Biology Chapter: Origin and History of Life

Origin of Life

• Miller-Urey experiment showed organic molecules can form from inorganic compounds under early Earth conditions.
• Protobionts are simple, cell-like structures, thought to be precursors to cells.
• RNA was likely the first genetic material.
• Early Earth conditions included environmental changes like oxygenation, volcanic activity and glaciation.
• Photosynthetic cyanobacteria introduced oxygen to the atmosphere.

History of Life on Earth

• Multicellularity evolved, followed by major diversification during the Cambrian Explosion.
• Animals emerged 600 million years ago
• Evolution included diverse body plans, digestive systems and nervous systems.
• Cephalization, or development of a head region, occurred in some lineages.

Prokaryotes vs. Eukaryotes

• Prokaryotes are single-celled organisms without a nucleus (e.g., bacteria, archaea).
• Eukaryotes have a nucleus and membrane-bound organelles (e.g., plants, animals).
• Eukaryotes are generally larger and more complex than prokaryotes.

Three Domains of Life

• Bacteria, Archaea, and Eukarya are the three domains based on genetic differences.
• Archaea and Eukarya share a more recent common ancestor than either do with Bacteria.

Origin of Eukaryotic Cells

• Endosymbiosis theory proposes that mitochondria and chloroplasts originated from prokaryotic cells engulfed by a larger cell.

Major Animal Phyla

• Cnidaria (radial symmetry, stinging cells).
• Platyhelminthes (flatworms, no body cavity).
• Annelida (segmented worms).
• Mollusca (shell, diverse body plans).
• Nematoda (roundworms, pseudocoelomate).
• Arthropoda (exoskeleton, segmented bodies).
• Echinodermata (radial symmetry as adults).
• Chordata (notochord, dorsal nerve cord).

Evolutionary Trends in Animals

• Multicellularity arose in various lineages.
• Body plans and cavities become more complex.
• Digestive and nervous systems diversified.
• Cephalization, the development of a head region and concentration of sensory organs, evolved in some lineages.

Vertebrates

• Jawless fish evolved into cartilaginous and bony fish, then amphibians, reptiles, birds, and mammals.
• Key chordate traits include notochord, dorsal nerve cord, pharyngeal slits, and a post-anal tail.

The Amniotic Egg

• The amniotic egg was a major adaptation allowing for terrestrial reproduction, offering protection for the developing embryo.

Evolution of Mammals

• Three main groups are monotremes (lay eggs), marsupials (pouch development), and eutherians (placental mammals).

Evolution of Humans

• Defining traits of humans include bipedalism, large brain size, tool use, and complex social structure.

Explore the fascinating journey from the origin of life on Earth through key events like the Miller-Urey experiment and the evolution of multicellularity. This quiz covers essentials on prokaryotes vs. eukaryotes and major developmental milestones in life's history. Test your knowledge on the building blocks of life and their progression through time.