Bellringer 1.How did the Earth form? 2.What is evolution? 3.What is natural selection?

Origin and History of Life Evolution

Abiogenesis AKA: Spontaneous generation  the 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 1 st attempt to disprove abiogenesis (to prove biogenesis) Proved maggots come from flies.

Pasteur’s Experiment  Used 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: UnicellularHeterotrophic ProkaryoticAnaerobic

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 time Remember – 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 EVOLUTION Takes 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 reproduce Why? 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