8
Science 8
Quarter 4 – Lessons 1-3:
Living Things and their Environment
ILLUSTRATION: RICARDO B. RUIZ
LAYOUT: ARVIN C. AUSTRIA
Department of Education ● Republic of the Philippines
Science 8
Alternative Delivery Mode
Quarter 4 – Lessons 1-3: Living Things and Their Environment
First Edition, 2020
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2
Lesson
Digestive System
1
Living things need energy to do work. The energy which the animals and
humans need comes from food. Food fuels the body cells with the energy they need
to operate. But the food that living thing takes in is a complex material and it must
be broken down into smaller pieces which the body can absorb and utilize.
In this lesson, you will be able to learn how the parts of the digestive system
work harmoniously in a healthy individual and discover how each organ is
structurally designed to perform its function. This will also give you a clearer
understanding on how intricate the processes are which cannot be duplicated even
by the most advanced technology.
What I Know
Directions: Choose the letter of the correct answer. Write your answers before each
number.
1. Digestion takes place in a long tube-like canal called alimentary canal, or the
digestive tract. Food travels through these organs in the following order.
a. mouth – esophagus – stomach – small intestine – large intestine - rectum
b. mouth – esophagus – stomach – large intestine – small intestine – rectum
c. mouth – stomach – esophagus – small intestine – large intestine – rectum
d. mouth – stomach – gullet – small intestine – large intestine – rectum
2. What structures in the small intestine absorb the nutrients that result from the
digestive process?
a. villi
b. duodenum
c. intestinal glands d. intestinal muscles
3. What happens when food reaches the stomach?
a. Nothing. No digestion occurs in the stomach
b. The food moves quickly into the small intestine
c. Juices mix with the food and stomach muscles squeeze it
d. The food is completely digested and is absorbed by tiny blood vessels in the
walls of stomach
4. How do you call to the movement of the digestion products, electrolytes, vitamins
and water across the gastrointestinal tract epithelium and into the underlying
blood and lymphatic vessels?
a. ingestion b. absorption
c. digestion
d. secretion
5. The following are preventive measures to avoid digestive problems EXCEPT
________.
a. drinking plenty of water
c. consuming high calorie fast food
b. avoiding excessive intake of alcohol d. eating food rich in fibers
3
What’s In
Food plays a major role in the survival of species. Food gives organism energy
that enables them to carry out many activities they do each day by day. Organisms
are able to obtain energy from the foods they eat through the process of digestion.
Digestion is the process of breaking down foods into smaller nutrients. These
nutrients are circulated to the different parts of the body through the bloodstream
and assimilated by the cells
What’s New
If you’re an ice cream lover, then just the sight of this
yummy ice cream cone may make your mouth water. The “water”
in your mouth is actually saliva, a fluid released by glands that
are part of the digestive system. Saliva contains digestive
enzymes, among other substances important for digestion. When
your mouth waters at the sight of a tasty treat, it’s a sign that
your digestive system is preparing to digest food.
Figure 1.1. Ice cream
Source:https://hips.hearstapps.com
What is It
The food you eat takes an incredible journey through your body -- from top
(your mouth) to bottom (your anus). Along the way the beneficial parts of your food
are absorbed, giving you energy and nutrients. The digestive system is used for
breaking down food into nutrients which then pass into the circulatory system and
are taken to where they are needed in the body. It consists primarily of the alimentary
canal (digestive tract) and accessory organs. Figure 1.2. shows where food is digested
in man. The parts are enumerated in Table 1 together with the organs that assists
in digestion. The food tube of man is about nine (9) meters long.
Table 1: Parts of the Digestive System and their Functions
Alimentary Canal
(Digestive Tract)
Mouth
Esophagus
Stomach
Small intestine
Large intestine
Rectum
Anus
Accessory Organs
Liver
Gall bladder
Pancreas
Function
mechanically breaks down the food by your teeth
muscular tube through which food passes from the mouth into
stomach
big muscular pouch where digestion begins
absorption of food particles takes place here
known as colon which absorbs water, secretes mucus and eliminates
undigested materials
stores the feces
opening where the feces is eliminated
Function
secretes bile, a greenish fluid that emulsifies fats and neutralizes the
stomach acid and increase the efficiency of digestion and absorption
where bile is stored
secretes digestive enzymes that breakdown proteins, carbohydrates,
and fats
4
Digestion starts when food is taken into the mouth.
As you chew, you are breaking the food into small pieces
as a means of mechanical digestion. The pieces mix with
saliva which is, a watery liquid made by the salivary
glands. It softens and wets the food in the mouth and also
initially starts chemical digestion through the enzymes
present in it. Enzymes are molecules that speed up
chemical reactions. Enzymes in saliva known as salivary
amylase or ptyalin helps breakdown food starches or
carbohydrates into maltose, a double sugar. Maltase,
another type of enzyme will breakdown maltose into
glucose, a simple sugar. Then the food passes through the
esophagus. Muscle contractions in the esophagus help
move the food down to the stomach. This wavelike
contraction of the food tube is called peristalsis.
Figure 1.2. Digestive System
Source:https://www.niddk.nih.gov
The stomach is made up of muscles that churn and help mix the food with
gastric juices and acids and break it into even smaller pieces. Other enzymes such
as lipase and protease help breakdown proteins in the stomach and fats in the small
intestine, respectively.
Digested molecules of food are absorbed through the small intestine. The
walls of the small intestine contain many folds that are lined up with tiny fingerlike
protrusions called villi and microvilli. During absorption, these nutrients pass
through the walls of the intestine and into the
bloodstream where they get transported to the
different parts of the body.
Secretions of the liver and pancreas also
enter the small intestine, playing an important role
in digestive process. The pancreas secretes variety
of
digestive
enzymes
that
breakdown
carbohydrates into simple sugars, proteins into
amino acids and fats into fatty acids. Moreover, it
also makes insulin, chief hormone in your body for
metabolizing sugar.
Figure 1.3. Liver, Gall Bladder and Pancreas
Source: https://img.webmd.com/
Because digestive enzymes cannot act efficiently on large fat globules, the
liver secretes bile – a greenish fluid that emulsifies fat globules into smaller droplets.
These small droplets are easily digested by digestive enzymes. The gallbladder is a
green muscular sac attached to the liver where bile is stored.
The undigested parts of food or those that were not absorbed by the body
passes through the large intestine and stores the feces at the rectum until they are
eliminated in the opening known as anus. This process is called elimination or
defecation
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Digestive Processes
Your digestive system is uniquely constructed to do its
job of turning your food into the nutrients and energy you
need to survive. And when it’s done with that, it handily
packages your solid waste, or stool, for disposal when you
have a bowel movement.
Here are the different activities include in the digestive
processes:
1. Ingestion – process where food is taken in through
the mouth and broken down by teeth
and saliva.
Figure 1.4. Digestive Processes
2. Digestion – breaking down of food into small pieces.
Source:https://bodell.mtchs.org/
a. Mechanical Digestion – physical breakdown
of large pieces of food into smaller pieces.
b. Chemical Digestion – carried out by the enzymes that
speeds up the chemical reaction.
3. Absorption – process by which food molecules move into the blood stream
to be carried to the cells of the body.
4. Assimilation – incorporation of food molecules into the cells of the body to
be used as energy, structural materials or storage products.
5. Egestion – process of eliminating undigested food from the body
What’s More
Activity 1: Matchy Matchy!
Objective:
Identify the key parts of the digestive system
Materials:
Worksheet
Pen
Directions: Match the name of each organ with the
letter that represents on the diagram
below.
______ 1. Stomach
_____8. Small intestine
______ 2. Gall bladder
_____9. Pharynx
______ 3. Oral cavity
_____10. Anus
______ 4. Liver
_____11. Pancreas
______ 5. Large intestine
____ 12. Esophagus
______ 6. Rectum
____ 13. Tongue
______ 7. Salivary glands
Figure 1.5. Digestive System
Activity 2: Trace my Path!
Objective:
Trace the pathway of food through the digestive tract
Materials:
Worksheet Pen
6
Directions:
Complete the paragraph below:
In humans, the process of digestion begins in the _____________ where
food is chewed into small pieces by the teeth. Once the food is swallowed, it
passes through the ____________ and into ____________. Once in the stomach,
the food is ___________. After spending some time in the stomach, the food is
sent into the ____________ where nutrients are ___________.
The ___________helps by producing some digestive juices called bile. The
undigested food goes into the _______________. The rectum stores the
__________ and eliminated through the process of defecation by the _________.
Activity 3: Arrange and Explain!
Objective:
Arrange and explain the different digestive processes in the body.
Materials:
Worksheet
Pen
Directions: Arrange the following processes in order of which they occur and give a
brief sentence to explain each one
Digestive
Description
Processes
1.
2.
3.
4.
5.
What I Have Learned
1. Explain the difference between
mechanical and chemical digestion.
_____________________________________
2. How does digestive system break down
food to nourish the body?
______________________________________
What I Can Do
I Can Do it!
Create a paper doll of the digestive system
using the given template. Draw the different
organs of the digestive system and label them.
Assessment
A. Multiple Choice. Choose and write the letter of the best answer before each
number.
1. Which of the following is NOT an organ of the digestive tract?
a. mouth
b. stomach
c. liver
d. esophagus
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2. What is the primary function of small intestine?
a. vitamin conversion
c. absorption of nutrients
b. mineral secretion
d. waste secretion
3. Which of the ff. accessory organs acts as a temporary storage site for bile.
a. gall bladder
b. pancreas
c. liver
d. intestine
4. Which of the following organs is NOT correctly matched with its respective
function?
a. pharynx – passage of air & food
c. small intestine – absorption
b. stomach – defecation
d. mouth – ingestion
5. The digestive system processes food into usable and unusable materials are
sent to the body’s cells as food. What happens to unusable materials? It goes
___.
a. into the pancreas to await disposal
b. to the right ventricle to await disposal
c. into the large intestine to await disposal
d. to the small intestine to await disposal
B. Match Column A to Column B by writing the letter of the correct answer before
each number.
COLUMN A
COLUMN B
1. Breakdown of large, insoluble food molecules into small a. Egestion
water-soluble molecules using mechanical and chemical b. Digestion
processes.
c. Assimilatio
2. Movement of digested food molecules into the cells where
n
they are used.
d. Absorption
3. Intake of substances into the body through the mouth.
e. Ingestion
4. Passing out of undigested food as feces through your anus
5. Movement of digested food molecules across the walls of
intestines into the blood or lymph.
Lesson
2
Cellular Reproduction
You have learned that every organism possesses a unique characteristic and
one of these characteristics is reproduction. The cellular level of reproduction, in the
form of cell division, provides the backdrop for the organism level of reproduction.
In this lesson, you will be able to determine the stages of cellular reproduction
and explain how cells grow and divide to form new cells.
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What I Know
Directions: Choose the letter of the correct answer. Write your answers before each
number.
1. Which of the following best describes the cell cycle?
a. Cells growth and development takes place during interphase while its
reproduction takes place during mitotic phase.
b. Cells growth and development takes place during mitotic phase while its
reproduction takes place during interphase
c. The nucleus of a cell divides during interphase while the cytoplasm of the
cell divides during mitotic phase.
d. The nucleus of a cell divides during mitotic phase while the cytoplasm of
the cell divides during interphase.
2. Which of the following shows the correct sequence of the cell cycle?
a. S - G1- G2- mitosis- cytokinesis c. Cytokinesis- mitosis- G1 - S- G2
b. G1-S - G2- mitosis – cytokines
d. Mitosis -G1 - S- G2 - cytokinesis
3. Which of the following is not a function of mitosis?
a. Development (baby in mother’s womb)
b. Repair of damaged cells in multicellular organisms
c. Production of gametes
d. Asexual reproduction in unicellular organisms
4. What is the correct order of the stages of mitosis?
1- METAPHASE
2 - TELOPHASE
3- ANAPHASE
4 - PROPHASE
a. 4,1,2,3
b. 2,3,1,4
c. 4,1,3,2
d. 1,2,3,4
5. What is the key difference between spermatogenesis and oogenesis?
a. Spermatogenesis is the formation of 4 sperm while oogenesis is the
formation of one egg cell.
b. Spermatogenesis is the formation of 2 sperm while oogenesis is the
formation of one egg.
c. Spermatogenesis results in only 1 sperm; oogenesis results in 2 eggs.
d. Spermatogenesis results in only 1 sperm; oogenesis results in 4 eggs.
What’s In
Every second of an hour in your daily lives, there
is an important event going on in your body and that is
- cells are dividing. When a cell divides, it will make new
cells. We call this process “cell division” and “cell
reproduction”. A dividing cell undergoes series of
growth and development stages between its “birth”
(formation by the division of a mother cell) and
reproduction (division to make new daughter cells)
which is also known as the Cell Cycle.
Figure 2.1
Source: https://www.twinkl.ae/illustration/
9
What’s New
Does it made you think, when you find some cut on any part of your body and
a few days later, it’s gone and healed? When you look at the mirror and you notice
that you grow a lot bigger than you were when you were six years old and got looks
from both of your parents? You don’t even think anything other than the amazing
process that cause it to happen. All of these things happened because of cell division.
The cut in your arm that was healed after a few days and increase in your height
happened because of division and production of new cell called Mitosis. And having
looks from both of your parents is caused by another type of cell division called
Meiosis. Mitosis and Meiosis are part of the Cell Cycle.
What is It
Cell cycle is composed of interphase and cell division phase. The bulk of the cell
cycle is spent in the “living phase”, known as interphase. Interphase
is further broken down into 3 distinct phases: G1 (Gap 1), S
(Synthesis) and G2 (Gap 2).
G1 phase - cell increases in size, cellular contents duplicated
S phase - DNA Replication or DNA Synthesis, each of the 46 chromosomes is
replicated by the cell
G2 phase - cell grows more and organelles develop in preparation for cell division
Cell Division
Alternating with the interphase is the cell division phase. In eukaryotic cells,
there are two types of cell division: mitosis and meiosis.
Mitosis is a type of cell division that
produces two identical cells with the same
number of chromosomes. Mitosis is
divided into four phases.
 Prophase - The nuclear membrane
and nucleoli still present. The
chromosomes are thicker and
shorter because of repeated coiling.
Figure 2.2. Mitosis
At this stage, each chromosome is
Source: https://image.shutterstock.com/image-illustration/animal-cellmitosis-illustration-chromosomes-260nw-1539718535.jpg
made up of two identical sister
chromatids attached at one point,
called the centromere. Spindle fibers are formed
 Metaphase - The nuclear membrane has disappeared while the coiled
chromosomes align at the metaphase plate. Spindle fibers are attached to a
protein called kinetochore at the centromere of each sister chromatid of the
chromosome.
 Anaphase - The paired centromeres of each chromosomes separate toward the
opposite poles of the cells as they are pulled by both spindle fibers through their
10
kinetochores. This liberates the sister chromatids. Each sister chromatid is now
a single chromosome.
 Telophase - The chromosomes are at the opposite poles and start to uncoil. The
nucleoli and nuclear membrane reappear while the spindle fibers disappear.
There is also cytokinesis (division of the cytoplasm) to form two separate
daughter cells immediately after mitosis.
Meiosis reduces the chromosomes number in half. Cell undergoes two rounds of cell
division (Meiosis I and Meiosis II) to form four daughter cells, each with half the
chromosome number as the original parent cell and with a unique set of genetic
material as a result of crossing over (a segment of a sister chromatid of one
chromosome is exchanged with the same segment of the chromatid of the
homologous chromosome)
Meiosis I
•Prophase I - Meiosis starts with this stage
•Metaphase I - Homologous chromosomes align at the equatorial plate
•Anaphase I - The homologous chromosomes separate from each other and start
their movement
toward the opposite poles.
•Telophase I - Two nuclei are produced, each containing only half the
chromosome number of the original parent cell.
Meiosis II is similar to mitosis. It consists of the
following stages: prophase II, metaphase II
anaphase II and telophase II. Each doublestranded chromosome attaches to a spindle
fiber then its centromere splits into two and the
two strands of the chromosome move to
opposite poles. At the end of the cell division,
four haploid daughter cells are produced.
Figure 2.3 Gametogenesis in animals
Surce:https://www.jing.fm/iclipt/ibJhbii/
Gametogenesis
The production of an egg cell and a sperm
https://www.vcbio.science.ru.nl/en
cells is called gametogenesis. Gametogenesis involves
meiosis to produce haploid
/imagegametes in preparation for sexual reproduction.
gallery/show/labels/PL0286/
Spermatogenesis is the production of sperm cells in testes of male animals.
Meiosis produces four small cells of similar size. These cells become spermatozoa or
sperms.
Egg cells are produced in the ovary of female animals through the process
of oogenesis. When a cell in the ovary undergoes meiosis I, two cells -one big and
one small (polar body)- are produced.
Meiosis in gametogenesis may not always proceed normally. In humans,
accidents like failure of the chromosomes to separate during meiosis I may cause
abnormal conditions.
11
What’s More
Activity 1: Cell Cycle
Objective:
Describe the stages of the cell cycle.
Materials:
Worksheet, Pen, coloring materials
Directions:
On the given diagram, lightly color the G1
phase BLUE, the S phase YELLOW, the G2 phase
RED, and the stages of mitosis ORANGE. Color
the arrows indicating all of the interphases in
GREEN. Color the part of the arrow indicating
mitosis PURPLE and the part of the arrow indicating
cytokinesis YELLOW.
Source: https://www.pinterest.ph/pin/426645764684730019/
Guide Questions:
Use the diagram to answer the following questions:
1. What is the longest stage of the cell cycle?
_________________________________________________________________________________
2. In what stage does the G1, S and G2 phases happen?
__________________________________________________________________________________
3. In what phase of the cell cycle does cell division occur?
__________________________________________________________________________________
4. In which phase of the cell cycle does the cell grows?
__________________________________________________________________________________
5. During what phase of the cell cycle is DNA replicated?
__________________________________________________________________________________
6. During what phase of the cell cycle does the cell prepares for Mitosis?
__________________________________________________________________________________
7. What are the stages of Mitosis?
__________________________________________________________________________________
Activity 2: ACROSS THE STAGES!
Objective:
Identify the changes in each stage of mitosis and meiosis
Materials:
Worksheet
Pen
12
Part A. Below are the illustrations of the stages of Mitosis. Determine the events in
each stage by looking at each illustration. Put a check on all descriptions of the
events in each stage.
PROPHASE
METAPHASE
ANAPHASE
__1. The chromatin
condenses into
sister chromatids
__2. Nuclear
membrane starts
to disappear
__3. Centrioles start
to form spindle
fibers
__4. Chromosomes
separate
__1. The sister
chromatids
disappear.
__2. Spindle fibers are
attached to the
centromere of sister
chromatids.
__3. Centrioles start to
form spindle fibers.
__4. Sister chromatids
line up along the
equatorial plate.
__1. Sister chromatids
separate into
chromosomes.
__2. Sister chromatids
are pulled toward
opposite poles.
__3. Shortening of spindle
fibers.
__4. Formation of
cleavage furrow.
TELOPHASE
__1. Reappearance of
nucleolus and
nuclear membrane
__2. Chromosomes
condenses
__3. Spindle fibers
disappear
__4. Cleavage furrow
deepens that divides
the cell
__5. Chromosomes start
to uncoil.
Guide Questions:
1. At the end of telophase, cytokinesis occurs. What do you think will happen to the
cell? _____________________________________________________________________________
2. How many daughter cells will be produced in Mitosis?
__________________________________________________________________________________
3. How will you compare the chromosome number of each daughter cell and the
parent cell? ______________________________________________________________________
Part B. DOUBLE MATCHING TYPE: Match Column A to its correct illustration in
Column B and its corresponding description in Column C. Write your answer in the
space provided.
A to B
A to C
A
I. Prophase I
II. Metaphase I
III. Anaphase I
IV. Telophase I
V. Prophase II
B
1
2
3
4
5
C
Chromosomes gather at the
poles. Cytoplasm divides
A
The nuclear envelope breaks
down, genetic
material is exchanged
through crossing over
B
Pairs of homologous
chromosomes line up
at the equator
C
Chromatids remain attached
at their centromeres as
the spindle fibers move
the homologous
chromosomes to
opposite poles
A new spindle forms around
the chromosomes.
D
E
13
6
VI. Metaphase II
7
VII. Anaphase II
VIII. Telophase II
8
Chromosomes line up at the
equator
F
A nuclear envelope forms
around each set of
chromosomes, the
spindle breaks down
and cytoplasm divides,
resulting in four haploid cells.
Centromeres divides enabling
the chromatids
now called chromosomes
to move to opposite poles
of the cell.
G
H
Part C. Complete the Venn diagram to compare mitosis
and meiosis. Use the phrases on
each box by writing its corresponding number inside the diagram.
Mitosis
BOTH
Meiosis
1.Crossingover
2. Synapsis
3. Formation
of spindle
fibers
4. Produces
haploid
cells
5. For
formation of
egg cells and
sperm cells
9. Cytokinesis
and
Karyokinesis
take place
6.Formation
of two
daughter
cells
10. Produces
four
daughter
cells
7. Occurs in
plant and
animal cells
8. Involves
cellular
division
11.Produces
cells
identical to
parent cells
12.For
growth and
repair of
damaged
body cells
Activity 3: Spermatogenesis vs. Oogenesis
Objective:
Differentiate spermatogenesis from oogenesis
Materials:
Worksheet
Pen
Word Bank
Directions: Complete the graphic organizer below by writing
the correct statement on each box. Choose your answer inside
the Word Bank.
Point of Comparison
Location
Number of gametes produced
Products of meiosis
When does the process
begins
When does the process stops
If cytokinesis during meiosis
is equal
Spermatogenesis
Oogenesis
- ovary
- seminiferous tubules in
testes
- one per month
-millions per day
- cytoplasm split unequal
- equal division of cytoplasm
- 1 egg cell, 3 polar bodies
- 4 cells
- puberty
- during development of fetus
- at menopause
-until death
14
What I Have Learned
Directions: Read the paragraph and fill in the missing words. Choose the correct
words from the box below.
Cells reproduce in a process called (A______________), which split into two
main parts. The first part is called (B.____________) where cell absorbs nutrients and
grows in size. During this time, it also copies its (C_____). Once the cell is big enough,
it begins the second part called (D.____________) All of these steps together are called
the (E.__________.
(F.________) the process of cell division that usually forms the male sperm in
animals and female (G. ______). It occurs in two successive divisions. One diploid
cell (2n) in the male or female reproductive organs (testes and ovaries) produces
(H._______) haploid daughter cells. These cells become the (I._____) sperm cells in
males, or one egg cell and (J_______) polar bodies in females.
(K._______) is the process that produces cells with the chromosome number
(L._____) as the parent cell. Usually one diploid cell produces (M._____) new ‘daughter
‘cells. It produces all human body cells except the gametes.
(N._____), (O._____), (P._____) and (Q._____) are the 4 phases in both meiosis
and mitosis
Interphase
DNA
cell division cell cycle Mitosis four two
three
Metaphase Prophase
ovum (egg)
Anaphase
Meiosis Prophase same Telophase
What I Can Do
Directions: Answer the following questions.
1. Why is cell division important in the life of an organism?
___________________________________________________________________________________________
2. How does cell division helps our body stay healthy?
___________________________________________________________________________
3. Why is meiosis vital to sexually reproducing organisms?
___________________________________________________________________________
Assessment
Multiple Choice. Choose and write the letter of the best answer before each
number.
1. What is the correct sequence in which the stages of mitosis occur??
a. Metaphase-anaphase-prophase-telophase.
b. Prophase-metaphase-anaphase-telophase
c. Telophase-anaphase-metaphase-prophase
d. Anaphase-telophase-prophase-metaphase
15
2. Which terms are mismatched?
a. Interphase: DNA replication
b. Prophase I -synapsis
c. Cytokinesis-cell plate formation
d. Metaphase- centromere division
3. What type of cell division results in daughter cells having an exact copy of
chromosomes from parent cell?
a. Mitosis
b. Meiosis
c. Interphase
d. Synapsis
4. Which of the following phase sister chromatids move towards opposite poles?
a. Prophase
b. Metaphase
c. Anaphase
d. Telophase
5. Which of the following is not a function of mitosis?
a. Growth
c. Replacement of dead cells
b. Recovering from injuries
d. Formation of sex cells
6. Which of the following describes the number of daughter cells produced in
mitosis and meiosis?
a. 4 haploid daughter cells in mitosis and 2 diploid daughter cells in meiosis
b. 4 diploid daughter cells in mitosis and 2 haploid daughter cells in meiosis
c. 2 diploid daughter cells in mitosis and 4 haploid daughter cells in meiosis
d. 2 haploid daughter cells in mitosis and 4 diploid daughter cells in meiosis
7. What happens during crossing over?
a. chromosomes collide
b. chromosomes exchange genetic material
c. chromosomes die
d. chromosomes replicate
8. Which of the following happens during gametogenesis?
a. Mitosis
b. Meiosis
c. Mitosis and Meiosis
d. Synapsis
9. In what stage of Meiosis I does crossing over occurs?
a. Leptotene
b. Zygotene
c Pachytene
d. Diplotene
10. Which of the following is the purpose of meiosis in gametogenesis?
a. growth of spermatogonium and oogonium
b. maturation of oogonium and spermatogonium
c. replicate DNA in the cell
d. reduces the number of chromosomes in resulting daughter cells
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Lesson
Mendelian Pattern of Inheritance
3
Reproduction process is an anchor to the variation of an organism. The
importance of blending the traits contributed by both parents for the succession of
a specie. Understanding how we can predict and make control of traits not to be
inherited but needs quality development for mankind.
In this lesson, you will be able to describe Mendel’s principle of inheritance,
identify expressed traits and predicting probability transfer of traits from parents to
offspring by using Reginald Punnett diagram. We cannot deny that yielding a good
variety of offspring specially our natural resources such as plant and animals can
make a general change in all aspects of our life, health, environment and society
What I Know
Choose the letter of the correct answer. Write your answers on a separate sheet of
paper.
1. Which of the following express a phenotype of an offspring?
a. An infant having XY gametes.
c. A dwarf fruit bearing mango tree.
b. A kitten of XX gametes.
d. A puppy of XXY allele.
2. A green (pod color) is crossed with another green (pod color) phenotype. What
possible ratio of an offspring it will produce?
a. ¾ yellow, ¼ green
c. 100 % green
b. ½ yellow, ½ green
d. 100 % yellow
3. Male black dog was cross breed to a female white fur dog. The pair produces
4 black fur puppies and 2 white. What can you say about it?
a. White fur of female dog is the dominant trait.
a. Black fur of male dog is the dominant trait.
b. Black fur of male dog is a recessive trait.
c. White and black fur are equally dominant.
4. Which describes an allele expresses in TT, Rr, rr, XY, XX?
a. Genotype
b. Hybridization c. Phenotype
5.
d. Mutation
In a cross between heterozygous round (Rr) and wrinkled
(rr). What is the phenotypic ratio of the offspring?
a. 3:1
c. 4:0
b. 1:1
d. 2:1
X
R
r
r
Rr
rr
r
Rr
rr
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What’s In
You have just learned that the human body is composed of different kinds of
cells which made up your tissues and organs, with special function that help build
you as a new Individual. Reproduction is the biological process by which new
individual organisms- “offspring”- are produced from their “parents”. It happens
when there is a union of male (Father) and female (Mother) reproductive cells
known as gametes. Gametes are the sex cells known as sperm and egg cell of your
parents that each carries chromosome where genes or traits embed. As you have
previously learned, Homologous Chromosomes during meiosis, undergoes crossing
over of genes causes synapse that allows shared DNA sequence. Have you ever
wondered, why you do not exactly look alike with neither your father, mother nor
your siblings?
What’s New
BUILD ME UP!
Directions: Arrange the scrambled letters to reveal the word best describe by the
following statements. Write your answer on the space provided.
(GROGER LEMEND) a monk scientist known as “Father of Genetics” who
designed the “Pea experiment”. __ __ __ __ __ __ __ __ __ __ __ __
2. (ODIMNTAN) a trait more expressed of offspring from their parents.
__ __ __ __ __ __ __ ___.
3. (GEEN) a factor of traits or unit of inheritance. ___ ___ ___ ___
4. (AGMESET) refer to sex cells- the egg and sperm. __ __ __ __ __ __ __
5. (CREESSVIE) a trait which did not appear in F1 generation.
__ __ __ __ __ __ __ __ __
6. (LALESEL) pair of factors or genes which controls the appearance of a
particular trait.
__ __ __ __ __ __ __
7. (HEPNOTYEP) refers to the appearance or external expression of traits such
as dwarf, tall, short, round, curly. __ __ __ __ __ __ __ __ __
8. (NEGNOPEYT) refers to the particular alleles such as TT, bb or Rr.
__ __ __ __ __ __ ___ __
9. (EHREDTIY) is the transmission of traits from one generation to the next.
__ __ __ __ __ __ __ __
10. (EGNETCIS) a science of heredity and variation. __ __ __ __ __ __ __ __
1.
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What is It
Genetics is a branch of science that deals with the
study of heredity and variation. Gregor Johann Mendel
(1822-1884), An Austrian monk, is known as the “Father of
Genetics”. After 8 years statistically experimenting garden
peas, he was able to publish a paper in 1866 on the
mechanism of Heredity or transmission of traits from one
generation to the next. Why Pea plant? Garden pea is
considered a good material because its stamen and pistil are
enclosed by petals protecting the stigma from stray pollen,
with pair of contrasting traits, easy to cultivate, short
generation time and thus, ensure cross and self-pollination.
The table below shows the characteristics of garden pea
plant studied by Gregor Mendel.
Figure 3.1. Gregor Mendel
Figure 3.3
Figure 3.2: Characteristics of Garden Pea Plant
Source: https://qph.fs.quoracdn.net/main-qimg ff8d4ffe93e2d18da91e98586b713d4b





Mendel studied how traits are being passed from one generation to the next.
Mendel first produced pure-breeding plants. He allowed his pea plant to self
-pollinate for many generations until all the offspring had the same features
as the parents, generation after generation. Pure -breeding peas make up the
parental or P1 generation.
Mendel began cross pollinating of parental (P1) generation peas with
contrasting traits. For example: Pea plant (P1) of round seed x Pea plant (P1)
of wrinkled seed = all the offspring had round seeds. These offspring of
parental cross are called the first Filial (F1) generation.
First filial (F1) generation are also called hybrid, resulted from a cross
between two pure-breeding plants with contrasting traits.
When the plants from the F1 generation were crossed with each other or selfpollinated the offspring (F2) Second filial generation were of two types.
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External traits expressed such as round, wrinkled seed shape is considered
the Phenotype (physical characteristics). The most distinct physical trait is a
dominant trait. For example, round and wrinkled seed shape produces round seed
shape offspring.
On the other hand, Genotype refers to letter or a variable (T, t, R, r)
demonstrating an allele of paired factor or genes with contrasting trait. Factor or
gene serves as the unit of inheritance. A characteristic not visible in an offspring is
a masked trait known as recessive trait.
Dominant genes are demonstrated by a big letter, for example green seed coat
is expressed in pair of letter GG mean for being dominant, while yellow seed coat
presented in pair of small gg to show being recessive. Expression of genes with
similar letters neither big or small (TT, tt) tells the trait is homozygous while a
combination of big and small (Tt) indicates a heterozygous.
THE MENDELIAN LAWS OF HEREDITY
 The Law of Independent Assortment - The appearance of a particular
trait in each organism is controlled by pairs of gene or factors
 The Law of Dominance – the dominant trait prevents the expression of the
recessive trait
 The Law of Segregation - the pair of genes segregate or separate from each
other during gamete formation.
Monohybrid Cross using Punnett Square
Punnett Square is a simple diagram named
after Reginald Punnett which will help you visualize
the results of a cross. Using this device, the symbols
for all the possible alleles carried by male gametes
are arranged on the top portion whereas the female
gametes are located on the left side. By combining
the alleles of both male and female gametes, all
possible gametes combination of the offspring can
now be determined.
Figure 3.4: Monohybrid Cross using Punnett Square
Source:vhttps://www.thoughtco.com
What’s More
Activity 1: Oh My! It’s a Genre.
Objective:
Describe the Mendelian Principle of Inheritance in a Pea plant Experimentation.
Materials:
Worksheet
Pen
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Directions: Write numbers 1 to 5 on the space provided before each box to show the
sequence of the Pea Plant experimentation, then answer the guide
questions accurately.
Transferred pollen from stamens of white flower to carpel of purple flower
Examined all purple flower offspring.
Pollinated carpel matured into pod
Removed stamens from purple flower
Plant seeds from pod
Guide Questions:
1. What characteristic of the pea plant was transferred?
__________________________________________________________________________
2. How do you call that process of transferring of pollen from stamen to carpel
of a flower? ______________________________________________________________
3. What is the resulting color of the offspring?
__________________________________________________________________________
4. Does the pea plant offspring get its resulting color from its pea plant parent?
__________________________________________________________________________
5. Do you think there will be a chance for a white pea plant flower to exist?
Why? _____________________________________________________________________
Activity 2: Twinning to be True ……
Objective:
Predict phenotypic and genotypic expressions of traits following simple
patterns of inheritance
Materials:
Worksheet
Pen
Part A. Procedure:
1. Analyze the given trait transferred from parent to offspring of Mendel’s Pea plant
experimentation
Monohybrid Test Cross
Mendel crosses height of a pure breed tall pea plant with a dwarf pea plant.
What do you think will be the inherited factor and characteristic of the offspring?
Will it be all tall or dwarf? Use the Punnett Square below and answer the following
questions.
Father Phenotype: Tall
Mother Phenotype: dwarf
Genotype: TT
Genotype: tt
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Monohybrid Cross
a.
b.
c.
d.
e.
List down the genotypes of offspring.
List down the phenotypes of offspring
Write its genotypic ratio.
Write its phenotypic ratio.
Percentage of tall offspring? dwarf offspring?
2. Cross pollinate F1 (First Filial generation) to another F1 (Filial generation) to
produce F2 Second Filial generation
Monohybrid Cross
f.
g.
h.
i.
j.
List down the genotypes of offspring.
List down the phenotypes of offspring
Write its genotypic ratio.
Write its phenotypic ratio.
Percentage of tall offspring? dwarf
offspring?
Part B. Guide Questions:
1. What is the expressed characteristic of F1 offspring? in F2?
_________________________________________________________________________________
2. When F1 generation cross pollinated to another F1 generation, how many trait
/s is /are observed to all offspring? What are these traits?
__________________________________________________________________________________
3. How do you call this trait or characteristic that expressed the greatest number of
offspring? _______________________________________________________________________
4. How about the least expressed trait of an offspring?
__________________________________________________________________________________
5. When did dwarf recessive trait express?
__________________________________________________________________________________
What I Have Learned
1. How did Johan Gregor Mendel trace the traits transferred of Parent pea plant
to offspring?
____________________________________________________________________________
2. Describe the Three Mendelian Principle of Inheritance.
____________________________________________________________________________
3. What is the difference between Phenotypic and Genotypic ratio?
_____________________________________________________________________________________________
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What I Can Do
Mirror, Mirror!
1. Make a Photo Scrapbook presentation of your Family Map generation from your
grandparents, parent, siblings and siblings Family (if have their own)
2. List down all observable traits in your family. Use a table chart to present it.
3. Put a heart if traits are manifested either from your mother or father.
1.
2.
3.
4.
CHARACTER/TRAITS
COMPLEXION (Fair/Dark)
COLOR OF THE EYES
EAR LOBES (Attached /Free)
HAIR TYPE (Curly/ Straight)
Guide Questions:
1.
2.
3.
4.
5.
What are the traits manifested from your family?
Which of these traits you have inherited from your mother, father or both?
What do you mean by inherit?
How are these traits passed on from parents to offspring?
How many percent of the traits were expressed from your grandparent to your
siblings? How about from your father or mother? Calculate the phenotypic and
genotypic ratio expressed in your family.
Assessment
A. Multiple Choice. Choose and write the letter of the best answer before each
number.
1. Which of the following is an example of Mendellian Law of Dominance?
a. The short trunk of palm tree.
c. Heterozygous tall palm tree.
b. Homozygous tall palm tree.
d. Dominant tall palm tree.
2. Which phenotypic ratio will be expressed if a green (pod color) plant is crossed
with another of the same phenotype?
a. ¾ yellow, ¼ green
c. 100% green
b. ½ yellow, ½ green
d. 100% yellow
3. In a cross between heterozygous round and wrinkled, what is the phenotypic
ratio of the offspring?
a. 3:1
b. 1:1
c. 4:0
d. 1:3
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4. If in a cross, a pure yellow seeded pea plant is crossed with a pure greenseeded plant, all F1 generation are yellow. What conclusion can you make?
a. yellow seed is the dominant trait.
b. green seed is the dominant trait
c. yellow and green are equally dominant
d. neither yellow nor green combined.
B. Draw a smiling emoji if the describe trait is a dominant trait and sad emoji if it
is a recessive trait
____1. BB black mice
______3. cc curly hair
______5. FF fair skin color
____2. ww white cat
______4. LL long eyelashes ______6. CC straight hair
C. Monohybrid Cross Problem.
1. In mice, black fur (B) is dominant over white (b). Cross a homozygous
dominant mouse with a white mouse. What are the possible phenotypes and
genotypes in the offspring? Write the genotypic and phenotypic ratio. Draw
a Punnett square
2. In summer squash, white fruit color (W) is dominant over yellow fruit color
(w). If a squash plant homozygous for white is crossed with a plant
homozygous for yellow, what will the phenotypic and genotypic ratios of the
offspring. Draw a Punnett square.
Additional Activities
To learn more about Cross with Two factors (dihybrid) and Inferring genotypes of
Blood types you can watch video lesson entitled Dihybrid Genetic Cross
https://www.youtube.com/watch?v=1QU2phs-hws
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