2. Evolution Pt6 Flashcards
What is selective breeding?
(Artificial selection)
- the process where humans breed plants & animals for particular genetic characteristics
- humans have done this for thousands of years
How is selective breeding done?
- Choosing the parents with the desired characteristics from a mixed population
- They’re bred together
- From the offsprings those with the desired characteristics are bred together
- This is continued for many generations until the desired characteristic is shown
What sort of characteristics are desired in selective breeding?
(Usefulness or appearance)
- disease resistance in fair crops
- animals which produce more meat or milk
- domestic dogs with a gentle nature
- large or unusual flowers
What’s the main problem with selective breeding?
It can lead to ‘inbreeding’ where some breeds are particularly prone to disease or inherited defects
What’s genetic engineering?
A process which involves modifying the genomes of an organism by introducing a gene from another organism to give a desired characteristic
Why might a plant be genetically engineered?
To be resistant to crops or to produce bigger better fruits
Why might a bacteria be genetically engineered?
To produce useful substances such as human insulin to treat diabetes
What are disadvantages of genetic engineering?
- GM crops could effect wild flowers reducing biodiversity
- some people believes its safe
- and that the effects of eating GM crops on humans health hasn’t been fully explored
- transplanted genes might get into the natural environment
What are advantages of genetic engineering?
- it can increase yield, make more food
- people in developing countries lack nutrients, crops could be engineered to contain more nutrients
- GM crops are being grown in some places without problems
- there’s a possibility it can overcome inherited disorders
What are GM crops?
Genetically modified crops
What happens in genetic engineering?
Genes from chromosomes of humans and other organisms can be ‘cut out’ and transferred to cells of other organisms
What are the 3 steps of genetic engineering?
- enzymes are used to isolate the required gene, the gene is inserted into a vector (usually a bacterial plasmid or a virus)
- The vector is used to insert the gene into the required cells
- Genes are transferred to the cells of the animal, plants or microorganism at an early stage in their development so that it’ll develop with the desired characteristics
Why was the theory of evolution by natural selection slow to be accepted?
- it challenged the idea that god made all the animals & plants that live on earth
- there wasn’t enough evidence at the time it was published to convince many scientists
- the mechanism of inheritance & variation was unknown until 50 years before the theory was published
What’s tissue culture?
- Using small groups of cells from part of a plant to grow identical new plants
- This is important for preserving rare plant species or commercially in nurseries
How is culture carried out?
- a few plants are put in a growth medium with hormones and they grow into a new plants (clones of the parent plant)
- can be made very quickly and with little space and be grown all year
What’s cutting?
-simpler than tissue culture and older method, used by gardeners to produce many identical new plants from a parent plant
What’s an embryo transplant?
Splitting apart cells from a developing animal embryo before they become specialised, then transplanting the identical embryos introduced host mothers
How is adult cell cloning done?
- the nucleus is removed from an unfertilised egg cell
- the nucleus from an adult body cell, such as skin cell, is inserted into the egg cell
- an electric shock stimulates the egg cell to divide to form an embryo
- these embryo cells contain the same genetic information as the adult skin cell
- When the embryo has developed into a ball of cells, it’s inserted into the womb of an adult female to continue its development
Explain the theory of evolution by natural selection?
- individual organisms within a particular species show a wide range of variation for a characteristic
- individuals with characteristics most suited to the environment are more likely to survive to breed successfully
- the characteristics that have enabled these individuals to survive are then passed on to the next generation
How did Charles Darwin come up with his theory?
- the result of observations on a round the work expedition
- years of experimentation
- discussions
- linked to the developing knowledge of geology and fossils
What Wallace know for?
- he worked worldwide gathering evidence of evolutionary theory
- he most famous for his work in warning colouration in animals and his theory of speciation
Explain the process of speciation?
1) isolation by a physical barrier
2) conditions on either side of the barrier are different
3) due to different environment different characteristics become common
4) different characteristic make them better suited for survival
5) they’ll have changed so much that they will no longer be able to breed to produce a fertile offspring. So they 2 species
What did Gregory Mandel do?
- in the mid 19th century he carried out breeding experiments on plants
- one of his observations was that the inheritance of each characteristic is determined by ‘units’ that are passed on to descendants unchanged
What happened in the late 19th century?
Behaviour of chromosomes during cell division was observed
What happened in the early 20th century?
It was observed that chromosomes and Mendel’s ‘units’ behaved in similar ways. This led to the idea that the ‘units’ now called genes were located on chromosomes
What happened in the mid 20th century?
The structure of DNA was determined and the mechanism of gene function was worked out
Why was Mendel never famous while he was alive?
- At the time, no one had seen a chromosome and people did not understand his theories.
- He did not publish his work so died before his work was recognised
- the importance of his discovery wasn’t recognised until after his death
What conclusion did Mendel reach?
- characteristics of plants are determined by ‘hereditary units’
- hereditary units are passed on to offspring unchanged from both parents on unit from each parent
- hereditary units can be dominant or recessive
What are fossils?
The ‘remains’ of organisms from millions of years ago, which are found in rocks
