Lecture Notes on Biology and Evolution

Introduction

• Earth began around 4.5 billion years ago as a fiery mass.
• Early bombardments by space rocks brought water to Earth.
• Cooling led to the formation of water bodies.

Origin of Life

• Life possibly originated from hydrothermal vents, rich in chemicals.
• Biology is essentially chemistry, involving molecules like carbohydrates, lipids, proteins, and nucleic acids.

Molecular Fundamentals of Life

• Carbohydrates: Quick energy.
• Lipids: Store energy and form membranes.
• Proteins: Form tissues and act as enzymes.
• Nucleic Acids: Make DNA.

Enzymes

• Special proteins that act as catalysts in chemical reactions.
• Example: Lactase breaks down lactose.

Characteristics of Life

• Ability to produce energy, grow, develop, reproduce, and respond to the environment.
• Life is cellular: Eukaryotes (with organelles) vs. Prokaryotes (like bacteria, without organelles).

Taxonomy and Classification

• Kingdoms: Protists, fungi, plants, and animals.
• Scientific naming: Genus and species.

Homeostasis

• Organisms maintain internal stability (e.g., temperature, pH balance).
• Cell membrane controls entry/exit of substances using diffusion.

Cellular Processes

• Diffusion: Movement along the concentration gradient.
• Active Transport: Moving particles against the gradient using ATP.

Energy & Metabolism

• ATP is the energy currency, produced via cellular respiration in mitochondria.
• Autotrophs (e.g., plants) produce glucose via photosynthesis.
• Heterotrophs (e.g., humans) obtain glucose from food.

DNA and Genetic Information

• DNA structure: Double helix of nucleotides (adenine, thymine, cytosine, guanine).
• Genes code for proteins which determine traits.

Transcription and Translation

• Transcription: DNA -> mRNA (copying genetic info).
• Translation: mRNA -> proteins (building blocks are amino acids).

Chromosomes and Genetic Variation

• DNA packed in chromosomes, tightly coiled around histones.
• Humans have 23 pairs of chromosomes.

Inheritance

• Dominant and recessive alleles determine traits (e.g., eye color).
• Variations can result from intermediate inheritance or co-dominance.

Cell Reproduction

• Mitosis: Produces identical cells for growth and repair.
• Meiosis: Produces gametes (sperm/egg) for reproduction.

Cell Cycle and Cancer

• Interphase is the most time-consuming stage of the cell cycle.
• Abnormal cell replication leads to cancer.

Mutations

• Can be beneficial, neutral, or harmful (e.g., Down syndrome from chromosomal mutation).
• Drive natural selection and evolution.

Microorganisms

• Bacteria vs. Viruses: Bacteria are cells, viruses are non-living.
• Antibiotics work on bacterial infections, not viral.

Human Physiology

• Nervous System: Neurons transmit signals via action potentials.
• Signals are electrical impulses interpreted by the brain.

Conclusion

• Emphasized understanding through practical application (sponsored message on learning with Brilliant).

These notes summarize the main points of a detailed lecture on biology, covering the origins of life, cellular biology, genetics, physiology, and evolution. They provide a foundational overview of key biological concepts and processes.