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Questions and Answers
What was the primary conclusion of Francesco Redi's experiment regarding spontaneous generation?
Which of the following best describes the Endosymbiotic Theory proposed by Lynn Margulis?
What was a major flaw in John Needham's experiment that led to the belief in spontaneous generation?
What aspect of abiogenesis theory persisted for nearly 2000 years within the scientific community?
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Which of the following correctly defines dichotomous keys?
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What conclusion did Lazarro Spallanzani reach regarding Needham’s experiment?
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Which aspect of Pasteur's swan-neck flask experiment was crucial to disproving abiogenesis?
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Which of the following statements correctly describes the cell theory developed by Schleiden and Schwann?
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Which scientist is credited with first using the term 'cell' to describe microscopic structures?
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What was a significant limitation criticized in Spallanzani's experiment with sealed flasks?
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Study Notes
Endosymbiotic Theory
- Proposed by Lynn Margulis in 1970 with the book, The Origin of Eukaryotic Cells
- Suggests eukaryotic cells evolved from a symbiotic relationship between different prokaryotic organisms
Miller & Urey Experiments
- Attempted to demonstrate how organic compounds could have formed on early Earth
- Simulating lightning through a mixture of gases: methane, ammonia, hydrogen and water vapor
- Observed that after one week, 10% - 15% of the carbon was present as amino acids
Dichotomous Keys
- A tool used to identify organisms like trees, wildflowers, mammals, reptiles, rocks, and fish
- Keys consist of a series of choices leading to the correct name of an item
- "Dichotomous" means "divided into two parts," so each step presents two choices
Abiogenesis
- Developed by Aristotle (384-322 BC)
- The theory that life can originate from non-living matter
- Supported by the scientific community for nearly 2000 years
- Notably, Van Helmont provided “scientific evidence” in the 17th century by suggesting that mice arose from grains of rice in a piece of fabric
Francesco Redi’s Experiment (1668)
- Designed to test if rotting meat turns into flies
- Found that rotting meat does not produce flies, flies only come from other flies
- Disproved the theory of spontaneous generation
John Needham's Experiment (1748)
- Believed that spontaneous generation could occur
- Boiled chicken broth (thought to kill all life), then left it open to the air
- The broth became cloudy, leading Needham to believe organisms arose spontaneously from the broth
- Sent many scientists down the wrong path
Lazarro Spallanzani's Experiment (1776)
- Continued Needham's work
- Identified errors in Needham's experiment:
- Broth wasn’t boiled long enough to eliminate all life
- Flasks were not sealed tightly enough
- Boiled flasks longer and sealed them more securely, preventing microbial growth
- Critics argued against sealed flasks claiming air was needed for life
Louis Pasteur's Swan-Neck Flask Experiment (1864)
- Successfully disproved abiogenesis
- Believed bacteria was present in air with dust
- Designed a swan-neck flask to prove his theory:
- Broth was boiled to kill microbes
- Neck of flask was heated and shaped into an S-curve
- This prevented dust particles with microbes from reaching the broth
- Breaking the neck of the flask allowed air to reach the broth and growth occurred
- Tilting the flask with the S-shaped neck allowed microbes to enter the broth and promote growth
- This experiment solidified the theory of biogenesis
Biogenesis
- The idea that living things can only arise from other living things
- Life only comes from life
- Bio - Life
- Gen - To be produced
Microscopes
- Anton Van Leeuwenhoek began making and using simple microscopes
- He often created a new microscope for each specimen
- Examined water and observed tiny organisms: fungi, algae single-celled protozoa (animalcules)
- These organisms were later termed microbes in the 19th century
Cells
- Robert Hooke observed a sliver of cork through a microscope lens and observed “pores” or "cells"
- He was the first to use the word "cell" when describing microscopic structures
Cell Theory
- Developed by Schleiden (botanist) and Schwann (zoologist)
- States that life consists of cells and they are the basic unit of life
- Further clarified by Virchow who established that cells come from pre-existing cells
Key Points of the Cell Theory
- All living things are made of cells
- Cells are the basic units of life
- All cells arise from pre-existing cells
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Description
Test your knowledge on key concepts surrounding spontaneous generation and the notable experiments that challenged this idea. This quiz covers Francesco Redi's experiments, the Endosymbiotic Theory, and major flaws in historical experiments. Dive into the foundational theories that have shaped our understanding of abiogenesis and biological classification.
