Biology 1002B Chapter Notes - Chapter 3.1: Radiometric Dating, Reducing Atmosphere, Formaldehyde
29 Apr 2018
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3.1 What is Life?
3.1a Characteristics Shared By All Life Forms
• Life is defined by a list of seven attributes that all forms of life possess
1. Display order - arranged in ordered manner with cells being the fundamental
unit
2. Harness and utilize energy - acquire energy from environment and use it to
maintain self
3. Reproduce - ability to make more if its own kind
4. Respond to stimuli - make adjustments in structure, function, behaviour to
changes in external environment
5. Exhibit homeostasis - regulate internal environment
6. Grow and develop - increase in size and/or number of cells
7. Evolve - populations of living organisms change over generations to adapt to
environment
• Viruses are not living
o Can reproduce and evolve over time
o Yet must infect living cells and use their metabolism to reproduce - viruses
lack metabolism
3.1b The Characteristics of Life Are Emergent
• These properties emerge from simpler interactions that, in themselves, do not
have the properties found at higher levels
• Ex. Ability to harness and utilize energy is not a property of molecules, proteins, or
membranes in isolation, rather the ability emerges from interaction of ALL THREE
parts in metabolism
• Structural or functional complexity of living systems is more than the sum of its
part
3.2 The Chemical Origins of Life
3.2a Earth Is 4.6 Billion Years Old
• Radiometric dating: method that uses radioactive isotopes to calculate ages of
rocks
• Life started 4 bya
• First clear fossil evidence of prokaryotic cells dated 3.5 bya
• Fossil evidence of eukaryotes dated 2 bya
• Relative to other forms of life, humans have existed for a very short period of time,
150 thousand years
3.2b Earth Lies Within the Habitable Zone around the Sun
• When Earth was formed, temperature was very hot
• Over time, heat radiated away, took 500 million years to cool
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