so I've decided that the best use of my
time is going to be attempting to
breed the largest Canadian goose
possible and so I have a population of a
hundred geese and among these geese my
average for height is thirty seven and a
half inches with a standard deviation of
two inches my broad sense broad sense
heritability is 0.85 and my realized
heritability is 0.67 in order to achieve
my goal of breeding the tallest goose
possible I will only be breeding the top
10% tallest geese within my population
in order to do this and calculate the
average of my offspring population we're
also going to need to know the selection
intensity and the standardized selection
point these can be found in standardized
tables and my value for selection
intensity is 1.755
and the selection point is 1.282 so our first step is going to
be calculating the truncation point I've
written the formula on the screen here
and as such I will do so for all the
following formulas and we get our
truncation point to be 40.06 inches only geese larger than
40.06 inches are going to be
allowed to reproduce in the next
generation in other words this is the
cutoff point for the top 10% largest geese
next we need to determine the selection
differential we do this by multiplying
the intensity times the standard
deviation and we get 3.51
which is the difference between the
average mean of our original goose
population and the truncation point next
we need to determine the response from
selection in order to determine the
offspring population average we do this
by multiplying our realized heritability
0.67 times our selection differential
with this we get 2.35
finally we need to determine the mean of
the offspring population we do this by
adding the response from selection to
our original average and we get 39.85 inches to be the
new mean of our offspring population so
I've created a histogram of our original
goose population in the middle we can
see the average to be 37.5
inches and our truncation point at
40.06 inches all the geese
larger than this in other words our
parents their average is 41.55
inches and the selection difference
the difference between the truncation
point and the average is 3.51 inches next I've created the
histogram for our offspring generation
as well and we see here that the mean of
the offspring is 39.85 inches and the mean of our original
population is 37.5
the difference between these is the
response from selection which in our
case is 2.35 inches now
I could keep breeding these geese over
and over only picking the top ten
percent of geese and eventually
hopefully getting a geese around five
feet tall however eventually the
response from selection is going to be
continuously decreasing and this in part
comes from the anatomy of our goose
geese are birds and as such have hollow
bones that allow them to take flight
but these hollow bones cannot support
the weight that we normally see in other
animals so as these geese get larger and
larger these hollow bones are not going
to be able to support the weight of our
larger geese which is going to make them
inviable and as such will decrease the
response from selection
