Fossils• Ancient and extinct species• Not complete

– Conditions are rare• What can become a fossil?

– Hard parts most likely– Entire organisms– Part of organisms– Embryos– Footprints– Burrows– Scat

What can we learn from fossils?

• Body structures– Evolutionary

relationships• Movement of

animals• Climate

Relative Dating

• Lower layers are older• Look at what layer the fossil is in• Works locally

Radiometric Dating• Determine actual age• Uses breakdown of radioactive elements

– Consistent rate of decay– Half-life

• Recent fossils– Carbon-14 dating– Process of using– Fossil needs to

• Have been alive• Less than 60,000 yrs. old

• Older fossils– More than 60,000 yrs.– Use rock layer– Use other elements

• K• U

– Age of rock = age of fossil

Early History of Earth• Formation

– 4.5 billion years ago• Bombarded• 3.9 billion yrs.

– Oceans formed• Brown color

– Atmosphere• Composition• Color

First Organic Molecules• Miller and Urey

– Simulated early environment– Produced amino acids– Current research

• Microspheres– 200-300 million yrs– Cooler and liquid water– Fossil bacteria?– Bubbles of organic molecules– Selectively permeable membranes– Stored, released energy

• RNA and DNA– Unknown origin– RNA first

• Production of oxygen– Fossil prokaryotes

• 3.5 billion yrs.• Anaerobic

– Photosynthetic bacteria• 2.2 billion yrs.• Formed rust

– Oxygen in atmosphere• Formed ozone• Took several million yrs.• Toxic to bacteria

Daily Review #1

1. Describe the difference between relative and absolute dating.

2. What has the Miller Urey experiment and microspheres told us about early life on Earth?

3. What was the early Earth like?4. What can fossils tell us about life on Earth?

Origin of Eukaryotic Cell• Endosymbiotic theory

– Prokaryotic cell membranes

– Lived inside other cells– Mitochondria– Chloroplasts

• Modern evidence– Lynn Margulis– DNA– Ribosomes– Reproduction

• Sexual reproduction

Lesson Overview Genes and Variation

Genes and Variation

• Darwin and Mendel– Data available– Connection not made

• Genetics and natural selection– Works on phenotype– Higher fitness phenotype survives– Acts on entire organism

Lesson Overview Genes and Variation

Populations• Research on allele

frequency• Gene pool• Relative frequency• Evidence of

evolution– Change in relative

frequency

Lesson Overview Genes and Variation

• # of phenotypes depends on genes

• Single-gene trait– # of phenotypes– Example

• Polygenic trait– # of genes– Phenotypes– Example– Creates a normal

distribution curve

Lesson Overview Genes and Variation

Single-Gene Traits• Leads to changes • Lizards

– Single-gene trait– Normal,

mutations– Red lizards– Black lizards– Change in

phenotypes

Lesson Overview Genes and Variation

Polygenic Traits

• More complex• Directional selection• Stabilizing selection• Disruptive selection

Lesson Overview Genes and Variation

Lesson Overview Genes and Variation

Speciation• Definition• Species• Isolating

mechanisms– Interbreeding stops– Genes don’t spread– Reproductively

isolated– Form separate

species

Lesson Overview Genes and Variation

• Behavioral isolation– Rituals

• Geographic isolation– Geographic

barrier

• Temporal isolation– Reproductive

timing

• Speciation video