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in this video you are going to learn
part 2 of chapter 18 variation and selection
selection
in the previous video we covered
variation now let's turn our attention
to selection
first let's talk about natural selection
in a nutshell natural selection is the
process where certain traits become more
common in a population over time because
they help organisms survive and
reproduce better in their environment
let's break it down now
natural selection is a process where
within a population there is genetic
variation and many offspring are produced
produced
as these Offspring grow they face a
struggle for survival including
individuals that are better adapted to
their environment have a greater chance
of reproducing compared to others
these individuals pass on their alleles
or genetic traits to the Next Generation
leading to a gradual change in
so once again natural selection is a
process where within a population there
is genetic variation and many offspring
are produced as these Offspring grow
they face a struggle for survival
including competition for resources
individuals that are better adapted to
their environment have a greater chance
of reproducing compared to others
these individuals pass on their alleles
or genetic traits to the Next Generation
leading to a gradual change in
population over time
let's look at an example
in a population of beetles let's say
there is a natural variation in body
coloration with most beetles being green
and the others being Brown the insects
live on a brown tree bark providing
bitter camouflage for the brown beetles
compared to the green ones Predators
such as Birds hunt the insects for food
they can easily spot and capture the
green beetles against the brown tree
bark while the brown beetles blend in
and are less likely to be detected
as a result the brown beetles have a
higher chance of surviving and escaping
predation due to their bitter camouflage
they are more likely to reach
reproductive age compared to the green
beetles the brown beetles that survive
and reach reproductive age mate and
produce Offspring they pass on their
genetic traits for brown coloration to
the Next Generation over successive
Generations the proportion of brown
beetles increases while the green
beetles become less common in the
population this shift occurs because the
brown beetles have a survival advantage
and are more likely to pass on their
traits this illustrates how natural
selection favors traits that help
organisms survive and reproduce in their
environment over time these advantageous
traits become more prevalent as
individuals with those traits have
higher reproductive success
adaptation is the process resulting from
natural selection by which populations
become more suited to their environment
the development of strains of antibiotic
resistant bacteria is an example of
when antibiotics are used most bacteria
of a certain strain die however by
chance some bacteria may have a genetic
mutation that makes them resistant to
the antibiotics
these resistant bacteria survive and
reproduce quickly leading to a large
number of bacteria with the same resistance
resistance
as a result the antibiotic becomes
ineffective because of the widespread
presence of resistant bacteria this is
an example of natural selection in action
action
next let's explore selective breeding
selective breeding is a process where
humans choose individuals with desirable features
features
these selected individuals are then bred
from this new generation individuals
displaying the desired features are
further chosen
using this method organisms can pass on
favorable traits to their offspring
resulting in more organisms with desired characteristics
characteristics
selective breeding is also known as
artificial selection
so once again here's the process of
selective breeding selection by humans
of individuals with desirable features
Crossing these individuals to produce
the Next Generation
selection of Offspring showing the
selective breeding also known as
artificial selection is a method used
over multiple generations to enhance
desirable traits in crop plants and
domesticated animals
humans selectively breed plants to
enhance various traits such as disease
resistance in food crops
increased crop yield
adaptation to challenging with the
conditions example drought tolerance
Improvement in taste and flavor of fruits
fruits
cultivation of plants with large or
so for example say we want to
selectively breed crops to increase
their disease resistance first we have
to identify plants that display
resistance to specific diseases then
cross breed these resistant plants to
produce the Next Generation next select
Offspring with increased disease resistance
resistance
continue the cycle of breeding and
selecting for disease resistance to
develop new varieties that are more
resilient to diseases
humans selectively breed animals by
choosing individuals with desired traits
and breeding them together over multiple
Generations until a new breed with
consistent desired characteristics is
established animals are selectively bred
by humans to develop specific traits
such as cows goats and sheep that
produce lots of milk or meat
domestic dogs with a gentle nature
sheep with good quality wool
horses with fine features and great speed
speed
so for example if we want to selectively
breed sheep for better quality wool
identify sheep with good quality wool
breed these sheep to produce the Next
Generation select Offspring with
improved wool quality repeat the
breeding and selection process to
gradually enhance the wool quality in
finally let's compare the differences
between natural and artificial selection
natural selection occurs naturally
without human intervention while
artificial selection occurs with human
natural selection results in adaptations
that enhance survival and reproduction
in a specific environment so it's driven
by survival advantages
artificial selection often focuses on
traits that are advantageous or
desirable from a human perspective so
it's driven by human preferences and goals
goals
natural selection can lead to the
gradual change and diversification of
species over time so it usually takes a
long time to occur and artificial
selection can result in rapid changes in
traits within a population over a
relatively short period so it takes less time
so that concludes part 2 of chapter 18
variation and selection
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