Lecture Notes: Introduction to Biology and Characteristics of Living Organisms

Overview of Biology

• Definition: Biology is the branch of science that deals with the study of living organisms.
• Origin: The term comes from Greek words: "bios" meaning life and "logos" meaning study.
• Focus: Includes growth, reproduction, environmental sensing, and response.

Objectives of the Lesson

• Define life and living organisms.
• Identify characteristics of living organisms.
• Understand cellular structure and organization.
• Explore metabolism and growth processes.
• Discuss consciousness and movement.
• Examine reproduction and diversity in the living world.

What is Living?

• Life Definition: Distinguishes objects with self-sustaining biological processes.
• Complexity: Unique cellular organization and biochemical reactions leading to growth and adaptation.
• Scope: Includes plants (botany) and animals (zoology).
• Viruses: Intermediary between living and non-living; reproduce only inside living cells.

Characteristics of Living Organisms

Cellular Structure

• Living beings are made of cells, the structural and functional unit of life, mostly composed of protoplasm.

Organization

• Internal hierarchy of parts forming larger systems, leading to organized individual organisms.

Energy

• Constant energy requirement sourced from food to perform activities and maintain order.

Homeostasis

• Regulation and maintenance of stable internal conditions despite external changes.

Metabolism

• Total of all chemical reactions; divided into:
  • Catabolism: Breakdown of complex substances.
  • Anabolism: Building complex substances from simpler ones.

Growth

• Results from higher anabolism than catabolism, leading to increase in size and development.

Consciousness

• Awareness and response to external stimuli (sensitivity).

Movement

• Movement of parts or whole body (locomotion); animals perform both, plants show part movements.

Variation

• Genetic mutations and gene reshuffling lead to variations; essential for diversity.

Adaptation

• Modifications helping organisms adjust to environmental changes (e.g., snow leopards, cacti).

Reproduction

• Production of offspring ensuring continuation of species.

Coordination

• Different body parts work together for functional harmony (e.g., heart, lungs, digestive system).

Irritability

• Response capability to stimuli; protoplasm property shown by all organisms.

Evolution

• Formation of new species through accumulated variations.

Interaction

• Interaction within organisms and with the environment at various levels.

Emergent Properties

• New characteristics appearing at specific organizational levels.

Life Cycle and Death

• Defined lifecycle stages: birth, growth, maturity, reproduction, aging, and death.

Diversity in the Living World

• Biodiversity: Vast range of species, plants, and animals due to 3.5 billion years of evolution.
• Extinction: Many species have become extinct over time.

Did You Know?

• Protoplasm: Called the physical basis of life by Huxley in 1868.
• Cell Theory: Lamarck suggested no life without cellular parts in 1809.
• Regeneration Study: Tremly first studied regeneration in Hydra.

Summary

• Living organisms are complex and share key characteristics like cellular structure, metabolism, reproduction, etc.
• Viruses act as a link between living and non-living.
• Interaction and adaptation are crucial for survival in diverse environments.
• Study of living systems occurs at cellular, organizational, and population levels.