Let Us Enhance Our Learning
1. List the similarities and differences in life cycles of plants and animals.
Answer:
- Similarities:
- Both start life (seed/egg/birth).
- Both involve growth and development.
- Both reach maturity and reproduce.
- Both eventually die.
- Differences:
- Mobility: Animals often move during their life cycle stages (e.g., tadpole swimming), while plants remain anchored (though they grow).
- Form Change: Many animals (like frogs/butterflies) undergo metamorphosis (drastic shape change). Plants generally maintain the same structural plan (root/shoot) just increasing in size and complexity (adding flowers/fruit).
- Seed vs Egg: Plants typically grow from seeds which can remain dormant for long periods; animals grow from eggs or birth and usually develop continuously.
2. Analysis of Table Data (Growth and Respiration)
Scenario: Analyze objects based on “Does it grow?” and “Does it respire?”.
| Case | Grows? | Respires? | Example | Reason/Remarks |
|---|---|---|---|---|
| 1 | No | No | Stone / Chair | Non-living things do neither. |
| 2 | No | Yes | Not Possible | Respiration produces energy for life processes like growth and maintenance. A thing cannot respire without being alive, and if it is alive, it usually shows some form of growth or repair. |
| 3 | Yes | No | Cloud / Crystal | Clouds “grow” by accumulation of water vapor, but they do not respire. This is non-biological growth. |
| 4 | Yes | Yes | Tree / Child | Typical characteristics of living beings. |
3. Proper storage of grains and pulses.
Question: You have learnt that different conditions are required for seed germination. How can we use this knowledge for proper storage of grains and pulses?
Answer: Seeds germinate when they have water (moisture), air, and suitable temperature. To store grains (which are seeds) without them sprouting or rotting:
- Keep them dry: Remove moisture to prevent germination and fungal growth.
- Airtight containers: Limit exposure to moisture in the air.
- Cool place: High temperatures can encourage spoilage or pests, though some warmth is needed for germination, keeping them cool preserves dormancy.
- Key Strategy: The most critical factor to control is moisture. Dry seeds remain dormant.
4. Advantage of a tail in the tadpole stage.
Question: What is the advantage of having a tail in the tadpole stage?
Answer: Tadpoles live strictly in water. The tail serves as a swimming organ (fin-like structure). It helps the tadpole propel itself through water to find food and escape predators. As it metamorphoses into a frog and moves to land, the tail is reabsorbed, and legs develop for jumping.
5. Wooden Log: Living or Non-living?
Question: Charan says a wooden log is non-living (cannot move). Charu says it is living (made of wood from trees). Give arguments.
Answer:
- Charan is correct that it is Non-living.
- Reasoning: While wood was once part of a living tree, a cut wooden log no longer carries out life processes. It does not respire, excrete, eat, or grow. It is dead organic matter. Therefore, it is classified as non-living (or dead).
6. Similarities and differences in life cycles of a mosquito and a frog.
Answer:
- Similarities:
- Both lay eggs in water.
- Both undergo metamorphosis (distinct larval stages different from adult).
- The young ones (larva/tadpole) are aquatic and breathe dissolved oxygen.
- Adults can live in air (aerial/terrestrial).
- Differences:
- Stages: Mosquito has 4 stages (Egg -> Larva -> Pupa -> Adult). Frog generally described in 3 main phases (Egg -> Tadpole -> Adult) though detailed as multiple steps.
- Pupa: Mosquito has a pupal stage (inactive feeder); Frogs do not have a pupal stage.
- Adult Habitat: Adult mosquitoes fly (aerial); Adult frogs are amphibious (land/water) and hop.
7. Plant Prediction (Fig 10.9)
Question: A plant is placed horizontally. What happens after one week?
Answer:
- Shoot: Will bend and grow upwards (away from gravity, towards light).
- Root: Will bend and grow downwards (towards gravity).
- Reason: This is due to geotropism. Roots are positively geotropic (go down), and shoots are negatively geotropic (go up).
8. Tara and Vijay’s Experiment (Fig 10.10)
Question: What do they want to find out? (Image shows a seedling in a box with a hole).
Answer:
- Aim: To demonstrate Phototropism (plant movement in response to light).
- Setup: The plant is in a dark box with light entering from only one hole.
- Observation: The shoot will bend towards the hole.
- Conclusion: Plants grow towards the source of light.
9. Experiment Design: Temperature and Germination.
Question: Design an experiment to check if temperature has an effect on seed germination.
Answer:
- Take two sets of identical bean seeds (e.g., 10 in each).
- Control Variables: Provide both sets with equal moisture (wet cotton) and air.
- Variable:
- Set A: Place inside a refrigerator (Very low temperature).
- Set B: Place in a room at normal temperature (25°C - 30°C).
- Observation: Observe after 5 days.
- Expected Result: Seeds in the room (Set B) will germinate. Seeds in the fridge (Set A) will likely not germinate or be very slow.
- Conclusion: Suitable temperature (warmth) is necessary for germination.