General-Biology2_Week-2

ORIGIN OF LIFE

Special Creation/Divine Creation: Life forms may have been placed on Earth by divine forces, central to many religions, where a divine God is viewed as the creator.Extraterrestrial Origin (Panspermia): Proposes that meteors or cosmic dust carried complex organic molecules to Earth, initiating life. Evidence suggests early carbon materials may be extraterrestrial, but remains unproven.Spontaneous Origin: The widely accepted scientific hypothesis posits life evolved from inanimate matter as molecular associations became complex, promoting stability and ultimately leading to cell evolution.Theories of Life's Origin on Earth:

• At the ocean’s edge: Life could have emerged from bubbles forming at the ocean's edge.

• Under frozen oceans: Conditions similar to Europa may have been suitable for life's origin beneath frozen oceans.

• Deep in the Earth’s crust: Gunter Wachtershauser (1988) proposed life arose from volcanic activity with sulfur and metals forming amino acid precursors.

• Within clay: Clay's positive charges may attract organic molecules for early chemistry.

• At deep-sea vents: Life could have originated at hydrothermal vents where metal sulfides synthesize prebiotic molecules.

EARTH’S GEOLOGICAL TIMESCALE

Miller and Urey Experiment: A significant breakthrough in studying life's emergence, raising questions on the first living organisms and their survival during atmospheric changes.Geological Time Scale Overview:

• Eon: Largest division, divided into Phanerozoic, Proterozoic, Archaean, and Hadean.

• Phanerozoic: Age of multicellular life (~0.5 billion years).

• Proterozoic: Transition from oxygen appearance to the age of hidden life.

• Archaean: Earth’s crust cooled, allowing life formation.

• Hadean: Formative period of Earth.

Division of Time Units:

• Era: Spans tens to hundreds of millions of years.

• Period: Basic unit of the geological time scale, linked with rock formations.

• Epoch: Subdivision of geological periods.

GEOLOGICAL TIME SCALE

ORGANISMS THROUGH TIME

Key Organisms and Their Ages:

• Cyanobacteria: ~3.5 billion years; contributed to oxygen production.

• Coronacollina acula: 560 million years; precursor to Cambrian sponges.

• Trilobites: Prevalent during the Cambrian explosion, indicating Paleozoic diversity.

Mesozoic Era Organisms:

• Myosaurus grailis: Early Triassic, herbivorous with tusks.

• Tyrannosaurus rex: Jurassic apex predator.

• Mosasaurus: Cretaceous aquatic reptile.

Cenozoic Era Organisms:

• Plesiadapiforms: First primate-like mammals from the Paleogene.

• Ardipithecus ramidus: Oldest known hominid ancestor showing early bipedalism (~4.4 million years ago).