Bellringer

1. How did the Earth form?

2. What is evolution?

3. What is natural selection?

Origin and History of LifeEvolution

Abiogenesis

• AKA: Spontaneous generationthe idea that life comes from nonliving things.

NO.

Biogenesis

The idea that life can only come from pre-existing life

Proven by several experiments.

Redi’s Experiment

• 1st attempt to disprove abiogenesis (to prove biogenesis)

• Proved maggots come from flies.

Pasteur’s ExperimentUsed an S-shaped flask to prove that the

microorganisms only came from other microorganisms

Clearly proved biogenesis and disproved abiogenesis (spontaneous generation)

Early Earth• Earth formed over 4 billion years ago• Oldest rocks on Earth are 3.9 byo• Conditions on early Earth were HARSH with

no oxygen in the atmosphere (and very HOT)

The first forms of life had the following characteristics:

Unicellular HeterotrophicProkaryotic Anaerobic

Oparin’s hypothesis• Hypothesized that energy from the sun,

lightning, and Earth’s heat triggered chemical reactions that formed small organic compounds using molecules from the atmosphere.

Miller & Urey• Performed an experiment supporting

Oparin’s hypothesis• The sample created contained amino acids

Endosymbiosis

Theory describing how eukaryotic cells evolved from prokaryotic cells.

What is EVOLUTION?Process by which the frequency of different alleles

in a GROUP or POPULATION of organisms changes over timeRemember – alleles are different versions of a gene

When one allele becomes more common in a population, its corresponding phenotype also becomes more common

This is EVOLUTIONTakes place of many generation!

Theories…

Lamarck’s Theory• Organisms develop traits by use or disease• Organisms acquire characteristics/traits as

they need it and pass it on to their offspring– EX: a guy goes through surgery to lengthen his legs and

gains two inches. All of his future sons will be taller because of the surgery.

• DISPROVED by experiments

Darwin’s Theory• Based on observations and evidence

collected on a 5 year voyage around the world (and multiple experiments in labs)

• 4 main ideas:– Overproduction each species produces more

organisms than can survive and reproduceWhy? Because most offspring do not survive!

– Competition organisms compete for the same resources for survival

– Variations differences among traits that occur among members of the same species• Variations occur by…

–Mutation

–Crossing over in meiosis

–Sexual reproduction

If there are no variations then evolution CANNOT occur!

– Survival of the fittest organisms with alleles that give them phenotypes that make them well adapted to their environment have a better chance of surviving & reproducing.

Fit means the one best suited for the environment,

NOT the strongest!!

This leads to NATURAL SELECTION

• If this environment stayed the same, then over time the number of darker colored moths in the population would increase because they have a better chance at surviving to reproduce.

This is EVOLUTION by natural selection.

When nature selects the traits that are best for the environment.

Which column of giraffe evolution represents Lamarck’s theory and which represents Darwin’s theory?

Adaptation

trait/phenotype that makes an organism more fit/gives it an advantage at surviving in its environment

Ex: a polar bear’s black skin and clear fur

Camouflage

An adaptation that allows an organism to bend with its environment

Mimicry

An adaptation in which one organism mimics another more deadly/toxic organism

EVOLUTION by natural selection in the news…

1. PESTICIDE RESISTANCE when pesticide does NOT kill its target

(pesticides can be for insects, plants, for fungi)

Use of pesticides is changing the environment in which insects live

Some insects have alleles that make them more fit for the new environment

Those insects that are more fit survive and reproduce (pass on their alleles)

Future populations of that insect are now resistant to the pesticide and the pesticide does not work anymore.

EVOLUTION has occurred.

Overuse of pesticides has helped insects and weeds become pesticide resistant.

Antibiotic Resistance

When an antibiotic does NOT kill the bacteria

Due to incorrect and overuse of antibiotics

Evolution by chance?Called EVOLUTION by genetic drift

When a chance event allows a specific phenotype (determined by a set of alleles) to become more of less common in a population.

Occurs in small populations