Natural Selection and Genetic Modification Flashcards
What is evolution?
A gradual change in the characteristics of a species over time
How old are homo habilis fossils?
2.4-1.4 million years old
Describe homo habilis
Short with long arms but walked upright
Describe homo erectus
Tall (1.79m) and strongly built
Who was Ardi?
Most complete set of 4.4 million year old fossilised bones from a female of an extinct human-like species
Describe Ardi
About 1.2m tall and 50kg
Who was Lucy?
- Lived 3.2 million years ago and was 1.07m tall
- Could probably walk upright, though her toe bones were arranged in the same way as those of modern humans but much more curved
What is the order of the homo species?
Homo habilis, homo erectus and homo sapiens
What is genetic variation?
The characteristics of individuals vary due to differences in genes
What is natural selection?
Individuals that have characteristics that allow them to survive better than others in a certain area
What is a common ancestor?
Animals that evolved from the same animal
Why is it bad for people to stop taking an antibiotic to treat an infection early because they feel better?
Because it leaves resistant bacteria still alive which reproduce and spread, causing infections that cannot be treated with the antibiotic because all the bacteria are now resistant
What is classification?
Dividing organisms into groups based on what they looked like
What are the main groups of classification?
Kingdoms - animals, plants, fungi, protists and prokaryotes
What are the main characteristics of animals?
- Multicellular with cells arranged as tissues and organs
- Cells have nuclei
- No cell walls
What are the main characteristics of plants?
- Multicellular with cells 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
- Cells walls contain chitin (not cellulose)
What are the main characteristics of protists?
- Mostly unicellular
- Cells have nuclei
- Some have cell walls made of different substances but not chitin
What are the main characteristics of prokaryotes?
- Multicellular
- Cells do not have nuclei
- Flexible cell walls
What do all organisms besides prokaryotes have?
Unused sections of DNA in their genes - most of a gene is used to make a protein, but these ‘unused’ sections do not help with this
What are the 3 domains that all organisms are divided into?
- Archaea = cells with no nucleus, genes contain unused sections of DNA
- Bacteria = cells with no nucleus and no unused sections in genes
- Eukarya = cells with a nucleus, unused sections in genes
What is artificial selection?
When humans choose certain organisms because they have useful characteristics
What is selective breeding?
- When humans breed plants and animals for particular genetic characteristics
- Repeating this over and over again, humans end up with organisms with the desirable characteristics
- Still done today to produce new breeds of animal species and new varieties of plant species
Name some reasons why plants and animals are often selectively bred
- Disease resistance
- Yield
- Coping with certain environmental conditions
- Fast growth
- Flavour
What is genetic engineering?
Involves changing the DNA of one organism (genome), often inserting genes from another
What does GMO stand for?
Genetically modified organisms
What is wrong with genetic engineering?
Although it is much faster than artificial selection, it is much more expensive
What is tissue culture?
The growing of cells or tissues in a liquid containing nutrients or on solid medium (like nutrient agar)
How can it be easier for a person’s body to not reject a new organ?
By using stem cells from their bone marrow so the immune system would not attack the new organ
What may tissue culture form?
A callus (clump of undifferentiated cells) that can be treated to make them differentiate (become specialised)
Give examples as to what tissue culture is used to produce
- New plants of very rare species which are at risk of extinction
- New individuals of plant species that are difficult to grow from seed (like orchids)
- Produce clones of GM plants
Describe the process of tissue culture
- Plant is placed in bleach solution to sterilise it
- A small piece of plant is cut off and placed on sterile nutrient medium to grow
- The piece of plant is treated with hormones so it grows roots and shoots
- When plants large enough, planted into soil or compost
Why is tissue culture useful in medicine?
- Study viruses which cannot replicate outside of cells
- Study how cancers develop and spread
- Investigate how infected cells respond to new medicines without risk to animals/humans
Why are alleles a selective breeding risk?
In selective breeding, only certain alleles are selected so others become rare or disappear, so these alleles that might be useful in the future are no longer available
Why is farming in huge numbers a selective breeding risk?
All the organisms are very similar and so if condition changes affects one organism, all the others are affected
Why is animal welfare a selective breeding risk?
The animals are often exposed to adaptations that cause them pain and suffering (e.g. chickens who produce so much breast meat they can hardly stand up)
What are herbicides?
Weed killers - kill the weeds but not the crop
What useful products do GM bacteria produce?
Insulin (treats type 1 diabetes)
What does a bacterium have as DNA?
One large loop of DNA and plasmids
What needs to be done to genetically engineer bacteria?
Additional genes added to a plasmid (example of recombinant DNA)
What are restriction enzymes used for?
To cut a useful gene out of an organism’s DNA, leaving strands of DNA with sticky ends
What happens when 2 sticky ends match?
They can be joined together using ligase enzyme
What is a vector?
Any DNA molecule used to carry new DNA into another cell
What is yield?
The amount of useful crop
How can insect pests be controlled?
By spraying the crop with chemical insecticides
Name an advantage of GM Bt toxin
It only affects insects that chew the plant tissues, as the toxin is released when the cells are broken
Name a disadvantage of insecticide
The sprays may kill a wide range of insect species
Name a problem with growing crop plants that make their own insecticide
The insects can develop resistance to the toxin, meaning it no longer harms them
What is biological control?
Using organisms to control pests
What are mineral salts?
Naturally occurring compounds found in rocks and salts
What mineral ions do fertilisers contain?
Nitrogen, potassium and phosphorus
What happens if not all the fertiliser is absorbed by a crop?
Some may get into nearby streams, livers and lakes, which could cause pollution and lead to the death of organisms in the water; this could also cause health problems for humans and animals if they drink the water
