Natural Selection And Genetic Modification Flashcards
Who proposed that humans had evolved from monkeys or apes?
James Burnett, Lord mondoddo but most people thought he was mad
What is evolution?
It’s a gradual change in characteristics of a species over time. scientists use fossils to find out about human evolution. They work out how old fossils are and out then in age order, the fossils do not show smoothie changes over time because some are undiscovered
In 1992 what did scientists discover?
4.4 million year old fossilised bones from a female of an extinct human-like species. More fossils of this species were found and named Ardipthecus ramidus. Most complete set of these fossils is nicknamed Ardi
Describe Ardi
Ardi was about 1.2m tall and 50kg. Her leg bones show that she may have been able to walk upright. She had very log arms, though, and very long big toes that stuck out to the sides of her feet and would have allowed her to climb trees
When was Austraopithecus afarensis discovered?
In 1994. She lived 3.2 million years ago and was about 1.07m tall. She could probably walk upright, but although her toe bones were arranged in the same way as of modern humans, they were much more curved
What is the order of species evolved into each other?
Ardipthecus ramidus (Ardi) Australopithecus afarensis (Lucy) Homo hablis Homo erectus Homo sapiens (humans)
When was homo habilis discovered?
1960s, the fossils are 2.4-1.4 million years old, the animals were quite short with long arms but walked upright
When was homo erectus discovered?
In Asia in the late 19th century, and so many scientist thought that modern humans evolved in Asia. An almost complete 1.6 million year old skeleton was found by Richard Leakey in Kenya providing evidence that hipumans evolved in Africa, this species was tall (1.79m) and strongly bout
Go to page 77 and look At the
Diagram
Describe stone tools
Earliest evidence of human like animals using stone tools date back to about 3.3 million years ago. Scientists can work out the ages of different layers of rock. They then assume that a stone tool is about the same age as that layer of rock
The oldest stone tools are very simple, but would have helped with skinning an animal or cutting up meat. Tools found in more recipe get rocks are more sophisticated
Who discovered that organisms slowly evolve into others?
Charles Darwin and Alfred Russell Wallace
What is genetic variation?
When the characteristics of individuals vary to a difference in genes
What is environment change?
Conditions in an area change, eg the lack of recourse (such as food) causes more competition between organisms
What is natural selection?
By chance, the variations of some individuals make them survive better at coping with the change than others, and more likely to survive (also called survival of the fittest)
What is inheritance?
The survivors breed and pass on their variations to their offspring. So the next generation contains more individuals with the better adapted versions
What is evolution?
If the environmental conditions remain unchanged, natural selection occurs over and over again, and species evolve with the individuals having the better adapted versions
Until the 17th century, most Europeans did not think humans were animals, when did ideas start to change?
When Carl Linnaeus (1707-1778) published his system classification and suggested that humans were related to apes and monkeys. His biominal system, using two Latin words for naming species is still used today
How did elephants and woolly mammoths evolve from the same animal?
They share a common ancestor, scientists think that an area in which this ancestor lived started getting colder. Due to genetic variation, some animals by chance had harrier skin. They were more likely to survive the cold than less hairy animals, especially when food was scarce. More of these individuals survived and bred. Over time the animals became hairier and hairier, forming a new species
How were most rats resistant to warfarin?
Due to genetic variation they had always been some rates that were resistant. As the poison killed the non-resistant rats, the only ones left to breed were resistant.
How can some bacteria in people not be killed?
In a population of bacteria, some bacteria are more resistant than others and take longer to be killed. People who take an antibiotic to treat an infection often stop taking it early because they feel better. This leaves resistant bacteria still alive. They reproduce and spread, causing infections that cannot be treated with the antibiotic because all the bacteria are now resistant
When was resistant bacteria not present?
When antibiotics were first used
Go to page 79
And look at he diagram
In 1835 what did Charles Darwin do to make him wonder whether species could change form?
He visited the Galápagos Islands where he noticed differences in mocking birds on different islands
What gave Darwin the idea that organisms normally produce more offspring that could survive?
he read a essay by Thomas Malthus (1766-1834) which argued that, if people had too many children, there would not be enough food. Resulting struggle for survival, some children would die. Only those individuals best suited to the surroundings would survive and reproduce to pass on their characteristics. But he knew this was a controversial idea so he spent 20 years piecing together evidence
Why was Darwin more famous than wallace?
Because he wrote a book called the origin of species which was a bestseller and so the theory (about on,y those individual who was best suited to the environment would survive) was slowly being accepted
What a pentadactyl limb?
Limbs with 5 fingers
See page 81 and look at the diagram
All these animals have the same bones just in different shapes and sizes
What did Carl Linnaeus do in 1735 and describe it
He published his classification system, dividing organisms into groups based on what they looked like. His largest groups (kingdoms) where plants and animals, which divided into ever smaller and smaller groups. The characteristics of the organisms in a group got more and more similar as the groups go smaller and smaller. The last group contained one type of organism. Linnaeus used the last two groups (genus and species) to give each organism a binomial name
Why does using characteristics for classification cause problems and how did scientists over come this?
It caused problems for organisms that have evolved similar characteristics but which are not closely related. But once scientists accepted the idea of evolution, they started to work out how different organisms had evolved and to alter the classification system so that the smaller groups contained organisms that had evolved from recent ancestors
How many kingdoms did Linnaeus have and how many are they today?
Then - 2
Today - 5
What are the main characteristics of animals?
Multicellular (with cells arranged as tissues and organs)
Cells have a nuclei
No cell walls
What are the main characteristics of plants?
Multicellular (with tissues arranged as tissues and organs)
Have chloroplasts for photosynthesis
Cells have nuclei
Cellulose cell walls
What are the main characteristics of fungi?
Multicellular (apart from yeasts)
Live in or on the dead matter on which they feed
Cells have nuclei
Cell walls contain chitin (not cellulose)
What are the main characteristics of protists?
Mostly unicellular (a few are multicellular)
Cells gave nuclei
Some have cell walls (made of different substances but not chitin)
What are the main characteristics of prokaryotes (bacteria)?
Unicellular
Cells do not have a nuclei
Flexible cell walls
What are the three-domain system of classification?
Bacteria
Archaea
Eukarya
What does the domain eukarya include?
Animals Fungi Plants Protist with cilia Protists with flagella
What organisms would fall into the arches section?
Cells with no nucleus, genes contain unused sections of DNA
What organism would fall intone Bactria section?
Cells with no nucleus, no unused sections in genes
What organisms would fall into the eukarya section?
Cells with a nucleus, unused sections in genes
The more DNA two organisms have in common the more ……….
Recently the have evolved from a common ancestor and the more closely related they are
What is artificial selection?
When humans choose certain organisms because they have useful characteristics
Why is selective breeding done today!
To produce new breeds of animal species and new varieties of plant species
Why are plants and animals often selectively bred?
Disease resistance (how well they cope with diseases)
Yields (how much useful product they make)
Coping with certain environmental conditions
Fast growth
Flavour
What is genetic engineering?
Genetic engineering involves changing the DNA of one organism (it’s genome), often by inserting genes from another. This creates genetically modified organisms (GMOs). The process is much faster than artificial selecting but much more expensive
How is golden rice a GMO?
Two genes are inserted into its genome, one from a daffodil, one from a bacterium. They allow rice to produce s carotene in its grain. Humans need beta-carotene to make vitamin A, a lack which can cause blindness
What useful substances can GM bacterium make?
Antibiotics and other medicines
How can a stem cell not reject a new organ?
It it’s covered in stem cells from the patients bone marrow
What is tissue culture?
The growing of tissues if cells in a liquid containing nutrients or on a solid gold medium (zucchini as nutrient afar). This is a useful way to grow many identical cells. These may form callus (a club of undifferentiated cells). Sometimes the cells are then treated to make them differentiate (become specialised)
What is tissue culture used for?
To produce new plants of very rare species which are at risk of extinction. It is also used to produce new individuals of Kant species that may be difficult to grow from seed, such as orchids. The technique also used to produce clones (identical copies) of GM plants
Go to page 87
And look at the diagram
How does tissue culture have many uses in medicine?
Culturing a thin layer of cells on a solid medium makes it easier to study how cells communicate with each other. Cell cultures are also needed to study viruses, which cannot replicate outside if cells. Cultures of cancer cells have been developed to study how cancers develop and spread. Using cell cultures, scientists have investigated how infected cells respond to new medicines without risking harm to animals if humans
How can cultures of human cells be developed into tissues?
Is correctly supported
What are the selective breeding risks?
Genes exist in different forms, called alleles which cause variations in characteristics. In selective breeding, only certain alleles are selected. Others become rare or disappear. So alleles that might be useful in the future are no longer available
Farming huge numbers of the same breed or variety is a problem, all the organisms are very similar and so if a change in conditions affects one organism all the others are affected too
Animal welfare to another concern, some selectively bred chickens produce so much Brest mean they can hardly stand up
Genetic engineering issues
Seeds for GM plants are very expensive
Some people think that GM crops will reproduce with wild plant varieties and pass on their resistance genes, and these genes may also have unknown consequences in wild plants
Some people think that eating GM organism are bad for health (there is no evidence for this)
What useful substance can GM bacteria produce
Insulin, insulin used to be extracted from dead pigs and cows, but insulin from GM bacteria is cheaper and more suitable for vegans. However it is slightly different to insulin from mammals and so not all diabetic people can use it
Go to page 89 and look at genetic engineering of
Bacteria
What is a restriction enzyme?
The enzyme that take a plasmid out of a bacterium and splits it open
What is the enzyme ligase?
DNA is cut using restriction enzyme to leave exposed bases, these match up with the complimentary bases of the DNA they are to be joined using ligase enzyme. The sticky ends refer to the complimentary base pairs A=T and G=C
What are plasmids?
A small loop of DNA found in the cytoplasm of bacteria
What is the first step of genetic engineering of bacteria?
Restriction enzymes make staggered cuts in DNA molecules, producing sections with a few unpaired bases at each end - sticky ends. A section of DNA containing the gene for making insulin is cut from a human chromosome in this way
What is the second step in genetic engineering of bacteria?
Restriction enzymes are also used to cut plasmids open. By using the same restriction enzyme as was used on the human chromosome DNA, the cut plasmids have the same sticky ends
What is the third step in genetic engineering of bacteria?
Sections of DNA containing the insulin gene are mixed with the cut plasmids. The complimentary bases on the sticky ends pair up. An enzyme called ligase is used to join the ends together
What is the fourth and last step in genetic engineering of bacteria?
The plasmids are then inserted back into bacteria, which are then grown in huge tanks. The insulin they now make can easily be extracted
What is Bacillus thuringiensis?
A soil bacteria that naturally make Bt toxin (insecticidal crystal protein which kills caterpillars)
How can a plant produce its own insecticide?
Remove the Bt toxin gene and insert it into a plant, then the pest will die when feeding on any plant part
What are the advantages of cops that are modified to include the T gene?
Bt toxin is harmless to non-target caterpillars
Bt genes in plants increase overall crop yield, so more profit for farmers
Crops that have a Bt toxin gens will not need to be sprayed with expensive insecticides that might also harm non-target species like bees (pollinators) or ladybirds (predator of aphids)
The GM crops only kills caterpillars of insects that eat it
Describe the steps to a GM crop that has a Bt toxin?
The plasmid is removed from the bacterium, and the T-DNA is cut by a, restriction enzyme
Foreign (Bt toxin) DNA is cut by the same enzyme
The foreign DNA is inserted into the T-DNA of the plasmid
The plasmid is then reinserted into a bacterium
The bacterium is used to insert the T-DNA carrying the foreign gene into the chromosome of a plant cell
The plant cells are grown in tissue culture
A plant is generated from a cell clone. All of its cells carry the foreign gene and may express it as a new trait
What are the disadvantages of crops that’s are modified to include Bt toxins?
Aphids, which are pests, are not killed by the Bt toxin as they eat sap rather than the leaves
We don’t know what the long-term effects of using GM crops are
As a result of constant exposure to Bt toxin, caterpillars may build up a tolerance and develop some resistance to the effect
The caterpillars that are killed when they eat the leaves of a Bt toxin plant, are food for another animal eg birds
GM variety seed is usually more expensive than non-GM varieties
Selling GM crops for people to eat is not legal in some parts of the world, but can only be used as animal feed
What is biological control?
Using organisms to control pests
What is recombinant DNA?
it’s DNA made by joining two sections of DNA together
