During DNA replication, the two parental strands separate and each acts as a template to direct the enzyme catalysed synthesis of a new com-plementary daughter strand following the base pairing rule. Three basic steps involved in DNA repli-cation are Initiation, elongation and termination.

1. GOODMORNING!

2. PRAYER
Father God,
Come be with us today
Fill our hearts with joy
Fill our minds with learning
Fill our classroom with peace
Fill our lesson with fun
Fill our friendships with kindness
Fill our school with love
Amen.

4. St. Blaise Community Academy Inc. is dedicated to
the development of a God fearing Individual
empowered with moral, intellectual, social and
physical commitment to the achievement of the
highest quality of life. It envisions producing
scientifically, technologically and globally competitive
individual who also values the virtue of reaching out
and helping others.

5. St. Blaise Community Academy Inc. shall promote academic
excellence, stimulate and ignite scientific curiosity and
provide the opportunities to attain their individual potentials.
Quality education and meaningful learning experience will
be provided that will prepare students for post secondary
opportunities and empower them with the 21st century skills-
communication, collaboration, creativity, critical thinking,
productivity, leadership and technology literacy resulting in
their development into mature, independent and responsible
citizen.

6. ATTENDANCE CHECKING

7. CLASSROOM RULES
1. Have RESPECT so you earn it too.
2. Come to class on time.
3. Be ready to learn.
4. Listen and follow instructions.
5. Raise your hand to speak.
6. Believe yourself.
7. Work hard and have fun!

8. MECHANISMS OF
EVOLUTION

9. Learning
Objectives:
After going through this lesson, you should be able to:
1.explain that genetic variation is the prerequisite and should
therefore be present for any genetic process to cause change in
populations generation to generation;
2.state the Hardy-Weinberg Principle; and
3.enumerate the conditions that should be present for a gene or
in alarger scale, a population, to attain Hardy-
Weinberg equilibrium.

10. WHAT I KNOW?
Direction: Choose the letter of the corect answer.
1.A mathematical equation that can be used to calculate the genetic variation of a population
at equilibrium.
a.Hardy-Weinberg equation b. Mean C. Standard Deviation
2.It is life’s way of bringing variety in similarity.
a.Recombination b. Unity c.Dna Sequencing
3.It involves the movement of genes into or out of a population, due to either the movement
of individual organisms or their gametes (eggs and sperm, e.g., through pollen dispersal by a
plant).
a.Gene Flow b. Gene Cloning c.Vector
4. It occurs when individuals with certain genotypes are more likely than individuals with
other genotypes to survive and reproduce.
a.Natural Selection b.Artificial Selection c.Selective Breeding
5.The law that states that in an infinitely large, interbreeding population in which mating is
random.
a. Jones Law b. Constitution c. Handy Weinberg Law

11. WHAT’S NEW? Paint a Thousand Words
Examine closely the picture below. What have you noticed?

12. LESSON 2: Mechanisms that Produce
Change in Populations
 Hardy–Weinberg law The law that states that in an infinitely large,
interbreeding population in which mating is random and in which there is
no selection, migration, or mutation, gene and genotype frequencies will
remain constant from generation to generation.

13. In practice these conditions are rarely strictly
present, but unless any departure is a marked one, there
is no statistically significant movement away from
equilibrium. Consider a single pair of alleles, A and a,
present in a diploid population with frequencies of p and
q respectively. Three genotypes are possible, AA, Aa,
and aa, and these will be present with frequencies of p2,
2pq, and q2 respectively.

14. The five conditions that must be met for genetic
equilibrium to occur include:
1. No mutation (change) in the DNA
sequence.
2. No migration (moving into or out
of a population).
3. A very large population size.
4. Random mating.
5. No natural selection

15. The Hardy-Weinberg equation is a mathematical equation
that can be used to calculate the genetic variation of a
population at equilibrium. he equation is an expression of
the principle known as Hardy-Weinberg equilibrium, which
states that the amount of genetic variation in a population
will remain constant from one generation to the next in the
absence of disturbing factors.

16. p2 + 2pq + q2 = 1 where p is the frequency of the "A" allele
and q is the frequency of the "a" allele in the population. In the
equation, p2 represents the frequency of the homozygous
genotype AA, q2 represents the frequency of the homozygous
genotype aa, and 2pq represents the frequency of the
heterozygous genotype Aa. In addition, the sum of the allele
frequencies for all the alleles at the locus must be 1, so p + q
= 1. If the p and q allele frequencies are known, then the
frequencies of the three genotypes may be calculated using
the Hardy-Weinberg equation.

17.  Natural selection, genetic drift, and gene flow are the mechanisms that
cause changes in allele frequencies over time. When one or more of these
forces are acting in a population, the population violates the Hardy-Weinberg
assumptions, and evolution occurs.Natural selection occurs when individuals
with certain genotypes are more likely than individuals with other genotypes to
survive and reproduce, and thus to pass on their alleles to the next generation.
MECHANISMS OF EVOLUTION: What causes a change in
gene frequency?
Gene and the DNA don’t change overnight and don’t change with no cause.
There are various mechanisms that bring forth changes to the gene
frequency, let us investigate and explain them one by one

18. Natural selection. Finally, the most famous mechanism of evolution! Natural selection
occurs when one allele (or combination of alleles of different genes) makes an
organism more or less fit, that is, able to survive and reproduce in a given
environment. If an allele reduces fitness, its frequency will tend to drop from one
generation to the next. We will look in detail at different forms of natural selection that
occur in populations.

19.  Mutation. Although mutation is the
original source of all genetic variation,
mutation rate for most organisms is
pretty low. So, the impact of brand-new
mutations on allele frequencies from
one generation to the next is usually
not large. (However, natural selection
acting on the of evolution.

20.  Gene flow. Gene flow involves the
movement of genes into or out of a
population, due to either the movement
of individual organisms or their
gametes (eggs and sperm, e.g.,
through pollen dispersal by a plant).
Organisms and gametes that enter a
population may have new alleles, or
may bring in existing alleles but in
different proportions than those already
in the population. Gene flow can be a
strong agent of evolution.

21.  Non-infinite population size
(genetic drift). Genetic drift
involves changes in allele
frequency due to chance
events – literally, "sampling
error" in selecting alleles for
the next generation. Drift can
occur in any population of
non-infinite size, but it has a
stronger effect on small
populations. We will look in
detail at genetic drift and the
effects of population size

22.  Artificial Selection
Darwin saw that when humans choose
organisms with specific characteristics
as breeding stock, they are performing the
role of the environment. This is where
artificial selection or selective breeding
started. One of the causes of change in
the gene frequency of some species
specifically domesticated plants and
animals is artificial selection or
selective breeding. It is when humans
selectively choose to breed animals and
plants with specific traits that they deemed
beneficial for different purposes.

23.  Recombination
Recombination or gene shuffling is life’s way
of bringing variety in similarity. It occurs during
meiosis, the cell replication process used for
reproduction. Recombination is also the
reason behind gene variation between siblings a
nd
twins and makes genetic diversity possible.Durin
g meiosis, crossing over happens where
homologous chromosomes line up to prepare for
cell division. In this instance, chromosomes
exchange information and shuffle parts of the
DNA which resulted in a very random
variation yet the same copy of the original gene.

24. Activity 1. COMPLETABLE: Name the pieces of
evidence on the evolution of life Pick your answer
from the terms inside the box. WRITE YOUR
ANSWER IN THE SPACE PROVIDED AT THE
BACK OF THIS LEARNING MODULE (ANSWER
SHEET).
WHAT’S MORE?

25. Zircon crystal Stromatolites Cyanobacteria
First Eukaryotes
Multicellular Organisms Trilobite fossils Homo erectus
Timeline Evidences
4.6 to 3.6 Billion Years
Ago
1.
3.5 Billion Years Ago 2.
3.0 Billion Years Ago 3.
2.0 Billion Years Ago 4.
1.2 Billion Years Ago 5.
500 Million Years Ago 6.
250 thousand years ago 7.

26. WHAT’ I CAN DO?
INFOGRAPHICS
Organizations that aim to protect therights of animals have been battling leisure
breeders to stop selective breeding because
they view it as a form of abuse or cruelty to animals.Selective breeding or
artificial selection is mechanism that has brought a huge impact on
the gene frequency of animals especially domesticated ones like dogs and
cats.There are cases when breeding animals such as dogs resulted in diseases and
malformation or abnormalities in the resulting offspring. In your point of view as
senior high school STEM student, is it proper to continue selective breeding?
Express your answer through an info graphics.

27. Direction: Identify what is being described below.
1.A mathematical equation that can be used to calculate the genetic variation of a population at equilibrium.
Hardy-Weinberg equation
2.It is life’s way of bringing variety in similarity.Recombination
3.It involves the movement of genes into or out of a population, due to either the movement of individual
organisms or their gametes (eggs and sperm, e.g., through pollen dispersal by a plant). Gene Flow
4.It occurs when individuals with certain genotypes are more likely than individuals with other genotypes to
survive and reproduce. Natural Selection
5.The law that states that in an infinitely large, interbreeding population in which mating is random.Hardy-
Weinberg Law
6.Involves changes in allele frequency due to chance events – literally, "sampling error" in selecting
7.alleles for the next generation. Genetic Drift
8.original source of all genetic variation.Mutation
9.refers to how common a specific gene is in a group of specie within a specific area. Gene Frequency
10.He saw that when humans choose organisms with specific characteristics
as breeding stock, they are performing the role of the environment. Charles Darwin
ASSESSMENT

28. SELF EVALUATION
Which category in 21st Century skills do you think the core of our topic
falls in? (Communication, collaboration, creativity, critical thinking,
productivity, leadership and technology literacy). Explain why. WRITE
YOUR ANSWER IN THE SPACE PROVIDED AT THE BACK OF THIS
LEARNING MODULE (ANSWER SHEET)
WHAT CAN I SHOW?

29. THANK
YOU
FOR
LISTENING!