Hey everybody! This is Matthew Hernandez; welcome to my video on natural selection.
In this video, I will be defining the
theory of evolution as well as natural selection,
a mechanism of evolution. More
importantly you will understand how natural selection produces evolution.
Let's start off by defining theory of evolution.
It refers to a change in
allele frequency and there are some implications you should remember.
Evolution involves allele frequencies
measured at the population level not
individual. This change occurs at the
genetic level. Evolution occurs in traits.
Charles Darwin known as the father of
evolutionary thinking devised a theory
of natural selection to explain the
process of evolution. This theory
suggests that beneficial alleles
increase in frequency over time in a
population as a result of increased
survival and reproduction of those with
beneficial alleles. You might have heard
of "survival of the fittest". Basically,
it refers to how the species is most
responsive to change will survive, not
the strongest or most intelligent. Natural selection was based on some key
observations: variation overproduction
selection and adaptation.
The first key understanding was that traits were inherited via genes passed on from the
parent to offspring. In this process, 
comes variation this means offspring all
have slightly different traits.
Overproduction occurs which means too many offspring are produced leading to limited resources,
and inevitably, competition.
There are some better suited or advantageous traits.
The advantageous traits are passed on to the next generation. Selection occurs as a result of competition from overproduction.
Adaptation refers to how a population will adapt to its environment
and have
more reproductive success from one generation to the next.
Pictured here at Galapagos or Darwin
finches, representing a group of 12
species known for a remarkable beak form
and function diversity. Populations of
birds on different islands became
isolated from each other, adapted to
their environment and food sources
leading to the changes. Some develop
stronger bills for cracking nuts while
others finer ones for insect picking.
The following is a good example of how
natural selection produces evolution.
A group of mice, some with black and others with tan fur has moved into a new area
with black rocks. In this environment, the
Hawks like to eat mice; the tan ones
stick out. Many more of the tan mice are
eaten since they are more easily seen.
Only the surviving tan mice will
reproduce while the black mice with
better survival, will reproduce more. After
several generations, the population will
be majority black.
Let's remember some key points about natural selection. It depends on the environment, it emphasizes traits and alleles and occurs in
populations not individuals, it acts on
existing heritable variation.
Here are the key terms and definitions related to this concept including page numbers.
Feel free to pause the video and review
before continuing.
At this point, I have reviewed evolution as well as natural selection and have included examples.
Now it's your turn to practice with a POP
QUIZ!
Which of the following is not a key component of natural selection?
A. Traits for strength and vitality are favored over other traits.
B. Random variation
exists for every trait in a population
C. There will always be competition for
resources
Or D. Those with advantageous traits will outproduce others.
Feel free to pause. If you get stuck, it's in the lab manual in chapter 4.
Welcome back! Did you get it? Let's take a look...
The correct answer is A. You may remember the example from
the book. Bigger and stronger is not
necessarily advantageous as with the
dwarf mammoths for whom smaller was most advantageous since they needed
fewer resources and that's how the
future generations evolved.
I hope you enjoyed learning about the theory of evolution, Charles Darwin, natural selection
and reproductive success I
included all my references at the very end.
Thanks for watching. Bye, everybody!
