Unit 4 - Genetic diversity and adaptation Flashcards
Definition of genetic diversity
The number of different alleles of genes in a population.
Genetic diversity is a factor of enabling natural selection to occur.
What are the principles of natural selection in the evolution of populations
- A random mutation can result in new alleles of a gene
- Many mutations are harmful but in certain environments the new allele of a gene might benefit its possessor, leading to increased reproductive success
- The advantageous allele is inherited by members of the next generation
- As a result over many generations the new allele increases in frequency in the population
Directional selection
If the environment changes, the phenotypes that are best suited to the new conditions are most likely to survive.
Directional selection therefore results in phenotypes at one extreme of the population being selected for and those at the other extreme being selected against
describe directional selection using the example of antibiotic resistance
- Some bacteria in a population have alleles that give them resistance to an antibiotic
- The population is exposed to the antibiotic, killing bacteria without the resistant allele
- The resistant bacteria survive and reproduce without competition, passing on the allele that gives antibiotic resistance to their offspring
- After some time, more organisms in the population will carry the antibiotic resistance allele
Stabilising selection
If the environment remains stable, it is the individuals with the phenotypes closest to the mean that are favored.
These individuals are more likely to pass their alleles on to the next generations.
The individuals with phenotypes at the extremes are less likley to pass on alleles - eliminating these phenotypes
Example of stabalising selection - Human birth weight
- Humans have a range of birth weights
- Very small babies are less likely to survive - find it hard to maintain body temp.
- Giving birth to large babies can be difficult so large babies are less likely to survive too.
- Conditions are most favorable for medium- sized babies- so weight of human babies tend to shift towards the middle range
Behavioral adaptation
ways an organism acts to increase its chance of survival and reproduction.
For example - swallows migrate to Africa from the Uk in Autumn to avoid a food shortage
Physiological adaptation
Process inside an organism’s body that increase the chance of survival.
For example - brown bears hibernate over winter. They lower their rate of metabolism, this conserves energy so they don’t need to look for food in months when its scare.
Kangaroo rats oxidise fat rather then carbohydrate to produce additional water.
Anatomical adaptation meaning
Structural feature of an organisms body that increases its chances of survival
For example
- Whales have a thick layer of blubber which helps keep them warm in the cold sea.
- Artic foxes have small ears and thick fur coat to conserve heat.
Investigation of Antibiotics using Agar Plates
- Use a sterile pipette to transfer the bacteria to an agar plate
- Spread the bacteria over the plate using sterile plastic spreader
- Use sterile forceps to place paper discs socked in different antibiotics spaced apart on the plate. (Add a negative control disc only soaked in sterile water)
- Lightly tap the lid and invert
- Incubate the plate at about 25 degrees for 48 hours - allows the bacteria to grow.
- Anywhere the bacteria can’t grow can be seen by a clear patch - inhibition zone.
- The size of the inhibition zone tells you how well the antibiotic worked
Aseptic Techniques to prevent contamination of microbial cultures
Aseptic technique prevents contamination of cultures by unwanted microorganisms.
- regularly disinfect work surfaces
- Put contaminated utensils in a beaker of disinfectant
- Work near a bunsen flame. Hot air rises so any microbes in the air should be drawn away
- Minimise the time spent with the lid off the agar plate
