The Origin of Life & Evolution

The Origin of Life

• Heterotroph Hypothesis: 1st organisms were heterotrophs

• Conditions– Raw materials: H2, NH3, CH4, H2O

– Temperature: VERY HOT!– Other energy sources: Lightening, solar

radiation, volcanos

http://science.discovery.com/videos/100-greatest-discoveries-shorts-origin-of-life.html

Origin of Life: Results of Experiment

• Synthesis Reaction!– “Build” aggregates (clumps) of simple sugars

& amino acids• Amino acids building blocks for proteins!

• “Reproduction”- amino acids split

• Lead to simple single celled organisms

Origin of Life: Cont’d

1. Anaerobic respiration– Energy + CO2 + H2O

released

2. Autotrophs use CO2 & H2O release O2

3. Aerobic Respiration Use O2 & glucose release CO2

Evolution

• Evolution- process of change over time

• Theory of organic evolution– Compare existing to previous forms of life

Evidence for Evolution

Age of Earth Recent Fossil Finds Homologous Structures

Embryology Life’s Common GeneticCode

Homologous Molecules

Biogeography

Pgs. 465-471

The History of Evolution: LaMark

• LaMark (1802)- “Changes occur in species for their improvement”

• Develop traits due to a need for them– Example: Giraffes grow tall

necks because they need to reach leaves at the tops of trees

• Transmission of acquired characteristic– If a trait is acquired, it will be

passed on

• Evolution– Add up all characteristics,

there is overall change

The History of Evolution: Weismann

• Weismann – Traits develop NOT based on need– Acquired traits cannot be passed on

The History of Evolution: Darwin

• Darwin (1854)– Adaptations: Traits

that enable an organism to survive within a specific niche

– Natural selection• Survival of fittest• The driving force

behind evolution

– Transmission of favorable characteristics

• Pass on adaptations to next generation

Variation in species (adaptations)

Competition & Environmental Conditions

Survive!

Pass on traits to next generation

Don’t survive

Traits not passed on

Overall change in species:EVOLUTION

Natural Selection

The History of Evolution: DeVries

• DeVries (1886): “Variation is the result of mutation”

• Results from:– Random mutation– Sexual reproduction

• Meiosis/Gamete formation• Different DNA!

Modern Theory of Evolution

• Sources of variation– Random mutation– Sexual reproduction

• Meiosis/gamete formation• Differing DNA transferred to next generation

• Natural selection– Survival of the fittest– Influences how quickly species adapt

Modern Theory of Evolution: Cont’d

• Rate of Evolution Relies on Environment– Unchanging/Stable Environment

• Favored traits passed on• Unfavored traits not passed on• Slow adaptation

– Changing/Unstable Environment• High turnover for survival of fittest• Must continue to adapt to changing

environment• Limited resources

Changes in Species

• Gradualism– Slow, constant change in species over time

Changes in Species

• Punctuated Equilibrium– Long periods of time with little change in

environment with short bursts with great change in species

Cladogram

Determine similaritiesby comparing DNAsequences (gel electrophoresis)