History of life and phylogenetic

Conditions for Origin of Life

• Early Earth Conditions:
  • Provided a suitable environment for the origin of life.
  • Presence of essential inorganic molecules: water ($H<em>2O$), methane ($CH</em>4$), ammonia ($NH_3$), and hydrogen cyanide ($HCN$).

Four Main Stages of Cell Formation

• Stage 1: Abiotic Synthesis of Organic Molecules

  • Inorganic molecules combined to form small organic molecules such as amino acids and nitrogenous bases.

• Stage 2: Formation of Macromolecules

  • Small organic molecules linked together to form macromolecules (e.g., proteins, nucleic acids).

• Stage 3: Formation of Protocells

  • Macromolecules packaged into protocells—droplets with membranes that maintained internal chemistry different from their surroundings.

• Stage 4: Emergence of Self-replicating Molecules

  • Self-replicating molecules enabled the possibility of inheritance, leading to evolution.

Miller-Urey Experiment

• Objective:
  • Showed that organic compounds could form under prebiotic conditions.
• Method:
  • A mixture of gases ($H<em>2O$, $CH</em>4$, $NH<em>3$, $H</em>2$) was subjected to electrical sparks to simulate lightning, resulting in amino acids and organic compounds.

Ribozymes

• Definition:
  • RNA molecules that can catalyze chemical reactions, including their own replication.
• Significance:
  • They provide evidence for RNA as an early genetic material, suggesting that RNA could have been a catalyst in the origin of life processes.

Protocells and Early Life

• Protocells
  • Simple membrane-bound structures that could perform basic life functions.
  • Contributed to the development of cellular life through encapsulation of organic molecules.

Evolution and Prokaryotes

• First Life Forms:

  • Prokaryotes were the first organisms to inhabit Earth, thriving in anaerobic environments.

• Importance of Oxygen:

  • The so-called "Oxygen Revolution" led to significant changes in Earth's atmosphere, allowing for more complex life forms to evolve.

Evolution of Eukaryotes

• Endosymbiotic Theory:

  • Explains the origin of eukaryotic cells from symbiotic relationships between prokaryotic cells.

• Key Developments:

  • Formation of the nucleus and organelles (mitochondria, chloroplasts) through endosymbiotic processes.

Phylogenetics and Evolutionary Relationships

• Phylogenetic Trees:

  • Diagrams illustrating the evolutionary history and relationships among various biological species based on their shared common ancestors.

• Key Components:

  • Nodes: Points where branches split, indicating common ancestors.
  • Branches: Represent populations through time.
  • Tips: Endpoint of branches representing existing or extinct groups.

Classes of Evolutionary Groups

• Monophyletic Group:

  • Includes an ancestor and all of its descendants.

• Paraphyletic Group:

  • Includes the ancestor and some, but not all, descendants.

• Polyphyletic Group:

  • Does not include the most recent common ancestor of the members of the group.

Determining Evolutionary Relationships

• Shared Ancestral Traits:

  • Traits shared by all members of a clade, indicative of common ancestry.

• Derived Traits:

  • Traits not present in the common ancestor of the group; help distinguish different lineages.

Principles of Systematics

• Parsimony Principle:
  • The simplest explanation, requiring the fewest changes, is often preferred when constructing phylogenetic trees.

Three Domains of Life

• Domains:

  • Bacteria and Archaea (prokaryotes) and Eukarya (eukaryotes).

• Key Characteristics:

  • Prokaryotes lack a nucleus, while eukaryotes have membrane-bound organelles and a true nucleus.