Crash Course in Evolution!

Biology Objectives for EOC Exam

A. Spontaneous Generation (& Redi, Needham, Spallanzani, and Pasteur)

No, not really!!!

• Spontaneous Generation – idea that some living things arose spontaneously from non-living matter– Ex: in the 17th century, one recipe for “producing”

mice involved putting sweaty underwear and husks of wheat into a jar and waiting 21 days.

– AND: maggots from rotting meat, fish from mud, beetles from cow dung

• Francesco Redi (1668)– experimented with meat to see if maggots were spontaneously created, OR the result of flies laying their eggs in it– Conclusion: He suspected it was the flies, but said that

SG still occurred in some cases!

• John Needham (1745)– experimented to see if microorganisms grew after chicken broth was boiled (so that previously existing microorganisms were killed). They did!– Conclusion: Spontaneous generation DOES occur!

• Lazzaro Spallanzani – not convinced by Needham’s experiment, said that microorganisms could have come from the air, modified Needham’s experiment to test this.– Conclusion: Spontaneous generation did not occur! (But

others said that he only proved it did not occur without air present.)

• Louis Pasteur (1859) – combined Redi & Spallanzani’s experiments. Working with meat broth in a flask, he allowed air to get in but shaped the flask so that microorganisms “settled out” of the air before getting to the broth. – Conclusion: Spontaneous generation does not occur!

B. Evolution is…• Descent with modification– Genetic change in a species over a period of time

• Some scientists say that life on earth has evolved to be very diverse, but shared common ancestors.

C. Chemical & organic evolution

• Chemical evolution - chemical changes on the primitive Earth that allowed life to exist.

• Organic evolution – the slow, gradual change in life forms throughout history (from simple single-celled organisms to more complex multi-celled organisms)

Heterotrophs vs. Autotrophs

• Heterotrophs: obtain energy by feeding on others.

• Autotrophs: make their own food via photosynthesis

• Heterotroph hypothesis suggests that heterotrophs were the first organisms on Earth and that autotrophs evolved from them. Does not try to explain the origin of the first heterotrophs though!

D. Darwin, survival of the fittest, and natural selection

• British naturalist, loved/studied nature

• Embarked on a 5 year journey around the world on the HMS Beagle

• Studies of specimens & diverse life around the world led him to develop this theory of evolution and views on natural selection

“Survival of the fittest” Darwin’s idea that organisms best-suited for their environment will survive, reproduce, and pass on their traits.

http://www.youtube.com/watch?v=AMtT5_AQmLg

Natural Selection

http://evolution.berkeley.edu/evolibrary/article/evo_25

• Must begin with genetic variation!• Ex: Peppered moth

E. Influences on Darwin’s ideas…• Malthus – “overproduction” in nature, more

offspring are produced than can survive (became part of Darwin’s idea of natural selection)

• Wallace – developed a theory of evolution similar to Darwin’s, acted as a collaborator, shared research with him

• Lyell – geologist, Darwin used his book about about geology/rock formations to help him understand more about fossils he gathered

• Lamarck – believed that organisms evolved toward perfection, species didn’t become extinct just changed into different species, and that “acquired” characteristics could be passed on (Ex: giraffe’s necks got longer when they stretched for food)

• The Journey (HMS Beagle) – 5 years of studying, gathering information about life forms from around the world, Darwin was impressed with the diversity of life!

F. Lamarck vs. Darwin

G. Behaviors that have evolved through natural selection

–Courtship rituals - http://newswatch.nationalgeographic.com/2013/02/14/wild-romance-weird-animal-courtship-and-mating-rituals/ –Migration – birds flying south for winter,

etc.–Defense mechanisms – skunks’ odor,

mimicry, porcupine quills, http://webecoist.momtastic.com/2008/11/04/9-of-the-most-bizarre-animal-defense-mechanisms/

H. Conditions required to be a species

• Species group of related organisms that can interbreed in nature and produce fertile offspring. (reproductively separated from other species)

• Speciation (creating of new species) can occur by: – Reproductive isolation: members of two groups are

unable to reproduce (different courtship rituals, different breeding seasons, sex organs aren’t compatible etc.)

– Geographical isolation: members of a species become separated by river, earthquake, etc.

I. Types of selection

J. Natural selection and evolutionary consequences explain the fossil record

• Fossils will show similar adaptations because species had to adapt to a specific environment in order to survive.

• Fossil record will show that species that have gone extinct lack the adaptations needed to survive in their environment.

L. Evidence from geology, biochemistry, embryology, comparative anatomy, &

comparative physiology

• Geology – fossil record, rock layers• Biochemistry – similarities in DNA, molecules

making up organisms• Embryology – similarities in the embryonic

development of various species• Comparative anatomy & physiology –

similarities in body structure and function

N. Catastrophism, gradualism, punctuated equilibrium

• Catastrophism – idea that Earth’s crust has been scarred by catastrophic events

• Gradualism – idea that evolution occurs at a slow, steady pace and is constant

• Punctuated Equilibrium – idea that evolution occurs in spurts, not constantly