Variation and evolution (IVE pt2) Flashcards
What is variation?
Differences in the characteristics of individuals in a population
What are differences in variation due to?
- genes they inherited
- conditions in which they have developed
- a combination of genes and the environment
What creates new alleles?
mutations
What changes phenotype?
- mention mutations and environment
Mutations occur continuously. Very rarely a mutation will lead to a new phenotype.
If the new phenotype is suited to an environmental change it can lead to a relatively rapid change in the species.
What is evolution?
a change in the inherited characteristics of a population over time through a process of natural selection which may result in the formation of a new species.
evolution occurs through the natural selection of variants that give rise to phenotypes best suited to their environment.
What does natural selection state?
all species of living things have evolved from simple life forms that first developed more than three billion years ago.
When are two new species formed?
If two populations of one species become so different in phenotype that they can no longer interbreed to produce fertile offspring they have formed two new species.
How is selective breeding carried out?
1) choose parents with the desired characteristics from a mixed population
2) breed them together
3) From the offspring, breed the ones with desired characteristics
4) continue over many generations until all the offspring show the desired characteristic
What is selective breeding?
The process by which humans breed plants and animals for particular genetic characteristics.
What have humans been doing selective breeding for thousands of years to produce?
- food crops from wild plants
- domesticated animals from wild animals
What are the types of characteristics that could be selected include?
- disease resistance in food crops
- animals which produce more meat or milk
- domestic dogs with a gentle nature
- large or unusual flowers
What is one disadvantage of selective breeding?
can lead to ‘inbreeding’ where some breeds are particularly prone to disease or inherited defects.
What is genetic engineering?
a process which involves modifying the genome of an organism by introducing a gene from another organism to give a desired characteristic.
How is genetic engineering carried out?
1) enzymes are used to isolate the required gene
2) This gene is inserted into a vector, usually a bacteria plasmid or a virus
3) the vector is used to insert the gene into the required cells
4) genes are transferred to the cells of animals, plants or microorganisms at an early stage in their development so that they develop with the desired characteristic
Why are crops and bacteria genetically engineered?
Plant crops have been genetically engineered to be resistant to diseases or to produce bigger better fruits. = increases yield
Bacterial cells have been genetically engineered to produce useful substances such as human insulin to treat diabetes.
What is 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?
the method used by gardeners to produce many identical new plants from a parent plant.
What can identical plants be produced from?
- tissue culture
- cuttings
What can animal clones be produced by?
Embryo transplants: splitting apart cells from a developing animal embryo before they become specialised, then transplanting the identical embryos into host mothers
How is adult cloning carried out?
1) The nucleus is removed from an unfertilised egg cell.
2) The nucleus from an adult body cell, such as a skin cell, is inserted into the egg cell.
3) An electric shock stimulates the egg cell to divide to form an embryo.
4) These embryo cells contain the same genetic information as the adult skin cell.
5) When the embryo has developed into a ball of cells, it is inserted into the womb of an adult female to continue its development.
What are the pros of cloning?
- lots of ideal offspring
- study of animal cloning would lead to a greater understanding of the development of the embryo and of ageing and age-related disorder
- could be used to help preserve endangered species
What are the cons of cloning?
- reduced gene poll = easily wiped out by disease
- cloned animals may not be as healthy as normal ones
- unsuccessful attempts of cloning humans
What is genetic engineering?
when genes are cut out and transferred to cells of other organisms (e.g bacteria)
