Topic 4 - Natural Selection and Genetic Modification Flashcards
What does natural selection mean?
Survival of the Fittest
Why do individuals in a population show genetic variation?
Because of differences in their alleles
How do new alleles arise?
Mutations
What are examples of selection pressures
Predation
Competition
Disease
What do selection pressures do?
Affect an organisms chance of surviving and reproducing
Why do selection pressures lea to survival of the fittest?
The organisms with the characteristics that make them better adapted will be more likely to survive and breed - passing on its gene
How many organisms mutate?
Every SINGLE organism
How does a bacterial population become resistant to a particular antibiotic?
Antibiotic administered, bacteria without resistance allele die faster, but the bacteria with the allele are more likely to survive and therefore reproduce passing on its resistant allele.
This continues increasing the abundance of the allele within the population
How does antibiotic resistance provide evidence for evolution?
It shows organisms slowly becoming better adapted to an environment
What is a fossil?
Any trace of an animal or plant that lived a long time ago
How do fossils provide evidence for evolution?
If chronologically ordered, gradual changes can be observed showing species change and develop over billions of years
What did Darwin notice?
There was variation in members of the same species
Organisms more suited to the environment were more likely to survive
What does evolution suggest?
We have all descended from a common ancestor
What are human beings and ancestors known as?
Hominids
When was Ardi around?
4.4 million years ago
Describe the features of Ardi?
Tree feet
Long arms but short legs
Small brain
Walked upright
When was lucy alive?
3.2 million years ago
Describe Lucy’s features?
Arched feed (less climbinb)
Arms and legs crossbreed of apes and humans
Small but larger brain than Ardi
Walked upright
How old were the fossils Leakey found?
1.6 million years old
What did Leakey find?
Homo erectus skeleton that had short arms and long legs
Brain size of ours
List the order of fossils? (Lucy, Ardi and Turkana Boy)
Ardi
Lucy
Tukana Boy
Outline the major changes observed between the fossils of Ardi and Lucy?
Lucy’s feet were more arched than Ardi’s
Lucy had n ape-like big toe unlike Ardi
Lucy had a larger brain than Ardi
Describe Wallace’s role in developing the theory of evolution by natural selection?
Wallace provided evidence for natural selection and worked with Darwin to develop the theory
How does the development of stone tools provide evidence for evolution?
As tools become more complex, our brains must of been getting larger
How do we tell how old a tool is?
Complexity (simpler likely to be older)
Stratigraphy (level of rock it was found, deeper more likely to be older)
Carbon dating
Why can’t wood tools be found?
Because they have rotted away
What is a species?
A group of organisms that will reproduce to produce a fertile offspring
What are the advantages of standing up for apes?
Back isnt exposed to sun as much, so less energy spent cooling
Suggest why tools are often found on their own?
The organism using it is likely to of rotted away
What is a pentadactyl limb?
A limb with five digits
How do pentadactyl limbs provide evidence for evolution?
Because many species have similar bone structures it could be suggested we all have evolved from a common ancestor
Why do pentadactyl limbs disprove we all had different ancestors?
Because it’d be highly unlikely that we would share a similar bone structure
State one method a scientist could use to find the age of a stone tool?
Stratigraphy
Carbon-14 dating
A scientist found a pointed stone tool among bones
What does the shape of the tool suggest about the fossils?
They belong to more recent species
How were organisms originally classified?
Based on observable characteristics
What are protists?
Eukaryotic single-celled organisms
What is the domain classification based off?
The genome of the species rather than their observable characteristics
What is selective breeding?
When humans artificially select organisms that are going to breed so that the genes for particular characteristics remain in the population
Give examples of selective breeding in action?
Animals with more meat or milk
Crops with disease resistance
Dogs with a gentle temperament
Plants that produce bigger fruit
How do you do selective breeding?
Select the organisms with the characteristics and breed them
Select the best of the offspring and then breed them together
Continue this process and the trait will get stronger and stronger
What is the main disadvantage to selective breeding?
Reduces the gene pool
What is the problem with reducing the gene pool?
Leads to inbreeding
What does inbreeding lead to?
Health problems as theres more chance of harmful genetic defects (build up of recessive alleles)
Lack of protection against disease as less chance of resistance alleles being present
Give three potential downsides selective breeding can cause?
Lack of protection against disease
Health problems (build up of recessive alleles
Ethical issues
What does tissue culture involve>
Growing cells on an artificial growth mediu
What are the advantages of growing whole plants using tissue culture?
Quick
Requires little space
All the time
What are all the cells produced via tissue culture?
Clones
Whats the advantage of tissues from tissue culture being clones?
Same beneficial features
or
If testing on, provides a control
How do you grow tissues?
Choose the plant you want to clone
Remove several small pieces of tissue (best if fast-growing roots/shoots)
Grow the tissue in growth medium in aseptic conditions
When shoots and roots produced, can be moved to potting compost
What is the growth medium made of?
Nutrients and growth hormones
Why is tissue culture done in aseptic conditions?
To prevent the growth of microbes that could harm the plant
What is the advantage of testing on animal tissue?
Means you can use medicine on tissues in isolation (experiment without complications from other processes)
How do you undergo animal cell tissue culture?
Extract a sample of the tissue
Separate the cells in the sample using enzymes
Place it in a culture vessel and bath it in a growth medium allowing them to grow and multiply
Leave to divide, split up and place in separate vessels to encourage further growth
How are the cells in animal tissue culture separated?
Using enzymes
Why are the cells in animal tissues placed in growth medium?
As medium contains nutrients it allows them to grow and multiply
Why are the cells in animal tissue culture placed into separate vessels?
To encourage further growth
What do restriction enzymes do?
Recognise specific sequences of DNA and cut it out, leaving sticky ends
What are sticky ends?
The ends of DNA that has been cut
What enzymes are used to join two pieces of DNA together?
Ligase
WHat is recombinant DNA?
Two DIFFERENT bits of DNA stuck together
What is a vector?
Something that’s used to transfer DNA into a cell
What are plasmids?
Small, circular molecules of DNA that can be transferred between bacteria
How do viruses act as vectors?
They insert DNA into the organisms they infect
How do you undergo genetic engineering?
Cut the DNA you want to insert with a restriction enzyme and cut the vector DNA using the SAME restriction enzyme
As both DNA’s left with sticky ends, join together with ligase enzymes forming recombinant DNA
The recombinant DNA n the vector is inserted into other cells causing these cells to have the gene you inserted to make the protein you want
What must you do when cutting the DNA of the cell and the vector?
Use the SAME restriction enzyme
How does the cut DNA and the vector DNA join together?
The ligase enzymes let them join at their sticky ends
How is genetic engineering useful?
Can modify crops to be resistant to herbicides
Can modify bacteria to produce useful proteins and substances for humans and animals
What are the problems with genetic engineering?
Hard to predict the effect of modifying genomes
Crops may affect the health of animals up the food chain
Resistant genes may make it out to other organisms (creating super weeds)
How do organisms evolve by the process of natural selection?`
Individuals have varying characteristics
A change in the environment (lack of resoruce, increased competition or climate)
The variations allow certain individuals better at coping allowing them to survive and breed passing on their variations so new offspring have same characteristics
If environment stays changed, a new species will evolve with all the individuals having the better adaptation
Describe the rough steps of natural selection?
Genetic Variation Environment changes Survival of Fittest Inheritance Evolution...
Name the areas of modern biology that have been influenced by Darwin and Wallace’s theory of evolution?
Classification
Antibiotic resitance
Conservation (genetic diversity)
Which fossil is older - ‘Ardi’ or ‘Lucy’?
Ardi
What are hominids?
Human beings and our ancestors
How can selective breeding be used to improve yields in the meat industry?
Larger sized cattle can be bred over generations leading to larger yields
What is a gene pool?
The number of DIFFERENT alleles in a population
Why does selective breeding reduce gene pools?
As ‘best animals’ bred - all of the population will be closely related, reducing the variation of genes
What are restriction enzymes used for in genetic engineering?
Cutting the DNA and allowing it to be mixed with another to form recombinant DNA
What is a vector?
An organism that is used to transfer DNA into a cell
