Biology Lecture Notes

Formation of Earth

• Earth formed around 4.5 billion years ago.
• Initially a hot mass bombarded by space rocks, some carrying water.
• Hydrothermal vents at the ocean bottom are significant in early chemical reactions.

Chemistry of Life

• Biology is essentially chemistry; organisms are complex molecules.
• Key biomolecules:
  • Carbohydrates: Provide quick energy.
  • Lipids: Store long-term energy and form membranes.
  • Proteins: Comprise tissues, act as enzymes, and transport molecules.
  • Nucleic Acids: DNA and RNA, store genetic information.

Characteristics of Life

• Living organisms metabolize, grow, develop, reproduce, and respond to their environment.
• Composed of cells: Eukaryotes (complex, membrane-bound organelles) and Prokaryotes (simple, no membrane-bound organelles).

Homeostasis

• Maintaining internal balance using enzymes that work in specific conditions.
• Cells use semi-permeable membranes to regulate chemical concentrations.

Transport and Energy in Cells

• Diffusion: Movement along a concentration gradient.
• Active Transport: Moves particles against gradient using ATP.
• ATP: Energy currency of the cell, produced in mitochondria.

Photosynthesis vs. Respiration

• Photosynthesis: Plants convert light into glucose in chloroplasts.
• Cellular Respiration: Organisms convert glucose into ATP.

DNA and Genes

• DNA composed of nucleotides, forms genes coding for proteins.
• Gene transcription into RNA; RNA translates to proteins at ribosomes.

Genetic Variation and Inheritance

• Gene alleles can be dominant or recessive, affecting phenotype (observable traits).
• Inheritance patterns: complete, incomplete, and co-dominance.
• Sex Chromosomes: X-linked genes cause traits like colorblindness to be more common in males.

Cell Division

• Mitosis: Produces genetically identical cells for growth and repair.
• Meiosis: Produces genetically diverse gametes.

Mutations

• Changes in gene sequences can be neutral, harmful, or beneficial.
• Chromosomal Mutations: Result in conditions like Down syndrome.

Natural Selection and Evolution

• Favorable traits increase survival rate, passing onto future generations.
• Genetic Drift: Random changes in allele frequencies.

Bacteria vs. Viruses

• Bacteria are single-celled organisms treated with antibiotics.
• Viruses require a host to replicate, are not alive.

Human Body Systems

• Nervous System: Neurons transmit signals via action potentials.
• Uses neurotransmitters to communicate between neurons.

Additional Information

• DNA is tightly packed in cells into chromatin and chromosomes.
• Humans have 20,000 genes; non-coding DNA makes up the majority.
• DNA is stored in the nucleus, expressed differently in various cell types.

Commercial Note

• Mention of Brilliant as a resource for interactive learning in math and science.