Development of Life through Evolution

• Evolution explains gradual change in living organisms over time, from simple life forms to complex forms.
• It organises and explains the diversity of life and relationships among organisms.
• Evolution is a natural, slow, continuous, irreversible process of biological change.
• Evolution occurs through variations in genetic material and the action of natural selection.

• All living organisms have descended with modification from ancestral life forms through adaptive changes.
• Evolution provides a historical perspective for understanding how present‑day diversity has arisen.
• It also explains interactions among organisms and with their environment and the dynamic nature of the living world.

Biological evolution is presumed to have begun with the formation of the first true cells.

These earliest cells:

• did not require free oxygen (anaerobic).
• lived by using organic molecules present in the surrounding water (heterotrophic).

As nutrients were depleted, new cells capable of photosynthesis appeared, using carbon dioxide and light energy to synthesise food.

• Over long periods, evolution produced organisms that became extinct as well as the diverse life forms existing today.
• Present diversity ranges from simple single‑celled organisms to many kinds of plants and animals, including humans.
• There is evidence that all life forms are interrelated and that higher forms evolved from lower forms.

• Evolution explains the gradual change in living organisms over time, leading from simple life forms to complex ones.
• It provides a framework to understand the diversity and relationships among all living organisms.
• Evolution is a natural, slow, continuous, and irreversible process driven by genetic variation and natural selection.
• All present-day organisms, including humans, have evolved from earlier ancestral forms over millions of years.