This is my presentation on  how mass selection
can improve the speed of box turtles
given an original population. So, we will be looking at how fast a random mix of
box turtles can run 50 meters. This bell
curve shows the normal distribution in
our population of racing turtles. Our
average speed of the whole population is
shown here by this black line in the
middle of the bell curve, measuring at 25
minutes. Our standard deviation is 6,
which represents the variation within
our population of turtles. If we look at
our broad sense and narrow sense
heritability values, they are relatively
close to one, which means there is a
good chance of having success with our
breeding program, resulting in faster
turtles if we select from the fastest
10% of our population to breed, which is
shown by this pink shaded area of the
graph. After we have completed our
breeding program, here are our results. We have our original population in black,
the selected individuals from our
original population are shaded in pink,
and our offspring generation in green. We
have three vertical lines, each
representing the mean for that
population. The black line is the mean of
the original population, the green line
is the mean of the offspring population,
and the pink line is the mean of the
selected individuals from the original
population. The blue star represents our
truncation point. This value is the
threshold for selected individuals for
the breeding program. In this case, it is
the slowest run time a turtle can have
to be selected as a parent and if they
are slower they are excluded from the
breeding program. The other two values on
our graph are the selection differential
and response to selection. The selection
differential (S) represents
the difference between the average speed
of our selected individuals and the
average speed of our entire original
population. The response to selection
represents the change in average speed
from our original population to our
offspring generation. In this case, the
offspring generation is 7.06 minutes
faster than the original population on
average. The question now is what will
happen if we continue this breeding
program indefinitely. Well, over time our
response will decrease until we get
basically no response to selectively
breeding the fastest turtles. Of course,
there are also mathematical explanations
to this as well. Most likely, four or five
offspring generations in, you will start to
see a more narrow graph, meaning the
standard deviation or variation among
your population will decrease
drastically. This means your population will be so
similar it is hard to improve your
average speed by breeding with a turtle
that is only two minutes faster than the
average. There are also the environmental
factors that contribute to variation,
ultimately altering and limiting the
speed of our turtles. There are also
limits in nature and no matter how many
times you breed the fastest of the fast
turtles,
you will never get a turtle that can
flat-out outrun a rabbit. And here is my
consolidated list of my values and
calculations
