Life’s Origin and Classifying Organisms

Where does life come from? Spontaneous Generation Spontaneous Generation –Belief that living things could come from non-living organisms. –Was accepted for 100’s of years until controlled experiments proved it wrong –Believed from the 4 th century until the 1600’s.

SCIENTISTS USE EXPERIMENTAL DESIGN SPONTANEOUS GENERATION FIRST DISPROVED BY ITALIAN SCIENTIST SPONTANEOUS GENERATION FIRST DISPROVED BY ITALIAN SCIENTIST FRANCESCO REDI - ions/content/scientificmethod.html ions/content/scientificmethod.html ions/content/scientificmethod.html  JOHN NEEDHAM PERFORMED THE HEATED BROTH EXPERIMENT  LAZZARO SPALLANZANI BROILED BROTH IN FLASK FOR LONGER TIME  LOUIS PASTEUR DISPROVED SPONTANEOUS GENERATION FOR THE LAST TIME  nk nk nk

Where does life come from? Biogenesis Biogenesis –Theory that living things can only come from other living things.

Life’s Origins Scientists estimate the earth to be around 4.6 billion years old. Scientists estimate the earth to be around 4.6 billion years old.

Oparin’s Hypothesis Russian scientist Russian scientist Hypothesized in 1924 that Earth’s early atmosphere had no oxygen- was made of gases ammonia, hydrogen, methane, and water vapor. These combined to form more complex compounds. Hypothesized in 1924 that Earth’s early atmosphere had no oxygen- was made of gases ammonia, hydrogen, methane, and water vapor. These combined to form more complex compounds.

Stanley Miller and Harold Urey Tested Oparin’s hypothesis in Showed, but did not conclude, that chemicals found in living things could be produced this way. Tested Oparin’s hypothesis in Showed, but did not conclude, that chemicals found in living things could be produced this way. watch?v=j9ZRHoawyOg watch?v=j9ZRHoawyOg watch?v=j9ZRHoawyOg watch?v=j9ZRHoawyOg Stanley Miller Harold Urey

Why do Scientists Classify? Imagine a grocery store… How are they organized? What would happen if they were not organized? How is your life organized?

Why do Scientists Classify? Almost 2 million kinds of organisms on Earth Need to keep organized! (Easier to study!) Classification = process of grouping things based on their similarities

Why do Scientists Classify? Taxonomy =scientific study of how living things are classified Useful because: once classified, scientists will know a lot about an organism

Early Classification Systems Aristotle (4 th century B.C.) -observed animals -watched appearance, behavior, movement -fly, swim, and walk/crawl/run -observed similarities and differences -used differences to divide into smaller subgroups

Linnaeus Carolus Linnaeus (1750s) -used observations as basis of his system -placed organisms based on similar structures Devised naming system for organisms: Binomial Nomenclature 1DuW28&feature=related

Classification Today Species with similar evolutionary histories are classified more closely together. -when organisms share a common ancestor, they share an evolutionary history -Before classifying an organism scientists look at its phylogeny (evolutionary history) - fossils - DNA - early stages of development

Modern Classification Today’s classification system separates organisms into six kingdoms. Today’s classification system separates organisms into six kingdoms. Kingdoms are the first and largest category Kingdoms are the first and largest category Smallest category is species Smallest category is species Organisms that belong to the same species can mate and produce offspring. Organisms that belong to the same species can mate and produce offspring.

The Old System

6 Kingdom Proposal Archebacteria EUbacteria

Binomial Nomenclature =2 part naming system used by Linnaeus -uses Latin words First word- Genus- is capitalized Second word- species- is NOT. If you can’t italicize, underline the genus and species!

Scientific Name Genus species Felis concolor Genus species Felis concolor –AKA cougar, panther, puma, mountain lion The second word tells something about the species: The second word tells something about the species: –What it looks like, where it is found, or who discovered it

Why use scientific names? To avoid mistakes To avoid mistakes To show how organisms are related To show how organisms are related To give descriptive information (Ilex vomitoria) To give descriptive information (Ilex vomitoria) To allow information to be organized easily To allow information to be organized easily

Levels of Classification -based on contributions of both Aristotle and Linnaeus There are 7 levels of classification. Remember the first letter of this sentence: King Philip Came Over For Good Spaghetti. bTMuU&feature=related

7 Levels of Classification Kingdom broadest level Phylum Class Order Family Genus Speciesmost specific

Using the Classification System Field guides help identify organisms. -they highlight differences between similar organisms (like trees) give descriptions and illustrations Taxonomic Key (AKA Dichotomous Key) -paired statements that describe the physical characteristics of different organisms- detailed list

Dichotomous Keys 1a. Organism has 4 legsGo to # 2 1b. Organism has more than 4 legsGo to # 20 2a. Organism has a tailGo to # 3 2b. Organism has no tailGo to # 35 3a. Organism has stripesBengal Tiger 3b. Organism has no stripesAfrican Lion

Dichotomous Key Try this one: Try this one: 1a. Organism walks on all 4 legs (quadruped)2 1b. Organism walks on 2 legs (biped)8 2a. Organism has visible fur3 2b. Organism has no visible fur20 3a. Organism lives in warm climates7 3b. Organism lives in cold climates4 4a. Organism has brown or black furUrsus americanus 4b. Organism has white furUrsus maritimus