9.1 Geologic Time, The Fossil Record, and the Origin of Life

KEY CONCEPTS1. How old is the earth?

2. What is the difference between spontaneous generation and biogenesis?

3. What are the first living things on the earth?

4. What does the fossil record tell us?

VOCABULARY

Spontaneous generation

Abiogenesis

Fossils

Carbon dating

Law of superposition

Spontaneous GenerationSpontaneous generation – the idea that living things arise from non-living things (also called Abiogenesis.)

Francisco Redi – performed experiments with maggots meat that disproved spontaneous generation.

Spontaneous GenerationLouis Pasteur & later Lazzaro Spallazaniperformed similar experiments and found the same results.

How does their experiment

relate to science?

Trials (accuracy),

repeatable

experiments to

support results.

BiogenesisBiogenesis – law that living things only come from other living things.

Biogenesis = LIFE FROM LIFE!

Early EarthThe earth formed about 4.6 BILLION years ago.

The earth formed from a cloud of condensing dust and gases.

The atmosphere was made of carbon dioxide, nitrogen, ammonia, methane, and water vapor. What was missing?

(There was no Oxygen!)

As the earth cooled, water vapor condensed into water and formed the oceans.

Origins of LifeScientists believe that living cells evolved from simple organic molecules.

Alexander Oparin – developed a theory that organic molecules were created by chemical reactions stimulated by lightening and UV light on early earth.

Stanley Miller and Harold Urey tested Oparin’s hypothesis in a lab and created amino acids, ATP, DNA and RNA.

- these are the ingredients needed for life!

Origins of LifeSimple organic molecules reacted to produce large polymers, membranes, RNA, and eventually living cells.

Origins of Life - first living cells The first living cells were heterotrophic – they obtained food by absorbing it from their environment.

Hetero = “Other” Trophic = “Feeder”

Ex. Microbial mats (mostly bacteria)

Microbial mats are the

earliest form of life on Earth

for which there is

good fossil evidence,

from 3500 million years ago

Geologic Time Scale

Fossil RecordFossils – the remains or imprints of the remains of once-living organisms.

Fossils are formed in layers of SEDIMENTARY ROCK or in VOLCANIC ASH.

They can help show how life has changed over time and provide evidence for evolution.

Dating FossilsThe Principal of Superposition – age is determined from a fossil’s position in rock layers. Older fossils are below younger fossils.

This is a RELATIVE DATING method.

Youngest

Oldest

Dating FossilsActual/Absolute AGE of fossils can be determined using radioactive dating.Carbon-14 Dating (also called Radioactive Dating:

Radioactive element carbon-14 decays into stable carbon-12.

The half-life of carbon-14 is 5600 years. (time for half the carbon-14 in a sample to decay into carbon-12)

By comparing the amount of carbon-14 to carbon-12 you can determine age.

WHAT DOES THIS ACTUALLY MEAN?

Using math & ratios Scientists can determine the actual age of a fossil!