warm up 2/27 what is allele frequency? what are the four ways evolution occurs?
Post on 22-Dec-2015
216 Views
Preview:
TRANSCRIPT
After the Lab Staple all Teammates’ papers together.
I will grade 1 of them…. You don’t know whose it is.
Quick Review… Change in allele frequency in a population is called
Change in allele frequency due to random/chance is called (remember the coywolves)
A change in the DNA sequence that offers an advantage and results in that change being passed on to other generations is evolution by
Mutation
Change in allele frequency in a population due to MIGRATION is:
Gene Flow
Change in allele frequency due to selection pressures in their environment is called:
Natural Selection
EVOLUTION
Genetic Drift
Disruptive Selection
Disruptive selection – FAVORS EXTREMES
It is a type of natural selection that selects against the
average individual in a population.
Disruptive selection is the rarest of the three types of
natural selection.
Disruptive Selection
Remember, it favors EXTREMES.
London Peppered Moth Industrial areas – black moths. Rural areas – light colored moths.Very few medium colored moths.
Stabilizing Selection Stabilizing selection – FAVORS AVERAGE
It is a type of natural selection that favors the
average individuals in a population.
This process selects against the extreme
phenotypes
Diversity in a population is decreased due to
stabilizing selection
Stabilizing Selection - Example
Stabilizing selection works mostly on traits that are polygenic.
Since stabilizing selection favors the middle of the road, a blend of the genes is often what is seen.
Many human characteristics are a result of stabilizing selection. Human birth weight is not
only a polygenic trait, but it is also controlled by environmental factors.
Infants with average birth weight are more likely to survive than a baby that is too small or too large.
Directional Selection
Directional Selection – FAVORS *ONE* EXTREME
Think – this drives selection in one DIRECTION over the other
This phenomena is usually seen in environments that have changed over time. Changes in weather, climate, or food availability lead to directional selection.
Directional Selection - Example
The Texas Longhorn is an example of the effects of directional selection. The long horns were advantageous for defending young calves from predators - so horn length increased in feral herds in the American Southwest between the early 1500s-1860's. The trend is now maintained through artificial selection by ranchers. Do you think the horn length would change if the now predator-free cattle were not being selected for artificially?
Moon Bounce
Choose one person to be the astronaut. The other teammates hold each elbow and waist of the astronaut. Count 3-2-1, the astronaut jumps
and the teammates boost the astronaut at the top of their jump.
Types of Natural Selection
http://education-portal.com/academy/lesson/types-of-natural-selection.html
Scenario 1
Tongue length in anteaters in polygenetic and therefore tongues come in a range of lengths. Give (1) example of how directional selection might be acting upon this trait, with a graph and pictorial representation.
If it was particularly hot one summer and ants were making their hills farther below the surface, anteaters with shorter tongues wouldn’t be able to find food.
Practice Scenarios
You will receive a scenario – work it in your spiral.
When everyone at your table is done, rotate the scenarios.
Once you have completed all 4, compare with your team.
Teams for your scenarios….
Team 1 Team 2 Team 3 Team 4 Team 5 Team 6 Team 7
Alexia Addison Lance Alexa Luis Malcolm Benjamin SC
Dirk Ashleigh Lauren Alexis Benjamin S Angela Halea
Justin Anthony G Rebecca Henry Kaila Thomas Anthony R
Susan Matthew Jonathan Christopher Ethan Noe
top related