Download Unit 1.5 Name: Section Title: Speciation and Population Genetics

Unit 1.5
Name:
Section Title: Speciation and Population Genetics
Opening Activity:
Review of Old Information: None
New Information: Speciation
1. Microevolution -populations and species change through time resulting from relatively
small genetic variations
a. Causes:
i. __________________
ii. __________________
iii. __________________
iv. __________________ (directional, stabilizing, disruptive, sexual)
2. Microevolution can result in…
a. Speciation - the process of new species forming from old species. Driven by
geographic and reproductive isolation.
3. Species - a group of _______________ individuals that share a ____________
pool and are reproductively ______________ from other species.
a. Two types of speciation are:
i. Allopatric speciation (Geographic and Reproductive
Isolation)
ii. Sympatric speciation (Reproductive Isolation)
4. _______________ speciation
a. Occurs when two populations are _______________ isolated from one
another. They are separated by ______________ or an impassable barrier.
i. Example: Grand Canyon squirrels
b. Allopatric: (allo = other, patric = place)
5. _______________ speciation
a. New species develops when members of a population develop a genetic
____________________ that prevents them from reproducing with
members of the original species.
b. Sympatric: (sym = same, patric = place)
c. Occurs due to ______________ isolation.
i. Reproductive isolation may be caused by:
1. A) ________________ isolating mechanisms
a. Example: - Behavioral rituals
b. - Differing mating seasons
2. B) ________________ isolating mechanisms
a. Example: - prevention of insemination, offspring may be
sterile
6. _______________ _______________
a. All of these mechanisms to ______________ can lead to adaptive radiation.
b. Adaptive radiation is the emergence of numerous ___________ from a
common ancestor that spreads to _____ _________________.
i. Example: - Darwin’s finches
New Information: Hardy-Weinberg Equilibrium
1. How do we know if microevolution is occurring?
a. Hardy-Weinberg Equilibrium
i. Hardy-Weinberg Equilibrium – genetic frequencies of a given population
will remain the same unless acted on by _______________
______________.
ii. Hardy Weinberg Equilibrium = genetic equilibrium = no more gene
change
IX. Reasons why it will remain the same:
1.
2.
3.
4.
5.
No Net ______________ Occurs
Individuals do not enter or leave the population (No _______________)
The population is ________________
Individuals mate _______________
Natural Selection does ______________ occur
X. Hardy Weinberg Math
• Hardy and Weinberg used equations to calculate the amount of alleles that were in a
population
• The number of Homozygous dominant (________) = p
• The number of heterozygous (________) = 2pq
• The number of homozygous recessive (_______) = q
• Adding these numbers together should give you a total of 1
• So …… ___________________________
2
2
XI. Hardy Weinberg Practice Problem
Activity: Hardy Weinberg Practice Problem
Sickle-cell anemia is an interesting genetic disease. Normal homozygous individials (SS) have
normal blood cells that are easily infected with the malarial parasite. Thus, many of these
individuals become very ill from the parasite and many die. Individuals homozygous for the
sickle-cell trait (ss) have red blood cells that readily collapse when deoxygenated. Although
malaria cannot grow in these red blood cells, individuals often die because of the genetic
defect. However, individuals with the heterozygous condition (Ss) have some sickling of red
blood cells, but generally not enough to cause mortality. In addition, malaria cannot survive
well within these "partially defective" red blood cells. Thus, heterozygotes tend to survive
better than either of the homozygous conditions. If 9% of an African population is born with
a severe form of sickle-cell anemia (ss), what percentage of the population will be more
resistant to malaria because they are heterozygous (Ss) for the sickle-cell gene?
Within a population of butterflies, the color brown (B) is dominant over the color white (b).
And, 40% of all butterflies are white. Given this simple information, which is something that
is very likely to be on an exam, calculate the following: A. The percentage of butterflies in
the population that are heterozygous. B. The frequency of homozygous dominant individuals.