LECTURE 1: CLASS 10: LIFE PROCESSES

  Edunes Online Education

Board: CBSE and SEBA (Assam)

Subject: Science

🔵 UNIT I: Life Processes and Nutrition

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Autotrophic, Heterotrophic And Saprotrophic Nutrition

Edunes Online Education

CLASS X | SCIENCE | LIFE PROCESSES

Life is not just existing — it is a continuous set of chemical and physical activities that keep an organism alive. These activities are called Life Processes.

🧠 Big Idea: If these processes stop → Life stops.

A. CHARACTERISTICS OF LIVING THINGS

To understand life processes, first ask: “What makes something alive?”

1. Living things can move by themselves.
2. They need food, air, and water.
3. They grow.
4. They respond to stimuli (are sensitive).
5. They respire.
6. They excrete.
7. They reproduce.

🧠 Memory Trick: M N G S R E R (Move, Need food, Grow, Sensitive, Respire, Excrete, Reproduce)

B. WHAT ARE LIFE PROCESSES?

Life processes are the basic functions that maintain life in an organism.

Think of a machine. If it needs fuel, cooling, waste removal and control systems — Living organisms are much more complex machines.

• Nutrition & Respiration
• Transport & Excretion
• Control & Coordination
• Growth
• Movement
• Reproduction

🧠 Think of Life as a System: Energy In → Use Energy → Remove Waste → Control → Grow → Reproduce

C. NUTRITION – THE FOUNDATION OF LIFE

Every cell needs energy. Energy comes from food.

What is Food?

Food is an organic substance. The simplest food molecule is glucose.

Types of Nutrients

Nutrient	Main Role
Carbohydrates	Energy source
Fats	Stored energy
Proteins	Body building & repair
Minerals & Vitamins	Regulation & protection

🧠 Energy = Carbs + Fats Structure = Proteins Regulation = Vitamins & Minerals

Definition of Nutrition

Nutrition is the process of intake and utilisation of nutrients by an organism.

D. MODES OF NUTRITION

Ask this question: Does the organism make its own food?

• Autotrophic
• Heterotrophic

🧠 AUTO = Self HETERO = Other

E. AUTOTROPHIC NUTRITION

Autotrophs make their own food from CO₂ and water using sunlight.

How?

Chlorophyll traps sunlight → Sunlight energy converts CO₂ + H₂O → Glucose This process is called Photosynthesis.

Green plants and some bacteria are autotrophs.

🧠 Sunlight + CO₂ + Water → Food (Remember: Plants are food factories)

F. HETEROTROPHIC NUTRITION

Heterotrophs cannot make their own food. They depend on other organisms.

All animals, most fungi and many bacteria are heterotrophs.

🧠 No chlorophyll → No self-food → Depend on others

G. TYPES OF HETEROTROPHIC NUTRITION

1. Saprotrophic Nutrition

Organism feeds on dead and decaying matter.

Fungi like mushroom, yeast, bread mould.

🧠 SAPRO = Rotten food eater

2. Parasitic Nutrition

Parasite feeds on a living host without killing it.

Plasmodium (malaria parasite), Cuscuta.

🧠 Parasite lives ON host.

3. Holozoic Nutrition

Complex food is ingested → digested → absorbed → egested.

Steps: 1. Ingestion
2. Digestion
3. Absorption
4. Assimilation
5. Egestion

Humans, animals, Amoeba.

🧠 I → D → A → A → E
(Ingest, Digest, Absorb, Assimilate, Egest)

🧠 FINAL NEURO-MAP

Life = Energy Flow System
Food → Glucose → Respiration → ATP → Life Activities
No Nutrition → No Energy
No Energy → No Life

Life processes are interconnected. They work together like organs in an orchestra. If one fails, the whole system collapses.

DETAILED NOTES AND EXPLANATIONS

G. TYPES OF HETEROTROPHIC NUTRITION

A heterotrophic organism cannot prepare its own food and depends on other organisms. Based on how they obtain food, heterotrophic nutrition is classified into three main types. This is an important 3–5 marks exam topic.

• 1. Saprotrophic Nutrition
• 2. Parasitic Nutrition
• 3. Holozoic Nutrition

SAPROTROPHIC NUTRITION

Saprotrophic nutrition is the mode of nutrition in which an organism obtains its food from dead and decaying organic matter.
The organisms digest the food outside their body by secreting digestive enzymes and then absorb the simpler substances.
This process is called extracellular digestion.

Organisms having saprotrophic mode of nutrition are called saprophytes.
Saprophytes feed on rotten leaves, dead animals, decaying plants and spoiled food like bread.
Examples: Fungi (mushroom, bread mould, yeast) and many bacteria.
Importance: They act as decomposers and help in recycling nutrients in the ecosystem.

Exam Point: Saprotrophs perform digestion outside the body and absorb soluble nutrients.

PARASITIC NUTRITION

Parasitic nutrition is the mode of nutrition in which an organism derives its food from a living organism called the host.
The parasite depends on the host for food and shelter.
The parasite usually harms the host but does not immediately kill it.

The organism that obtains food is called a parasite.
The organism from which food is obtained is called the host.
Examples:

• Plasmodium – malaria parasite
• Cuscuta (dodder plant)
• Tapeworm, roundworm
• Some fungi and bacteria

Exam Point:
Most disease-causing organisms are parasites.
Plasmodium is a common example asked in board exams.

HOLOZOIC NUTRITION

Holozoic nutrition is the mode of nutrition in which organisms take in complex organic food into their body.
The food undergoes digestion, absorption and assimilation inside the body.

It involves five steps:

1. Ingestion – Taking food into the body
2. Digestion – Breaking down complex food into simple soluble substances
3. Absorption – Nutrients enter bloodstream or cells
4. Assimilation – Utilisation of absorbed nutrients
5. Egestion – Removal of undigested food

Examples: Humans, dog, cat, cow, lion, deer and Amoeba.

Exam Point:
Holozoic nutrition includes ingestion and internal digestion.
Amoeba is a frequently asked example.

COMPARISON TABLE
(Very Important for 5 Marks)

Feature	Saprotrophic	Parasitic	Holozoic
Source of Food	Dead & decaying matter	Living host	Complex food materials
Digestion	Outside body	From host tissues	Inside body
Effect on Host	No host involved	Host harmed	No host involved
Examples	Fungi, bacteria	Plasmodium, Cuscuta	Human, Amoeba

Final Revision Tip:
Saprotroph → Dead matter
Parasite → Living host
Holozoic → Ingest and digest

🧠 NEP Aligned Worksheet – Class X Science

Chapter: Life Processes | Focus: Nutrition

Exam Insight (CBSE 2026 Pattern): Questions are now competency-based → Case study, Assertion-Reason, Diagram-based, HOTS & Application. Focus on concept clarity + reasoning + real-life linkage.

SECTION A: Memory Activation (MCQs)

1. Which of the following is the simplest form of food used directly in respiration?

1. Protein
2. Glucose
3. Starch
4. Fat

Answer: (b) Glucose

2. Which statement correctly differentiates autotrophs and heterotrophs?

1. Autotrophs depend on others; heterotrophs make their own food.
2. Autotrophs make food from CO₂ and water; heterotrophs depend on others.
3. Both depend on others.
4. Both make their own food.

Answer: (b)

🔥 Memory Code:
AUTO = SELF (like automatic car moves itself)
HETERO = OTHER (depends on others)

SECTION B: Assertion – Reason (HOTS)

3. Assertion (A): Fungi are called saprophytes. Reason (R): They obtain food from dead and decaying organic matter.

1. Both A and R are true and R is correct explanation of A.
2. Both A and R are true but R is not correct explanation of A.
3. A is true but R is false.
4. A is false but R is true.

Answer: (a)

Logic Trigger 🧩: Saprophytes release digestive enzymes outside the body → break down complex matter → absorb nutrients.

SECTION C: Case Study Based Question

A farmer observed that a yellow thread-like plant wrapped around his crop plants and gradually weakened them.

4. Identify the plant and its mode of nutrition. Explain how it survives.

Plant: Cuscuta (Dodder) Mode: Parasitic Nutrition It absorbs ready-made food from the host plant through special sucking organs called haustoria.

🌿 Visual Hook: Imagine Cuscuta as a “thief vine” stealing food through pipelines (haustoria).

SECTION D: Competency-Based Short Answers

5. Why are green plants called primary producers?

Because they synthesize food by photosynthesis using sunlight, CO₂ and water and form the base of the food chain.

6. Differentiate between Saprotrophic and Parasitic nutrition.

Feature	Saprotrophic	Parasitic
Source of Food	Dead & decaying matter	Living host
Effect on Host	No host involved	Harms host
Example	Mushroom	Plasmodium

SECTION E: Long Answer (3–5 Marks)

7. Explain Holozoic nutrition with steps and one example.

Steps: 1. Ingestion
2. Digestion
3. Absorption
4. Assimilation
5. Egestion
Example: Human beings, Amoeba

🧠 Brain Formula:
I D A A E → “I Dig And Absorb Everything”

SECTION F: Higher Order Thinking (Application)

8. If all autotrophs disappeared from Earth, what would happen? Explain scientifically.

All food chains would collapse because autotrophs are primary producers.
Oxygen level would decrease.
Heterotrophs would eventually die due to lack of food.

Critical Thinking Trigger 🚀
Energy Flow: Sun → Autotroph → Herbivore → Carnivore
Remove Autotroph = Entire chain breaks.

🎯 Final Revision Trigger (30-Second Recall Test):
Autotroph → Photosynthesis → Chlorophyll → Glucose
Heterotroph → Saprotrophic / Parasitic / Holozoic
Holozoic Steps → IDAAE

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Prepared as per CBSE examination and NEP 2020 guidelines