CBSE Class 6- Science Chapter 10: Living Creatures: Exploring Their Characteristics – Study Notes (PDF)

Study Notes: Living Creatures: Exploring Their Characteristics (Class 6-NCERT(Curiosity) Science

1. Differentiating Living and Non-living Things

The world around us is composed of living beings and non-living things. Living beings share a set of common, essential characteristics that distinguish them from non-living objects like pencils, books, or cars.

Core Characteristics of Living Beings:

• Movement: While animals move from place to place, plants also exhibit movement, such as the opening of flowers, the trapping mechanism of insectivorous plants like Drosera, and the winding of climbers around supports.
• Growth: All living beings grow. This is evident in a child growing into an adult or a seed growing into a plant. Non-living things, like a car, do not grow.
• Nutrition (Need for Food): Living beings require food to get energy for their growth, development, and other life processes.
• Respiration: This is the process of taking in and giving out air. In animals, it involves breathing. In plants, tiny pores on the leaf surface called stomata facilitate the exchange of air.
• Excretion: This is the process of removing waste products from the body. Animals excrete waste in the form of sweat and urine. Plants excrete excess water and minerals, often visible as small droplets on leaves (e.g., on grass and roses).
• Response to Stimuli: A stimulus is any event that causes a living being to react. For example, a person pulling their hand away from a hot object is a response. Plants also respond to stimuli; the touch-me-not plant (mimosa) folds its leaves when touched, and some plant shoots grow towards sunlight.
• Reproduction: This is the process by which living beings produce new individuals of their own kind. Reproduction is essential for the continuity of life on Earth.
• Death: All living things have a finite lifespan and eventually die. A living being is considered dead when it can no longer exhibit its life characteristics, even with access to resources like food, air, and water.

2. Plant Life: Germination, Growth, and Movement

2.1 Essential Conditions for Seed Germination

Germination is the process where a seed develops into a sprout or seedling. For this to occur, specific conditions are necessary.

• Water: Water is crucial as it softens the seed coat, allowing the tiny embryo inside to emerge and grow. It also enables the internal processes necessary for growth.
• Air: Seeds need air for respiration. They utilize the air present in the spaces between soil particles.
• Soil: The spaces between soil particles not only provide air but also allow the new roots to grow and expand easily.
• Light/Darkness: For most seeds, like bean seeds, sunlight is not essential for the initial germination process. However, sunlight becomes vital for the continued growth of the seedling after it has sprouted.
  • Some seeds, like Coleus and Petunia, specifically require light to germinate.
  • Other seeds, such as Calendula and Zinnia, require darkness to germinate.

2.2 Plant Growth and Movement in Response to Stimuli

Plants exhibit distinct growth patterns and movements in response to their environment, particularly sunlight and gravity.

• Shoot Growth: The shoot (stem and leaves) of a plant grows upwards, away from gravity. It also exhibits movement towards sunlight. If a plant receives light from only one direction, its shoot will bend and grow in that direction.
• Root Growth: The root of a plant grows downwards, into the soil. This happens regardless of the plant’s orientation; even if a seedling is placed upside down, its root will bend to grow downwards.
• Historical Context: Indian scientist Jagadish Chandra Bose (1858–1937) invented the crescograph, a machine that could measure the minute growth of plants and demonstrate their response to various stimuli like light, heat, and gravity.

3. The Life Cycle of a Plant

The life cycle describes the series of changes a living being undergoes from its beginning to producing the next generation.

Stages in a Bean Plant’s Life Cycle:

1. Seed (Stage I): The dormant stage, containing the embryo.
2. Seed Germination (Stage II): The seed sprouts when provided with the right conditions (water, air).
3. Seedling/Young Plant (Stage III): The sprout grows, developing roots, a shoot, and leaves.
4. Mature Plant (Stage IV): The plant grows larger and develops flowers.
5. Reproduction (Stage V): The flowers develop into fruits (in this case, pods) which contain seeds.
6. Death: After producing seeds, the plant ages, turns yellow and dry, and eventually dies. The seeds it produced can then start a new cycle.

4. The Life Cycle of Animals

Animals also undergo distinct life cycles, often with dramatic transformations between the young and adult stages.

4.1 Life Cycle of a Mosquito

Mosquitoes undergo a four-stage life cycle, with the early stages being aquatic.

• Stage I: Egg: Female mosquitoes lay eggs on or near stagnant water.
• Stage II: Larva: The eggs hatch into worm-like larvae that live in the water. Larvae must come to the water’s surface to breathe air.
• Stage III: Pupa: The larva transforms into a pupa, which also lives in water and breathes at the surface.
• Stage IV: Adult: An adult mosquito emerges from the pupal case, rests briefly on the water, and then flies away.
• Control Measures: Since mosquitoes breed in stagnant water, preventing water from collecting in coolers, pots, and open containers is crucial. Spraying kerosene oil on stagnant water creates a thin film that prevents larvae and pupae from accessing air, causing them to die.

4.2 Life Cycle of a Frog

Frogs undergo significant changes, known as metamorphosis, moving from a fully aquatic life to a semi-aquatic one.

• Stage I: Spawn/Embryo: Frogs lay eggs in a jelly-like cluster called spawn. These develop into embryos.
• Stage II: Tadpole: The embryo hatches into a tadpole. Early tadpoles have a tail for swimming but no legs. Later, they develop hind legs. Tadpoles are fully aquatic.
• Stage III: Froglet: The tadpole develops into a froglet, which looks like a small frog but still has a tail. It begins to spend some time on land.
• Stage IV: Adult Frog: The froglet’s tail disappears, and its legs become strong for jumping. The adult frog can live both in water and on land.

+++++++++++++++++++++++++++++++++++++++++++++++++++++

Quiz

Short-Answer Questions (25 Questions)

(Answer in 2-3 sentences)

1. What is the key difference between the movement of a car and the movement of a living being?
2. Provide two examples of movement in plants, even though they are fixed in one place.
3. Define the term “excretion” and give one example for both an animal and a plant.
4. What is a stimulus, and how does the touch-me-not plant demonstrate a response to it?
5. Why is the process of reproduction considered essential for living beings?
6. Explain the function of stomata in plants.
7. What three conditions are generally essential for a seed to germinate?
8. Is sunlight necessary for the germination of all seeds? Explain with an example.
9. Describe the role of water in the process of seed germination.
10. Who was Jagadish Chandra Bose and what was his contribution to the study of plants?
11. How does the shoot of a plant respond to a light source that is coming from only one side?
12. How does the root of a plant grow if the plant is placed upside down (inverted)?
13. Briefly outline the five main stages in the life cycle of a bean plant.
14. Why are people advised not to let water stagnate in or around their homes?
15. Describe the larva stage in a mosquito’s life cycle.
16. How does spraying kerosene oil on stagnant water help control the mosquito population?
17. What are the four main stages in the life cycle of a mosquito?
18. What is frog spawn and where is it typically found?
19. Describe a tadpole. What is its primary mode of movement and habitat?
20. What is a froglet, and how is it different from both a tadpole and an adult frog?
21. Explain the change in habitat that occurs during a frog’s life cycle.
22. What happens to a tadpole’s tail as it matures into an adult frog?
23. What are insectivorous plants? Give the example mentioned in the text.
24. How is breathing in animals related to the broader process of respiration?
25. How can you tell if a living being is dead, according to the text?

Multiple-Choice Questions (20 Questions)

1. Which of the following is NOT a characteristic of all living beings? a) Growth b) Movement from place to place c) Respiration d) Reproduction
2. The trapping mechanism of the Drosera plant is an example of: a) Respiration b) Excretion c) Movement d) Germination
3. The removal of waste products like sweat and urine from the body is called: a) Nutrition b) Respiration c) Excretion d) Reproduction
4. Tiny pores on the surface of leaves that help plants take air in and out are called: a) Roots b) Stomata c) Embryos d) Seed coats
5. Which of the following is an example of a plant responding to a stimulus? a) A bean seed germinating b) A mimosa plant folding its leaves when touched c) Grass excreting water droplets d) A climber winding around a pole
6. According to the text, what is the primary role of water in seed germination? a) To provide nutrients to the seed b) To soften the seed coat and enable growth processes c) To protect the seed from sunlight d) To help the seed breathe
7. Which of these seeds require light to germinate? a) Bean and Gram b) Calendula and Zinnia c) Coleus and Petunia d) All seeds require light
8. The shoot of a plant generally grows: a) Downwards and away from sunlight b) Upwards and towards sunlight c) Towards the nearest water source d) In a random direction
9. The root of a plant generally grows: a) Upwards, towards the light b) Sideways, along the ground c) Downwards, into the soil d) Towards the stem
10. The crescograph was a machine used to: a) Observe the life cycle of mosquitoes b) Measure the growth of plants c) Identify different types of seeds d) Analyze the components of soil
11. In the life cycle of a bean plant, what develops directly from a flower? a) The root system b) A new seedling c) The fruit or pod containing seeds d) The first leaves
12. The egg, larva, and pupa stages of a mosquito are primarily: a) Aquatic b) Terrestrial c) Aerial d) Subterranean
13. What stage in the mosquito life cycle comes immediately after the larva stage? a) Egg b) Adult c) Pupa d) Spawn
14. A female mosquito lays its eggs: a) On plant leaves b) In dry soil c) In or near stagnant water d) On other animals
15. The cluster of frog eggs is known as: a) Larva b) Pupa c) Spawn d) Froglet
16. Which stage in a frog’s life cycle has a tail but no legs initially? a) Adult frog b) Froglet c) Embryo d) Tadpole
17. A froglet is best described as: a) An adult frog that lives only in water b) A tadpole that has developed legs but still has a tail c) The jelly-like egg mass of a frog d) A fully terrestrial young frog
18. An adult frog’s habitat is: a) Only on land b) Only in water c) Both in water and on land d) Inside trees
19. Which process ensures the continuity of a species? a) Growth b) Excretion c) Respiration d) Reproduction
20. A seed contains a tiny ____ inside it that develops into a plant. a) Stomata b) Pupa c) Embryo d) Tadpole

+++++++++++++++++++++++++++++++++++++++++++++++++++++

Answer Keys

Short-Answer Questions – Answer Key

1. A car’s movement is caused by an external force (its engine), while a living being’s movement is an inherent characteristic. Additionally, a car cannot perform other life functions like growing or reproducing, which sets it apart from living things.
2. Two examples of plant movement are the opening and closing of flowers and the way an insectivorous plant like Drosera moves its hairs inward to trap an insect.
3. Excretion is the removal of waste products from the body. An example in animals is sweat, which consists of water and salts. In plants, an example is the removal of excess water and minerals in the form of small droplets on leaves.
4. A stimulus is an event that prompts a living being to respond. The touch-me-not plant demonstrates this by folding its leaves inward when touched, with the touch being the stimulus and the folding being the response.
5. Reproduction is essential because it is the process through which living beings create new individuals of their own kind. This ensures the survival and continuity of their species from one generation to the next.
6. Stomata are tiny pores found on the surface of plant leaves. They are crucial for respiration, as they help the plant in taking air in and out for gaseous exchange.
7. The three generally essential conditions for seed germination are the right amount of water, the presence of air (for respiration), and a suitable medium like soil for root growth.
8. No, sunlight is not necessary for all seeds to germinate; some, like Calendula, require darkness. For many seeds like beans, sunlight is not needed for germination itself but becomes essential for the seedling’s growth after it sprouts.
9. Water plays a vital role by softening the tough outer seed coat. This allows the small embryo inside to break through and begin its development into a plant.
10. Jagadish Chandra Bose was an Indian scientist who built a machine called a crescograph. This device was significant because it could measure the very slow growth of plants and demonstrate that they can sense and respond to stimuli.
11. The shoot of a plant will bend and grow in the direction of the light source. This movement is a response to the light stimulus, as the plant seeks to maximize light for its growth.
12. If a plant is placed upside down, its root will still bend and grow downwards. This is because roots are genetically programmed to grow in the direction of gravity.
13. The five stages are: Seed, Seed Germination (sprouting), Seedling (appearance of leaves), Mature Plant (appearance of flowers), and Fruit/Pod Formation (production of new seeds).
14. People are advised to prevent water stagnation because mosquitoes lay their eggs and complete their larval and pupal stages in such water. Eliminating stagnant water disrupts their life cycle and helps prevent mosquito breeding.
15. The larva is the second stage in a mosquito’s life. It is a worm-like creature that hatches from the egg, lives in water, and must repeatedly come to the surface to breathe air.
16. Kerosene oil forms a thin layer on the water surface. This layer acts as a barrier, preventing the aquatic larvae and pupae from reaching the surface for air, which causes them to suffocate and die.
17. The four main stages are: egg, larva, pupa, and adult.
18. Frog spawn is the cluster of frog eggs, which has a white, jelly-like appearance. It is typically found on the surface of water in ponds or attached to plants in or near the water.
19. A tadpole is the larval stage of a frog that hatches from an egg. It lives entirely in water, breathes through gills, and moves by swimming with its tail.
20. A froglet is the transitional stage between a tadpole and an adult frog. It looks like a small frog with strong legs but still has a tail, which the adult frog lacks.
21. A frog begins its life as a fully aquatic tadpole. As it develops into a froglet and then an adult, it transitions to a semi-aquatic life, living both in water and on land.
22. As a tadpole grows into a froglet and then an adult frog, its tail is gradually absorbed by the body and disappears completely. The energy from the tail is used to fuel other developmental changes.
23. Insectivorous plants are plants that depend on insects for their nutrition. The text provides the example of Drosera, which has sticky hairs on its leaves to trap insects.
24. Breathing is the physical act of inhaling and exhaling air. It is a part of the larger biological process called respiration, which involves the exchange of gases to produce energy.
25. A living being is considered dead when it is no longer able to exhibit any of the essential characteristics of life (like growth, respiration, reproduction, etc.), despite the availability of necessary resources like food, air, and water.

Multiple-Choice Questions – Answer Key

1. b) Movement from place to place
2. c) Movement
3. c) Excretion
4. b) Stomata
5. b) A mimosa plant folding its leaves when touched
6. b) To soften the seed coat and enable growth processes
7. c) Coleus and Petunia
8. b) Upwards and towards sunlight
9. c) Downwards, into the soil
10. b) Measure the growth of plants
11. c) The fruit or pod containing seeds
12. a) Aquatic
13. c) Pupa
14. c) In or near stagnant water
15. c) Spawn
16. d) Tadpole
17. b) A tadpole that has developed legs but still has a tail
18. c) Both in water and on land
19. d) Reproduction
20. c) Embryo

+++++++++++++++++++++++++++++++++++++++++++++++++++++

Essay Questions & Answers (For Teachers)

1. Discuss the essential characteristics that define a living being, using specific examples for each from the text.
   • Answer: Living beings are defined by a set of shared characteristics. These include movement, seen not just in animals but also in plants like the Drosera trapping an insect. They exhibit growth, as a child becomes an adult. All living things need nutrition (food) for energy and development. They perform respiration; animals breathe, and plants use stomata for air exchange. They must perform excretion to remove waste, such as sweat in humans or water droplets on grass. A key feature is the response to stimuli, like a person pulling a hand from a hot object or a touch-me-not plant folding its leaves. Finally, they reproduce to ensure the continuity of their kind and, after a certain lifespan, they die.
2. Explain the experiment described in the text (Activity 10.2) to determine the essential conditions for seed germination. What were the results and conclusions?
   • Answer: The experiment used four pots of bean seeds under different conditions. Pot A had sunlight but no water. Pot B had sunlight and excess water. Pot C had moist soil but was kept in the dark. Pot D had moist soil and direct sunlight. The experiment demonstrated that seeds germinated only in Pots C and D. This shows that a moderate amount of water and the presence of air (which was available in moist soil but not in the waterlogged soil of Pot B) are essential for germination. The results also showed that sunlight is not essential for the germination of bean seeds, as they sprouted in the dark (Pot C) as well as in the light (Pot D).
3. Compare and contrast the movements of plants and animals as described in the source.
   • Answer: The primary difference in movement is that animals are mobile and can move their entire bodies from one place to another, while plants are generally stationary. However, plants do show specific types of movements. For example, they show growth movements, where the shoot grows upwards towards light and roots grow downwards. They also show responsive movements, such as the opening of flowers, the rapid folding of a touch-me-not plant’s leaves, or the trapping action of an insectivorous plant. Therefore, while animals exhibit locomotion, plants exhibit movements related to growth and response to environmental stimuli.
4. Describe the complete life cycle of a bean plant, detailing what happens at each major stage.
   • Answer: The life cycle of a bean plant begins with a seed, which contains a dormant embryo. Under suitable conditions of water and air, the seed undergoes germination, sprouting a root and a shoot. This grows into a young plant or seedling, which develops leaves and increases in size. As the plant matures, it produces flowers. These flowers, after pollination, develop into fruits, which for a bean plant are pods. Inside the pods are new seeds. After producing seeds, the parent plant completes its life cycle, ages, and dies. The new seeds can then begin the cycle all over again.
5. Detail the four stages of a mosquito’s life cycle. Explain why controlling stagnant water is an effective method for preventing mosquito-borne diseases.
   • Answer: A mosquito’s life cycle has four distinct stages. It begins with the egg, laid in or near water. The egg hatches into a larva, a worm-like creature that lives in water but breathes air at the surface. The larva then transforms into a pupa, which is also aquatic and must surface to breathe. Finally, the adult mosquito emerges from the pupa. Controlling stagnant water is effective because the first three stages (egg, larva, pupa) are entirely dependent on water. By eliminating breeding grounds like puddles, open containers, and coolers, we interrupt the life cycle, preventing larvae from developing into adult mosquitoes that can transmit diseases like malaria and dengue.
6. Trace the life cycle of a frog, highlighting the significant physical and habitat changes (metamorphosis) it undergoes.
   • Answer: The frog life cycle is a classic example of metamorphosis. It starts as spawn, a jelly-like mass of eggs in water. An egg hatches into a tadpole, a fully aquatic larva with a tail for swimming and gills for breathing. The tadpole then grows hind legs, becoming a late-stage tadpole. It further develops into a froglet, which resembles a small frog but still has a tail and lives partly in water and partly on land. Finally, the tail is absorbed, the legs grow strong, and it becomes an adult frog that lives both on land and in water. This transformation involves changing from a gill-breathing, tailed swimmer to a lung-breathing, four-legged jumper.
7. Explain the experimental setup (Activity 10.3) designed to observe the growth direction of a plant’s root and shoot. What were the three main conclusions from this activity?
   • Answer: The experiment involved three beakers with seedlings. Beaker A held an upright seedling in full sunlight. Beaker B held an inverted seedling in full sunlight. Beaker C held an upright seedling in a box with light coming from a single hole. The conclusions were: 1) In an upright plant, the shoot grows upwards and the root grows downwards. 2) In an inverted plant, the shoot bends to grow upwards, and the root bends to grow downwards, showing their fixed orientation relative to gravity. 3) When light comes from one direction, the shoot grows towards the light, while the root continues to grow downwards, unaffected by the light’s direction.
8. Based on the text, argue whether a dry seed should be categorized as living or non-living.
   • Answer: A dry seed should be categorized as a living being, although it may appear dormant. It does not actively show all characteristics of life, like movement or visible growth. However, it contains a living embryo and has the potential to germinate, grow, respire, and reproduce once it is provided with the necessary conditions (water and air). The fact that it can initiate all life processes under the right circumstances proves it is living, not non-living.
9. Compare the life cycles of a mosquito and a frog. What are the key similarities and differences?
   • Answer: Both mosquitoes and frogs have life cycles that start with eggs laid in or near water, and both have aquatic larval stages that are very different from the adult form. The key similarity is that both undergo a significant transformation (metamorphosis). However, there are major differences. A mosquito has four distinct stages (egg, larva, pupa, adult), including a pupal stage, which the frog lacks. A frog’s larval stage is a tadpole, which gradually develops legs and loses its tail, transitioning through a froglet stage. The mosquito’s adult form is an insect that flies, while the frog is an amphibian.
10. Discuss the importance of reproduction and life cycles for the “continuity of their kind.”
    • Answer: Reproduction is the biological process by which a living organism creates offspring, and the life cycle is the series of stages the offspring goes through to become an adult capable of reproducing. These two concepts are fundamental to the “continuity of their kind.” Without reproduction, a species would cease to exist after the current generation dies. The life cycle ensures that the offspring develop properly to reach a stage where they can reproduce themselves, thus passing on their genetic information and continuing the existence of the species through time.

+++++++++++++++++++++++++++++++++++++++++++++++++++++

Glossary of Key Terms

• Breathing: The process of taking air into and out of the body; it is a part of respiration.
• Crescograph: A device invented by Jagadish Chandra Bose to measure plant growth and their response to stimuli.
• Death: The end of life, when a living being is no longer able to exhibit any of its essential characteristics.
• Embryo: The tiny, undeveloped plant or animal in its earliest stages, such as inside a seed or an egg.
• Excretion: The process of removing waste products from the body.
• Froglet: An immature frog that has developed legs but still retains its tail; a transitional stage between a tadpole and an adult frog.
• Germination: The process by which a seed sprouts and begins to grow into a young plant.
• Growth: An increase in size and development, a key characteristic of living beings.
• Larva: The immature, worm-like stage in the life cycle of some insects (like a mosquito) and other animals, which hatches from an egg.
• Life Cycle: The series of changes an organism undergoes from its beginning until it produces the next generation.
• Living: Possessing the characteristics of life, such as growth, respiration, reproduction, and response to stimuli.
• Movement: A characteristic of living things; can be locomotion (changing place) or movement of parts (like a flower opening).
• Non-living: Not possessing the characteristics of life.
• Nutrition: The process of taking in food for growth, metabolism, and repair.
• Pupa: The non-feeding, inactive stage in the life cycle of a mosquito and other insects, between the larva and adult stages.
• Reproduction: The biological process by which new individual organisms (“offspring”) are produced from their “parents.”
• Respiration: The biological process in living organisms involving the exchange of gases, essential for life.
• Response: The reaction of a living being to a stimulus.
• Seed Coat: The protective outer covering of a seed.
• Spawn: The jelly-like mass of eggs laid by frogs and other amphibians.
• Stimulus: Anything or any event that prompts a living being to respond or react.
• Stomata: Tiny pores, typically on the underside of plant leaves, that allow for the exchange of gases like air.
• Tadpole: The larval stage of a frog, which is aquatic, has a tail, and breathes with gills.