Evolution of Life on Earth Notes With PDF

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Origin of Earth and Early Life

Primitive Earth’s Atmosphere

• Composition: Contained methane, ammonia, water vapor, carbon dioxide, carbon monoxide, nitrogen, hydrogen, and neon.
• Absence of Oxygen: Oxygen was absent in the primitive atmosphere.
• Accumulation of Oxygen: Oxygen accumulated over millions of years, produced as a by-product by single-celled organisms.

Emergence of Life

• Age of Earth: Approximately 4.6 billion years old.
• Emergence of Life: Life appeared approximately 2 billion years ago.
• Oldest Known Organisms: Blue-green algae (Cyanobacteria).
• Role of Cyanobacteria: They performed photosynthesis, releasing oxygen, which was crucial for the evolution of other life forms.

Theories of Evolution

Key Theorists and Their Contributions

• Lamarck (1809):
  • First to publicly explain a theory of evolution.
  • Proposed the inheritance of acquired characteristics.
  • Proposed the concept of “use and disuse of organs.”
• Charles Darwin (1859):
  • Proposed the theory of evolution by natural selection.
  • Wrote the foundational work “On the Origin of Species.”
• Hugo de Vries:
  • Enunciated the Mutation Theory of evolution.
  • Stated that new species arise through sudden, large mutations.

Core Concepts of Evolution

• Darwin’s Theory of Natural Selection is based on:
  1. Overproduction of offspring.
  2. Struggle for existence and the presence of variation.
  3. Survival of the fittest.
• Natural Selection is considered a main factor of evolution.
• Mutations (permanent changes in genetic material) are a primary factor for the origin of new species.
• Adaptation is the reason for large-scale diversity among organisms.

Matching Concepts with Proponents

• Theory of Mutation: Hugo de Vries
• Theory of Evolution: Charles Darwin
• One Gene-One Enzyme Hypothesis: Beadle and Tatum
• Operon Concept: Jacob and Monod

Evidence and Examples of Evolution

Evolutionary Links

• Archaeopteryx:
  • A connecting link between reptiles and birds.
  • Considered the most ancient bird from the Jurassic age (~150 million years ago).
• Snakes:
  • The loss of limbs is explained by Lamarck’s concept of “use and disuse of organs.”

Human Evolution

• Cro-Magnon Man:
  • Considered the latest ancestor of modern humans.
  • Robust, early modern humans from around 43,000 years ago.

Prehistoric Animals

• Mammoth:
  • An extinct ancestor of the modern elephant.
  • Shared a common ancestor with modern elephants about 6 million years ago.
• Dinosaurs:
  • Mesozoic Era reptiles.
  • Lived from about 250 to 65 million years ago.

Correct Evolutionary Sequence

• A correct sequence of evolution (oldest to most recent) is:
  1. Salamander (Amphibian)
  2. Python (Reptile)
  3. Kangaroo (Mammal)

Quick Revision

• Oldest Known Organisms: Blue-green algae (Cyanobacteria).
• Theory of Mutation: Hugo de Vries
• Theory of Evolution: Charles Darwin
• One Gene-One Enzyme Hypothesis: Beadle and Tatum
• Operon Concept: Jacob and Monod
• Dinosaurs: Mesozoic Era reptiles.
• Salamander is an Amphibian.

Know More About Evolution of Life on Earth:

• Evolution of Life on Earth – Old Year Questions
• Evolution of Life on Earth One Liner Questions & Answers