B14 Flashcards
What is evolution?
Science shows that species which exist today have developed over millions of years
What organisms did evolution start with?
Unicelluar organisms which lived in water and over time evolved to become multicellular
Where does the evidence from evolution come from?
Fossils
What is selective breeding?
Selective breeding is when humans artificially select the plants or animals that are going to breed so that the genes for particular characteristics remain in the population.
Why are organisms selectively bred? Give examples
Organisms are selectively bred to develop features that are usefullor attractive.
for example:
-Animals that produce more meat or milk.
-Crops with disease resistance.
-Dogs with a good, gentle temperament.
-Decorative plants with bgi or unusual flowers.
How can you do selective breeding?
1) From your existing stock, select the ones which have the characteristics you’re after.
2) Breed them with each other.
3) Select the best of the offspring, and breed them together.
4) Continue this process over several generations, and the desirable trait gets stronger and stronger.Eventually, all the offspring wil have the characteristic.
What is the main drawback (con) of selctive breeding?
The main problem with selective breeding is that it reduces the gene pool - the number of different aleles (forms of a gene) in a population. This is because the farmer keeps breeding from the “best” animals or plants - which are are closely related. This is known as inbreeding.
Why is inbreeding bad?
Inbreeding can cause health problems because there’s more chance of the organisms inheriting harmful genetic defects when the gene pool is limited. Some dogbreeds are particularly susceptible ot certain defects because of inbreeding- e.g. pugs often have breathing problems.
There can also be serious problems if anew disease appears, because there’s not much variation in the population. All the stock are closely related to each other, so if one of them is going to be killed by a new disease, the others are also likely to sucoumb to it.
What is genetic engineering?
Genetic engineering is a process which involves modifying the genome of an organism by introducing a gene from another organism to give a desired characteristic.
What are GM crops?
Crops that have had their genes modified in this way are called genetically modified (GM) crops.
What are the concerns about GM crops?
Concerns about GM crops include:
-The effect on populations of wild flowers and insects
-The effect of eating GM crops on human health have not been fully explored
Pros and cons of GMO’s
Pros:
-the characteristics chosen for GM crops can increase the yield, making more food.
-People living in developing nations often lack nufrients in their diets. GM crops could be engineered to contain the nutrient that’s missing. For example, ‘golden rice’ is a GM rice crop that contains beta-carotene - lack of this substance causes blindness.
-GM crops are already being grown in some places, often without any problems
Cons:
-Some people say that growing GM crops will affect the number of wild flowers (and so the population of insects) that live in and around the crops - reducing farmland biodiversity.
-Not everyone is convinced that GM crops are safe and some people are concerned that we might not fully understand the effects of eating them on human health. E.g. people are worried they may develop allergies to the food - although there’s probably no more risk for this than for eating usual foods.
-A big concern is that transplanted genes may get out into the natural environment. For example, the herbicide resistance gene may be picked up by weeds, creating a new ‘superweed’ variety.
What is tissue culture?
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.
What are cuttings?
Cuttings: an older, but simple, method used by gardeners to produce many identical new plants from a parent plant.
What are embryo transplants?
Embryo transplants splitting apart cells from a developing animal embryo before they become specialised, then transplanting the identical embryos into host mothers.
