Chapter 10: Living Creatures: Exploring Their Characteristics
Explore the fundamental traits of living organisms, essential conditions for seed germination, plant movements in response to stimuli, and the life cycle of plants[cite: 3].
1. What Sets the Living Apart from the Non-living?
Living organisms are defined by key processes such as movement, nutrition, growth, respiration, excretion, response to stimuli, reproduction, and an eventual lifespan[cite: 3]. Non-living things lack these processes[cite: 3].
2. Key Characteristics of Living Beings
Click on any card below to explore essential features of living organisms[cite: 3]:
Movement
Animals move from place to place, while plants display internal movements like opening flowers or trapping insects (e.g., Drosera)[cite: 3].
Respiration & Stomata
Organisms take in oxygen and release carbon dioxide[cite: 3]. Plants exchange gases through microscopic pores called stomata[cite: 3].
Response to Stimuli
Living organisms respond to external triggers (stimuli)[cite: 3]. For example, Touch-me-not (Mimosa) folds its leaves upon touch[cite: 3].
3. Essential Conditions for Seed Germination
Seed germination requires optimal environmental conditions[cite: 3]. Below is a summary of experimental conditions and their effects on bean seed sprouting[cite: 3]:
| Condition / Pot | Air | Sunlight | Water | Germination Result | Reason |
|---|---|---|---|---|---|
| Pot A | Available | Direct Sunlight | No Water | No | Water is necessary to soften the seed coat and activate the embryo[cite: 3]. |
| Pot B | Restricted | Direct Sunlight | Excess Water | No / Poor | Excess water blocks air spaces in soil required for seed respiration[cite: 3]. |
| Pot C | Available | Dark Location | Moist Soil | Yes | Most seeds do not require light for initial germination[cite: 3]. |
| Pot D | Available | Direct Sunlight | Moist Soil | Yes | Optimal balance of air, water, and suitable environment[cite: 3]. |
4. Growth and Movement in Plants
Plants respond dynamically to directional environmental factors such as gravity and light[cite: 3]:
Geotropism & Phototropism: Shoots grow upwards toward sunlight (phototropism), while roots consistently grow downwards toward gravity regardless of orientation (geotropism)[cite: 3].
Mathematical expression for plant growth rate over time:
$$\text{Growth Rate} = \frac{\Delta H}{\Delta t} = \frac{H_2 - H_1}{t_2 - t_1}$$5. Life Cycle of a Plant
The sequence of changes from a germinating seed, maturing into a plant, producing flowers and fruit/pods, and generating new seeds defines the complete life cycle[cite: 3]. When a plant stops vital activities despite resource availability, it enters the stage of death[cite: 3].
6. Textbook Exercises & Solved Examples
Q1. What is a stimulus? Give an example from plant life.
Ans: A stimulus is any change or event in the environment that causes a living organism to react[cite: 3]. An example is touching the leaves of a Touch-me-not (Mimosa) plant, which causes its leaves to fold[cite: 3].
Q2. Why does excess water inhibit seed germination?
Ans: Excess water fills the air pockets present between soil particles, depriving the buried seeds of oxygen needed for respiration during germination[cite: 3].
7. Practice MCQs
Q1. Which instrument was invented by Sir Jagadish Chandra Bose to measure plant growth?