Cell and Molecular Biology - Diversity of Life Notes

Characteristics of Life

• Cellular organization: Arrangement of components inside a cell.

• Reproduction: Producing offspring (sexual or asexual).

• Metabolism: Chemical reactions converting macromolecules into energy.

• Homeostasis: Maintaining a constant internal state.

• Heredity: Passing genetic information to the next generation.

• Response to stimuli: Sensing and responding to environmental changes.

• Growth and development: Increases in size and maturity.

• Adaptation through evolution: Becoming better suited to the environment over generations.

Tree of Life

• Phylogenetic tree showing how all life is related.

• Constructed using DNA sequences.

• Three domains:

  • Bacteria

  • Archaea

  • Eukarya

Phylogenetic Trees

• Diagram showing relationships between species.

  • Branches: lines on the diagram.

  • Length represents time/differences between species.

  • Nodes: Points where lines split; represent the last common ancestor.

• Closer species are more closely related.

Eukaryotes vs Prokaryotes

• Eukaryotes:

  • Organisms from domain Eukarya.

  • Single or multi-celled.

  • Large cell size (10-100 µm).

  • Have organelles (nucleus, Golgi body, mitochondria).

  • Photosynthetic ones have chloroplasts.

• Prokaryotes:

  • Organisms from Archaea and Bacteria domain.

  • Single-celled.

  • Small cell size (1-5 µm).

  • Lack organelles.

Common Cell Structures

• All cells have:

  • Cell or plasma membrane.

  • Cytosol (cellular fluid).

  • Ribosomes.

  • Chromosome(s) (DNA or RNA).

• Some cells have a cell wall.

Endosymbiont Theory

• Mitochondria and chloroplasts were originally free-living prokaryotic cells.

  • Mitochondria from proteobacteria (aerobic bacteria).

  • Chloroplasts from cyanobacteria (photosynthetic bacteria).

• Engulfed by a larger host cell.

• Symbiosis: mutually beneficial relationship.

• Mitochondria and chloroplasts:

  • Semi-autonomous.

  • Have their own DNA and ribosomes.

  • Synthesize some of their own proteins.