Genetic Change
lessons on genetic change.... AKA evolution
So what do us sciencey folk mean by evolution.... generally not quite the same thing as creationists... and that's half the problem. As far as science goes evolution is no more a theory than gravity is a theory.... it is a scientific fact... heard of MRSA or HIV? Both are the result of evolution, and both can do away with you, whether you believe in them or not.
So lets get on and find out what science understands evolution to be....
So lets get on and find out what science understands evolution to be....
Genetic change works at the population level (gene pools)
If members of a population leave different numbers of offspring (ie some have more babies than others) then a change in the allele frequency in a population may occur.... that's what we biologists call evolution... does it happen?
lets say green and red show incomplete dominance where a heterozygous frog is blue (some revision for you)
total alleles in this population is _____ (its 30!)
total green alleles _____
total red alleles _____
total blue alleles (a trick question!)
lets say everyone in the population gets to have 2 baby frogletts (with no selection, ie at random), what will happen to the frequency (or %) of each allele in the next generation?
What will happen if a Frenchman comes along and eats a few blue frogs?
lets say green and red show incomplete dominance where a heterozygous frog is blue (some revision for you)
total alleles in this population is _____ (its 30!)
total green alleles _____
total red alleles _____
total blue alleles (a trick question!)
lets say everyone in the population gets to have 2 baby frogletts (with no selection, ie at random), what will happen to the frequency (or %) of each allele in the next generation?
What will happen if a Frenchman comes along and eats a few blue frogs?
http://www.newscientist.com/article/mg14319382.900.html
Forty years ago, a unique breeding experiment to test the limits of natural selection began in the US. The experiment involved red flour beetles. Today, some of the beetles are five times as heavy as their ancestors, while others are a quarter the original weight. 'It's the equivalent of breeding an 8-kilogram dog up to the size of a 40-kilogram pig, and down to the size of a 2-kilo Chihuahua,' says William Muir of Purdue University, Indiana, who is currently running the experiment.
In 1954, zoologist Earl Bell placed 1000 red flour beetles (Tribolium castanium) in a plastic box of flour, and allowed them to feed and breed. After one generation, Bell selected the largest 100 males and females and placed them in a second box, while he placed the smallest 100 in a third box.
'We have followed the same selection technique for 240 generations,' says Muir,
This is an example of SELECTIVE BREEDING, aka arranged marriages
Forty years ago, a unique breeding experiment to test the limits of natural selection began in the US. The experiment involved red flour beetles. Today, some of the beetles are five times as heavy as their ancestors, while others are a quarter the original weight. 'It's the equivalent of breeding an 8-kilogram dog up to the size of a 40-kilogram pig, and down to the size of a 2-kilo Chihuahua,' says William Muir of Purdue University, Indiana, who is currently running the experiment.
In 1954, zoologist Earl Bell placed 1000 red flour beetles (Tribolium castanium) in a plastic box of flour, and allowed them to feed and breed. After one generation, Bell selected the largest 100 males and females and placed them in a second box, while he placed the smallest 100 in a third box.
'We have followed the same selection technique for 240 generations,' says Muir,
This is an example of SELECTIVE BREEDING, aka arranged marriages
Darwin's impressions of our fine nation!!!!
"I believe we were all glad to leave New Zealand. It is not a pleasant place.
Amongst the natives there is absent that charming simplicity which is found in Tahiti;
and the greater part of the English are the very refuse of society.
Neither is the country itself attractive."
"I believe we were all glad to leave New Zealand. It is not a pleasant place.
Amongst the natives there is absent that charming simplicity which is found in Tahiti;
and the greater part of the English are the very refuse of society.
Neither is the country itself attractive."
Evidence for speciation (flies example above) click here
Russian bloke domesticating foxes click here It can go in reverse too.... eg NZ feral pigs click here Oliver chimp YouTube click here |
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Our Salmon
What about these fishies... if you were a fish farmer might you sort out some arranged marriages.
How would that affect the gene pool over future generations?
How would that affect the gene pool over future generations?
What about these guys....they all share a common ancestor so what happened?
Words to use to explain this:
ancestor, population, isolation, genetic adaptations, environmental factors, genetic variation, selection, reproductive success, allele freq changes, time
Note: divergence occurs when two groups no longer mix their genes (ie they do not reproduce)
Words to use to explain this:
ancestor, population, isolation, genetic adaptations, environmental factors, genetic variation, selection, reproductive success, allele freq changes, time
Note: divergence occurs when two groups no longer mix their genes (ie they do not reproduce)
"... the human pubic louse does not look like the human head louse, but instead is similar to the gorilla louse, Phthirus gorillae. DNA comparisons also demonstrate that these two species are closely related and shared a common ancestor 3.3 mya. What hominins existed at that time? The Australopithecines. What probably happened is that gorilla lice jumped from gorillas to the Australopithecines at that time and then evolved into the human pubic lice we have today. There was an unoccupied niche that was present and this was filled when our ancestors perhaps used old gorilla nests or preyed on ancestral gorillas.
From:
http://www.trueorigins.us/#/human-lice-human-history/4540119488
Why was the niche unfilled? (think of environmental conditions on different parts of a human body)
From:
http://www.trueorigins.us/#/human-lice-human-history/4540119488
Why was the niche unfilled? (think of environmental conditions on different parts of a human body)
Genetic drift
Australian Sheep Blowfly, Lucilia cuprina, taken in Melbourne Australia, April 2007
They arrived in NZ in 1988
Do you think the NZ population will be the same as the Oz one today?
They arrived in NZ in 1988
Do you think the NZ population will be the same as the Oz one today?
Founder effect
Founder effect
A founder effect occurs when a new colony is started by a few members of the original population. This small population size means that the colony may have:
A founder effect occurs when a new colony is started by a few members of the original population. This small population size means that the colony may have:
- reduced genetic variation from the original population.
- a non-random sample of the genes in the original population.
Examples of a bottleneck
Northern elephant seals have reduced genetic variation probably because of a population bottleneck humans inflicted on them in the 1890s. Hunting reduced their population size to as few as 20 individuals at the end of the 19th century. Their population has since rebounded to over 30,000 — but their genes still carry the marks of this bottleneck: they have much less genetic variation than a population of southern elephant seals that was not so intensely hunted.
What about the way they breed, would that make things worse???
Cheetahs are very inbred. They are so inbred, that genetically they are almost identical.
The current theory is that they became inbred when a "natural" disaster dropped their total world population down to less than seven individual cheetahs - probably about 10,000 years ago. They went through a "Genetic Bottleneck", and their genetic diversity plummeted. They survived only through brother-to-sister or parent-to-child mating.
If a species does not have much genetic diversity, it will not be able to adapt well to changes in their environment - such a climate change, or new bacteria or viruses. But if they do have a lot of genetic difference from one individual to the next, at least a few of them will be able to survive the changing times.
According to enzyme studies, humans rate at about 70% identical. But laboratory rats and cheetahs rate at 97% identical. Laboratory rats have been inbred for at least 20 generations of brother-to-sister mating. So cheetahs are at least as inbred as laboratory rats.
What about the way they breed, would that make things worse???
Cheetahs are very inbred. They are so inbred, that genetically they are almost identical.
The current theory is that they became inbred when a "natural" disaster dropped their total world population down to less than seven individual cheetahs - probably about 10,000 years ago. They went through a "Genetic Bottleneck", and their genetic diversity plummeted. They survived only through brother-to-sister or parent-to-child mating.
If a species does not have much genetic diversity, it will not be able to adapt well to changes in their environment - such a climate change, or new bacteria or viruses. But if they do have a lot of genetic difference from one individual to the next, at least a few of them will be able to survive the changing times.
According to enzyme studies, humans rate at about 70% identical. But laboratory rats and cheetahs rate at 97% identical. Laboratory rats have been inbred for at least 20 generations of brother-to-sister mating. So cheetahs are at least as inbred as laboratory rats.
Four of the six below refer to population bottlenecks, one is for the founder effect, and one has undergone such a bottleneck it is most likely extinct now.......which ones are which? and what are their names? (you might want to know some examples)
images knicked from:
http://blog.forestandbird.org.nz/underbird-wonderbird/
http://www.scoop.co.nz/stories/AK1001/S00052.htm
http://horsetalk.co.nz/2012/09/19/przewalskis-horse-shows-averting-extinction-possible/#axzz2Sk8Hvo1l
http://commons.wikimedia.org/wiki/File:Kokako.jpg
http://www.massey.ac.nz/massey/about-massey/news/article.cfm?mnarticle_uuid=0A207F34-96BF-57FE-A3AF-FE34E6C40381
http://blog.forestandbird.org.nz/underbird-wonderbird/
http://www.scoop.co.nz/stories/AK1001/S00052.htm
http://horsetalk.co.nz/2012/09/19/przewalskis-horse-shows-averting-extinction-possible/#axzz2Sk8Hvo1l
http://commons.wikimedia.org/wiki/File:Kokako.jpg
http://www.massey.ac.nz/massey/about-massey/news/article.cfm?mnarticle_uuid=0A207F34-96BF-57FE-A3AF-FE34E6C40381
Lets watch this DVD
Note to me.....its here C:\working\all movies
pp 173 - 180 in your workbook... way you go
BUT, before we go remember.... evolution occurs when there is a genetic change in a population, whether that change is brought about by arranged marriages (breeding) or through natural selection, or via genetic drift, population bottle necks or the founder effect....
you just need to be able to explain it .... easy
BUT, before we go remember.... evolution occurs when there is a genetic change in a population, whether that change is brought about by arranged marriages (breeding) or through natural selection, or via genetic drift, population bottle necks or the founder effect....
you just need to be able to explain it .... easy