states that all living things came from other living things
opposes spontaneous generation theory
Antoni van Leeuwenhoek Francesco Redi John Needham Rudolf Virchow Louis Pasteur
Antoni van Leeuwenhoek
call by many as the "father of microbiology" but is given the title of father of bacteriology and protozoology
improved the microscope and was the first to see microscopic organismsand called them animalcules
he saw protozoans, fungi, and bacteria
described them in a letter to the Royal Society of London
his microscope open up the debate related to microscopic life forms
An amateur microbiologist, Antoni van Leeuwenhoek, observed small organisms in dirty water and some material he scrapped from his teeth. These organisms were called 'animalcules' that we call as protozoans, today. This discovery took Europe by storm and scientists were thrilled to find these animalcules. The most pricking question in the minds of many was the origin of these animalcules. This doubt had only one answer, spontaneous theory of generation.
boiled mutton broth the sealed containers but the clear broth in the container became cloudy
Needham experiment lent support to spontaneous generation
Needham's work was contradicted by another religious investigator, the Italian physiologist Lazzaro Spallanzani. Spallanzani, who was educated in the classics and philosophy at a Jesuit college, went on to teach logic, metaphysics, Greek, and physics. About 20 years after Needham announced the results of his own investigation of spontaneous generation, Spallanzani showed that when broth was heated after being sealed in a flask, it did not generate life forms. He suggested that Needham's broths had probably supported growth after being heated because they had been contaminated before being sealed in their containers.
Possible reasons the clear broth turned cloudy:
Needham did not boil long enough to completely sterile the broth
there were endospore in the broth and they are very hard to kill if not by prolong heating or autoclaving (there were no autoclaves in 1748)
enclosed in the epigram Omnis cellula e cellula ("every cell originates from another existing cell like it.") which he published in 1858.
the first to recognize leukemia cells
He was one of the first to accept the work of Robert Remak who showed that the origins of cells was the division of preexisting cells
he did not initially accept the evidence for cell division, believing that it only occurs in certain types of cells
boiled broth in swan neck flask
these flask allowed air to enter (this was a problem because many said Spallazani's flask did not have)
the purpose of the bent neck was to prevent untreated air with dust and microbes could not enter
the contents of the flask remained sterile
note that Pasteur was fortunate that the foods he boiled into broths did not contain bacterial spores since such spores are resistant to killing by boiling
his experiment disproved spontaneous generation
some of his flask are still sterile today
Spontaneous Generation Theory
synthesized by Aristotle
states that non-living things can give rise to living things (life started from inanimate matter)
logs gave rise to crocodiles
dirty sewers gave rise to rats
Maggots came from cadavers
the generation of living things from other life forms
the theoretical process of going through successive stages during the embryonic period of an animal's life that duplicate the evolutionary stages the species experienced repetition of evolutionary stages
a | In principle, there are a number of ways that organelle biogenesis can occur in proliferating cells. Biogenesis can occur by de novo synthesis, which in its purest sense means that a new copy of the organelle is generated in the absence of a template or existing copy of the organelle. Alternatively, organelle biogenesis can occur through templated assembly and growth, or through growth followed by fission.
b | The principles that govern organelle inheritance will depend on how many copies of the organelle are present in the cell. A single-copy organelle can be duplicated and then segregated prior to cell division, or broken down into parts that are then shared out between the two daughter cells. Multiple-copy organelles can, in theory, simply be shared out and do not need to be dismantled. In this case, a stochastic-partitioning mechanism can explain efficient inheritance of the organelle, but for low-copy-number organelles this mechanism is not sufficient to ensure equal partitioning, and an active segregation process needs to be invoked.