Life Processes Lesson: Understanding the Basics
Lesson Overview
- Nutrition
- Respiration
- Transportation
- Excretion
- Life Processes
- Sample Questions for Critical Thinking
- Key Takeaway
All living organisms-plants, animals, or microbes-perform certain essential functions to stay alive. These include nutrition, respiration, transportation, and excretion. These functions, known as life processes, ensure survival, growth, and reproduction. This lesson simplifies each concept for Grade 7 learners, offering examples, diagrams, and tables for better understanding.
Nutrition
A. Autotrophic Nutrition in Plants
Plants make their own food via photosynthesis using:
| Required Factor | Function |
| Sunlight | Provides energy for photosynthesis |
| Carbon dioxide | Source of carbon for glucose |
| Water | Provides hydrogen, absorbed by roots |
| Chlorophyll | Traps sunlight in leaf cells |
Photosynthesis Equation:
Carbon Dioxide + Water -(Sunlight/Chlorophyll)-> Glucose + Oxygen
B. Heterotrophic Nutrition in Animals
Animals rely on ready-made food. Ingestion, digestion, absorption, and egestion are the key steps.
- Peristalsis: Rhythmic contractions in the esophagus that push food to the stomach.
- Digestion: Enzymatic breakdown in the stomach and small intestine.
- Bile: Produced by the liver, bile emulsifies fats (breaks large droplets into smaller ones).
| Digestive Component | Role |
| Mouth | Chewing + saliva |
| Esophagus | Peristalsis |
| Stomach | Protein digestion |
| Bile | Fat emulsification (not enzyme) |
| Villi | Nutrient absorption in small intestine |
Respiration
Respiration is the process of breaking down food to release energy.
A. Breathing Mechanism
| Phase | Diaphragm Shape | Chest Volume | Air Flow |
| Inhalation | Flattened | Increases | Air in (O₂) |
| Exhalation | Arched (relaxed) | Decreases | Air out (CO₂) |
B. Cellular Respiration
Takes place in mitochondria, converting glucose into ATP (energy).
Aerobic Respiration (with oxygen):
Glucose + O₂ → CO₂ + H₂O + ATP
Anaerobic Respiration (without oxygen):
Occurs in yeast, producing alcohol and CO₂ (less energy output).
| Type | Oxygen Used? | End Products | Energy Yield |
| Aerobic | Yes | CO₂ + Water + ATP | High |
| Anaerobic | No | Alcohol + CO₂ + ATP | Low |
Transportation
A. In Animals (Circulatory System)
The heart, blood, and blood vessels form the transport network.
Correct Pathway:
Atria → Ventricles → Arteries → Veins
| Component | Function |
| Arteries | Carry blood away from heart (oxygenated) |
| Veins | Carry blood toward heart (deoxygenated) |
| Pulmonary Vein | Exception: carries oxygenated blood to heart |
| Pulmonary Artery | Exception: carries deoxygenated blood to lungs |
B. In Plants
| Tissue | Function | Direction |
| Xylem | Transports water from roots to leaves | Upward only |
| Phloem | Transports food to all parts | Multi-directional |
Transpiration pull helps water rise in xylem due to evaporation from leaves.
Excretion
Excretion removes harmful metabolic waste (e.g., urea, CO₂).
A. In Humans
| Organ | Waste Removed |
| Kidneys | Urea, excess water |
| Lungs | CO₂ from respiration |
| Skin | Sweat (water + salts) |
Kidneys filter blood to form urine.- Kidneys are part of the excretory system, not the digestive system.
Life Processes
| Life Process | Key Organs/Tissues | Purpose |
| Nutrition | Mouth, stomach, villi | To obtain and digest food |
| Respiration | Lungs, mitochondria | To release energy from food |
| Transportation | Heart, xylem, phloem | To move substances throughout the body |
| Excretion | Kidneys, lungs, skin | To remove metabolic waste |
Sample Questions for Critical Thinking
- Why can yeast survive without oxygen but humans can't?
- What might happen if bile was not produced by the liver?
- How does the body ensure blood doesn't flow backward in veins?
- Why do herbivores have longer intestines than carnivores?
- What role does transpiration play in tall trees?
Key Takeaway
Understanding life processes helps us see how living organisms maintain themselves. From the food we eat to the air we breathe, every system-digestive, respiratory, circulatory, and excretory-works together. Mastering these concepts will not only help you succeed in your quizzes but also build a foundation for future science learning.
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