Chapter 1.5 - The Origin of Cells Flashcards
How are cells formed?
Cells can only be formed by division of pre-existing cells
What happens before cells can divide?
All of the genetic material in the nucleus was copied
What has been the first cell of every human’s body?
the zygote (produced by the fusion of a sperm and an egg)
What did scientists create in 2010?
they created the first artificial cell
How did scientists create a new cell in 2010?
The base sequence of the DNA of a bacterium was synthesized artificially with few deliberate changes
What is spontaneous generation?
Spontaneous generation is the formation of living organisms from non-living matter
Until when did people believe in spontaneous generation?
Until the 17th century
Why did people believe in spontaneous generation for so long?
Because they did not know about cells, microorganisms and and the nature of sexual reproduction
Why do scientists nowadays believe that cells only come from pre-existing cells?
- A cell is a highly complex structure and no natural mechanism has been suggested for producing cells from simpler subunits
- No example is known of increases in the number of cells without cell division occurring
- Viruses are produced from simpler subunits but they do not consist of cells
Which scientist made experiments to test spontaneous generation?
Pasteur
What was the scientists proof for spontaneous generation?
They boiled broth so that no bacteria would be left in there, however (if they were open to air) there would be bacteria again after a while
How is spontaneous generation also called?
Abiogenesis
How did Louis Pasteur proof spontaneous generation wrong?
He used a swan-necked flask. In this way the boiled broth was still open to air, but no bacteria could go in there by accident. Even after 36 hours, there were no new bacteria in there
What are the four hypotheses of for how some of the main stages of the development of living organisms could have occurred?
- Production of carbon compound such as sugars and amino acids
- Assembly of carbon compounds into polymers
- Formation of membranes
- Development of a mechanism for inheritance
What is meant by “production of carbon compounds such as sugars and amino acids”?
Stanley miller and Harold Ursey passed steam through a mixture of methane, hydrogen and ammonia (representing the atmosphere of the early Earth). Electrical discharges were used to simulate lightning. They found that amino acids and other carbon compounds needed for life were produced.
