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19.3 Phylogeny -- Part 8
Prokaryotes range in size from 1 to 10 um in length and from 0.7 to 1.5 um in width.
The average human is about 1.5 m tall, or 1 million times longer than a bacterium.
According to the fossil record, the prokaryotes were alone on Earth for 2.5 billion years.
They became very diverse in structure and metabolism during that time.
Prokaryotes are adapted to living in most environments because they have a wide variety of ways to get and use energy.
Page 362 has a cell wall outside of the membrane.
Depending on the type of prokaryote, there may be another layer outside the cell wall.
The flagellum of a bacterium has a hook and a body.
A well-organized glycocalyx is called a capsule, whereas a poorly organized one is called a slime layer.
These outer coverings help protect the cell from the host defenses.
The flagellum has a helix with strands of the flagellin wound.
The hook is anchored by a body.
The rotation of the flagellum causes the cell to spin.
The archaeal flagellum is more slender and lacks a body.
Short, bristlelike fibers extending from the surface.
The membranous organelles of a eukaryotic cell is absent in a prokaryotic cell.
ribosomes are smaller than eukaryotic ribosomes and are used to synthesise prokaryotic cells.
Imagine becoming a scientist.
The image of a scientist is changing.
For about $250, you can purchase materials to perform a sophisticated experiment to create a glowing plant in your own home.
A project like this is part of a movement called do-it-yourself biology, where amateurs are doing modern biology experiments in their kitchens, garage, and community lab spaces.
The project requires a gene that codes for green fluorescent protein, which glows when exposed to ultraviolet light.
It isn't a mechanical device to get the genes into the plant.
The plant transformation is done by themediated plant transformation.
Some of the seeds produced by the original plant will grow into glowing plants if the procedure is done correctly.
In prokaryotes, it is not possible to form a spindle apparatus.
Prokaryotes divide to reproduce when conditions are favorable.
The daughter cells have the same genetic material as the parent cells, so this is a form of asexual reproduction.
As the cell enlarges, the two copies separate as the single circular chromosome replicates.
The cell is separated into two cells by a wall.
Under favorable conditions, prokaryotes can have a generation time as short as 12 minutes.
The offspring are passed on more quickly than in otheryotes.
Natural selection determines any possible adaptive benefit in the particular environment because prokaryotes are haploid.
Sexual reproduction results in genetic recombination.
There are three ways of genetic recombination that have been observed in prokaryotes.
A conjugate pilus is used to link two bacteria temporarily.
The donor cell passes its genetic material to the recipient cell.
A portion of a cell's genetic material is carried from one cell to another.
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