B14 - Variation and Evolution Flashcards
What is variation
Differences in the characteristics of individuals in a population
What two things contribute to variation?
- Genetics (Nature)
- Environment (Nurture)
Variation can be caused by a combination of these factors
Examples of variation caused by genetics
- Eye colour
- Gender
- Blood type
Examples of variation caused by environment
- Scarring
- Language
- Muscle strength
How does a mutation cause variation
- Mutations are uncontrollable, constantly occuring changes in DNA
- This may lead to a new phenotype
- This may give an organism desired characteristics making it better suited to an environment
What is evolution
Changes in the inherited characteristics in a population over time through the process of natural selection
Outline the stages in the theory of evolution by natural selection (5 steps)
- Mutations which cause variation
- Survival - better adapted to environment
- Reproduction
- Pass on beneficial alleles
- More offspring with allelle (alleic frequency increases)
What is selective breeding
Where humans breed animals or plants in order to get offspring with certain desired characteristics
Describe the main steps in the process of selective breeding
- Find parents with desired characteristics in population and breed them
- Breed the offspring with the best characteristics
- Continue for many generations until all have desried characteristics
Examples of characteristics that could be selected in selective breeding
- Animals that produce lots of milk or meat
- Domestic dogs
- Disease resistant plants
- Types of flowers
Problems with selective breeding
- Lack of variation - leaves organisms vunerable to changes in environment
- Can unknowingly spread genetic defect
What is genetic engineering
Modifying the genome of an organism by introducing a gene from another organism to give a desired characteristic
Describe the process of genetic engineering
- Enzymes isolate the required gene
- The gene is the put into a bacterial plasmid which acts as a vector
- The vector inserts the genes into the required cells
- The genes are insterted in early development allowing the organism to develop with desired characteristics
Uses of genetic engineering
- Bacterial cells to produce insulin
- Plants + GM Crops - bigger, increased yield, resistant to diseases
Benefits of genetic engineering
- Increased crop yield
- Faster results compared to selective breeding
- Herbicide/insect/drought resistance
- Increased nutritional value
Problems/risks with genetic engineering
- Gene could get into other species or environment causing herbicide resistant weeds
- Some people see it as “playing God”
- Unknown effects on humans
2 methods of cloning plants
- Taking cuttings
- Tissue culture
Describe the method of cloning plants by using cuttings
- Old, simple method used by gardeners
- Branch from parent taken
- Placed in damp compost with nutrients and hormones
Describe the method of cloning plants by tissue culture
- USed to preserve rare plant species
- Explants are placed in agar that contains nutrients and hormones
- Platelets grow
- They are then placed in compost
Describe the process of animal cloning by embryo transplants
Using cows for example
- Cow given fertitlity drugs and artificially inseminated with sperm from a bull
- Zygotes develop into embryos and then taken from cow
- Embryos are split into smaller embryos
- All embryos are genetically identical and are placed in surrogate mothers
Describe the process of adult cell cloning
- Nucleus removed from egg cell
- Nucleus from adult cell e.g. skin cell placed in egg
- Egg is then shocked to start cell division
- Embryo has same genetic info as nucleus from skin cell
- Once embryo has developed, it is placed in a surrogate mother
Benefits of adult cell cloning
- Save animals from extinction
- Bring back animals that are already extinct
Drawbacks of adult cell cloning
- Could lead to human cloning which is illegal
- Reduces variation making a species vunerable to environment changes
- Designer babies
