Lecture 1: Introduction to Biology

Overview of Biology

• Biology is a vast and diverse field.
• Different focuses in biology education: ecosystems, phyla, etc.
• MIT's perspective on teaching biology in course 7.012.

Levels of Organization of Life

1. Biosphere

   • Definition: All ecosystems on Earth working together.
   • Approximately 10^6 eukaryotic species; many unknown microbes.
   • We will not focus on this level.

2. Ecosystem

   • Definition: Interacting communities of organisms (e.g., forests).
   • Includes various organisms (trees, animals, fungi).

3. Whole Organisms

   • Focus on individual organisms and their physiology.
   • Example: A human (MIT student).

4. Organs

   • Definition: Groups of tissues organized for a function.
   • Example: The eye, which includes muscles and photoreceptors.

5. Tissues

   • Homogeneous groups of cells (e.g., retina).

6. Cells

   • Defined by membranes and nuclei (eukaryotic).
   • Example: Photoreceptor cells in the retina.

7. Organelles

   • Distinct components within a cell (e.g., mitochondria).

8. Molecules

   • Various types of molecules (e.g., sugars, DNA, ATP).

Focus of the Course

• Emphasis on lower levels of organization (molecules, organelles, cells).
• Importance of universal principles across life forms (e.g., genetic code, signaling systems).
• Aim to layer unique differences after understanding commonalities.

Important Dates in the History of Life

• 4.0 billion years ago: Earth cooled; no life.
• 3.7 billion years ago: First evidence of life (prokaryotic organisms).
• 1.5 billion years ago: Emergence of nucleated cells (eukaryotes) through prokaryotic fusion.
• 0.5 billion years ago: Development of multicellular organisms with body plans.
• 0.005 billion years ago: Appearance of humans.
• 0.00000015 billion years ago: Founding of MIT.

Types of Cells

• Prokaryotes

  • Primitive cells without a true nucleus.
  • Typically smaller (1-2 microns).

• Eukaryotes

  • Cells with true nuclei and various organelles (e.g., mitochondria, chloroplasts).
  • Larger size (10-40 microns) compared to prokaryotes.
  • Include all animals, plants, fungi.

Conclusion

• The lecture sets a foundation for understanding biological principles.
• Future lectures will delve deeper into these topics.