Chapter 1 – The Living World
1. Introduction to the Living World
The Earth is full of different kinds of living organisms. These organisms include plants,
animals, fungi, bacteria, and many microscopic life forms. Scientists study these organisms
to understand their structure, functions, and relationships with the environment.
The study of living organisms is called Biology. The living world shows a great variety in size,
shape, and behaviour. Some organisms are very small like bacteria, while others are very
large like elephants and trees.
Because of this huge diversity, scientists classify organisms into different groups.
Classification helps scientists study organisms in an organized way.
2. Characteristics of Living Organisms
Living organisms show certain characteristics that make them different from non-living
things.
2.1 Growth
Growth is the increase in size and mass of an organism.
In plants, growth continues throughout life.
In animals, growth occurs only for a certain period.
Non-living things may also increase in size, but their growth is different from living
organisms.
Example
A crystal grows by accumulation of particles, but a plant grows by cell division.
2.2 Reproduction
Reproduction is the process by which organisms produce new individuals of their own kind.
There are two main types:
• Asexual reproduction
Only one parent is involved.
Offspring are genetically similar to the parent.
Example: bacteria, amoeba
, • Sexual reproduction
Two parents are involved.
Offspring show variation.
Example: humans, animals, flowering plants.
2.3 Metabolism
Metabolism refers to all chemical reactions occurring inside the body of an organism.
Two types:
• Anabolism
• Building up reactions
Example: formation of proteins
• Catabolism
• Breakdown reactions
Example: digestion of food
• Metabolism is considered one of the most important characteristics of life.
2.4 Cellular Organization
All living organisms are made up of cells.
The cell is the smallest structural and functional unit of life.
There are two main types of cells:
• Prokaryotic cells
• Simple cells without nucleus
Example: bacteria
• Eukaryotic cells
• Complex cells with nucleus
Example: plants and animals
2.5 Consciousness and Response to Stimuli
1. Introduction to the Living World
The Earth is full of different kinds of living organisms. These organisms include plants,
animals, fungi, bacteria, and many microscopic life forms. Scientists study these organisms
to understand their structure, functions, and relationships with the environment.
The study of living organisms is called Biology. The living world shows a great variety in size,
shape, and behaviour. Some organisms are very small like bacteria, while others are very
large like elephants and trees.
Because of this huge diversity, scientists classify organisms into different groups.
Classification helps scientists study organisms in an organized way.
2. Characteristics of Living Organisms
Living organisms show certain characteristics that make them different from non-living
things.
2.1 Growth
Growth is the increase in size and mass of an organism.
In plants, growth continues throughout life.
In animals, growth occurs only for a certain period.
Non-living things may also increase in size, but their growth is different from living
organisms.
Example
A crystal grows by accumulation of particles, but a plant grows by cell division.
2.2 Reproduction
Reproduction is the process by which organisms produce new individuals of their own kind.
There are two main types:
• Asexual reproduction
Only one parent is involved.
Offspring are genetically similar to the parent.
Example: bacteria, amoeba
, • Sexual reproduction
Two parents are involved.
Offspring show variation.
Example: humans, animals, flowering plants.
2.3 Metabolism
Metabolism refers to all chemical reactions occurring inside the body of an organism.
Two types:
• Anabolism
• Building up reactions
Example: formation of proteins
• Catabolism
• Breakdown reactions
Example: digestion of food
• Metabolism is considered one of the most important characteristics of life.
2.4 Cellular Organization
All living organisms are made up of cells.
The cell is the smallest structural and functional unit of life.
There are two main types of cells:
• Prokaryotic cells
• Simple cells without nucleus
Example: bacteria
• Eukaryotic cells
• Complex cells with nucleus
Example: plants and animals
2.5 Consciousness and Response to Stimuli
