The Origin of Life

I. The Early Ideas

Spontaneous generation Nonliving material can produce life

Disprove Francesco Redi

Used maggots in covered and uncovered jars Louis Pasteur

Used curved flasks with heated broth

I. The Early Ideas

A. Francesco Redi 1668 Rotting meat kept

away from flies would not produce flies

Maggots only on meat exposed to flies Eggs laid on meat

I. The Early Ideas

B. Louis Pasteur Mid- 1800s Used curve-necked

flasks Microorganisms were

prevented from entering the flask

Curved necks broken, broth became cloudy with microorganims

I. The Early Ideas

Biogenesis All living things come from other living

things Louis Pasteur Completely disproved spontaneous

generation

II. The Modern Ideas

Alexander Oparin Life began in the oceans Energy from sun + lightning+ Earth’s heat =

simple compounds

Stanley Miller and Harold Urey

Used Oparin’s hypothesis to setup experiment

Conditions of early earth

II. The Modern Ideas

Water vapor, ammonia, methane, hydrogen

Sent electric current through Cooled gases, collected liquid Produced amino acids, sugars, and others

II. The Modern Ideas

III. Formation of Protocells Sidney Fox Produced protocells

Large, ordered structure, enclosed by a membrane

Carries out some life activities (growth and division)

Heated amino acids

IV. The First True Cells

Prokaryotes evolved from a protocell Heterotrophs (obtained food) Anaerobic

Archaebacteria Prokaryotic Autotrophs Deep-sea vents and hot springs

Photosynthesizing prokaryotes Increased oxygen in

atmosphere 2.8 bya

Eukaryotes evolved from prokaryotes Ozone provided protection

IV. The First True Cells

V. Endosymbiotic Theory

Bacteria (cyanobacteria) and chloroplasts resemble each other in size and photosynthesize

Chloroplast and mitochondria contain separate DNA, reproduce separately, have own ribosomes

V. Endosymbiotic Theory

In Conclusion: Aerobic prokaryotes evolved into

modern mitochondria

Photosynthetic cyanobacteria evolved into chloroplasts plant

Draw, Label, and Describe the Endosymbiotic Theory.

May use text book Pages 427-428

Endosymbiotic Theory

Charles DarwinCharles Darwin

British naturalist1809-1882

Founder of modern evolutionary theory

I. DarwinI. Darwin

Naturalist on HMS Beagle in 1831

collected, studied, stored biological specimens throughout South

America and South Pacific published “On the Origin of

Species by Natural Selection” in 1859

HMS Beagle

I. DarwinI. Darwin Traveled to Galapagos Islands Species of reptiles, insects, birds, flowering plants were

unique to the islands but similar to species elsewhere

Galapagos IslandsGalapagos Islands

I. DarwinI. Darwin Found that individuals struggled for existence

Competition for: Food Space Predators shelter

                  

Food

Predators

Space

Shelter

Finding mates

I. DarwinI. DarwinArtificial Selection• Breeding organisms with specific traits in order to produce offspring with identical traits

DogsHorses

I. DarwinI. DarwinNatural Selection Mechanism for change in populations

Organisms with favorable variations for a particular environment survives, reproduce, and pass these variations on to the next generation

English moths

I. DarwinI. Darwin

Natural Selection Alfred Russel Wallace

Wrote similar ideas to Darwin Jointly presented Origin of Species written

Adaptations: Evidence for Evolution

II. Structural AdaptationsII. Structural Adaptations

A. Mimicry Enables one species to resemble another. Example: Bee orchid, yellow jackets

B. Camouflage Organisms blend with its surroundings Example: flounder

Praying mantis

Frog

Flounder

II. Structural Adaptations

III. Physiological Adaptations

Changes in an organism’s metabolic processes Direct evidence for evolution

Penicillin-resistance by some bacteria Pesticide-resistance by some insects

IV. Other EvidenceIV. Other Evidence

A. Fossils Provide a record of

early life and evolutionary history

Incomplete Found throughout

the world

IV. Other EvidenceIV. Other EvidenceB. Anatomy1. Homologous structures

Structural features with a common evolutionary origin Similar in structure, function or both Does not always mean that two species are related

2. Analogous structures Any part that is similar in function but different in structure Not used to indicate evolutionary relationship

• Birds and butterflies use wings to fly• Butterfly wings made of chitin• Bird wings made of bones

IV. Other Evidence

3. Vestigial structures Body structure in a present-day organisms that no

longer serves its original purpose Probably useful to ancestor Ex. Appendix in humans, pelvis and femur in whales

IV. Other Evidence

IV. Other EvidenceIV. Other EvidenceC. Embryology Embryo – earliest stage of growth and development of

plants and animals

Similarities in stages of embryonic development leading to distinct organism Ex. Frogs and humans

IV. Other EvidenceIV. Other EvidenceD. Biochemistry Use of DNA, RNA, ATP, and comparisons

Amino acid sequence of cytochrome c differ among different species

More reliable

More similarities – closely related

Indicates levels of relationships

Mechanisms of Evolution

Only populations evolve and not individual organisms Populations genes and frequencies change

over time Gene pool

The sum of all genes in a population Tells us that evolution occurs

I. Population Genetics

I. Population Genetics

Allelic Frequency The percentage of a particular allele in the

gene pool

Genetic Equilibrium A population in which the frequency of alleles

remains the same over generations Genetic equilibrium = no evolution No equilibrium = evolution occurs

I. Population Genetics

Gene Flow Transport of genes by migrating individuals Immigration – individuals enter pop. genes

added to pool Emigration – individuals leave pop. genes are

lost from pool

I. Population Genetics

Mutation Results in useful variation

Genetic drift Alteration of allelic frequencies by chance events Affect small populations

Ex. Amish population

II. Changes in Equilibrium

III. Types of natural selection

A. Stabilizing selection Favors average individuals in a population

Ex. Plants - too short, not be able to compete for sunlight- too tall, susceptible to wind damage- select for medium height will increase

                                                               

Ex. Woodpecker - selection for long beaks

B. Directional selection Favors one of the extreme variations of

a trait

                                                               

Ex. Limpets- light and dark colored limpets are favored

C. Disruptive selection Favors either extreme of a trait’s variation

IV. The Evolution of Species

A group of organisms that have the ability to interbreed and produce fertile offspring

Species

Animal species

Plant species

A. Speciation Evolution of a new species Occurs when members of similar populations

no longer interbreed to produce fertile offspring within their natural environment

IV. Evolution of Species

B. Geographic Isolation Physical barrier divides a population

Droughts in forests, lava flows, sea level changes

IV. Evolution of Species

C. Reproductive Isolation Interbreeding organisms can no longer mate and

produce fertile offspring Ex. Tree frogs that mate in the summer cannot mate

with those that mate in the fall

IV. Evolution of Species

D. Change In Chromosome # Polyploids Species with a multiple of the normal set of

chromosomes Results from mistakes in mitosis or meiosis

IV. Evolution of Species

V. Rates of Speciation

A. Gradualism Species originate through a gradual change of

adaptations

V. Rates of Speciation

B. Punctuated Equilibrium Speciation occurs relatively quickly, rapid bursts Niles Eldredge, Stephen J. Gould

V. Rates of Speciation

Gradualism Punctuated Equilibrium

Gradualism vs Punctuated Equilibrium

VI. Patterns of Evolution

Adaptive Radiation When an ancestral species evolves into array

of species to fit a number of diverse habitats.

VI. Patterns of Evolution

Hawaiian honeycreepers

Divergent Evolution Similar species become more and more

distinct Adaptation to different environmental

conditions

VI. Patterns of Evolution

Convergent Evolution Distantly related organisms evolve similar traits Unrelated species occupy similar environments in

different parts of the world

VI. Patterns of Evolution

Coevolution: evolution of two or more interdependent species,

each adapting to changes in the other Predator/prey Insects/flowers they pollinate

VI. Patterns of Evolution