Biology: the science of life

What is life?

Freaky sea-vent worms

Growth and replication

aluminum potassium sulfatecrystallization

What’s missing?

nucleation =

replication?

prions?computer algorithms

EvolutionThree keys: reproduction, variation, selection

Improved

replicator

Improved

replicator

Neutralvariant

replicator

Life:Reproduction +

evolution

•Encapsulation and individuality

•Reproduction

•Energy and material processing(metabolism)

•Information storage

•Environmental response

Implementing life (physics + chemistry)

Life elsewhere?

•Liquid solvent (water)

•Mars, Europa, Titan (methane and ethane)

Our one data point: Life on Earth

Common descent

You are here

Genetic and morphological evidence are consistent with

all life on Earth sharing common ancestry

History of life on Earth

Microscopic life dominatesthe history of Earth.

Humans arose very recently (roughly 200,000

years ago).Do this as in-class

exercise

Scales in biology

Tobacco mosaic virus

3x10-7 m in length, 1.8x10-8 m in width~7x10-20 kg in mass

~6.4x103 bases in genome (single-strand RNA)

Have them

adding scales

Escherichia coli

prokaryotic: no cell nucleus~3x10-6 m in length~7x10-16 kg in mass

~5x106 base pairs in genome

Saccharomyces cerevisiae

eukaryotic: cell nucleus~5x10-6 m in diameter

~6x10-14 kg in mass~5x106 base pairs in genome

Arabidopsis thaliana

multi-cellular plant~0.2 m in height

~1.2x108 base pairs in genome

Drosophila melanogaster

multi-cellular insect~3x10-7 kg in mass (dry)

~1.2x108 base pairs in genome

Mus musculus

multi-cellular~3.5x10-2 kg in mass

~3.4x109 base pairs in genome

HeLa cell

human immortal cell line~25x10-6 m in diameter

~3.1x109 base pairs in genome

Exercise: How many cells in your body?

Exercise: How many bacterial cells in your gut?

Homework

How far apart are proteins in E coli?

How long (physically) is the human genome?How does that compare to the size of a typical cell?

Darwin: First Notebook on Transmutation of Species (1837)