Presentation on Selection

2.  A natural or artificial process that involves the survival and reproduction of
some kinds of organisms instead of others (because they have traits that are
better adapted to the environment or that are preferred by a breeder, for
example) and results in changes in the traits of a population or species.
selection
 the differential rate of reproduction of one phenotype in a population as
compared to other phenotypes. Hence an organism that produces more
offspring which survive to reproduce than another type is at a ‘selective
advantage’

3.  Both natural and artificial selection refer to processes
that determine which genetic traits pass from one
generation to the next. During natural selection, species
survival and reproduction determine those traits. Artificial
selection places humans in control of choosing which
traits show up in future generations, and which ones do
not. While humans may artificially enhance or repress an
organism's genetic traits through selective breeding,
nature concerns itself with traits that allow advantages to
a species' ability to mate and survive.

4.  Natural selection is the differential survival and reproduction of individuals due to
differences in phenotype. It is a key mechanism of evolution, the change in
heritable traits of a population over time. Charles Darwin popularised the term
"natural selection", and compared it with artificial selection.
 Variation exists within all populations of organisms. This occurs partly because
random mutations arise in the genome of an individual organism, and offspring can
inherit such mutations. Throughout the lives of the individuals, their genomes
interact with their environments to cause variations in traits. The environment of
a genome includes the molecular biology in the cell, other cells, other individuals,
populations, species, as well as the abiotic environment. Individuals with certain
variants of the trait may survive and reproduce more than individuals with other,
less successful, variants; therefore, the population evolves.

6.  Artificial Selection is the breeding of certain traits (better traits) over other
traits. For example, breeding a good male horse with excellent racing
qualities with a healthy female horse so that the offspring will have the
desired traits such as the racing qualities. Another example is breeding good
size fruits or vegetable together to keep on getting the good size.
 Selection done by humans looking to maximize traits in animals under
domestication. These traits are not always for the benefit of the organism
though. Men raise these animals and mate the ones they think will breed true
for a man favored trait and cull the rest of the organisms by killing them, or
by not allowing them to breed

7.  Variation :Heritable differences that exist in every population are the basis
for natural selection.
 Overproduction : Competition between offsprings for resources.
 Adaptation : a trait that helps an organism survive and reproduce
 Descent with Modification: Natural Selection will result in species with
adaptation that are well suited for survival and reproduction.

8.  Those adaptations that are occurring in individuals due on a small scale to
mutations and being expressed due to the environment contribute variation
of alleles and traits to the overall population of the species. If all individuals
in a population were clones, then there would be no variation and therefore
no Natural Selection at work in that population.
 Increased variation of traits in a population actually increases the likelihood
of survival of a species as a whole. Even if part of a population is wiped out
due to various environmental factors (disease, natural disaster, climate
change, etc.), it is more likely that some individuals would possess traits that
would help them survive and repopulate the species after the dangerous
situation has passed.

10.  The first of these factors that must be present in order for Natural
Selection to occur is the ability of a population to overproduce
offspring. You may have heard of the phrase "reproduce like rabbits"
which means to have a lot of offspring quickly, much like it seems
rabbits do when they mate.
 The idea of overproduction was first incorporated into the idea of
Natural Selection when Charles Darwin read Thomas Malthus's essay
on human population and the food supply. The food supply increases
linearly while the human population increases exponentially. There
would come a time when the population would pass up the amount
of available food. At that point, some humans would have to die out.
Darwin incorporated this idea into his Theory of Evolution through
Natural Selection.

11.  It is now time for the environment to "choose" which of
the variations is the one that is advantageous. If all
variations were created equal, then Natural Selection
again would not be able to happen. There must be a
clear advantage to having a certain trait over others
within that population or there is no "survival of the
fittest" and everyone would survive.
 This is one of the factors that can actually change during
the lifespan of an individual in a species. Sudden
changes in the environment may happen and therefore
which adaptation is actually the best one would also
change. Individuals that were once thriving and
considered the "fittest" may now be in trouble if they
are no longer suited as well to the environment after it
changes.

12.  Individuals that possess those favorable traits will live long enough to reproduce and pass
down those traits to their offspring. On the other side of the coin, those individuals that lack
the advantageous adaptations will not live to see their reproductive periods of their lives
and their less desirable characteristics will not be passed down.
 This changes the allele frequency in the population's gene pool. There will eventually be less
of the undesirable traits seen as those poorly suited individuals do not reproduce. The
"fittest" of the population will pass down those traits during reproduction to their offspring
and the species as a whole will become "stronger" and more likely to survive in their
environments.

13.  the superiority of the individuals selected
for breeding, relative to the population
from which they were selected.

14.  a measure of the gain achieved by selection; the phenotypic superiority of
selected individuals, compared to the population from which they were
selected.
 Differential evolution is a simple algorithm for global optimization. Basically
it consists of three operations: mutation, crossover and selection. Despite
many research papers dealing with the first two, hardly any attention has
been paid to the third one nor is there a place for this operation in the
algorithm basic naming scheme. In the paper we show that employing
different selection strategies combined with some random perturbation of
population vectors notably improves performance in high-dimensional
problems

15.  Heritability measures the fraction of phenotype variability that can be
attributed to genetic variation. This is not the same as saying that this
fraction of an individual phenotype is caused by genetics. In addition,
heritability can change without any genetic change occurring, such as when
the environment starts contributing to more variation. As a case in point,
consider that both genes and environment have the potential to influence
intelligence. Heritability could increase if genetic variation increases, causing
individuals to show more phenotypic variation, like showing different levels of
intelligence. On the other hand, heritability might also increase if the
environmental variation decreases, causing individuals to show less
phenotypic variation, like showing more similar levels of intelligence.
Heritability increases when genetics are contributing more variation or
because non-genetic factors are contributing less variation; what matters is
the relative contribution. Heritability is specific to a particular population in
a particular environment.

16.  The increase in the level of a quantitative variable that results from recurrent
mass selection. For example, after one screening generation, there might be
a 5% increase in the yield, or in the level of horizontal resistance to a
particular species of parasite."
 Genetic advance is the measure of genetic gain under selection which
depends on three factors such as genetic variability, heritability and selection
intensity.