Natural and Artificial Selection Flashcards
Darwin’s theory of evolution by natural selection
-All populations contain genetic variation
-Genetic variants with advantageous characteristics have increased survival chances
-Surviving individuals are more likely to reproduce and pass on advantageous traits
-Over generations these traits become common in the population
MVASRGGE
Steps of evolution
Mutation
Variation
Adapted
Survived
Reproduced
Genes
Generations
Evolution
Bacterial resistance due to antibiotics
-Random mutation leads to new allele coding for antibiotic resistance
-When bacterial population is exposed to an antibiotic, unresistant bacteria die, while resistant bacteria survive
-Surviving bacteria are more likely to reproduce, passing on the resistant allele to their offspring
-Over generations the frequency of the allele increases, leading to a resistant strain of bacteria
Difficulty of controlling resistant bacterial strains
-Bacterial population can only be treated with a different antibiotic (sometimes several antibiotics)
-New antibiotics can take time to be developed
Evolution definition
When there is a cumulative change in heritable characteristics OVER TIME in a population (occurring via natural selection)
What can be affected by environmental factors
Characteristics determined by polygenic inheritance
Natural Selection definition
The process where organisms that are better adapted to an environment will survive and reproduce
Causes of variation
-Genetics
-Mutations
-Meiosis
-Random fertilisation
-Environment
Artificial selection definition:
When HUMANS artificially select organisms they want to breed together so that the genes with desirable characteristics can remain in a population
Selective breeding steps
Choose male and female with desired characteristics
Breed them together
Choose offspring which display desired characteristics
Breed these offspring together
Repeat this for several generations until all offspring have desired characteristics
Benefits of selective breeding
Desired characteristics can be obtained
Can use semen from one male to mate with many females
Safer for female animals
Cheaper/quicker to transport semen
Semen can be stored even after death of male
Problems with selective breeding
Reduction in gene pool (less alleles in a population) can lead to ‘inbreeding’
Prone to new diseases/genetic defects
Reduced genetic variation -> less likelihood to adapt
Natural Selection vs Selective Breeding
Occurs naturally vs occurs when humans intervene
Features adapted to environment and survival vs features useful to humans and not survival
Long time to occur vs less time to occur
Desired characteristics in plants
Disease resistance
Increased crop yield
Tolerance of weather conditions
Better tasting fruits
Large/unusual flowers
Desired characteristics in animals
Quantity of milk/meat
Large eggs
Domesticated animals
Quality wool
Horses with fine features and pace
Clone definition
Groups of cells/organisms that are genetically identical
Micropropagation
Explant cells cut from parent plant using sterile tools
The tissue is placed in sterile nutrient agar, containing a high concentration of hormones to stimulate cell growth
A mass of cells (callus) grows
Some callus cells can be transferred to a different medium with a diff. combination of minerals and auxins to develop roots/shoots
They grow into plantlets and can be grown in compost
Advantages of micropropagation
Clones are genetically identical
Can produce plants with desirable characteristics:
Cheaply
With a greater yield
Quickly (faster growth)
At any time of the year
Identically (maintain characteristics)
Disease free/resistant
Disadvantages of micropropagation
Trained personnel and sterile lab required
All plants produces are genetically identical i.e. all are vulnerable to the same diseases and pests
Embryo cloning e.g. cattle
The best (prize) cow is given hormones to make it produce egg cells
Sperm from a prize bull is collected and the cow is artificially inseminated
The fertilised egg divides into an embryo, which is then removed from the prize cow
The embryo is split up and each piece starts dividing into genetically identical embryos
The embryos are implanted into surrogate cows
Several clone calves are born
Adult cell cloning (nuclear transfer)
Exact copy of parent
Egg cells removed from ovaries with nucleus removed
Somatic (body) cells from animal B are grown in starvation conditions (return to embryonic state)
Nucleus from the somatic cell is injected into egg cell
Cell is stimulated (electric shock) to divide by mitosis
Embryo is implanted into surrogate mother
Cloned animal is identical to somatic cell donor
Benefits of animal cloning
Can be used to preserve endangered species or resurrect extinct animals
Could be used to grow new organs genetically identical to parent cells i.e. transplant patients could get identical organs to save their lives
Callus definition
A mass of undifferentiated/unspecialized cells
Callus definition
A mass of undifferentiated/unspecialized cells
Explant definition
Fragments of plant tissue that are transferred to a different medium
In vitro definition
Something that is grown outside a living organism
