs Mammals (closed).
Diagram Practice
Draw and label: (1) Human digestive system (small, labelled), (2) Simple heart diagram (showing chambers roughly), (3) Fish gill structure or insect trachea. Diagrams fetch marks in CBSE exams — neat, labelled sketches with arrows and short captions are highly effective.
CBSE Board Exam Tips (Systematic order)
- Start with definitions: Give one-line definitions for life processes asked in 1–2 marks questions.
- Short answers (2–4 marks): Use 3–5 bullet points. Include examples and one labelled mini-diagram if helpful.
- Long answers (5+ marks): Write a structured answer: Introduction, 3–5 numbered points with short explanations, and a concluding sentence.
- Diagrams: Always label, give a title, and add one-line caption. Use pencil for sketches and pen for labels if allowed.
- Value addition: Link structure to function in every answer — this shows deeper understanding and gains extra marks.
Practice — Short & Sample Questions
- Q1. Define respiration. (1 mark)
- A: Respiration is the process by which organisms obtain energy from food to carry out life processes.
- Q2. Name the organ of excretion in humans. (1 mark)
- A: Kidney.
- Q3. Give two differences between respiration in fish and insects. (2 marks)
- A: Fish use gills for gas exchange in water; insects use tracheal tubes that directly supply air to tissues.
- Q4. Explain the steps of human digestion briefly. (3 marks)
- A: Ingestion (mouth) → Mechanical and chemical digestion (mouth & stomach) → Absorption (small intestine) → Egestion (large intestine).
- Q5. Why is excretion important? (2 marks)
- A: Excretion removes metabolic wastes and helps maintain the body’s internal balance (homeostasis).
Final Revision Checklist
- Memorise key terms and definitions.
- Be able to explain each life process with a one-sentence definition and 2–3 supporting points.
- Practice at least 3 labelled diagrams from this chapter.
- Do a mixed set of 10 short answer and 5 long answer questions under timed conditions.
- Revise differences between animal groups in a 1-page summary sheet.
Note: This study module strictly follows NCERT-level explanations suitable for CBSE Class 7 examinations. Use additional practice worksheets for higher practice.