Chapter: Life Cycle, Growth, Reproduction & Metamorphosis (Class 6–8)

 Life Cycle - Every living organism undergoes a series of changes during its lifetime. These changes begin with birth (or germination/hatching), continue through growth and maturity, include reproduction, and end with death. This sequence of stages is called the life cycle.

The sequence of stages through which an organism passes from birth to death is called its life cycle.

Growth - Growth is a permanent increase in the size, weight, height, or number of cells of an organism.

Development - Development refers to the progressive changes in the structure, functions, and abilities of an organism as it matures.

Reproduction - Reproduction is the biological process by which living organisms produce offspring of their own kind.

Metamorphosis - Metamorphosis is a complete change in the body form and structure during the development of certain animals.

Characteristics of Growth 

• Growth is irreversible.
• It requires nutrients, water, oxygen, and energy.
• Growth occurs through cell division and cell enlargement.
• It is more rapid in young organisms.
• Living organisms stop growing after reaching maturity (in many animals), while many plants continue growing throughout life.

Reproduction - Reproduction is essential because it ensures the continuity of a species.

Types of Reproduction - 

Sexual Reproduction

• Involves two parents.
• Produces genetically varied offspring.

Examples: Human beings, Birds, Frogs, Fish

Asexual Reproduction 

• Involves one parent.
• Produces offspring that are genetically similar to the parent.

Examples: Amoeba (binary fission), Hydra (budding), Yeast (budding)

Metamorphosis Some animals undergo drastic changes in body form before becoming adults.

Butterfly : Stages   :- Egg - Larva (Caterpillar) - Pupa (Chrysalis) - Adult Butterfly

Important Features 

• Caterpillar feeds actively.
• Pupa is a resting and transforming stage.
• Adult butterfly reproduces.

Frog  : Stages  :-  Egg - Tadpole - Froglet - Adult Frog

Important Features

• Tadpole breathes through gills.
• Adult frog breathes through lungs and skin.
• Tail disappears during development

Plant Life Cycle  : Stages:- Seed - Germination - Seedling - Mature Plant - Flowering - Pollination - Fertilization - Fruit Formation - Seed Formation - Seed Dispersal

Human Life Cycle  : Stages:-  Infant - Child - Adolescent - Adult - Old Age

Interesting Facts

• A butterfly tastes food using its feet.
• A tadpole resembles a fish more than a frog.
• Bamboo is one of the fastest-growing plants.
• Some insects complete metamorphosis in just a few weeks.

Everyday Applications

• Farmers study plant life cycles to determine the best time for sowing and harvesting.
• Understanding mosquito life cycles helps in controlling mosquito-borne diseases.
• Knowledge of metamorphosis is useful in agriculture and pest management.

Remember

• Growth increases size.
• Development improves function.
• Reproduction ensures continuation of species.
• Metamorphosis is a major transformation in body structure.

MCQs

The first stage in a butterfly's life cycle is:

A. Larva

B. Pupa

C. Egg ✔

D. Adult

Which stage of a frog breathes through gills?

A. Adult

B. Froglet

C. Tadpole ✔

D. Egg

Growth means:

A. Increase in size ✔

B. Change in colour

C. Reproduction

D. Death

Revision Summary

• A life cycle includes birth, growth, development, reproduction, ageing, and death.
• Growth is a permanent increase in size.
• Development involves changes in structure and function.
• Reproduction produces offspring and ensures the continuity of a species.
• Metamorphosis is a major transformation seen in organisms such as butterflies and frogs.
• Plants pass through stages including germination, flowering, fertilization, and seed formation.