This document provides an overview of the key figures and concepts in the development of evolutionary thought from the 18th century to Charles Darwin's theory of evolution by natural selection in 1859. It discusses early beliefs in creationism and ideas from Georges Buffon, Georges Cuvier, James Hutton, Charles Lyell, Jean-Baptiste Lamarck, and finally Charles Darwin, who proposed natural selection as the mechanism of evolution. The document also defines important evolutionary terms like adaptation, variation, and population, and explains natural selection and survival of the fittest.

1. Science
Quarter 3 – Module 7
Evolution: Survival of the Wisest
Department of Education ● Republic of the Philippines
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2. Science – Grade 10
Alternative Delivery Mode
Quarter 3 – Module 7: Evolution: Survival of the Wisest
First Edition, 2020
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3. 1
Evolution is the change in the characteristics of species over several generations
and it relies on the process of natural selection. As such, evolution entails changes in the
inherited traits of a population from generation to generation. These traits are the expression
of genes that are copied and passed on to offspring during reproduction.
Evolution occurs when these heritable differences become more common or rare in a
population, either non-randomly through natural selection or randomly through genetic drift.
Natural selection is a process that causes heritable traits that are helpful for survival and
reproduction to become more common, and harmful traits to become rarer. This occurs
because organisms with advantageous traits pass on more copies of these heritable traits to
the next generation.
What’s New
Activity 1.1: SURVIVAL OF THE FITTEST!
Materials
 Cartolina/Construction paper (5 colors)
 Pair of scissors
 Stopwatch
Procedure
 Cut the construction papers into different shapes (same shape, same color).
 Cut 15 pieces (2 cm x 2 cm) with different colors and shapes.
 Hold all of the cut-out shapes and throw them out in the air (scattering all the papers
on the floor).
 In ten seconds, pick them up as fast you can and as many as you can.
 Count and record the number of cut-out paper that you have picked up.
 Do this three times.
SHAPE 1st Trial 2nd Trial 3rd trial
Guide Questions:
1. If each cut-out paper represents an organism in the environment, infer which one will
not likely be found by its predator?
2. Which one is the fittest?
3. What do you think is evolution through natural selection?
Lesson
1
The Origin of
Evolutionary Thought

4. What Is It
HOW DID LIFE FORMS START TO EXIST?
There are many theories as to how the different life forms start to happen on our
planet. In the mid-eighteenth century, most people believed in creationism, which held the
idea that all forms of life were already created in their present form and they have remained
unchanged since the beginning of time. Did you know that even the famous Carl von
Linnaeus, the Father of Taxonomy, believed in the fixity of species? However, the following
scientists have other ideas in mind.
George Louis Leclerc, known as Count Buffon, was a French
naturalist who first described descent with modification brought by
environmental influences, migration, geographical isolation and the
struggle for existence. Nevertheless, he was hesitant in sharing his
idea to the public.
In the late 18th century, Georges Cuvier, a vertebrate zoologist
and paleontologist proposed the theory of catastrophism. One day he
observed that a particular region had shown a succession of life forms
in the soil layers. His observation seemed to contradict his belief in the
special creation of each specie. Cuvier explained that there might have
been violent and sudden natural catastrophes such as great floods,
tectonic earthquakes, and rapid formation of mountain chains that
resulted to the death and extinction of most plants and animals. After
each catastrophe, God created new sets of life forms.
In contrast to catastrophism, James Hutton and
Charles Lyell believed that natural forces now changing the
shape of the earth’s surface have been operating since the
past at a much the same way. This idea is known as
uniformitarianism - large geological changes that occurred
not in catastrophic events but by the gradual accumulation of
small geological changes over long periods of time.
Jean Baptiste de Lamarck, on the other hand, was the first
biologist to believe that life forms do evolve. He proposed the
inheritance of acquired characteristics, which is also called as the
Lamarckian Evolution. He believed that every organism has the will to
survive and this will has allowed each organism to change to more
advantageous traits that are suitable to the environment. The acquired
traits are then inherited by the next generation. One example that
Lamarck gave is the elongation of giraffes’ necks because over time these
animals stretched out their necks to reach for food and then passed on a long neck to their
offspring. Today, Lamarck’s idea is proven to be incorrect. Phenotypic changes acquired
during an organism’s lifetime cannot be passed on to the next generations. In other words,
cutting a cat’s tail will not produce kittens without tails!
Finally, in 1859, Charles Darwin published his book, On the
Origin of Species by Means of Natural Selection. Contrary to
creationism, Darwin believed that organisms evolved from a common
ancestor. Because we all share a common ancestor, we are all related to
one another no matter how different we are.
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5. Charles Darwin was only 22 years old when he got a chance to set sail aboard the
Beagle to travel around the world and map the coasts of South America. During this travel,
he was an assistant to Captain Robert Fritz Roy. His Beagle voyage allowed him to develop
a theory that would contradict the special creation of every organism and imply that all
species evolved from a common ancestor through a process called natural selection.
While on his visit to Galapagos Islands, he had observed that organisms are geographically
distributed and isolated on separate islands. He noted that similar animal types show
distinct differences in body form and functions from island to island. He explained that these
differences represent adaptations to differing environments. Darwin believed that over the
course of time, isolated groups of animals had become reproductively isolated, and then
gradually they became separate species.
The following are some important terms in the study of evolution:
Adaptation is a set of genetically acquired traits that makes organisms better suited
to their environment. Individuals with advantageous adaptations are more likely to survive
and reproduce than those who lack the necessary adaptation skills.
Variation refers to any differences between cells, individual organisms, or groups of
organisms of any species that are caused either by genetic differences (genotypic variation)
or by the effect of environmental factors on the expression of the genetic potentials
(phenotypic variation). Variation may be shown through the physical
appearance, metabolism, fertility, mode of reproduction, behavior, learning and mental
ability, and other obvious or measurable characters.
Lastly, a population is made up of all the organisms of the same group or those
species who live in a particular geographical area and are capable of interbreeding.
Do organisms just simply change to fit or adapt to their environment?
No. Since adaptation is a set of inherited traits, you cannot just change yourself
depending on shifting environmental factors. Adaptation is not something you can do
purposively or intently. For example, bears and wolves are adapted to live in extremely cold
places like the polar region. Their thick fur gives them an advantage over animals without
fur. Other animals without fur, including humans, are not adapted to live in such places. No
matter how much we want to have fur to suit to that kind of environment, we simply cannot.
Remember that any modification or change during your lifetime is not called adaptation. If
you cut the tail of a mother mouse, do not expect her to produce tailless pinkies.
What is natural selection?
Natural selection is the mechanism Darwin proposed to show how evolution came
about. It refers to the differential survival and reproduction of organisms. He further stressed
that in a population, the fittest organisms are those possessing the characteristics that allow
them to acquire more resources, to survive, and to reproduce more than the less fit.
Darwin’s argument for natural selection is based on a series of five observations and three
inferences:
 Observation 1 – Organisms have great potential fertility.
 Observation 2 – Natural populations normally remain constant in size, except for
minor fluctuations.
 Observation 3 – Natural resources are limited.
 Inference 1 – There exists a continuing struggle for existence among members of a
population.
 Observation 4 – All organisms show variation.
 Inference 2 – There is differential survival and reproduction among varying
organisms in a population.
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6.  Inference 3 – Over many generations, differential survival and reproduction generate
new adaptations and new species.
What does the phrase “survival of the fittest” mean?
The phrase survival of the fittest relates to fitness. Fitness depends on how well
certain traits can function in a specific environment. It includes the organism’s ability to
survive, to mate, and to reproduce successfully. It does not necessarily mean biggest,
fastest, or strongest. In fact, a trait may have high fitness in one environment but it can
show low fitness in another.
How are the concepts of natural selection and survival of the fittest related?
Because some organisms survive better than others, natural selection tends to
eliminate less fit characteristics. The fittest are those with favorable traits adapted to a
specific environment. For example, camels and cactuses are adapted to live in dry places
like the desert. This is because camels can store large amounts of water on their backs.
Similarly, cactuses can store water on their fleshy tissues which can prevent them from
dehydration. Other plants and animals that lack these traits similar to camels and cactuses
cannot live in such excessively dry places.
What’s More
Activity 1.3: NATURAL SELECTION AT ITS FINEST😊
This activity is a variation from a common evolution activity. You will have different
'beaks,' making some better suited for a specific food source.
Materials
 Mongo beans
 Marbles
 Rice
 White beans
 Paper cups
 Spoons
 Forks
 Tweezers
 Clothespins
Procedure
 Assume that you are a bird with different types of beak (spoon, fork, tweezer or
clothespin).
 Place the same amount of each food source on each table (island). Spread them out
evenly.
 Time yourself for 30 seconds. You will “eat” as much food as you can.
 Make sure to fill in the table below.
Rules:
a. Each “beak” can pick up one food item at a time.
b. The picked food will be placed in your stomach (paper cup) before getting a
new food item.
c. You will be given thirty (30) seconds to obtain as much food as you can.
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7. ____________________________________________
____________________________________________
____________________________________________
____________________________________________
____________________________________________
____________________________________________
____________________________________________
____________________________________________
____________________________________________
__________________
BEAK
TYPE
# of mongo beans for
each island
# of rice for each
island
# of marbles for
each island
# of white beans
for each island
Fork
Spoon
Tweezer
Clothespin
AVERAGE
 Repeat the activity, but change the type of food on each island.
Example:
 Island 1: everything grows
 Island 2: only rice grows due to excessive moisture
 Island 3: only marbles and white beans grow due to a drought
 Island 4: only mongo beans remain because a hurricane destroyed the
environment’s other food sources
BEAK
TYPE
# of mongo beans for
each island
# of rice for each
island
# of marbles for
each Island
# of white beans
for each island
Fork
Spoon
Tweezer
Clothespin
AVERAGE
Guide Questions:
A. What will happen to the birds that are no longer well-suited to eat the only type
of food the island provides?
B. If each island specializes in a certain type of food, describe what will happen to
the bird population in the next hundreds of years? (Perhaps, you can describe
how they will look in each island.)
C. In your own understanding of this experiment, what is natural selection?
What I Have Learned
Activity 1.4: SCIENTIST AT ITS FINEST!
A. Write the contributions of these scientists in the field of evolution.
1. CHARLES DARWIN
Table 1.1
2. JEAN BAPTISTE DE LAMARCK
_____________________________________________
_____________________________________________
_____________________________________________
_____________________________________________
_____________________________________________
_____________________________________________
_____________________________________________
_____________________________________________
_____________________________________________
_________
Table 1.2
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8. B. What is the relationship between natural selection and survival of the fittest?
_____________________________________________________________________________
_____________________________________________________________________________
_____________________________________________________________________________
What I Can Do
Activity 1.5: FISH WITH FINGER - AN EVOLUTIONARY VIDEO
Instruction: Click the link below and answer the questions that follow.
https://www.pbslearningmedia.org/resource/tdc02.sci.life.evo.fishfingers/fish-with-
fingers/#.XwKa5SgzZ1s
1. What did old theories say about the evolution of land-dwelling animals and why was
the paleontologist, Jenny Clack, dissatisfied with these explanations?
2. What evidence did Clack find to disprove old theories?
3. What kind of explanation behind the evolution of land animals can Clack give based
on current fossil evidence?
Assessment
Multiple Choice: Choose the CAPITAL LETTER of the correct answer. Write your
answers on a separate sheet of paper.
1. Which type of speciation DOES NOT require a geographical barrier?
A. allopatric B. sympatric C. divergent D. convergent
2. Which idea stems from the theory of evolution?
A. The earth is relatively young.
B. Each organism is specially created.
C. Species are related by common descent.
D. A mix of fossils in a region indicates that a local catastrophe occurred.
3. GEORGE LOUIS LECLERC
_____________________________________________
_____________________________________________
_____________________________________________
_____________________________________________
_____________________________________________
_____________________________________________
_____________________________________________
_____________________________________________
_____________________________________________
_________
4. GEORGE CUVIER
____________________________________________
____________________________________________
____________________________________________
____________________________________________
____________________________________________
____________________________________________
____________________________________________
____________________________________________
____________________________________________
______________
B
____
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9. 3. What agent of evolutionary change can result to a population with members that are
alike in appearance, fitness and lifestyle?
A. mutation B. gene flow C. inbreeding D. genetic drift
4. Adaptation promotes __________________.
A. the chance to survive C. the chance to survive and reproduce
B. the chance to reproduce D. none of the above
5. Which of the following statements DOES NOT describe Darwin’s theory of natural
selection?
A. Members of a population will compete.
B. Populations tend to reproduce in small numbers.
C. Members of a population have heritable variations.
D. Some members of a population have adaptive traits.
6. Vertebrate forelimbs are most likely to be studied in _________________.
A. embryology C. biogeography
B. ecology D. comparative anatomy
7. Which pair of animals shows a correct example of homologous structures?
A. wings of a butterfly and wings of a bat
B. flipper of a whale and forelimb of a cat
C. fingers of a human and arm of a starfish
D. tongue of a frog and proboscis of a mosquito
8. Which is NOT true of fossils?
A. They are evidences of life in the past.
B. They indicate that life has a history.
C. They look exactly like modern-day species, regardless of their age.
D. The older the fossils, the less they resemble modern day species.
9. Which of the following statements DOES NOT describe evolution?
A. Evolution is continuous. C. If there is mutation, there is evolution.
B. Evolution refers to change. D. The world is stable and unchanging.
10. During the usual process of speciation, a species is first isolated _____________.
A. genetically B. behaviorally C. geographically D. reproductively
11. Which of the following phrases best describes the process of evolution?
A. the change of populations through time
B. the change of organisms from simple to complex
C. the development of man from monkey-life ancestors
D. the development of characteristics in response to need
12. Marine mammals have many structural characteristics in common with fish. The
explanation that evolutionary theory would give for this similarity is that
___________________.
A. fish and mammals are closely related
B. marine mammals never developed the use of limbs
C. marine mammals evolved directly from fish
D. fish evolved structures similar to those already existing in mammals
13. An alternation in the arrangement of nucleotides in a chromosome, possibly resulting
in either a structural or physiological change in the organism is called ___________.
A. gene flow C. a recessive gene
B. genetic drift D. natural selection
14. It is thought that there was a rapid evolutionary rate once animal life invaded land
from the oceans. The explanation given for this rapid evolution is that
________________.
A. the land was a perfect haven for life
B. the radiation from the sun caused many mutations
C. there were many potential habitats for new forms to fill
D. there were many climatic changes occurring at that time
15. The first animals to settle on land probably had which of the following characteristics?
A. They were quite mobile to escape from predators.
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10. B. They were partially dependent upon water for survival.
C. They had wings for flight from one habitat to another.
D. They were capable of completely adapting to the terrestrial environment in
their life span.
Lesson
2
Evidences of Evolution
Can the process of evolution be described theoretically,
or can it be actually observed? Evidences to support the theory of evolution have been
coming in from different areas in science. Let’s look at some of these evidences in this
lesson. The evidences are divided into two groups: direct and indirect. However, experts are
still arguing as to what the direct evidences and indirect evidences truly are. This issue is yet
to be resolved.
Organisms that dwell on Earth have changed overtime in terms of their structures,
traits and abilities which allowed them to adapt and survive in their environment. Data from
the fossil records, anatomy and morphology, embryonic development and biochemistry could
be analyzed to demonstrate if evolution of life on earth has really taken place.
What’s New
As mentioned earlier, there are two evidences to prove the existence of evolution, the
direct and indirect evidences.
Direct Evidence
Direct evidence is something that can be directly observed or seen. Fossils are the
remains or impressions that are preserved on the earth’s crust left by an animal or a plant.
Indirect Evidence
Indirect evidence refers to those proofs that does not involve actual observation of
evolution but for which we can infer that evolution has indeed taken place. Many scientists
considered genetics, comparative anatomy, embryology, and biogeography as indirect
evidences for evolution.
ACTIVITY 2.1: WHAT A THUMB CAN DO FOR YOU
Do you know how important your thumbs are? Only primates have hands capable of
grasping objects. The grasp is made possible by the opposable thumbs. Are you aware
that you perform a lot of tasks using your thumb and fingers? Have you experienced doing
a series of tasks without the aid of your thumb?
Ask your sibling to tape your thumbs to the palms of each hand with a masking tape.
Be careful not to wrap the tape too tightly because it will cut off the blood circulation to your
hand. Then do the following:
A. pick up a drinking glass
B. pick up your pencil
C. turn the doorknob
D. unbutton or rebutton a shirt
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11. Figure 2.1 Fossils provide direct evidence of evolution
Figure 2.2 Examples of homologous structures
Figure 2.3 Examples of analogous structures
E. write your name using a pen
Question
How is having an opposable thumb helping all primates, especially humans, to adapt
to their environment and survive better than other animals?
What Is It
Fossils: Evidence of Past Life
According to many experts, fossil provides direct evidence for evolution because it can
tell what has happened in the past. In other words, it can prove that change in time has
occurred. When certain fossils are arranged in the order of how old they are, we can make a
direct comparison of their body structures. Through these fossil evidences, experts can
confirm that species are not fixed but can evolve into other species over time.
Problems Encountered in
Interpreting Fossil Evidences
Experts are having
difficulty interpreting fossil
evidence because fossil records are
relatively incomplete. Why is this so? First, only a small number of fossils have been found.
Throughout history, many organisms just die and vanish without leaving a single trace.
Second, the quality of preservation also varies. Some are preserved so perfectly while some
are not. For instance, soft tissues are rarely preserved. Third, erosion and earthquakes can
destroy some fossils. Finally, some remains of organisms are preserved only in places with
favorable conditions.
How do homologous, analogous and vestigial structures indicate that evolution has
or has not occurred?
Comparing the anatomy and the development of
organisms reveals a unity of plan among those that are
closely related. The more body structures that two
species have in common, the more closely they are
related. It supports the idea of “descent from a common
ancestor”.
Homologous and Analogous Structures
Similar structures in different species irrespective of their functions are called
homologous structures. Homology seems to indicate descent from a common ancestor.
The limb skeletons of vertebrates are considered as homologous structures.
Analogous structures, on the contrary, are
structures, which are different in appearance but have
the same function. Analogy does not indicate common
ancestry. Examples of analogous structures are the
legs of insects and mammals and the wings of
butterflies and birds.
Trilobite fossil Dinosaur skull
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12. Lastly, vestigial structures also provide further evidence for evolutionary change.
Vestigial structures are anatomical features that are usually reduced and have no function in
many organisms. These are organs that were once functional in the ancestors of the
species but only became remnants in the present species. For example, skeletal limbs
found in some snakes have no known use to these animals. In humans, appendix is thought
to have no use, but in other mammals, it aids in the digestion of cellulose.
Vestigial Structures Found in Humans
Some Asserted Vestigial Organs in Man
Coccyx (tail bone) Adenoids
Thymus Appendix
Pineal Gland Body hair
Nodes on ears or “Darwin’s points” Ear muscles for wiggling
Tonsils Nictitating membrane of eye
Nipples on males Parathyroid
Little Toe Wisdom teeth
Evidence from Genetics and Molecular Biology
Living things share several similar biochemical molecules, such as DNA, ATP, amino
acids, and enzymes. This finding supports the claim that living things descended from a
common ancestor. The more closely related organisms are, the more similar is their
biochemical makeup.
How can biogeography prove descent from a common ancestor?
Biogeography is the study of the distributions of organisms. Darwin’s trip around
South America allowed him to observe the diversity of organisms in different areas and the
resemblance of such species of birds and tortoises in an island to a nearby mainland.
Darwin believed that the group of animals in each island is adapted to a different way of life.
However, he claimed that the common ancestors of these organisms had come from one
locale, spreading out into other accessible areas.
How does embryology support evolution?
The unity of plan shared by vertebrates extends to their embryological
development. The embryonic development of all vertebrates shows remarkable similarities.
At some time during development, all vertebrates have a supporting dorsal rod, called a
notochord, and exhibited paired pharyngeal pouches. This could indicate that an organism
passes through some of the embryonic stages that its ancestors passed through. Then
several modifications happened in ways appropriate to an organism’s final form.
Activity 2. 2: LESSON LEARNED - AN EVOLUTIONARY CONCEPT
Instruction: Visualize the relationships between various concepts of evidences that support
evolution and test your understanding on the complex subjects stated in the lesson.
For each question below, explain whether the evidence is comparative anatomy
(homologous structures), comparative anatomy (analogous structures), DNA
What’s More
10

13. analysis, or from a fossil record. Afterward, in complete sentences, explain why it
is an evidence for evolution. Use this as your guide:
Question A: What type of evidence is this?
Question B: Why is this an evidence of evolution?
1. Humans, chimpanzees, whales, and bats all have the same bones in their
arms, fins, or wings.
A. ______________________________________________________
B. ______________________________________________________
2. Scientists find fossilized bones of a huge animal that no longer exists today.
A. ______________________________________________________
B. ______________________________________________________
3. The human gene of your muscle protein is different from the monkey muscle
protein in 4 places and different from a chicken’s gene in 25 places.
A. _______________________________________________________
B. _______________________________________________________
4. Honey possums lick nectar from flowers using a long tongue made of soft
muscle. Butterflies lick nectar from flowers using a long tongue made of hard
protein.
A. _______________________________________________________
B. _______________________________________________________
5. Humans, rabbits, and zebras all have an appendix, an extra piece in their
digestive system; although in humans it’s much smaller.
A. ___________________________________________________________
B. ___________________________________________________________
What I Have Learned
Activity 2.3: TRUTH OR NONSENSE!
Modified True or False: Write True if the statement is true and if its false, underline the
word/s that make it incorrect and write the correct answer on the space provided.
_______________1. About 200 years ago, many people believed that the Earth
was only 6,000 years old.
_______________2. Artificial selection occurs when nature selects the beneficial traits.
_______________3. The individual Galápagos Islands are all similar to each other.
_______________4. Malthus argued that human populations grow faster than their
resources.
_______________5. Lamarck was one of the first scientists to propose that species
evolved by natural selection.
_______________6. Lyell was one of the first to say that the Earth must be far older than
most people believed.
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14. _______________7. Lamarck’s inheritance of acquired characteristics has become a
widely accepted scientific theory.
_______________8. Fossils proved to Darwin that species can evolve.
_______________9. The term fitness refers to an organism’s ability to outrun its hunters.
_______________10. Darwin published his findings soon after returning to England
from the voyage of the Beagle.
_______________11. According to Darwin, natural selection is what occurs and
evolution is how it happens.
_______________12. During his journey aboard the Beagle, Darwin found fossils from
the seas in the mountains.
_______________13. Galápagos tortoises have differently shaped shells depending on
where they live.
_______________14. Darwin’s book changed science forever.
_______________15. Alfred Russel Wallace developed a theory of evolution at the same
time as Darwin.
What I Can Do
Activity 2.4: WORD SEARCH MAKING
Instruction: Make a Word Search puzzle using the terms you have learned about evolution.
sample only
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15. Assessment
Multiple Choice: Choose the CAPITAL LETTER of the correct answer.
1. Individuals within a species tend to be genetically different. The primary mechanism
generating this individual variability is ___________.
A. meiosis D. duplications
B. mitosis E. asexual reproduction
C. polyploidy
2. The evolutionary theory proposed by Charles Darwin was the __________________.
A. spontaneous generation of new organisms
B. passing on of genes from one generation to the next
C. change in populations through time as a result of mutations
D. change in populations through time as a response to environmental
change
3. The presence of a tropical rain forest fossil forms in Canada can best be explained by
_______________________.
A. an uplifting of lowland areas
B. a major climatic shift on the earth
C. a drifting of continents into a northward direction
D. a shifting of environmental requirements by these types of species
4. The wing of a bat and the forelimb of a dog are said to be homologous structures.
This indicates that _____________________.
A. they both have the same function
B. bats evolved from a lineage of dogs
C. the limb bones of each are anatomically identical
D. they are structures which are similar due to common ancestry
5. Using radioactive dating techniques, the first life seems to have appeared on Earth
about _____________________.
A. 10 thousand years ago D. 4.5 million years ago
B. 270 million years ago E. 10 billion years ago
C. 3.3 billion years ago
6. When first proposed, Darwin's theory of natural selection did not fully explain how
evolution occurred. This was due to ____________________________.
A. Darwin's failure to recognize the tendency of organisms to over-
reproduce
B. Darwin's initial overemphasis of the significance of genetic drift
C. the fact that accurate mechanisms explaining genetic inheritance
were not widely known
D. the absence of accurate descriptions of the embryological
development of most plants and animals
E. the absence of biochemical techniques to determine the genetic
similarities between species
7. Which of the following phrases best describes the process of evolution?
A. change of populations through time
B. the change of organisms from simple to complex
C. the development of man from monkey-life ancestors
D. the development of characteristics in response to need
8. The most compelling evidence for a large-scale evolutionary change or
macroevolution is the ________________.
A. fossil records
B. occurrence of mass extinctions
13

16. C. domestication of plants and animals
D. observed increase of mutation rates across all species
9. Marine mammals have many structural characteristics in common with fish. The
explanation that evolutionary theory would give for this similarity is that __________.
A. fish and mammals are closely related
B. marine mammals evolved directly from fish
C. marine mammals never developed the use of limbs
D. marine mammals adapted to an environment similar to that of the fish
10. A sudden major climatic change would most likely initially result in _____________.
A. an increase in mutation rates
B. a rapid increase in extinction rates
C. a rapid increase in adaptive radiation
D. a sharp increase in the numbers of species
11. An alternation in the arrangement of nucleotides in a chromosome, possibly resulting
in either a structural or physiological change in the organism, is called _______.
A. gene flow C. genetic drift
B. mutation D. natural selection
12. The population of Florida panthers has been drastically reduced by the actions of
man. Which of the following most likely threatens their ability to continue to evolve
in response to the pressures of their environment?
A. There is no longer the prospect of over-reproduction.
B. There is no longer the prospect of a struggle for limited resources.
C. There is a lack of genetic variation for selection to act upon.
D. There is no longer the prospect of a trait conferring a reproductive
advantage.
13. It is thought that there was a rapid evolutionary rate once animal life invaded land
from the oceans. The explanation given for this rapid evolution is that
_________________.
A. there were many potential habitats for new forms to fill
B. the land was a perfect haven for life
C. there were many climatic changes occurring at that time
D. radiation from the sun caused many mutations
14. The first animals to settle on land probably had which one of the following
characteristics?
A. They were quite mobile to escape from predators.
B. They were partially dependent upon water for survival.
C. They were capable of completely adapting to the terrestrial
environment in their life span.
D. They had wings for flight from one habitat to another.
15. Two islands are found in the middle of the Pacific Ocean isolated from any other land
mass. These two islands were at one time connected by a land bridge and are of
recent origin. They have identical plant and animal life and are separated by 50 miles
of ocean. Assuming different selection pressures, which of these island populations
would be most likely to be reproductively isolated, possibly allowing for species
divergence?
A. birds C. dandelions with airborne seeds
B. mice D. coconuts with floating seeds
14

17. At the end of the lesson, you will be able to:
1. identify the process of evolution;
2. enumerate the specific conditions for evolution to occur; and
3. explain speciation and its two types.
Lesson
3
Process of Evolution
When Darwin wrote his book On the Origin of Species, he knew nothing about
genetics. Today, population geneticists apply the principle of genetics to determine
evolutionary relationships among species. From the geneticist point of view, evolution is
defined as a change in the gene pool. Do you know what a gene pool is? Gene pool
pertains to the genetic composition of individuals in a population. More on this will be
discussed later.
What I Need to Know
What’s New
Activity 3.1: AGENTS OF EVOLUTIONARY CHANGE
A. Instruction: Label each statement with the correct agent of evolutionary change. Write
the letter only on a separate sheet of paper.
A. Gene flow D. Natural selection
B. Genetic drift E. Non-random mating
C. Mutations
1. A female peacock chooses mates with the most colorful feathers.
2. Bacteria and insects have become resistant to agents that formerly killed them.
3. During the American and Vietnamese Wars, many U.S. soldiers had children
with Vietnamese women.
4. Giraffes with longer neck get a larger share of resources and tend to have more
offspring.
5. The Inca Indian population was founded by a small number of individuals, all of
which had type O blood.
B. Instruction: Answer the following questions:
1. Can you explain why some extinct plants and animals were not fossilized?
2. Imagine that your friend tells you, “men came from apes” because many structural
and biochemical similarities are found between them. How would you react to this?
3. What does it mean by direct evidence for evolution? Indirect evidence for evolution?
4. Do you agree that fossils provide direct evidence for evolution? Why or why not?
_______
_
_______
_
_______
_
_______
_
_______
_
15

18. What Is It
PROCESS OF EVOLUTION
In this section, you will explore on how genetics can help prove that evolution indeed
existed.
Gene Pool
Gene pool pertains to the genetic composition of individuals in a population. Let’s
say, in a population of puppies, the gene pool is 50 pure black puppies, 25 spotted (black
and white) puppies, and 25 pure white puppies. If all the males and females in the same
population will mate and reproduce, there is a tendency for the gene pool to remain the
same for generation after generation. This simply means that no change in the gene pool or
genetic composition will occur.
So how does evolution or change in the gene pool occur?
In real life, animals migrate and find other mates, their genes continually mutate, and
nature allows the fittest organisms to survive. When these conditions happen, evolution has
been proven to occur. Let’s discuss further the specific conditions on this event.
1. Non-random mating
By non-random mating, we mean that sexual selection is not merely by chance.
Individual’s choice of mate is influenced by some physical and behavioral characteristics.
For example, white rabbits preferentially mate with rabbits of their own color. Among
humans, tall women prefer tall men rather than short men.
Inbreeding, commonly observed in plants and in some kinds of animals, is a very
good example of non-random mating. Inbreeding in plants is sometimes called self-
fertilization. Animals like dogs, rats, cats, rabbits, pigs, and many other animals practice
inbreeding. Inbreeding can result to a population with members that are alike in
appearance, fitness, and lifestyle.
2. Mutation
An organism’s appearance is dictated by the information stored in its chromosomes.
So, if the chromosome’s structure or gene composition is changed, the appearance of the
organism will also change. Any change in the structure of chromosomes and gene
composition is called mutation.
What causes mutation? There are several agents for mutation (mutagens) like ultra
violet radiation and exposure to hazardous chemicals in the environment. These mutagens
can change the information stored in the individuals’ chromosomes or genes. Therefore,
when mutation occurs, the appearance of individuals in the population changes and the
gene pool becomes different from the original population.
3. Genetic drift
Genetic drift refers to the change in gene pool due to chance alone. Unpredictable
disasters or accidents such as earthquakes, floods, fires and diseases can reduce or totally
eliminate certain traits in the population. For instance, flood wiped out a population of ants.
No matter how good the ants were adapted to their environment, they could be killed by
such event. In this situation, the survival or death of individuals in the population has nothing
to do with their fitness.
Genetic drift is also observed when a harmful insecticide killed a big population of
fruit fly, leaving a few members with a particular trait. The next generation of fruit flies will
16

19. inherit only the trait present in the survivors. The success of this trait is due to chance but
not because it is the fittest trait.
Genetic drift also happens when a small population breaks off from a larger
population and forms a new population. The resulting population inherits the traits of the
founders, so the new population becomes very different from the ancestral population.
This mechanism is manifested among the cattle in Iceland. The ancestors of these
cattle are believed to have come from a small group that was brought to the island more
than a thousand years ago. Studies revealed that the genetic make-up of the Icelandic
cattle is now different from that of their cousins in Norway.
Do you know that some families or groups of people isolated themselves from the
surrounding populations?
One example is the Amish group of Pennsylvania. This isolated group was founded
by a family that carries a very rare condition known as Ellis-van Creveld Syndrome. The
Amish people with this syndrome has an unusual dwarfism and polydactylism, or extra
fingers. Today, this rare syndrome is still common among the Amish group.
4. Natural Selection
Nature selects which trait will survive and which will not. These organisms with
favorable traits, meaning those who are best suited in the environment, have a better chance
of survival. The survivors pass on the favorable traits to their offspring, then after many
generations, the population will produce organisms with traits that are very different from
their ancestors.
5. Gene Flow
Gene flow occurs when individuals migrate from one population to another. This
tendency increases variations in the population. An effective sharing of traits happens when
one migrates and interbreeds with the individuals of the newly found population. Often, this
results to an increase in the intermediate phenotypes in the group.
Gene flow can also occur without migration. When people travel to another area and
interbreed with the existing population there, an effective exchange of genes occurs between
the reproducing individuals, even though the traveler returns home. For example, during the
U.S and Vietnam War in early 1970’s, many American soldiers had children with Vietnamese
women. Because of that, the gene pool of the Vietnamese population was altered.
Look around you. Have you noticed that plants and animals are so diverse? There
are red, white, pink, and yellow rose flowers. There are white, brown, and black dogs, some
are big, and some are small. Gene flow or genetic exchanges made this abundant diversity
possible.
Human species is very diverse, too. Asians, Americans, Africans, Europeans are
physically different. However, no matter how diverse the human population has become,
humans still remain as one species as long as the members continue to interbreed
successfully and share a common gene pool.
What happens when gene flow does not occur between the populations?
If gene flow is absent, populations will become reproductively isolated and over time
the populations will become separate species – a process known as speciation.
What is speciation?
Speciation is simply the formation of new species. Oops! You should not confuse
evolution with speciation! Evolution can lead to speciation. Speciation requires numerous
changes in the gene pool of a population, usually over a long, long period of time. By
definition, a species is a group of organisms that are able to interbreed successfully and
produce fertile offspring who themselves can reproduce. Each species is reproductively
isolated from every other species.
Normally, gene exchange occurs only between the populations of a species but not
between populations of different species. In other words, members of a species cannot
17

20. interbreed with members of another species. For example, Felis tigris (tiger) is one of the
cat species, but they cannot reproduce with Felis domestica (domesticated cat), which is
another cat species. Man is a primate; it reproduces only with man but not with other
primates like apes and monkeys.
What are the two types of speciation?
There are two types of speciation: allopatric and sympatric. In allopatric
speciation, a population is split into two by a geographic barrier. The barrier may be a
mountain, river, ocean, valley, desert, or anything that physically prevents the mating
between individuals of two populations of the same species.
The two sub-populations can experience the mechanisms we have mentioned
previously (natural selection, mutation, or genetic drift). Gradual changes can also
accumulate to each of the sub-populations until they become very different from each other.
If they do come to occupy the same territory again and successful mating occurs, speciation
will not take place. But if they fail to reunite and produce offspring, speciation will take
charge and it will result to them becoming separate species.
Meanwhile, in sympatric speciation, two or more species arise from a single
ancestral species in the absence of physical barriers. Some pre-mating and post-mating
barriers such as food preference, mating behavior or sterility, prevent effective gene
exchange between the reproducing individuals. And when reproductive isolation has been
established, speciation is said to have occurred.
Instruction: Read the passage and answer the questions that follow.
The Voyage of the Beagle
In 1831, when Darwin was just 22 years old, he set sail on a scientific expedition on
a ship called the HMS Beagle. He was the naturalist on the voyage. As a naturalist, it was
his job to observe and collect specimens of plants, animals, rocks, and fossils whenever the
expedition went ashore.
Darwin was fascinated by nature, so he loved his job on the Beagle. He spent more
than 3 years of the 5-year trip exploring nature in distant continents and islands. While he
was away, a former teacher published Darwin’s accounts of his observations. By the time
Darwin finally returned to England, he had become famous as a naturalist.
Darwin’s Observations
During the long voyage, Darwin made many observations that helped him form his
theory of evolution. For example:
• He visited tropical rainforests and other new habitats where he saw many plants
and animals he had never seen before. This impressed upon him the great
diversity of life.
• He experienced an earthquake that lifted the ocean floor 2.7 meters (9 feet)
above sea level. He also found rocks containing the fossils of sea shells in
mountains high above sea level. These observations suggested that
continents and oceans had changed dramatically over time and continued to
change in dramatic ways.
What’s More
18

21. • He visited rock ledges that had clearly once been beaches that gradually built up
over time. This suggested that slow, steady processes also changed the
Earth’s surface.
• He dug up fossils of gigantic extinct mammals, such as the ground sloth. This
was hard evidence that organisms looked very different in the past. It
suggested that living things, like the Earth’s surface, can also change over
time.
The Galápagos Islands
Darwin’s most important observations were made on the Galápagos Islands. This is
a group of 16 small volcanic islands 966 kilometers (600 miles) off the west coast of South
America.
Individual Galápagos Islands differ from one another in important ways. Some of
these islands are very rocky and dry at the same time. Others have better soil and more
rainfall. While observing here, Darwin noticed that the plants and animals on the different
islands also differed. For example, the giant tortoises on one island had saddle-shaped
shells, while those on another island had dome-shaped shells. People who lived on the
islands could even tell the island where a turtle came from just by looking at its shell.
This circumstance started Darwin to think about the origin of species. He wondered
how each island came to have its own type of tortoise.
Guide Questions
1. What was Darwin’s role on the Beagle?
2. What was significant about the new habitats Darwin visited?
What I Have Learned
What are the things that you have learned from this module?
1. Creationism is the idea that living things are created and have remained unchanged
since the beginning.
2. Catastrophism is the idea that violent and sudden natural catastrophes have
resulted to the death and extinction of most plants and animals. After each
catastrophe, God created new sets of life forms.
3. Uniformitarianism claims that large geological changes occurred, not in catastrophic
events, but by the gradual accumulation of small geological changes over long
periods of time.
4. Jean Baptiste de Lamarck believed that the environment could bring about inherited
change.
5. Darwin proposed the theory of evolution through natural selection. He believed that
all organisms share a common ancestor.
6. Evidences for evolution come from many sources. Evidences are classified as direct
and indirect. Direct evidence means something that can be directly observed or
seen. Fossils provide direct evidence for evolution. Indirect evidence is something
19

22. that does not involve actual observation of evolution but for which we can infer that
evolution has taken place. Genetics, comparative anatomy, embryology, and
biogeography offer indirect evidences.
7. Similar structures in different species irrespective of their functions are called
homologous structures. Analogous structures are those that generally perform the
same function though possibly in very different ways. Vestigial structures are
anatomical features present in organism but have no function.
8. Natural selection is not the only driving force for evolution to occur, other
mechanisms include non-random mating, gene flow, genetic drift, andmutations.
9. Two types of speciation are identified: allopatric and sympatric. Allopatric speciation
happens when a population is split into two by a geographic barrier. In sympatric
speciation, a population is split into two or more in the absence of physical barriers.
What I Can Do
Activity 3.2: LETTER TO THE EDITOR
A. Take this situation: As you flip through a newspaper, you have suddenly noticed that
the front-page article talks about evolution. You are curious! Since you are becoming
an expert on evolution, you started to read it. These are the first 4 sentences of the
article:
There is no way that evolution happened. It is something that scientists
made up. There is no proof that it has ever happened. How can we even know
what happened millions of years ago?
After reading the whole article, you feel that it is your duty as a science scholar to
write a letter to the editor of this newspaper to provide facts about evolution to the
public.
Please follow these guidelines:
1. Begin the letter with: Dear Editor,
2. Write a paragraph (with at least 6 sentences) about how scientists know that
evolution indeed happened, or that life has truly changed over time.
3. In your paragraph, use, UNDERLINE, and explain the following terms: -
evolution, comparative anatomy, homologous structures, DNA, & fossil
3. At the end, sign your name.
20

23. Assessment
Multiple Choice: Choose the CAPITAL LETTER of the correct answer. Write the
chosen letter on a separate sheet of paper.
1. The extinct species Archaeopteryx had characteristics of both birds and reptiles. This
is an example of a/an ______________.
A. archetype C. intermediate form
B. trace fossil D. convergent species
2. The earliest fossils found in the geologic record are said to belong to the _________.
A. fungi C. protozoa
B. bacteria D. seed plants
3. Radiometric dating techniques rely on the fact that _____________________.
A. the bony portions of organisms decompose at a known rate
B. organisms which lived earlier in time will tend to be found in sediments
below the organisms which lived more recently
C. the magnetic field of the earth has reversed its polarity at known time
intervals in geological time
D. the earth contains elements that change into other elements at a
constant known rate
4. Which of the following best represents Lamarck's ideas on the evolutionary process?
A. neutral drift C. punctuated equilibrium
B. survival of the fittest D. inheritance of acquired characteristics
5. Which of the following is NOT a part of Darwin's theory of natural selection?
A. Individuals of a population vary.
B. Organisms tend to over-reproduce themselves.
C. There are limited resources for which individuals compete.
D. Modifications an organism acquires during its lifetime can be passed
on to its offspring.
6. The life histories of five birds of the same species are listed below. The most
evolutionally successful bird is the one that __________________.
A. lives 5 years, lays 12 eggs in a lifetime, and 4 will hatch
B. lives 2 years, lays 8 eggs in a lifetime, and 5 will hatch
C. lives 6 years, lays 2 eggs in a lifetime, and 2 will hatch
D. lives 4 years, lays 7 eggs in a lifetime, and 6 will hatch
7. Vertebrate forelimbs are most likely to be studied in _____________.
A. ecology C. biogeography
B. embryology D. comparative anatomy
8. Which is NOT true of fossils?
A. They indicate that life has a history.
B. They are evidences of life in the past.
C. The older the fossils, the less they resemble modern-day species.
D. They look exactly like modern-day species, regardless of their age.
9. Which idea stems from the theory of evolution?
A. The earth is relatively young.
B. Each organism is specially created.
C. Species are related by common descent.
D. A mix of fossils in a region indicates that a local catastrophe occurred.
10. Which pair of animals shows a correct example of homologous structures?
A. wings of a butterfly and wings of a bat
B. flipper of a whale and forelimb of a cat
C. fingers of a human and arm of a starfish
21

24. D. tongue of frog and proboscis of a mosquito
11. During the usual process of speciation, a species is first isolated ______________.
A. genetically C. geographically
B. behaviorally D. reproductively
12. Which of the following statements DOES NOT describe Darwin’s theory of natural
selection?
A. Members of a population will compete.
B. Populations tend to reproduce in small numbers.
C. Members of a population have heritable variations.
D. Some members of a population have adaptive traits.
13. What agent of evolutionary change can result to a population with members that are
alike in appearance, fitness and lifestyle?
A. mutation C. inbreeding
B. gene flow D. genetic drift
14. Which type of speciation DOES NOT require a geographical barrier?
A. allopatric C. divergent
B. sympatric D. convergent
15. Which of the following statements DOES NOT describe evolution?
A. Evolution is continuous.
B. Evolution refers to change.
C. The world is stable and unchanging.
D. If there is mutation, there is evolution.
Assessment (Post-Test)
Multiple Choice: Choose the CAPITAL LETTER of the correct answer. Write the
chosen letter on a separate sheet of paper.
1. Which idea stems from the theory of evolution?
A. The earth is relatively young.
B. Each organism is specially created.
C. Species are related by common descent.
D. A mix of fossils in a region indicates that a local catastrophe occurred.
2. Which of the following phrases best describes the process of evolution?
A. change of populations through time
B. the change of organisms from simple to complex
C. the development of man from monkey-life ancestors
D. the development of characteristics in response to need
3. An alternation in the arrangement of nucleotides in a chromosome, possibly resulting
in either a structural or physiological change in the organism, is called:
A. gene flow B. mutation C. genetic drift D. natural selection
4. The first animals to settle on land probably had which one of the following
characteristics?
A. They were quite mobile to escape from predators.
B. They had wings for flight from one habitat to another.
C. They were partially dependent upon water for survival.
D. They were capable of completely adapting to the terrestrial environment in
their life span.
5. During the usual process of speciation, a species is first isolated
A. genetically C. geographically
B. behaviorally D. reproductively
6. Which of the following statements DOES NOT describe evolution?
A. Evolution is continuous.
B. Evolution refers to change.
22

25. C. The world is stable and unchanging.
D. If there is mutation, there is evolution.
7. Which type of speciation DOES NOT require a geographical barrier?
A. allopatric B. sympatric C. divergent D. convergent
8. An alternation in the arrangement of nucleotides in a chromosome, possibly resulting
in either a structural or physiological change in the organism, is called:
A. gene flow C. natural selection
B. genetic drift D. a recessive gene
9. The first animals to settle on land probably had which one of the following
characteristics?
A. They were quite mobile to escape from predators.
B. They had wings for flight from one habitat to another.
C. They were partially dependent upon water for survival.
D. They were capable of completely adapting to the terrestrial environment in
their life span.
10. Individuals within a species tend to be genetically different. The primary mechanism
generating this individual variability is:
A. meiosis B. mitosis C. polyploidy D. duplications
7. Which of the following statements DOES NOT describe evolution?
A. Evolution is continuous.
B. Evolution refers to change.
C. The world is stable and unchanging.
D. If there is mutation, there is evolution.
12. Which idea stems from the theory of evolution?
A. The earth is relatively young.
B. Each organism is specially created.
C. Species are related by common descent.
D. A mix of fossils in a region indicates that a local catastrophe occurred.
13. Vertebrate forelimbs are most likely to be studied in _________.
A. ecology C. biogeography
B. embryology D. comparative anatomy
14. Which is NOT true of fossils?
A. They indicate that life has a history.
B. They are evidences of life in the past.
C. The older the fossils, the less they resemble modern day species.
D. They look exactly like modern-day species, regardless of their age.
15. The most compelling evidence for large-scale evolutionary change or macroevolution
is ________________.
A. the fossil record
B. the occurrence of mass extinctions
C. domestication of plants and animals
D. Kettlewell's release-recapture experiment with peppered moths
23

26. Answer Key

27. References
Department of Education - Learner’s Manual Science Grade 10, first edition, 2015
H. Acosta, et al., (Science 10 Learners Material (Pasig City: Rex Bookstore, 2015)
pp. 299-322.
Ronald Diana, Grade 8 Science Modules, 2015 edition (Tru-copy Publishing House,
Inc. 2015).pp.8-10.
ONLINE REFERENCES:
https://www.khanacademy.org/science/biology/her/evolution-and-natural-selection/a/darwin-
evolution-natural-selection.Accessed on June 24, 2020 by J.D. Gomonan
https://www.redlandsusd.net.Accessed on July 1, 2020 by J.D.Gomonan
http://www.iq.poquoson.org. Accessed on July 2, 2020 by J.D. Gomonan
https://www.britannica.com/biography/Georges-Cuvier.Accessed on July2, 2020 by J.D.
Gomonan

28. For inquiries and feedback, please write or call:
Department of Education – Bureau of Learning Resources (DepEd-BLR)
DepEd Division of Bukidnon
Fortich Street, Sumpong, Malaybalay City
Telefax: (088) 813-3634
E-mail Address: bukidnon@deped.gov.ph