Senior High School

Earth and Life

Science
Unifying Themes in the Study of Life
and Animal Reproduction
(Week 16)
 What I Know

Pretest: Read the sentences or questions carefully. Choose the letter of the
correct answer.

1. This is that which contains all life on earth.

a. ecosystem b. biosphere c. community d. earth

2. This is a chemical structure consisting of two or more atoms.

a. atomic number b. mixture c. solution d. molecule

3. This is the fundamental unit of structure and function among organisms.

a. cell b. tissue c. organ d. organ system

4. This is a type of cell that lacks a true nucleus and membrane-bound organelles.

a. prokaryotic b. eukaryotic c. sex cell d. muscle cell

5. This is the form of that genetic materials take in chromosomes.

a. DNA b. RNA c. Gene d. Chromatid

6. This is the entire collection of genetic instruction that an organism inherits.

a. genome b. gene expression c. genomics d. alleles

7. Producers in a food chain or web are _______ in nature.

a. heterotrophic b. singular c. single-celled d. photosynthetic

8. He is the father of evolution.

a. Alexander Graham Bell

b. Copernicus

c. Charles Darwin

d. Gregor Mendel

9. This is the ideal duration of pregnancy among humans.

a. 32 weeks b. 34 weeks c. 36 weeks d. 38 weeks

10. Which of the following is a type of sexual reproduction?

a. hermaphroditism b. fragmentation c. budding d. parthenogenesis

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 Unifying Themes in the Study
Lesson of Life
1
What I Need to Know

The study of life in general is very wide. And to help us understand this
vastness, are what we call themes. Themes are distinct characteristics, pattern, and
or quality. To help us understand better the study of life, we can look at themes
individually and as a collective. In this way, we can easily digest the commonalities of
those exhibiting life.

The unifying themes in the study of life are an organization, information, energy
and matter, interactions, and evolution. The study of organisms ranges from macro to
micro or vice versa. This means that the study of life can be from the planet earth as
a planet that can host life to the molecular level that comprises that life. The good
thing, however, is that these large chunks of concept can be broken into smaller ones.
Let us explore quickly these levels in the table below:

Table 1.1 Levels of Biological Organization

Levels Characteristics / Definition
1. Molecules These refer to chemical structures that are composed of
two or more atoms.
2. Organelles These are parts of the cell which are responsible for
function and integrity. Some are membrane bound while
others are not.
3. Cells These are the basic working and structural unit of an
organism. Different cells work in different organs. They are
structured according to function. Organisms can either be
single-celled or multicellular in nature.
4. Tissues These are simply cells grouped together and performs a
specialized function.
5. Organ This this a body part or a part of an organism which is
made up of a group of tissues. An organ functions,
specifically in a body.
6. Organism This refers to the individual living species. Each thriving
plant or animal is an organism.
7. Populations These refer to all individuals of a species living in a
specific area. Let us take for example a population of
crabs living in a coastal area.

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8. Communities These are the variety of species inhabiting a specific area.
An example would be a coastal community. In this
community, we would expect to see a variety of animal
and plant species that thrives in coastal areas. Thus, a
community is a combination of different populations.
9. Ecosystems These refer to the biotic and abiotic factors in an area. This
includes not only the interaction between living things but
also the interaction between living and nonliving.
10. Biosphere This consists of all the livable parts of the earth, by livable,
we are referring to all spaces which is inhabited by life.
This includes spaces in land, water, and air.

Source: https://www.simply.science/index.php/organization-of-life

Figure 1.1 The levels of Biological Organization

In the field of biology, not only is organization important as it gives a

compartmentalized focus on the different fields within biology but more importantly it
gives us a glimpse of new characteristics that are not present in the previous hierarchy
of organization. These characteristics we refer to as, emergent properties, are a
cause of the interaction and position or arrangements of the previous organization’s
parts. This allows for the subsequent organization to be more complex than the
previous.

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 What’s New
Activity 1: Designing an Experiment for Life

Objective: This activity is aimed at better understanding and appreciation of the

themes in the study of life. After this activity, you are expected to be able to determine
the themes of biology as they relate to the properties of life.

Materials: mung bean seeds

Pot
Soil
Measuring tools
Other materials (as needed by the experiment design)

Procedure:

1. Propose a hypothesis
From common knowledge, you already have an idea as to what plants need
to grow healthy, like water and sunlight. Think of other factors or substances
that will affect plant growth (suggestions: type of soil, fertilizer type, music
or human voice). Choose a variable, then propose a hypothesis about how
the presence and absence of that factor affects the growth or survival of a
plant.

2. Conduct your experiment

a. Outline the steps of your experiment. Identify the variable and
controls in your experiment. NOTE: There should only be one
experimental variable – the presence or absence of the factor you
are testing.
b. Determine the time period for your experiment.
c. Specify the data that you will observe in the experimental and control
setups. Choose the data that can be accurately measured and
compared.
d. Conduct your experiment and record your observations.

3. Analyze your data

a. Compare the measured data from the experimental and control
plants.
b. Organize your data into a table.
c. Make a graph to display your results.

4. Draw conclusion
Did the presence of your experimental variable make a difference in the
growth of the experimental and control plants? Was the effect more or
less than you had proposed?

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 What Is It

In this activity you are made to design an experiment that will allow you to
observe the growth of a plant in relation to several variables of your choosing. In this
activity you were expected to determine the themes of biology in relation to the growing
plant. You are expected to have observed the organization, interaction, matter and
energy, information, and evolution. Organization is when from a seed, the mung bean
sprouted and grew to another definite structure with differing functions. Interaction is
when during its growth, the mung bean internally maintained homeostasis for optimal
growth while interacting with external factors. Growth is a complex and energy
consuming process, therefore, the growth of the mung bean had to be supplied with
energy coming from the nutrients in the soil and water, among others. Information and
evolution in this activity are indirectly observed by whatever the mung bean is
presently. This pertains to its physical features, functions, and molecular make-up.

What’s More

Make a Concept Map

Complete the concept map below by adding the following terms: adaptation,
atom, cell, community, ecosystem, energy, development, growth, individual, molecule,
organ, organization, organ system, population, reproduction, response, tissue.

organisms

Have may have

Properties of life many levels of organization

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 What I Need to Know

Another theme to help us understand the study of biology is information. All

living things have to deal with the transfer and expression of genetic information. Inside
cells, chromosomes exist and inside chromosomes are genetic material in the form of
DNA or Deoxyribonucleic acid.

Recall in your grade 8, you learned about the two mechanisms in cell division,
mitosis and meiosis. Before each process happens and or is completed, the very first
thing that occurs is the replication of genetic materials. The replication or copying of
the DNA is to ensure that the daughter cells will receive the same complete set of
chromosomes with that of the parent cell. These DNA will then contain sections called
genes. This replication of the DNA prior to cell division will eventually be the template
for the trillions of cells that will make up an organism.

The structure of the DNA is responsible for its ability to store information. It is a
double helix of strands of building blocks called, nucleotides. The following
nucleotides are adenine, thymine, cytosine, and guanine – aptly abbreviated as A,
T, C, and G, respectively. The different sequence of these four nucleotides accounts
for the encoding of information in the DNA. Think of it this way, the way we arrange
the alphabet to form words is, in a way, like how these nucleotides are sequenced for
encoding information as shown in figure 2.

https://ghr.nlm.nih.gov/primer/basics/dna

Figure 1.2 DNA structure

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 The sequencing provides for a blueprint for most genes to make proteins. In
turn, these proteins accounts for different function in the body and in different
organism. Like for example, a single-celled gene may specifically create a protein that
will be able to breakdown a carbohydrate molecule, while a human gene may specify
a protein to act as an antibody to help fight off infections.

The protein production is controlled indirectly through another related molecule,

the RNA. The RNA in this process serves as an intermediary. The nucleotide
sequence along a gene is transcribed into a mRNA, then translated into the building
blocks of protein, amino acids. The amino acid in this case is a link series, after
completed, they form a specific protein with a unique shape and function. This whole
process where the information in a gene guides to create a cellular product is called,
gene expression.

What I Need to Know

Unity and Diversity of Life

Evolution is a much-debated topic in the past, but withstanding scientific

evidences, evolution has stood its ground and became a field. Evolution by
characteristic is the scientific thought which states that the organisms of today are the
modified descendants of their ancestors in the past as shown in figure 3.

Evolution is said to be the scientific thought that would explain or make sense
of all the organisms now. Fossil records show that organisms have been evolving for
billions of years now, and that this accounts for the vast diversity and variation of
organisms in the past and present. Fossil records also show evidences of unity aside
from variation. There are animals presently that may seem different from one another,
let’s take for example the arm of a human being, wing of the bat, leg of a dog, and
flipper of a whale, they might have different uses but their underlying anatomy are
similar to one another. They considered homologous structures.

One notable evolutionary view emerged in the 1800s, when the father of
evolution, Charles Darwin, published the book, “The Origin of Species”. This book
contained Charles Darwin’s studies and observations, which expressed two main
points. One, that “contemporary species arose from a succession of ancestors that
differed from them”. This is what we call, descent with modification and accounts for
the dual nature of life’s unity and diversity. Second, that “natural selection is the
primary reason of descent with modification”.

Natural selection sprung from Darwin’s observations from his studies. It states
that species with inherited traits are more adaptive to the environment which means
they are more likely to survive and reproduce than those who are not. This is because
the environment constantly selects for the production of traits from the random variant
traits naturally occurring within a population.

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 https://geneticliteracyproject.org/2018/07/23/evolution-is-aimless-how-do-we-explain-external-testicles/

Figure 1.3 Concept of Evolution

What’s New

In this activity, you will determine the degree of relatedness among some species
based on their amino acid sequences of cytochrome-c.

ACTIVITY 2: Relative Organisms

Objectives:
1. Compare the amino acid sequences of cytochrome-c of some organisms.
2. Calculate the degree of relatedness among some species based on the amino acid
sequences of cytochrome-c in their proteins.

Materials:

Pen and record notebook

Procedure:

1. Refer to the following table of amino acid sequences of cytochrome-c. compare the
amino acid sequences of the following pairs of organisms by encircling the portions
of the sequences where they differ. For each pair, count the total number of differing
amino acids.

a. human and chimpanzee d. chicken and turkey

b. human and rhesus monkey e. rattlesnake and fruit fly
c. horse and monkey

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 Amino Acid Sequences of cytochrome-c

Human GDVEKGKKIFIMMKCSQCHTVEKGGKHKTGPNLHGLFGRRTGQAPGYSYTAAN
KNKGIIWG
Chimpanz GDVEKGKKIFIMMKCSQCHTVEKGGKHKTGPNLHGLFGRRTGQAPGYSYTAAN
ee KNKGIIWG
Rhesus GDVEKGKKIFIMMKCSQCHTVEKGGKHKTGPNLHGLFGRRTGQAPGYSYTAAN
Monkey KNKGITWG
Horse GDVEKGKKIFVQKCAQCHTVEKGGKHKTGPNLHGLFGRKTGQAPGFTYTDANK
NKGITWK
Donkey GDVEKGKKIFVQKCAQCHTVEKGGKHKTGPNLHGLFGRKTGQAPGFSYTDANK
NKGITWK
Chicken GDIEKGKKIFVQKCQCHTVEKGGKHKTGPNLHGLFGRKTGQAEGFSYTDANKNK
GITWG
Turkey GDIEKGKKIFVQKCQCHTVEKGGKHKTGPNLHGLFGRKTGQAEGFSYTDANKNK
GITWG
Rattlesnak GDVEKGKKIFTMKCSQCHTVEKGGKHKTGPNLHGLFGRKTGQAVGYSYTAANK
e NKGITWG
Fruit fly GDVEKGKKLFVQRCAQCHTVEAGGKHKVGPNLHGLIGRKTGQAAGFAYTNANK
AKGITWQ

2. Calculate the percentage difference between the species of each pair by dividing the
number of differing amino acids by the total number of amino acids in the sequences
of the pair.

3. Record your data in the given table.

Data and Observations:

Human and Human and Horse and Chicken Rattle

Chimpanzee Rhesus Donkey and Turkey snak and
Monkey Fruit fly
Number of
differing
Amino Acids
in
cytochrome-c
Percentage
difference

Analysis Questions:
1. Which pair of organisms are most closely related? the least related? How do your
results compare with the taxonomic classification of the organisms?

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 2. How will you interpret those pairs of organisms having the exact amino acid sequence
of cytochrome-c?

3. What generalization or conclusion can be drawn from the activity?

Exploration:
Do you think that amino acid sequencing is a reliable basis for determining evolutionary
relationships among organism? Justify your answer.

What Is It

One of the recent evidences of evolution that reinforces the fossil records comes from
molecular biology. By using the technique called amino acid sequencing, researchers have
discovered that closely related organism have great similarity in their amino acid sequences,
indicating a common descendant, hence suggesting unity and diversity. In the activity, you
have determined the degree of relatedness among some species based on their amino acid
sequences of cytochrome-c.

What I Need to Know

A characteristic common to all forms of life is the need for energy. This is a
requirement for organisms to perform life processes. The various indicators of life and
processes like growing, reproducing, moving, and other intracellular processes require
that the organism spend energy.

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 The sun is the primary source of energy in the environment. All organisms rely
on the sun’s energy input to survive. It provides energy on earth in the form of light
and is received and utilized by the autotrophs or producers. These autotrophs or
producers are photosynthetic organisms. These organisms are able to harvest sunlight
to create their own food. The photosystems harvest light ang together with raw
materials like CO2, and water covert light energy into chemical energy. This process
is called photosynthesis. The chemical energy in the form of food molecules will then
be passed by plants and other photosynthetic organisms to other organisms that are
not able to produce their own food. Note that that there is already energy transfer
happening in this process. The organisms receiving the energy from producers are
called consumers, as shown in figure 4 below.

https://www.tutorialspoint.com/environmental_studies/environmental_studies_energy_flow_in_ecosystem.htm

Figure 1.4 Energy Flow in An Ecosystem

When an organism uses energy to perform work or certain processes, such as

cell division, or pumping of blood from the heart to circulation, some of the energy
used is lost in the environment in the form of heat. In a nutshell, energy in an
ecosystem flows through in one direction, enters as light and exits as heat. And in
contrast, chemicals used are recycled. The chemicals that a plant absorbs from the
soil and water is incorporated into the plant body, then later passed on to the animal
that eats the plant. Eventually, these chemicals will then be returned into the
environment by decomposers like bacteria that breaks down dead matter. These
chemicals will then be taken up by the soil (usually) and is ready to be again absorbed
by the plants. Then the cycle goes on, as shown in figure 5 below.

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 https://www.tutorialspoint.com/environmental_studies/environmental_studies_energy_flow_in_ecosystem.htm

Figure 1.5 Nutrient Cycle in an Ecosystem

Remember the organizational hierarchy presented in the beginning of this

lesson? From the molecular level to the ecosystem, and to the biosphere in general,
interaction is important. Interaction’s collegiate definition in the Meriam-Webster
Dictionary is the mutual or reciprocal action or influence. In biology, interaction at every
level of hierarchy is important as it ensures smooth operation and combination of parts
to function. This is very much evident in the interaction of molecules in the cell, and in
the parts or components of the ecosystem.

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 When we talk about the lower levels of hierarchy in biology, we are referring to
the interactions that make up the organism, this means, molecule level up to the organ
level. The interaction in the lower levels of hierarchy is important for operations of
certain regulations. Let us take for
example the regulation of waste
materials in the body, particularly
carbon dioxide. The body needs to
keep the levels of carbon dioxide in
the lungs low so that it can easily
diffuse from the blood to the lungs and
excreted via exhaling. This process
alone, allows for a lot of interaction in
between organs, cells, tissues, and
molecules. This ability to self-regulate
is made possible by a mechanism we
call, feedback.

https://byjus.com/biology/exchange-regulation-of-gases/

Figure1.6 Gas Exchange at the Alveolus

In an ecosystem, we see interaction at a macro level. Every organism interacts

with other organisms, and with the abiotic environment as well. The grass blade, for
example, can be eaten by a caterpillar and in turn is eaten by a bird. The bird, when it
dies will then undergo breakdown with the help of decomposers, and materials from
the decomposition like molecules will then be absorbed by the soil. You see,
interaction like this ensures that the ecosystem continues to thrive through having a
regulated function, as shown in figure 7 below.

https://young7science16.weebly.com/interactions-and-ecosystems.html

Figure 1.7 Simple Food Web/ Ecosystem Interaction

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 What Have I Learned

Activity 3: Analyzing Interactions In Your community

The inside of your home is a dwelling place, not only for you and your family
but for a whole community of species. You can investigate their interactions if you…

Objective: Investigate interaction in a community

Materials: pen and paper

Procedure:

1. Make a list of organisms that can be found living in your dwelling place.
Some may be invited, such as pets or houseplants. Other may be
uninvited, such as rodents, insects, or molds.
2. Make a table and record information about the food relationships among
members in this community. A sample table is provided for you below.

Organism Food source Food relationship

Invited Uninvited

Analysis of Results:

1. What do the animals eat? Do they rely on the human food supply, or do
they have their own sources of food?
2. Are there predators and prey in this community?
3. Describe how the community members compete for resources.

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 Reproduction of
Lesson Representative Animals
2
What This Lesson is About
We are products of billions of years’ worth of evolution, and we know this much
thanks to reproduction. Through reproduction, nature has selected organisms that
have a gene pool that is capable of surviving and thriving. Animals have both adapted
and evolved to better fit their environments thanks to variation.

While us, humans, have goals in life some animals were born to reproduce and die
immediately after. So now you ask, why is reproducing offspring so important to
animals? This is one of question that we will be answering into later, on this module.
In this lesson, we will understand key concepts about the complexities of reproduction
in animals and synthesize our learning at the end. Lastly, this lesson will also allow
you to appreciate the true importance of why a continuity of a species is important.

Source:https://pixabay.com/

Figure 2.1 Elephant herd crossing an African savannah

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 What I Need to Know

At the end of this lesson, you should be able to demonstrate understanding of

the four main concepts under animal reproduction:

1. Sexual and Asexual Reproduction

2. Mechanisms of Fertilization
3. The Factors that affect Successful Reproduction
4. The Journey of a Human Embryo

What I Need to Know

According to the UN, there are about 360,000 babies born every day in the
world. Reproduction is one of the key survivals of a species – it is a way to continue
life. A male and a female organism will mate and produce an offspring. These parent
organisms will then pass on genetic information to their offspring, and in time, their
offspring will pass their own genetic information as well.

From our previous lesson of mitosis and meiosis, we know that cellular division
plays an important role in reproduction. The relationship between these two processes
are vital to animal reproduction. Some organisms like cows, sheep, dogs and will
require two parent organisms (sexual reproduction) in order to reproduce an offspring,
while others do not (asexual reproduction).

In this lesson, we will be describing the different ways on how representative

animals reproduce. (S11/12LT-IIej-15)

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Sexual vs. Asexual

Figure 2.1 shows

how sexual and asexual
reproduction produces
offspring. In an asexual
reproduction, a parent
organism will not need a
mate or partner for it to
produce its own offspring.
The offspring of asexual
organisms are an exact
same copy of its parent
organism.
Figure 2.1 A diagram of Asexual and Sexual Reproduction

In sexual reproduction, a male and female gamete is needed in order to

produce an offspring. In most instances, there is a male and female organism to
produce the gametes but, this isn’t always the case. Finding a partner for sexual
animals can sometimes prove difficult, and so, as an adaptive mechanism and
evolutionary solution, some animals exhibit hermaphroditism. This is when an
organism has both male and female reproductive system. This is common among
sessile (stationary) animals. In hermaphroditism, the organism may or may not have
a partner for fertilization to occur. Unlike, an asexual offspring, a sexual offspring is
genetically unique from its parent organisms. Notice how there are two apparent sexes
in sexual organisms, while there is no definite sex in the asexual organism.

Types of asexual reproduction

1. Binary Fission – occurs in single celled organisms. It is when a parent cell

divides itself into two equal parts and create an offspring. This type of
reproduction is like cloning as shown in figure 3. To easily remember and
understand the reproduction process of binary fission it is valuable to
remember what the terms mean. The word binary means something having
two parts (the new daughter bacteria) while the word fission means the
movement of splitting (the dividing of two equal parts). Ex. Bacteria

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 Figure 2.3 Binary Fission in Bacteria

2. Fragmentation – occurs when an organism breaks a part of itself into a

fragment, and the fragment develops into a new organism as shown in figure
4. Ex. Starfish & acoel flatworms

Figure 2. 4 Starfish undergoing fragmentation

3. Budding – happens when a parent organism grows a bud attached to its

body. When the bud is developed it will detach itself from the parent and
form a new organism. Ex. Yeast and Jellyfish

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 https://courses.lumenlearning.com/boundless-biology/chapter/phylum-cnidaria/

Figure 2.5 Jellyfish Lifecycle

4. Parthenogenesis – occurs when the embryo of an organism can grow

and develop without fertilization.
Ex. Some species of ants & Honeybees.

https://www.britannica.com/animal/hymenopteran/Natural-history

Figure 2.6 Parthenogenesis in bees

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 Table 2.1 Advantages and Disadvantages in Sexual and Asexual Reproduction
Types Advantages Disadvantages

Sexual Reproduction - The population is less - Needs a partner to

likely to catch diseases reproduce.
all at once. - Takes more time to
- Has more chances of reproduce.
survival
- Has genetic variation.
Asexual Reproduction - Only one parent - Has less surviving
organism is needed to chances due to the
reproduce. lack of genetic
- Faster than sexual variation.
reproduction. - Population is more
likely to catch diseases
at the same time.

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 What I Have Learned

Identify the type of reproduction described in the organisms in column A. Write

your answer in column B.

A B

1. A single organism that functions

as both the male and female in

reproduction.

2. An organism that requires both

a male and a female to

reproduce.

3. This organism breaks a part of

itself to reproduce.

4. A male and a female pig mate to

reproduce piglets.

5. This organism’s embryo does

not need fertilization to develop

into an offspring.

6. This organism divides itself into

two equal parts to reproduce.

7. An organism that grows buds to

reproduce.

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 What I Need to Know

Organisms are diverse, unique and have equally unique features that help them
survive in their environment. These features tailor to the animal’s environment, size,
habitat, and so many more factors. One unique feature is the way these organisms
undergo fertilization.

In this lesson we will have the following objectives:

Compare and contrast internal and external fertilization

Mechanisms of Fertilization

There are two types of fertilization – internal and external. Internal fertilization occurs
when the fusion of gametes is inside the female body, while an external fertilization is
the opposite where fusion of gametes is outside the female body.

The 3 types of internal fertilization

1. Oviparity – the female has

fertilized eggs laid outside its body. The
young will get nourishment from its yolk
and will be protected by the external
covering of the egg. The types of eggs
will vary in different animals. Chicken
eggs will have high calcium carbonate
concentrations, while reptiles will
produce leathery eggs. Ex. Chickens
Source: https://pixabay.com/

Figure 2.7 Chicks from chicken eggs

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2. Viviparity – most common in mammals, the
offspring develops within the female and is
nourished by the mother’s blood in the
placenta. Ex. Bears

Source: https://pixabay.com/
Figure 2.8 Brown Bear frolicking in the grass

3. Ovoviviparity – like oviparity, ovoviviparity has

fertilized eggs that nourish the young from its yolk. The
key difference between them, is that ovoviviparous
animals only lay the eggs when they are ready to
hatch. Ex. Great White Sharks

Source: https://pixabay.com/
Figure 2.9 Great White Shark in the ocean

The table below will better summarize the key difference and similarities of the
two fertilization processes.

Table 2.2 Summary of Features for Internal and External Fertilization

INTERNAL EXTERNAL
FERTILIZATION FERTILIZATION
PROCESS - Egg is fertilized - Egg is fertilized
inside female body. outside female
body.
- Male gamete is
discharged unto the - Male gamete is
female gamete. discharged unto the
female gamete.

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SUCCESS RATE - Since the offspring is - Has a less chance of
developed inside the survival because the
body of the female, it offspring develops
will have more without protection in
chances of surviving the open
even in harsh environment.
environments
because it is
protected.
KEY FEATURES - Has three types: - Survives best in
1. Oviparity moist/aquatic
2. Viviparity environments.
3. Ovoviviparity
- Has a greater
- few offspring are number of offspring
produced. produced.
EXAMPLES - Elephants, goats, - Fish and Frogs
and cats

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 What I Have Learned

In your own words, describe the type of fertilization given below and give and
example of an animal that has that type of fertilization.
Description Animal

Viviparity

Internal fertilization

External fertilization

Oviparity

Ovoviviparity

II. Essay

Why do you think there is a difference in the types of fertilization among animals?
___________________________________________________________________

___________________________________________________________________

___________________________________________________________________

___________________________________________________________________

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 What I Need to Know

As mentioned in lesson 2, organisms have unique features that help them

survive in their environment. Animals are designed to survive their environment
through their form and function, and what better way to survive than to outsmart your
predators and continue your species through reproduction.
The male and female house bird will build a strong nest for its eggs to ensure
that it will hatch and survive. The female lion will teach its young cub to hunt and
protect it from predators when it is too young to defend itself.
In this lesson you will be able to identify and understand the factors that affect
the success of reproduction.

What’s New
Pick a species and draw it in its natural habitat in the box below.

Now that you have drawn them here are some follow up questions:

1. What is your chosen species and where does it live?

2. Why do you think it thrives in that environment?
3. Do you think that its environment is being disturbed by external factors?

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 What is It

The success of animal reproduction does not only end when an egg is fertilized.
It ends when the offspring can fully grow and eventually reproduce as well. As
mentioned before, reproduction is key to survival. We will all eventually die and we
need to make sure that our species continue through reproduction. Listed below are
the factors that affect reproductive success.

Factor #1: Predation

In the animal kingdom exists a food chain. At the top of the food chain there are
animals we call apex predators, while at the bottom of the food chain are animals that
are weak and easily hunted by predators. Apex predators are animals that hunt and
feed on other animals to survive and eventually reproduce. These predators are never
or rarely hunted by any other animal. On the other hand, since prey is easily hunted
their offspring is always compromised and in danger. The success for preys to
reproduce is greatly affected by the chances that these offspring get eaten when they
are still young or developing. The connection of these animals in the food chain help
maintain their progeny.

Factor # 2: Environment
To ensure a healthy offspring, the animal’s environment must also be nurturing
to the young. Temperature greatly affects the development and the urges of an animal
to mate. With the continuing rise of temperatures around the globe, some animals are
starting to dwindle in number and die before they even reproduce. When the water
becomes too warm, the fishes will have a hard time getting oxygen and can eventually
die when exposed to warm waters for longer periods of time. Glaciers and ice caps
are melting in the arctic, causing polar bears suffer health conditions due to
malnutrition.

Factor # 3: Human Interaction

Humans have been responsible for a lot of species extinction as we pose as
one of the greatest threats to animals. Polluting land, water, and air; hunting; and
deforesting are ways in which animal reproduction get disturbed. On the other hand,
there are some human interventions that try to reverse these effects and attempt to
save endangered species.

It is important to understand that the continuity of animals is vital to the balance

of ecosystems, and because there is a food chain, when one animal species is
threatened the whole food chain is threatened as well.

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 What’s More
Check your knowledge against the understanding that you have gained in the
lesson regarding reproductive success. Answer the following questions briefly and
concisely.

Essay
1. Why do you think natural selection favors animals with the greatest
reproductive success?

________________________________________________________________
________________________________________________________________
________________________________________________________________
________________________________________________________________
2. What do you believe is the greatest threat to animals and why?

________________________________________________________________
________________________________________________________________
________________________________________________________________
________________________________________________________________
3. Why is it important for animals to never go extinct?

________________________________________________________________
________________________________________________________________
________________________________________________________________
________________________________________________________________
4. How can we better preserve and protect animals so that they may continue to
live on?

________________________________________________________________
________________________________________________________________
________________________________________________________________
________________________________________________________________

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 What I Need to Know

The stages of development of a human baby are complex and truly fascinating.
In this lesson our objective will be able to understand how a human embryo develops.

Before an egg cell can be fertilized by a sperm cell, both gametes need to be
mature and become spermatozoa and oocyte. For it to be mature, it first has to
undergo stages of development.

Stages of Development

Spermatogenesis Oogenesis
1. Spermatogonia Oogonia
2. Spermatocyte Oocyte
3. Spermatid
4. Spermatozoa

What’s In

Before we continue with fertilization, remember your previous lesson in mitosis

and meiosis? Well, they play very important roles in the development of a human
embryo. Mitosis has a product of two identical daughter cells. These cells are in charge
of the growth and replacement of dead cells in the body. Whereas meiosis has a
product of four sex cells, that oversees the development of our gametes for us to
reproduce.

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 What I Need to Know

The first stages of Fertilization

There are two ways in which the human female reproductive cycle can end –
menstruation or pregnancy. If in the case it ends in pregnancy there are distinct stages
before a baby is born. After copulation, when the sperm cell successfully merges with
the egg cell, fertilization or conception happens. After 24 hours of the conception, the
zygote or the fertilized egg undergoes a series of cell division also called the cleavage.
After cleavage, the zygote will undergo a series of growth divided into three
trimesters, or in forty weeks, before the baby is born. The table below gives a clear
description on what happens all throughout the duration of the pregnancy.

Trimester Weeks Description

1st 0 – 12 - The female body undergoes drastic

changes to prepare to house the
unborn child. The body will also start
to experience pregnancy symptoms
like nausea and fatigue.

- The zygote starts developing

important features like the legs, feet,
arms, and hands.

- By the end of the 12th week your baby

will have all the organs present. It will
continue to develop to become
functional.
2nd 13 – 26 - The sex of baby can be determined.
- The heartbeat will be audible.

- The baby will move around the womb

more.

3rd 27 – 40 - The baby will be able to see and hear.

- The baby will be able to coordinate

better like blink her eyes and grasp.

- The female could go into labor at any

time.

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 What I Can Do

Knowledge is power! Let us put your synthesizing skills to the test through this
animal profiling activity.

1. Pick an animal and draw his ID picture in the box.

2. Fill in the rest of the information by checking the
right choice and filling out the blanks!

1. Animal and Species: _____________

2. ( ) Asexual ( ) Sexual
3. *if your animal is asexual, please specify what type: ______________
4. ( ) Internal Fertilization ( ) External Fertilization
5. *if you checked internal fertilization, please specify what type:
______________
6. Place where this animal preferably gives birth:__________________

Now that we’re done with general profiling, let’s compare and contrast this
animal’s reproduction with humans using the venn diagram below.

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Essay
Let us see how well our knowledge truly understand these ideas through essay
writing.

1. Why do you think is asexual reproduction present among animals?

______________________________________________________________
______________________________________________________________
______________________________________________________________
______________________________________________________________

2. Is it possible for humans to undergo asexual reproduction? Why?

______________________________________________________________
______________________________________________________________
______________________________________________________________
______________________________________________________________

3. Why is reproduction important for species survival?

______________________________________________________________
______________________________________________________________
______________________________________________________________
______________________________________________________________
4. What makes hermaphrodites unique organisms?

______________________________________________________________
______________________________________________________________
______________________________________________________________
______________________________________________________________
5. What is the difference between oviparity and ovoviviparity?
______________________________________________________________
______________________________________________________________
______________________________________________________________
______________________________________________________________

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Summary:

• Study of life anywhere on earth will always reveal unifying themes. These
themes allow for better understanding the so-called mystery called life.
Organization theme shows that emergent properties result from the
interplay of the lower levels of hierarchy. Reductionism allows for the
compartmentalization of larger and more complex systems to be easily
studied. In information theme, it is all about life’s processes revolving
around the expression and transmission of genetic information. And that this
genetic information is encoded in the nucleotide sequences of the DNA.
Energy and Matter as a theme is important as life processes requires
energy. The sun being the fundamental source of energy enters into the
ecosystem as light and exits it as heat. Producers are responsible for
converting light energy into chemical energy which is then passed into
consumers. Interaction theme is important to life for regulation, thus
enabling organisms to survive. Internal interactions are done through
feedback regulation. This is a process where either an accumulation or
decrease of an end product allows for the speed up or decrease for its
production. Evolution theme is the change among organisms that has
allowed for unity and diversity of life here on earth. Charles Darwin who
authored natural selection, saw it as a means of evolutionary mechanism
for adaption of organisms to their environment.

• To ensure species continuity, nature allows for both sexual and asexual
reproduction in the animal kingdom. Sexual reproduction requires the
union of female and male gametes to form a diploid zygote. Asexual
reproduction on the other hand can produce an offspring without the union
of gametes. Several mechanisms for asexual reproduction include
budding, fission, and fragmentation. There are also some variations
through reproduction can still occur. These are through hermaphroditism
and parthenogenesis, in which environmental and hormonal factors have
control in the reproductive cycles. Fertilization can either occur externally
when both materials are released outside the body, or internally when a
male fertilizes an egg in the female reproductive system. Unlike asexual
reproduction, sexual reproduction is a form of partnership between
organisms and at the same time, it promotes competition between
individuals and even between gametes.

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Post Assessment:

Multiple Choice. Read the sentences or questions carefully. Choose the letter of
the correct answer.

1. In what trimester is the baby ready to be born?

a. 4th
b. 3rd
c. 2nd
d. 1st

2. A house lizard is ________, in terms of mechanism of reproduction.

a. oviparous
b. viviparous
c. ovoviviparous
d. asexual

3. Earthworms are _____ in nature.

a. asexual
b. hermaphrodites
c. none of the above
d. all of the above

4. What do you call animals that are at the top of the food chain?
a. Apex predators
b. Prey
c. Ants
d. Lion

5. Which is not a factor for successful reproduction in animals?

a. Temperature
b. Humans
c. Predation
d. asexual reproduction

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 True or False. Write the word true if the statement is correct and the word false
if it is not.

1. Both internal and external fertilization has the male gamete discharged unto
the female reproductive system. ________
2. Internal fertilization has more offspring produces compared to external
fertilization. ________
3. The 3rd stage of sperm development is called spermatozoa. ________
4. Humans are ovoviviparous. ________
5. Parthenogenesis is when an organism has both the male and female
gametes. ________

34