Unit 1 Review: Scientists And Other Things To Know Flashcards
Redi
MAGGOTS & MEAT. DISPROVED SPONTANEOUS GENERATION
Italian scientist Francesco Redi noticed and described the different developmental forms of flies. He observed that tiny wormlike maggots turned into sturdy oval cases, from which flies eventually emerged. He also observed that maggots seemed to appear only where adult flies had previously landed. These observations led him to question the belief that flies were generated spontaneously from rotting meat. Redi conducted in 1668 to test his hypothesis that meat kept away from adult flies would be free of maggots. The experimental group consisted of netting-covered jars that contained meat. The control group consisted of uncovered jars that also contained meat. The netting allowed air to enter and prevented flies from landing on the meat. After a few days, maggots appeared on the meat in the open jars, while the net-covered jars had no maggots. Redi’s experiment showed that flies come only from eggs laid by other flies. (Redi’s hypothesis was confirmed)
Spallanzani
1ST MEAT BROTH- THOUGH MICROORGANISMS DONT COME FROM AIR, BUT OTHER MICROORGANISMS. (also disporved spontaneous generation?) MELTED THE NECKS CLOSED
In the 1700s, another Italian scientist, Lazzaro Spallanzani designed an experiment to test the hypothesis of spontaneous generation of microorgan-isms. Spallanzani hypothesized that microorganisms formed not from air but from other microorganisms. He knew that microorganisms grow easily in food. Therefore, he decided to test their growth in meat broth. He said that boiling broth in a flask would kill all the microorganisms in the broth, on the inside of the glass, and in the air in the flask. For his experimental group, Spallanzani boiled clear, fresh broth until the flasks filled with steam. Then he sealed the flasks by melting their glass necks closed while the broth was hot.
The control-group flasks of broth were left open. The broth in the sealed flasks remained clear and free of microorgan-isms, while that in the open flasks became cloudy due to contamination with microorganisms. Spallanzani concluded that the boiled broth became contaminated only when microorganisms from the air entered the flask.
Pasteur
CURVED NECK FLASK WITH MEAT BROTH
Pasteur made an experiment that won an award for clearing up the issue. Pasteur made a curve-necked flask that allowed the air inside the flask to mix with air outside the flask. The curve in the neck of the flask prevented solid particles, such as microorganisms, from entering the body of the flask. Broth boiled inside the experimental curve-necked flasks remained clear for up to a year. But when Pasteur broke off the curved necks, the broth became cloudy and contaminated with microorganisms within a day. Pasteur reasoned that the contamination was due to microorganisms in the air.
Miller-Urey
GAS CHAMBER. SIMULATED EARTHS ATMOSPHERE (created lightning?)
An experiment to test a hypothesis first proposed in the 1920s. Earlier scientists had proposed that an input of energy from lighting led to the formation of organic molecules from inorganic molecules present in the atmosphere of early Earth. Stanley L. Miller, and his professor, Harold C. Urey, set up an experiment using Oparin’s hypothesis as a starting point. Their apparatus included a chamber containing the gases Oparin assumed were present in the young Earth’s atmosphere. As the gases circulated in the chamber, electric sparks, substituting for lightning, supplied energy to drive chemical reactions. The Miller-Urey experiment, and other variations that have followed, produced a variety of organic compounds, including amino acids.
Margulis
ENDOSYMBIOSIS.
A large body of evidence now suggests that between about 2.0 and 1.5 billion years ago, a type of small aerobic prokaryote entered and began to live and reproduce inside larger, anaerobic prokaryotes. Researcher Lynn Margulis proposed that what may have started as an invasion became a successful, mutually beneficial relationship-called endosymbiosis. Endosymbiosis is a relationship in which one organism lives within the body of another, and both benefit from the relationship. It is thought that the aerobic prokaryote eventually gave rise to modern mitochondria, which are the site of aerobic respiration in eukaryotic cells..
Fox
FIRST CELL
Sidney Fox and others have done extensive research on the physical structures that may have given rise to the first cells. These cell-like structures form spontaneously in the laboratory from solutions of simple organic chemicals. The structures include microspheres, which are spherical in shape and are composed of many protein molecules that are organized as a membrane, and coacervates, which are collections of droplets that are composed of molecules of different types, including linked amino acids and sugars.
Oparin
ATMOSPHERE CONTAINED AMMONIA, HYDROGEN GAS, WATER VAPOR, METHANE etc.
Oparin suggested that the atmosphere of the primitive Earth was very different from that of today. He thought that the early atmosphere contained ammonia, hydrogen gas, water vapor, and compounds made of hydrogen and carbon, such as methane. At temperatures above the boiling point of water, these gases might have formed simple organic compounds. When the earth cooled and water vapor condensed to form lakes and seas, these simple organic compounds would have collected in the water. Over time these compounds could have entered complex chemical reactions, fueled by energy from lightning and ultraviolet radiation. Oparin stated that these reactions would have resulted in the macromolecules essential to life, such as proteins.
Lamarck’s Theory of Evolution
Jean Baptiste de Lemarck (1744-1829) was the first to propose a theory of evolution. He hypothesized that traits acquired over a lifetime are passed to offspring (mostly not true) and that structures formed through repetitive use OR structure could be lost through lack of use (both not true). i.e. long neck of giraffe formed by repetitive stretching then this trait passed to offspring
i.e. webbed toes of the duck formed by flexing toes, then passed on
4 pts:
1. Environment changes thus creating a “need” to change (making it sound voluntary)
- Development of new ACQUIRED features “in order to survive” or “so one can survive”. Acquired traits arise during the lifetime of an organism and don’t change its genotype. Ex: walking with a limp bc of previous broken leg
- Newly acquired traits (through use and/or non use) somehow get passed down to offspring
- New species eventually
Darwin’s theories
Descent with modification
Modification by natural selection
Descent with Modification theory (THREE points)
•States that newer forms appearing in the fossil records are actually the modified descendants of older species.
• Also stated that ALL living things descended from one, or a few common ancestors millions to billions of years ago
•This theory also accounted for the fact that similar organisms arise in the same geographical location (fig 15-6 pg. 281)
Modification by natural selection (3 pts)
Overproduction
Variation
Adaptation
Overproduction
more organisms are born than can ultimately survive. There is competition within the species for food, habitat, survival from being eaten
Variation
when organisms are born they are not all the same. There is variation (heritable differences that exist among individuals) that exists in every population. Natural-selection acts on existing variation and it acts on phenotypes (physical traits (observable)
Adaptation
the “strong” or “best suited” that are selected by the environment due to changes in climate, topography, food supply, predators ete) survive and pass these characteristics on to their offspring and these traits become more common in the population over time
“survival of the fittest” does NOT mean the “strongest” survive, “fit” is a measure of the ability to survive and produce more offspring
LUCA
LUCA is short for Last Universal Common Ancestor, and it is from this organism that every living cell on the planet has descended.
