Unit 8 was all about evolution, how all the species, and the earth
itself, have changed over time. We learned about what exactly was the
definition of evolution and how it was measured. All the alleles that
make up genes in population are called the gene pool. The frequency of
an allele in the population is called allele frequency. Evolution is
measured as a change in allele frequency in the gene pool, so all
species are constantly evolving. One allele becomes more or less
frequent due to natural selection. Natural selection ultimately ends up
choosing the genes in individuals that are more likely to survive and
reproduce, therefore, making the population look like the "winners". In
the
Hunger Games Lab,
which was the main lab this unit, we saw the disappearance of stumpys
over time. They had undesirable characteristics, and therefore did not
get a chance to survive and reproduce. The pinchers, on the other hand,
grew more in the population because they had the most desirable
characteristic to pick up food (using their thumb and index finger).
Natural selection also works in different ways. Directional selection is
when one extreme phenotype is favored. As we saw in the
bird beak lab,
the tweezer beaks were favored since they were the most helpful in
picking up food and soon the amount of offspring were mostly tweezer
beaks. Stabilizing selection is when intermediate phenotypes are
favored. Disruptive selection is when two extreme phenotypes are
favored. Natural is not the only thing that causes species to evolve.
Genetic drifts are random events that suddenly changes the allele
frequency. This change may be either good or bad. Gene flow is the
movement of alleles from one population to another. Mutations can cause a
change in DNA, and if desirable, will become frequent in the
population. Sexual selections that improve mating success but not help
the organisms survive better.
Speciation is the creation of new species. Species separate when they
are reproductively isolated. This means that the two species cannot
reproduce and have fertile offspring. Temporal isolation is when they
reproduce at different times. Geographic isolation is when they are
physically separated. This is a technique often used with dog breeders.
Behavioral isolation is when they have different techniques to attract
mates.
The theory of evolution is opposed, but there is evidence to support it.
When all organisms are an embryo, they all look very similar. This
suggests that we all share a common ancestor. We also have features that
helped our ancestors or that they had, such as our tailbone which shows
that we used to have tails. Some organisms have same structures with
different functions (homologous). Others have different structures with
the same function.
To be more assertive this unit, I tried to voice all my opinions in all the different labs we had to do, and while voicing them, I listened to others and I compromised with them. Hopefully in the future, I will get even more assertive.