Evolution
Evolution is the inheritance of genes and characteristics that make you more able to survive and to produce offspring, these genes are not found in every individual this is called variation. Variation is the cause of natural selection because all the individuals without the characteristics will die, this is called natural selection. An example of this is the E. coli bacterium I got this example from the internet: (see link 4)
The Simplest Example of Evolution
The process of evolution acts on an E. coli cell by creating a mutation in the DNA. It is not uncommon for the DNA strand in an E. coli bacterium to get corrupted. An X-ray, a cosmic ray or a stray chemical reaction can change or damage the DNA strand. In most cases, a particular E. coli cell with mutated DNA will die, fix the damage in the strand or fail to reproduce. In other words, most mutations go nowhere. But every so often, a mutation will actually survive and the cell will reproduce.
Imagine, for example, a bunch of identical E. coli cells that are living in a Petri dish. With plenty of food and the right temperature, they can double every 20 minutes. That is, each E. coli cell can duplicate its DNA strand and split into two new cells in 20 minutes.
Now, imagine that someone pours an antibiotic into the Petri dish. Many antibiotics kill bacteria by gumming up one of the enzymes that the bacteria need to live. For example, one common antibiotic gums up the enzyme process that builds the cell wall. Without the ability to add to the cell wall, the bacteria cannot reproduce, and eventually they die.
When the antibiotic enters the dish, all of the bacteria should die. But imagine that, among the many millions of bacteria living in the dish, one of them acquires a mutation that makes its cell-wall-building enzyme different from the norm. Because of the difference, the antibiotic molecule does not attach properly to the enzyme, and therefore does not affect it. That one E. coli cell will survive, and since all of its neighbours are dead, it can reproduce and take over the Petri dish. There is now a strain of E. coli that is immune to that particular antibiotic.
In this example, you can see evolution at work. A random DNA mutation created an E. coli cell that is unique. The cell is unaffected by the antibiotic that kills all of its neighbours. This unique cell, in the environment of that Petri dish, is able to survive.
E. coli are about as simple as living organisms can get, and because they reproduce so rapidly you can actually see evolution's effects on a normal time scale. In the past several decades, many different types of bacteria have become immune to antibiotics. In a similar way, insects become immune to insecticides because they breed so quickly. For example, DDT-resistant mosquitoes evolved from normal mosquitoes.
In most cases, evolution is a much slower process.
The Island of Mice
Dune mice - Bigger claws for digging
Beach mice - Bigger ears and eyes
These characteristics will spread through the whole population because the ones that don’t have the right characteristics will die or get eaten.
If the river narrows again there are two things that can happen:
1. The groups of mice will just get together and get back into their old habits and looks.
2. The groups of mice have evolved to two different species so they can’t reproduce any more.
Questions
The genetic factors in these colonies are the genes for bigger ears and eyes and the genes for bigger claws. The environmental factors are: the amount of food available, the amount of predators and the amount of mice on each part of the island and their gender. The use of asexual reproduction is theoretically possible if the individual mates with an other individual in its further life. Practically asexual reproduction in mice won’t be able because they will have to split like bacteria but that is not possible. With only asexual the whole population would die after some time.
Sources
Internet:
http://www.scienceagogo.com/news/20030421210938data_trunc_sys.shtml
http://evolutionlist.blogspot.com/2006/11/island-mice-may-evolve-faster-from-one.html
http://www.answersingenesis.org/articles/am/v1/n1/evolution-or-adaptation
http://science.howstuffworks.com/evolution4.htm
Evolution is the inheritance of genes and characteristics that make you more able to survive and to produce offspring, these genes are not found in every individual this is called variation. Variation is the cause of natural selection because all the individuals without the characteristics will die, this is called natural selection. An example of this is the E. coli bacterium I got this example from the internet: (see link 4)
The Simplest Example of Evolution
The process of evolution acts on an E. coli cell by creating a mutation in the DNA. It is not uncommon for the DNA strand in an E. coli bacterium to get corrupted. An X-ray, a cosmic ray or a stray chemical reaction can change or damage the DNA strand. In most cases, a particular E. coli cell with mutated DNA will die, fix the damage in the strand or fail to reproduce. In other words, most mutations go nowhere. But every so often, a mutation will actually survive and the cell will reproduce.
Now, imagine that someone pours an antibiotic into the Petri dish. Many antibiotics kill bacteria by gumming up one of the enzymes that the bacteria need to live. For example, one common antibiotic gums up the enzyme process that builds the cell wall. Without the ability to add to the cell wall, the bacteria cannot reproduce, and eventually they die.
When the antibiotic enters the dish, all of the bacteria should die. But imagine that, among the many millions of bacteria living in the dish, one of them acquires a mutation that makes its cell-wall-building enzyme different from the norm. Because of the difference, the antibiotic molecule does not attach properly to the enzyme, and therefore does not affect it. That one E. coli cell will survive, and since all of its neighbours are dead, it can reproduce and take over the Petri dish. There is now a strain of E. coli that is immune to that particular antibiotic.
In this example, you can see evolution at work. A random DNA mutation created an E. coli cell that is unique. The cell is unaffected by the antibiotic that kills all of its neighbours. This unique cell, in the environment of that Petri dish, is able to survive.
E. coli are about as simple as living organisms can get, and because they reproduce so rapidly you can actually see evolution's effects on a normal time scale. In the past several decades, many different types of bacteria have become immune to antibiotics. In a similar way, insects become immune to insecticides because they breed so quickly. For example, DDT-resistant mosquitoes evolved from normal mosquitoes.
In most cases, evolution is a much slower process.
The Island of Mice
Dune mice - Bigger claws for digging
Beach mice - Bigger ears and eyes
These characteristics will spread through the whole population because the ones that don’t have the right characteristics will die or get eaten.
If the river narrows again there are two things that can happen:
1. The groups of mice will just get together and get back into their old habits and looks.
2. The groups of mice have evolved to two different species so they can’t reproduce any more.
Questions
The genetic factors in these colonies are the genes for bigger ears and eyes and the genes for bigger claws. The environmental factors are: the amount of food available, the amount of predators and the amount of mice on each part of the island and their gender. The use of asexual reproduction is theoretically possible if the individual mates with an other individual in its further life. Practically asexual reproduction in mice won’t be able because they will have to split like bacteria but that is not possible. With only asexual the whole population would die after some time.
Internet:
http://www.scienceagogo.com/news/20030421210938data_trunc_sys.shtml
http://evolutionlist.blogspot.com/2006/11/island-mice-may-evolve-faster-from-one.html
http://www.answersingenesis.org/articles/am/v1/n1/evolution-or-adaptation
http://science.howstuffworks.com/evolution4.htm
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