The document discusses concepts of evolution, specifically artificial selection and natural selection. It explains that artificial selection involves humans breeding organisms for desired traits, while natural selection is a process through which populations adapt over time, leading to speciation. Additionally, it covers genetic drift, mutation, recombination, fossil evidence, comparative anatomy, and taxonomy, highlighting the importance of these mechanisms in understanding evolutionary processes.

1. EVOLUTION
BIOLOGY 2

3. Artificial selection, also called selective breeding, is the
process where humans identify desirable traits in animals
and plants and use these traits to develop desirable
phenotypic traits by breeding.
WHAT IS ARTIFICIAL SELECTION?
For instance: Dog breeds such as the Bulldog, the Afghan
Shepherd, the Pitbull or the Rottweiler.
It is through the science, then, the way in which it is possible to
increase the frequency of genetic changes between
successive generations.

4. Artificial Selection or Selective Breeding is a process in
which humans select the desired trait to pass in
next-generation offspring of plants or animals.
•The selection process by humans.
•A long and planned steps.
•Genetic changes.
•Allelic frequency increases.

5. English naturalist Charles Darwin developed the idea of natural
selection after a five-year voyage to study plants, animals, and fossils in
South America and on islands in the Pacific. In 1859, he brought the idea
of natural selection to the attention of the world in his best-selling
book, On the Origin of Species .
Natural selection is the process through which populations of living
organisms adapt and change. Individuals in a population are naturally
variable, meaning that they are all different in some ways.
This variation means that some individuals have traits better suited to the
environment than others.

6. Individuals with adaptive traits —traits that give them some
advantage—are more likely to survive and reproduce. These individuals then
pass the adaptive traits on to their offspring. Over time, these
advantageous traits become more common in the population. Through this
process of natural selection, favorable traits are transmitted
through generations.
Natural selection can lead to speciation , where one species gives rise to a
new and distinctly different species. It is one of the processes that
drives evolution and helps to explain the diversity of life on Earth.

9. Darwin chose the name natural selection to contrast with “artificial
selection,” or selective breeding that is controlled by humans. He pointed to
the pastime of pigeon breeding, a popular hobby in his day, as an example
of artificial selection. By choosing which pigeons mated with others,
hobbyists created distinct pigeon breeds, with fancy feathers or acrobatic
flight, that were different from wild pigeons.
What is natural selection?
•Natural selection is known as ‘the survival of the fittest’. The best
adapted organisms are able to survive.

10. Genetic drift is an evolutionary change in allelic frequencies of a
population as a matter of chance. It occurs in very small populations
but its effects are strong. It occurs due to an error in selecting the
alleles for the next generation from the gene pool of the current
generation.
What is meant by genetic drift?
Genetic drift is a mechanism of evolution in which allele
frequencies of a population change over generations due to chance
(sampling error). Genetic drift occurs in all populations of
non-infinite size, but its effects are strongest in small populations.

11. Types of Genetic Drift
1. Bottleneck Effect
In the bottleneck effect, the population size severely decreases due to
competition, predators, or diseases.
The frequency of certain alleles in a population changes because the
organisms that carry them are eliminated. The others increase in number
because they are the only alleles left.
This is observed during natural disasters like volcanic eruptions,
earthquakes, etc., leading to the death of most of the population.

12. 2. Founder Effect
In the founder effect, a new population is founded in a new location due to
physical or geographical barriers.
The new population formed does not interact and mate with the original
population.
As a result, the allelic frequencies of the new population will be different from the
original population.
There are many species that are found only on a particular island. This is due to
the founder effect. E.g., two birds of the same species reach an island. Their
alleles will be responsible for the diversity on that island.
These alleles will dominate, and mutations in the population will lead to the
formation of new species. The new population will diverge to such an extent that
they will no longer interbreed.

14. Mutation Definition
“Mutation is the change in our DNA base pair sequence due to various
environmental factors such as UV light, or mistakes during DNA
replication.”

21. Recombination is the procedure by which DNA fragments are disrupted and recombined to
generate new allele combinations. This recombination mechanism generates genetic diversity
at the gene level that reflects variations in the DNA sequences of various organisms.
Recombination
Definition
noun, plural: recombinations
(1) (genetics) The process or act of exchanges of genes
between chromosomes, resulting in a different genetic combination and
ultimately to the formation of unique gametes with chromosomes that are
different from those in parents.
(2) (general) The process or act of bringing together (dissociated materials)
once more.
Supplement
In genetics, recombination occurs
during meiosis when chromosomes exchange genes. Thus, recombination
is one of the important means to promote and increase
genetic diversity between generations.

24. 1. Fossils
They are the remains of the non-degraded parts of living
beings found within rocks. The layer from which the fossil is
recovered decides the age of the fossil. The fossils found deeper
down are older compared to the ones found in the upper layers.
They give an idea of the condition of the earth in that specific era.
The study of fossils is called palaeontology. Thus, fossils are called
paleontological evidences.

25. 2. Comparative Anatomy
It explains that many organisms have the same ancestor and many different
organisms evolved as a result of natural selection or genetic drift. Two types of
comparative anatomy were observed, namely homologous organs and analogous
organs.
Homologous organs: These organs have the similar structure in different
organisms but perform different functions. Thus, it clearly shows a common
ancestry. One species gave rise to many other species. This type of evolution is
called divergent evolution. For example, the limbs of human, cheetah, whale,
and wings of a bat. They all have different functions but have a similar structure
indicating a common ancestor.
Analogous organs: These organs have different anatomy but perform similar
functions. This shows that different species evolved and adapted to a particular
environment. This type of evolution is called convergent evolution. For example,
the wings of different birds and bats. The wings of birds have feathers for flight
whereas, bats have wings made up of streched skin and lack feathers. But, both
serve the function of flight.

26. 3. Embryonic Development
The embryos of various species show similar structure till a certain
period of gestation. For example, the embryos of humans, pigs,
reptiles, and birds show similar embryonic development. They develop
into the respective species as they grow. This again shows common
ancestry.

27. Taxonomy is a branch of science that deals with the nomenclature,
identification and classification of living organisms and the extinct organisms.
We have around millions of species on Earth which are known by their local
names. These names vary from place to place, creating a chaos among
scientist who want to study them for research. Hence, we need a standard
nomenclature
system. The nomenclature of an organism is only possible when we correctly
know all the specifications of the organism that describes them clearly. This
process of description of an organism is known as
identification
. Biologists all over the world follow a set of principles for the scientific
nomenclature of organisms. There are two parts in the name of an organism:
Generic name and specific epithet. This two-part system of biological
nomenclature is known as

28. Binomial Nomenclature
. This system of nomenclature was given by Carl Linnaeus. Let us
understand the system of binomial nomenclature by taking the
example of mango. The scientific name of mango is given
as Mangifera indica. Mangifera indicates the ‘genus’
while indica represents a particular specie or ‘specific epithet’.

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