The Living World 1

Introduction to The Living World and Biology

• Biology is formally defined as the study of life, living organisms, or living processes.

• The living world is characterized by an immense diversity of organisms.

• Early humans categorized all matter on Earth into two distinct categories based on their observations:

  • Animate matter/Living/Biotic matter: This category includes plants and animals.

  • Inanimate/Non-living/Abiotic matter: This category includes environmental factors such as wind, sea, and fire. These objects were perceived as lacking life.

• A common feature observed by early men regarding both animate and inanimate objects was the sense of awe or fear they evoked, leading to the deification of elements like fire and wind.

Diversity of the Living World

• The living world contains a vast number of species, with current estimates identifying between $1.7 \times 10^6$ to $1.8 \times 10^6$ different living organisms on Earth (equivalent to $17-18 \text{ lakh}$ species).

• This biodiversity is broadly divided as follows:

  • Plants and Fungus: Approximately $0.5 \times 10^6$ species.

  • Animals: Greater than $1.2 \times 10^6$ species.

• Systematic and monumental descriptions of these life forms were necessitated by the need for identification, nomenclature, and classification systems.

Views in Biology: Anthropocentric vs. Biocentric

• Anthropocentric View:

  • In this view, humans are considered superior to all other species on Earth.

  • Historically, societies that held this view experienced limited progress in biological knowledge because exploration of the surrounding species was not prioritized.

• Biocentric View:

  • In this view, all species on Earth are considered equal.

  • This perspective encourages the exploration of more species, which directly leads to an increase in biological knowledge.

Biological Similarities and Genetic Material

• Organisms exhibit similarities that can be categorized into two dimensions:

  • Horizontal Similarities: Similarities between individuals belonging to the same generation, such as siblings.

  • Vertical Similarities: Similarities between individuals of two different generations, such as parents and their progeny.

• A critical revelation in biology is that all present-day living organisms are related to each other and to all organisms that ever lived on Earth.

• All living organisms (past, present, and future) share the same type of genetic material known as Nucleic Acid.

• Types of Nucleic Acids:

  • DNA (Deoxyribonucleic Acid): This is the major genetic material for most organisms. It is preferred because it is more stable.

  • RNA (Ribonucleic Acid): This serves as the genetic material in a few viruses. It is generally more reactive and less stable than $DNA$.

Ernst Mayr (1904–2004): The Darwin of the 20th Century

• Background: Born on July 5, 1904, in Kempten, Germany. He lived to be 100 years old, passing away in 2004.

• Academic Career:

  • He was a Harvard University evolutionary biologist.

  • He joined Harvard's Faculty of Arts and Sciences in 1953 and retired in 1975.

  • He held the title of Alexander Agassiz Professor of Zoology Emeritus.

• Scientific Status: Recognized as one of the 100 greatest scientists of all time. His career spanned nearly 80 years, covering o