Origin of Cells

Hadean Eon

4-4.5 billion years ago
Lack of Oxygen —-> low amounts of ozone (O2)

High Concentrations of CO2 and methane → high temperatures and UV light penetration

Ammonia in the atomosphere —> toxic

Miller Urey

(1952) Conducted experiments imitating early earth conditions by simulating the ancient water cycle.They showed that simple organic molecules can spontaneously form under the right conditions. 

LUCA - Last Universal Common Ancestor

is an inferred evolutionary intermediate that links the abiotic phase of Earth’s early history with the first traces of microbial life in rocks that estimated to be 3.8 billion years of age

abiotic

non-living

biotic

living

Chemical Evidence of LUCA

Evidence of microscopic life can be trapped and analyzed using ratios of chemical isotopes.

Fossil Evidence of LUCA

“Biomarkers” are the molecular fossils of lipids and other organic compounds. 

Genetic Evidence of LUCA

The number of differences in the genomes of two species is proportional to the time since they diverged from a common ancestor.

genetic code

universal and used by all living organisms.

for life to have emerged, scientists hypothesize that four smaller complex structures must have formed first.

.  Carbon compounds (amino acids, fatty acids, etc.) must be produced as they are the building blocks of life.

2.  Carbon compounds must be able to assemble into polymers (proteins, polysaccharides, etc.) which contribute to cell structures.

3.  There must be a mechanism for inheritance, which passes genes on to offspring. It has been determined that RNA was most likely this molecule.

4.  Membranes must form from carbon compounds. This creates a space for internal chemistry to occur. 

RNA

First molecule to pass genetic information between generations

Functions of Life

Metabolism.reproduction.sensation.homeostasic,excretion,nutrition,growth

metabolism

- Chemical reactions inside the cell including photosynthesis and cell respiration

reproduction

 Producing offspring and passing on genes

sensation

Ability to react to changes in the environment

homeostasis

 Keeping internal conditions within tolerable and predetermined limits

excretion

Getting rid of waste products of metabolism

nutrition

Organisms must obtain food to provide energy for metabolism and growth

growth

 Gradual increase in size over lifetime