History of Life: Biogenesis, Earth's Formation, and Early Cell Evolution

Biogenesis

Living things come from other living things.

Earth's Age

4.6 billion years.

Formation of the Sun

About 5 billion years ago, a mass of gas and dust was pulled together by gravity and formed the sun (400 million year process).

Cooling of Earth

It took another billion years for Earth to cool down.

Radiometric Dating

A way to age materials.

Isotopes

Elements that differ in number of neutrons (ex: carbon-12, carbon-14).

Radioactive decay

Unstable nuclei release particles/radiant energy until they become stable.

Half-life

The amount of time it takes for half of a sample to decay to stable form (vary from less than a second to billions of years).

First Organic Compounds

All elements found in organic compounds existed when Earth formed.

Oparin and Haldane

Proposed that gases that existed in the atmosphere, at high temperatures, formed simple organic compounds.

Miller-Urey experiment

Tested the hypothesis of the formation of organic compounds successfully in the lab.

Microspheres

Spherical structures composed of many macromolecules organized in a membrane, forming spontaneously and are cell-like without direction of genes.

Roles of RNA

Genetics of early cells may have been RNA based, providing the hereditary information that microspheres lacked.

First Cells

Little to no oxygen existed in early Earth's atmosphere; first life was anaerobic, heterotrophic prokaryotes.

Chemosynthesis

First autotrophs that lived in harsh conditions and used oxidation of inorganics (like sulfur) to obtain energy.

Photosynthesis

Occurred around 3 billion years ago; oxygen was a by-product that was damaging to most life forms and led to the first mass extinction.

Aerobic organisms

Some organisms were able to bond with oxygen, leading to the first aerobic organisms.

Ozone layer

Created by oxygen gas reaching today's levels; protects from UV radiation.

Theory of endosymbiosis

Describes the relationship between prokaryotes and primitive eukaryotes.

Mitochondria

Formed when aerobic prokaryotes were engulfed.

Chloroplasts

Formed when photosynthetic prokaryotes were engulfed.