CBSE Class 10 Science Notes: Life Processes

What Makes Something ‘Living’? – Basic Characteristics

Defining life involves identifying key characteristics. Living organisms share a set of fundamental traits that distinguish them from non-living matter.

Key Characteristics:

• Cellular Structure: All living things are composed of cells, the basic units of life.
• Growth and Development: Living organisms increase in size and complexity over time.
• Reproduction: The ability to produce offspring, ensuring the continuation of the species.
• Metabolism: Chemical processes that occur within an organism to maintain life (e.g., nutrition, respiration).
• Response to Stimuli: The ability to detect and react to changes in the environment.
• Excretion: The removal of waste products from the body.

These characteristics collectively define life, making the processes discussed in this chapter essential for survival.

Nutrition

Nutrition is the process by which organisms obtain and utilize food for energy, growth, and repair. There are two main modes of nutrition: autotrophic and heterotrophic.

Autotrophic Nutrition (Photosynthesis)

Autotrophs (like plants) produce their own food using sunlight, water, and carbon dioxide. This process is called photosynthesis.

Core Principles:

• Chlorophyll: A green pigment found in chloroplasts, which absorbs sunlight.
• Raw Materials: Water ($H_2O$) absorbed from the soil and carbon dioxide ($CO_2$) taken from the atmosphere.
• Products: Glucose ($C_6H_{12}O_6$), a sugar (food), and oxygen ($O_2$), which is released into the atmosphere.

Photosynthesis Formula:

$6CO_2 + 6H_2O \xrightarrow{sunlight, chlorophyll} C_6H_{12}O_6 + 6O_2$

Heterotrophic Nutrition

Heterotrophs cannot produce their own food; they obtain it by consuming other organisms.

Types and Examples:

• Herbivores: Consume plants (e.g., cows, deer).
• Carnivores: Consume animals (e.g., lions, tigers).
• Omnivores: Consume both plants and animals (e.g., humans, bears).
• Saprophytes: Obtain nutrition from dead organic matter (e.g., fungi, some bacteria).
• Parasites: Live on or inside other organisms (hosts) and obtain nutrients from them (e.g., tapeworms, ticks).

Respiration

Respiration is the process of breaking down glucose to release energy (in the form of ATP). It’s fundamentally different from breathing.

Breathing vs. Cellular Respiration

• Breathing: Physical process of inhaling oxygen and exhaling carbon dioxide (exchange of gases).
• Cellular Respiration: Biochemical process of breaking down glucose to release energy inside cells.

Aerobic vs. Anaerobic Respiration

• Aerobic Respiration: Occurs in the presence of oxygen. Produces a large amount of energy.
  $C_6H_{12}O_6 + 6O_2 \rightarrow 6CO_2 + 6H_2O + Energy (ATP)$
• Anaerobic Respiration: Occurs in the absence of oxygen. Produces less energy.
  Examples:
  • In yeast: $C_6H_{12}O_6 \rightarrow 2C_2H_5OH (ethanol) + 2CO_2 + Energy$
  • In muscle cells (during strenuous exercise): $C_6H_{12}O_6 \rightarrow 2C_3H_6O_3 (lactic acid) + Energy$

Transport

Transport systems are vital for moving water, nutrients, and gases throughout plants and animals.

Plant Transport

• Xylem: Transports water and minerals from roots to the rest of the plant.
• Phloem: Transports food (sugars) produced by photosynthesis from leaves to other parts of the plant.

Animal Transport (Blood Circulation)

The circulatory system is responsible for transport in animals.

• Blood: A fluid connective tissue composed of:
  • Red blood cells (carry oxygen)
  • White blood cells (fight infection)
  • Platelets (help in clotting)
  • Plasma (the liquid part of blood)
• Blood Vessels: Arteries (carry blood away from the heart), veins (carry blood back to the heart), and capillaries (tiny vessels where exchange occurs).
• Heart: Pumps blood throughout the body.

Excretion

Excretion is the process of removing metabolic wastes from the body.

Animal Excretion

The kidneys are the primary organs of excretion in most animals.

• Kidneys: Filter blood to remove waste products like urea, producing urine.
• Urine: Waste products are stored in the bladder and then eliminated.

Plant Excretion

• Stomata: Small pores on leaves that release gases (like oxygen) and water vapor (transpiration).
• Transpiration: The loss of water vapor from leaves, which helps in cooling the plant and creating a suction force for water uptake.