Module 9Evolution

Abiogenesis

• Life first arose from non-living material in a “primordial soup”

• Experimentally tested by Miller and Urey

• Also called SPONTANEOUS GENERATION

Amino acids

CO2

COCH4

H2S

N2

Heterotroph Hypothesis

• Explains evolution of prokaryotic cells

• Earliest cells had to take in nutrients (heterotrophic)

• Earliest cells had to live in oxygen free conditions (anerobic)

O2

Heterotroph Hypothesis

• Photosynthetic prokaryotic cells evolved, allowing for release of free oxygen

• Led to ozone layer

O2

O2

O2

Heterotroph Hypothesis

• Oxygen led to evolution of aerobic cells

O2O2

O2

Endosymbiont Hypothesis

• Explains the evolution of eukaryotic cells

• A symbiotic relationship formed between larger and smaller prokaryotic cells – smaller cells became mitochondria and chloroplasts

• YouTube - The Evolution of Eukaryotic Organisms: Endosymbiotic Theory

Multicellular Life

• Multicellular organisms are made of eukaryotic cells

• The evolution of eukaryotic cells allowed multicellular life to evolve, and eventually colonize land

Biogenesis: Life comes from life

• Although life may have arisen spontaneously, life continues through other life!

• Spontaneous generation has been disproven by scientists

Biogenesis: Life comes from life

Disproven by: Francesco Redi

Biogenesis: Life comes from life

Disproven by: Louis Pasteur

Evolution = CHANGE over time

Occurs through the process of NATURAL SELECTION

Nature “selects” the best adapted organisms to survive and

reproduce

Natural Selection Stated Clearly(10 min)

What is an Adaptation?

• A “heritable” trait• Makes an organism

better suited to its role in the ecosystem

• May be structural, behavioral, or physiological

Structural: defensive structures, camouflage, mimicry

Behavioral: Herding, schooling, growling

Physiological: enzymes, oxygen transport, sight

Theory of Natural Selection

• Proposed by Charles Darwin• 4 “Requirements”

VariationDifferent

phenotypes in the population

OverproductionLeads to

competition

Natural Selection

Nature “selects” the

best adapted

Survival of the “fittest”

Best adapted individuals have

greater reproductive success

Individuals DON’T EVOLVE!

Individuals don’t evolve – populations do!

This requires a change in the “gene pool”

MUTATION:The raw material for change

Can be selected

FOR

Can be selected

AGAINST

3 Selection Mechanisms

Stabilizing Directional Disruptive

Speciation

Speciation: The development of a new species

Speciation: The development of a new species

Geographic Isolation

Natural Selection

Reproductive Isolation

Timeframe for Evolution

Gradualism

Punctuated Equilibrium

GRADUALISM:Occurs over a long period of time with the accumulation of small changes

PUNCTUATED EQUILIBRIUM:Occurs with speciation in rapid bursts with 1000’s of years of stability between changes

Evidence for Evolution

Fossil RecordMay give exact age or relative age

Evidence for Evolution

Biochemical EvidenceComparing amino acid sequences

REMEMBER…If amino acids are similar, DNA is similar because DNA is a code for making proteins!

Evidence for Evolution

Homologous StructuresSimilar bone arrangement, but

different functions

REMEMBER…Analogous structures do not give evidence of evolution from a common ancestor!

Evidence for Evolution

Vestigial StructuresNot functional, but may have been

important in an ancestor

Vestigial Structures - SciShow

Evidence for Evolution

Comparative EmbryologySimilar embryos give evidence of a

common ancestor

Evolution Today

Evolution is still happening!

However, it’s usually too slow to observe…

EXCEPT:

1) Pesticide Resistance

Evolution Today

Evolution is still happening!

However, it’s usually too slow to observe…

EXCEPT:

2)Antibiotic

Resistance