Living Creatures: Exploring their Characteristics Chapter Notes | Science Class 6 PDF Download

Introduction

Living creatures are all around us, and they have certain characteristics that make them different from non-living things like rocks or water. One of the key features of living creatures is their ability to move, whether it's animals walking, swimming, or flying, or plants slowly turning toward sunlight. They also grow over time, such as a baby growing into an adult or a small plant becoming a big tree. Breathing is another important characteristic, as all living things need air to produce energy. 

What Sets the Living Apart from the Non-living?

• Living Things: Living Things are things that are alive. They can grow, move, breathe, eat, and reproduce (have babies or make new plants). Examples include animals, plants, and humans.
• Non-living Things: Non-Living Things are things that are not alive. They do not grow, move, breathe, eat, or reproduce. Examples include rocks, water, and toys.

Movement in Plants

Can plants move like animals from one place to another?

No, plants do not move from one place to another like animals, but they show different types of movements such as the opening of flowers and the winding of climbers around objects.

Different movements of plants:

• Plants may not move from one place to another, but they do show different types of movements. While Some plants, like insectivorous plants, rely on insects for nutrition. Some plants, like climbers, wind themselves around objects that are close to them.
• Examples: Drosera is an example of an insectivorous plant. It has saucer-shaped leaves with hair-like projections that have sticky ends. When an insect lands on the leaf, the hairs move inward and trap the insect with their stickiness.
• While plants do not move from place to place, they exhibit various types of movements, such as the opening of flowers, the trapping of insects by insectivorous plants like Drosera, and the winding of climbers around nearby objects. 

Growth and Nutrition in Living Beings

• Growth: Growth is a characteristic of all living beings, involving an increase in size, complexity, and development over time.
• Nutrition: Living beings need food for energy, growth, repair, and maintenance of body functions. 

Breathing & Respiration in Living Beings

• Breathing is the process of taking air into the body (inhaling) and then pushing it out (exhaling). 
• Respiration is a broader process that involves using the oxygen we breathe in to release energy from food.
• All living things, including plants, animals, and even tiny microorganisms, need to respire to stay alive.

Excretion in Living Beings

Excretion is the process of removing waste products from the body. This process is important because it helps maintain the body's balance and prevents the buildup of harmful substances. 

Excretion in Animals 

• Animals excrete waste products through various organs. 
• For example: This is a liquid waste that is produced by the kidneys. The kidneys filter the blood to remove excess water, salts, and other waste products, which are then excreted as urine. 

Excretion in Plants 

• Plants also excrete waste products, although their methods are different from those of animals.
• For example: Plants excrete oxygen as a waste product during photosynthesis and carbon dioxide during respiration. 

Response to Stimuli in Living Beings

• A stimulus is anything that happens around us or to us that makes us react or respond in some way. 
• For example, if you touch something hot, the heat is the stimulus that makes you pull your hand away.

Reproduction in Living Beings

• Reproduction is the process by which living beings produce new individuals of their own kind.
• It is essential for the continuity of life on Earth.
• When a living being can no longer exhibit the characteristics necessary for life, such as movement, growth, and the need for food, despite having all the necessary resources like food, air, and water, it is considered dead.

When is a living being considered dead?

A living being is considered dead when it can no longer show characteristics necessary for life, such as movement, growth, and the need for food, even if it has access to resources like food, air, and water.

Essential Conditions for Germination of a Seed

Why is water important for seed germination?

Water is important for germination because it activates enzymes that start the growth process within the seed.

• Germination is the process by which a seed develops into a new plant under favorable conditions. It requires water, air, and suitable light or dark conditions to initiate the growth of the embryo within the seed.
• Essential Conditions: Water is necessary to activate enzymes that start the growth process. Air provides oxygen for respiration. Light or darkness is required depending on the type of seed.
• Example: A bean seed germinates when provided with adequate moisture, air, and light. The seed swells, the seed coat breaks, and the radicle (young root) and plumule (young shoot) emerge, developing into a new plant.

Conditions Essential for Seed Germination 

• Water: Seeds need water to germinate. Water helps soften the seed coat and allows the tiny embryo inside, like the bean seed, to grow into a plant. It also enables the necessary processes for growth to happen. 
• Air and Soil: Seeds require air for germination, which they get from the spaces between soil particles. These spaces also help the roots to grow easily. 
• Light and Dark Conditions: For bean seeds, light is not necessary for germination, and generally, most seeds don’t need light at this stage. However, after germination, sunlight is essential for the further growth of the seedling. 

Light and Darkness in Seed Germination
Some seeds of flowering plants, like Coleus and Petunia, need light to start growing. If you cover these seeds with soil, it stops them from sprouting. On the other hand, seeds like Calendula and Zinnia need darkness to germinate, so they should be covered with enough soil to block out the light.

Growth and Movement in Plants

• Upright Position: When a plant is kept upright, the root  grows downwards , and the shoot  grows upwards.
• Inverted Position: When a plant is kept inverted, the root  bends but still grows downwards, while the shoot  bends and grows upwards.
• Directional Sunlight: When a plant receives sunlight  from only one direction, the shoot  grows towards the light, while the root  continues to grow downwards  .

Life Cycle of a Plant

• Seed Germination: A seed sprouts into a young plant under suitable conditions.
• Growth and Maturation: The young plant grows and matures, eventually producing flowers and fruit.
• Seed Production: The fruit, such as a pod, contains seeds which will give rise to a new generation of bean plants.
• Life Cycle Process: The entire journey from seed to plant and back to seeds is known as the life cycle of a plant.
• Plant Death: When a plant stops growing and its life activities come to an end, even with all necessary conditions met, the plant is considered dead.

Life Cycle of Animals

Do all animals have the same life cycle?

No, different animals have different life cycles. Some animals undergo metamorphosis, like butterflies, while others, like humans, have a more direct development.

Life Cycle of a Mosquito

• Mosquitoes go through four stages in their life cycle: egg, larva, pupa, and adult. 
• The adult mosquito comes out of the pupa, rests on the water for a short time, and then flies away. 
• Adult mosquitoes can live for about 10 to 15 days.

Stages:

• Egg: Laid on or near water surfaces.
• Larva: Aquatic, feeds on organic matter.
• Pupa: Transitional stage, does not feed.
• Adult: Emerges from pupa, capable of flight and reproduction.

• The mosquito starts as an egg (stage I), then grows into a larva (stage II), which turns into a pupa (stage III), and finally becomes an adult mosquito (stage IV). 
• The female mosquito lays eggs on or near water, and the cycle repeats.
• At each stage, the mosquito looks different. 
• The egg doesn’t look like the larva, the larva looks different from the pupa, and the pupa looks very different from the adult mosquito. 

Life Cycle of the Silk Moth 

• The silk moth goes through four stages in its life cycle: egg, larva, pupa, and adult. 
• Eggs hatch into larvae, which grow in size. As they grow, larvae produce a thread-like material that they wrap around themselves. This process leads to the formation of pupae. 
• The thread-like material secreted by the larvae is used to make silk fabric. 
• In India, the Khadi and Village Industries Commission (KVIC) has established several centers to support silk production. 

Life Cycle of a Frog

Frogs have a distinct life cycle with stages that include egg, tadpole, froglet, and adult frog. Each stage shows significant changes in form and habitat.
Stages:

• Egg: Laid in water, often in clusters.
• Tadpole: Aquatic, has gills and tail.
• Froglet: Develops legs, lungs, and starts losing the tail.
• Adult Frog: Terrestrial or semi-aquatic, fully developed.

Example: Frogs lay eggs in water. Eggs hatch into tadpoles, which live in water and breathe through gills. Tadpoles undergo metamorphosis, developing legs and lungs, transforming into froglets. Froglets grow into adult frogs, capable of living on land and reproducing.

Key Points

• Living beings and non-living things surround us; understanding their differences is crucial in biology.
• Living beings exhibit movement; animals move visibly, plants show subtle movements like phototropism.
• Growth is an increase in size and number of cells, driven by nutrient intake.
• Living beings obtain and use food for energy, growth, and maintenance.
• Exchange of gases (oxygen and carbon dioxide) is essential for energy production in cells.
• Removal of waste products to maintain internal balance and prevent toxicity.
• Living beings respond to environmental changes for adaptation and protection.
• Producing new individuals to ensure the continuity of the species.
• Cessation of all life processes, marking the end of an organism's life cycle.
• Living beings show movement, growth, nutrition, respiration, excretion, response to stimuli, and reproduction; non-living things do not.