Senior High School
NOT
General Biology 2
Quarter 2 - Module 2
COMPARE AND CONTRAST
PROCESSES IN PLANTS AND ANIMALS
Department of Education ● Republic of the Philippines
Senior
High
School
Senior
High
School
General Biology
2
Quarter 2 - Module 2:
Compare and Contrast Processes in Plants
and Animals
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significant contributions to this module.
How to Learn from this Module
To achieve the learning competencies cited above, you are to do the following:
•
Take your time reading the lessons carefully.
•
Follow the directions and/or instructions in the activities and exercises diligently.
•
Answer all the given tests and exercises.
Icons of this Module
What I Need to
Know
This part contains learning objectives that
are set for you to learn as you go along the
module.
What I know
This is an assessment as to your level of
knowledge to the subject matter at hand,
meant specifically to gauge prior related
knowledge
This part connects previous lesson with that
What’s In
of the current one.
What’s New
An introduction of the new lesson through
various activities, before it will be presented
to you
What is It
These are discussions of the activities as a
way to deepen your discovery and understanding of the concept.
What’s More
These are follow-up activities that are intended for you to practice further in order to
master the competencies.
What I Have
Activities designed to process what you
Learned
have learned from the lesson
What I can do
These are tasks that are designed to showcase your skills and knowledge gained, and
applied into real-life concerns and situations.
ii
Lesson
1
Reproduction and
Development
What I need to know
Learning Competency
Compare and contrast the following processes in plants and animals: reproduction and
development. (STEM_BIO11/12-IVa-h-1)
At the end of the lesson, the learners will be able to:
•
•
•
•
•
•
•
differentiate asexual from sexual reproduction; and
describe different modes of sexual and asexual reproduction
describe the different stages of animal development
describe human reproductive organ systems
enumerate the different types of reproductive cycles
describe double fertilization in flowering plants; and
explain processes in plant development.
What I know
Definition of Terms:
1. Asexual Reproduction
11. Haploid
2. Sexual Reproduction
12. Diploid
3. Fission
13. Gametogenesis
4. Fragmentation
14. Fertilization
5. Budding
15. Cleavage
6. Sporulation
16. Gastrulation
7. Isogamy
17. Organogenesis
8. Heterogamy
18. Growth
9. Bisexual Reproduction
19. Folicular phase
10. Development
20. Ovulation
1
What’s new
PRE-ACTIVITY:
1. Differentiate Asexual Reproduction and Sexual Reproduction.
2. Identify the types of asexual reproduction and give examples.
Types of Asexual Reproduction
Examples
1.
2.
3.
4.
3. Summarize the differences between asexual and sexual reproduction.
Asexual Reproduction
Sexual Reproduction
Number of Parents Involved
Gametes
Genetic composition of
offspring
2
What’s is it
INTRODUCTION:
Development is the process by which a multicellular organism, beginning with a single
cell, goes through a series of changes, taking on the successive forms that characterize its life
cycle.
Animal and Plant Development
Fig. 1-1. Selected developmental stages and processes. Reference:
https://tinyurl.com/y5f896m7
FOUR KEY PROCESSES UNDERLIE DEVELOPMENT
The developmental changes an organism undergoes as it progresses from an embryo to
mature adulthood involve four processes:
❖ Determination sets the developmental fate of a cell—what type of cell it will become—
even before any characteristics of that cell type are observable. For example, in a
developing mammalian embryo, as well as in some adult organs, there are
mesenchymal stem cells that look unspecialized. But their fate to become muscle, fat,
tendon, or other connective tissue cells has already been determined.
❖ Differentiation is the process by which different types of cells arise from less
specialized cells, leading to cells with specific structures and functions. For example,
mesenchymal stem cells differentiate to become the cells listed above.
❖ Morphogenesis (Greek for “origin of form”) is the organization and spatial distribution
of differentiated cells into the multicellular body and its organs. Morphogenesis can
occur by cell division, cell expansion (especially in plants), cell movements, and
apoptosis (programmed cell death).
❖ Growth is the increase in size of the body and its organs by cell division and cell
expansion. Growth can occur by an increase in the number of cells or by the
enlargement of existing cells. Growth continues throughout the individual’s life in some
organisms but reaches a more or less stable end point in others.
Reference: https://tinyurl.com/y5f896m7
3
HUMAN REPRODUCTIVE SYSTEM
Organ system by which humans reproduce and bear live offspring. Provided all organs
are present, normally constructed, and functioning properly, the essential features of human
reproduction are (1) liberation of an ovum, or egg, at a specific time in the reproductive cycle,
(2) internal fertilization of the ovum by spermatozoa, or sperm cells, (3) transport of the
fertilized ovum to the uterus, or womb, (4) implantation of the blastocyst, the early embryo
developed from the fertilized ovum, in the wall of the uterus, (5) formation of a placenta and
maintenance of the unborn child during the entire period of gestation, (6) birth of the child and
expulsion of the placenta, and (7) suckling and care of the child, with an eventual return of the
maternal organs to virtually their original state.
Fig. 1-2. Human Reproductive System.
What’s more
ACTIVITY:
1. Identify and Describe the types of Life cycles.
Types of Life Cycles
1.
2.
3.
4
Description
Lesson
2
Nutrition
What I need to know
Learning Competency:
Compare and contrast the following processes in plants and animals: Nutrition.
(STEM_BIO11/12-IVa-h-1)
Specific Learning Outcomes:
At the end of the lesson, the learners will be able to:
•
•
•
•
define nutrient and cite the nutritional requirements of plants and animals
enumerate and describe the main stages of food processing;
describe the organs involved in food processing in the human digestive system and
their roles;
summarize the mechanisms of digestion, absorption, and delivery of nutrients into
cells;
What I know
PRIOR KNOWLEDGE: Definition of Terms
1. Nutrient
12. Fats
2. Autotrophs
13. Amino acids
3. Heterotrophs
14. Fatty acids
4. Symplast route
15. Phagocytosis
5. Apoplasts route
16. Pinocytosis
6. Root hairs
17. Digestive system
7. Root nodules
18. Endocytosis
8. Mycorrhizae (singular, mycorrhiza)
19. Ingestion
9. Calorie
20. Digestion
10. Carbohydrates
21. Absorption
11. Proteins
22. Elimination
5
What’s new
PRE-ACTIVITY:
Reference: https://www.evolvingsciences.com/Photosynthesis%20worksheet%20.html
6
What’s is it
INTRODUCTION:
PLANT NUTRITION
Nutrient – refers to any substance required for the growth and maintenance of an organism.
The two types of organisms based on the mode of nutrition are:
A. autotrophs – organisms that obtain energy from sunlight and chemicals to produce
their own food. Examples: plants; chemosynthetic bacteria.
B. heterotrophs – organisms that cannot make their own food and obtain their energy
from other organisms. Examples: animals, fungi.
The nutritional requirements of plants:
• water
• carbon dioxide
A. Further, note that water and carbon dioxide are the raw materials needed for
B. photosynthesis, the process by which plants convert the energy from sunlight into
• chemical energy.
C. essential nutrients or elements – which include macronutrients which are normally
required in amounts above 0.5% of the plant’s dry weight; and micronutrients which
are required in minute or trace amounts;
• examples of macronutrients: C, H, O, N, K, Ca, Mg, P, S
• examples of micronutrients: Cl, Fe, B, Mn, Zn, Co, Mo
The routes for the absorption of water and minerals across plant roots:
A. symplast route – through plasmodesmata
B. apoplast route – along cell walls
Note that the water and minerals from the soil need to reach the conducting tissues
of plants, specifically the xylem
ANIMAL NUTRITION
A Calorie is a unit of energy that indicates the amount of energy contained in food. It
specifically refers to the amount of heat energy required to raise the temperature of 1 kg (2.2
lb.) of water by 1oC (1.8oF). The greater the number of Calories in a quantity of food, the
greater energy it contains (Johnson and Raven, 1996).
THE NUTRITIONAL REQUIREMENTS OF ANIMALS:
•
•
Carbohydrates – serve as a major energy source for the cells in the body. These are
usually obtained from grains, cereals, breads, fruits, and vegetables. On average,
carbohydrates contain 4 Calories per gram.
Proteins – can also be used as an energy source but the body mainly uses these as
building materials for cell structures and as enzymes, hormones, parts of muscles, and
bones. Proteins come from dairy products, poultry, fish, meat, and grains. Like
carbohydrates, proteins also contain 4 Calories per gram.
7
•
Fats – are used to build cell membranes, steroid hormones, and other cellular structures;
also used to insulate nervous tissue, and also serve as an energy source. Fats also contain
certain fat- soluble vitamins that are important for good health. Fats are obtained from oils,
margarine, butter, fried foods, meat, and processed snack foods. They contain a higher
amount of energy per gram than carbohydrates or proteins, about 9 Calories per gram.
•
Essential Nutrients – include substances that animals can only get from the foods they
eat because they could not be synthesized inside the body. These include:
➢ Essential amino acids – needed for synthesis of proteins and enzymes;
among the 20 amino acids, eight could not be synthesized by humans: lysine,
tryptophan, threonine, methionine, phenylalanine, leucine, isoleucine and
valine.
➢ Essential fatty acids – used for making special membrane lipids; an example
is linoleic acid in humans.
➢ Vitamins – organic molecules required in small amounts for normal
metabolism; examples include fat-soluble Vitamins A, D, E, K, and watersoluble Vitamins B, B2, B3, B12, C.
THE MAIN STAGES OF FOOD PROCESSING:
1. Ingestion – the act of eating or feeding; this is coupled with the mechanical breakdown
of food into smaller pieces allowing for a greater surface area for chemical digestion.
2. Digestion – breakdown of food into particles, then into nutrient molecules small
enough to be Chemical digestion by enzymes involves breaking of chemical bonds
through the addition of water, i.e., enzymatic hydrolysis
3. Absorption – passage of digested nutrients and fluid across the tube wall and into the
body fluids; the cells take up (absorb) small molecules such as amino acids and simple
sugars.
4. Elimination –expulsion of the undigested and unabsorbed materials from the end of
the gut.
THE ORGANS INVOLVED IN FOOD PROCESSING IN THE HUMAN DIGESTIVE SYSTEM:
A. The Oral Cavity, Pharynx, and Esophagus
• Oral Cavity – it is where food is initially chewed into shreds by the teeth, and mixed
with saliva by the tongue. Saliva is secreted into the mouth by three pairs of salivary
glands located above the upper jaw and below the lower jaw.
• Pharynx –the region in the back of the throat that serves as the entrance to the
esophagus that connects to the stomach and trachea (windpipe) that serves as airway
to the lungs. To block breathing as food leaves the pharynx, a flap-like valve (the
epiglottis) and the vocal cords close off the trachea.
• Esophagus – connects the pharynx with the stomach. No digestion takes place within
the esophagus but the contractions within its muscular wall propel the food past a
sphincter, into the stomach. The rhythmic waves of contraction of the smooth muscle
wall of the esophagus are called peristaltic contractions or peristalsis. The esophagus
is about 25 cm (10 in.) long.
B. The Stomach
8
The stomach is a muscular, stretchable sac located just below the diaphragm. It has three
important functions.
➢ First, it mixes and stores ingested food.
➢ Second, it secretes gastric juice that helps dissolve and degrade the food,
particularly proteins.
➢ Third, it regulates the passage of food into the small intestine.
• The gastric juice is a combination of HCl and acid-stable proteases.
• The churning action of the stomach together with the potent acidity of the gastric juice
convert food into a thick, liquid mixture called chyme.
C. Small Intestine
•
•
•
•
The small intestine is approximately 6 meters long and is composed of three regions:
the duodenum, jejunum, and ileum.
It is where most enzymatic hydrolysis of the macromolecules from food occurs. The
complete digestion of carbohydrates, fats, and proteins occurs in the duodenum, about
the first 25 cm. of the small intestine.
The rest of the small intestine is devoted to absorbing water and the products of
digestion into the bloodstream.
Absorption of the end products of digestion takes place in the ileum, the surface area
of which is increased by villi and microvilli.
D. The Accessory Digestive Organs
•
•
•
Pancreas, Liver, and Gallbladder – review the functions discussed in previous meeting.
The Large Intestine or Colon
o The large intestine is much shorter than the small intestine, about 1 meter.
o It concentrates and stores undigested matter by absorbing mineral ions and
water. A small amount of fluid, sodium, and vitamin K are absorbed through its
walls.
o Unlike the small intestine, it does not coil up and does not have villi and has
only one thirtieth of the absorptive surface area of the small intestine.
o Many bacteria live and thrive within the large intestine where they help process
undigested material into the final excretory product, feces.
The Rectum and Anus
o The rectum is a short extension of the large intestine and is the final segment
of the digestive tract. It is where the compacted undigested food from the colon
are pushed via peristaltic contractions.
o The distention of the rectum triggers expulsion of feces.
o The anus is the terminal opening of the digestive system through which feces
are expelled.
9
What’s more
ACTIVITY:
1. Illustrate the steps in the digestive system. Label the organs involved and specify their
functions.
What’s I’ve learned
POST QUIZ:
1. Give three examples of nutrient deficiencies in plants and the corresponding symptoms.
2. Research on examples of parasitic plants and predator plants. Give an example for each.
What structural adaptations are present in these plants that allow them to acquire
nutrition through parasitism and predation?
3. What contributes to the absorption capacity of the small intestine?
4. Why doesn’t gastric juice destroy the stomach cells that make it?
5. What are the cells making up the gastric glands of the stomach?
10
Lesson
3
Gas Exchange
What I need to know
Learning Competency
The learners shall be able to compare and contrast gas exchange in plants and
animals. (STEM_BIO11/12-IVa-h-1)
Specific Learning Outcomes
At the end of the lesson, the learners will be able to:
•
•
•
•
state some basic principles IN gas exchange;
describe the structures for gas exchange in plants and animals;
describe the organs in the human respiratory system and their roles;
discuss the coordination of gas exchange and circulation;
What I know
PRIOR KNOWLEDGE: Definition of Terms
1. Respiration
2. Cellular Respiration
3. Positive pressure breathing
4. Negative pressure breathing
5. Air sacs
6. Oxygen Transport
7. Carbon dioxide transport
What’s new
PRE-ACTIVITY:
1. Identify the Organs of the Respiratory System and its functions.
2. Identify the Plant structures responsible for gas exchange and its functions.
11
What’s is it
INTRODUCTION:
Plants obtain the gases they need through their leaves. They require
oxygen for respiration and carbon dioxide for photosynthesis.
The gases diffuse into the intercellular spaces of the leaf through pores, which are
normally on the underside of the leaf - stomata. From these spaces they will diffuse into the
cells that require them.
Stomatal opening and closing depends on changes in the turgor of the guard cells.
When water flows into the guard cells by osmosis, their turgor increases, and they expand.
Due to the relatively inelastic inner wall, the guard cells bend and draw away from each other,
so the pore opens. If the guard cells loose water the opposite happens and the pore closes.
The guard cells lower their water potential to draw in water from the surrounding epidermal
cells, by actively accumulating potassium ions. This requires energy in the form of ATP which,
is supplied by the chloroplasts in the guard cells.
Respiration occurs throughout the day and night, providing the plant with a supply of energy.
Photosynthesis can only occur during sunlight hours so it stops at night. A product of
respiration is carbon dioxide.
This can be used directly by the plant in photosynthesis.
However, during the day, photosynthesis can be going 10 or even 20 times faster than
respiration (depending on light intensity), so the stomata must stay open so that the plant has
enough carbon dioxide, most of which diffuses in from the external atmosphere.
Reference:https://www.s-cool.co.uk/a-level/biology/gas-exchange/revise-it/gas-exchange-inplants#:~:text=Plants%20obtain%20the%20gases%20they,underside%20of%20the%20leaf%20%2D
%20stomata.
12
In animals, gas exchange follows the same general pattern as in plants. Oxygen and
carbon dioxide move by diffusion across moist membranes. In simple animals, the exchange
occurs directly with the environment. But with complex animals, such as mammals, the
exchange occurs between the environment and the blood. The blood then carries oxygen to
deeply embedded cells and transports carbon dioxide out to where it can be removed from the
body
Earthworms exchange oxygen and carbon dioxide directly through their skin. The
oxygen diffuses into tiny blood vessels in the skin surface, where it combines with the red
pigment hemoglobin. Hemoglobin binds loosely to oxygen and carries it through the animal’s
bloodstream. Carbon dioxide is transported back to the skin by the hemoglobin.
Terrestrial arthropods have a series of openings called spiracles at the body surface.
Spiracles open into tiny air tubes called tracheae, which expand into fine branches that extend
into all parts of the arthropod body.
Fishes use outward extensions of their body surface called gills for gas exchange. Gills are
flaps of tissue richly supplied with blood vessels. As a fish swims, it draws water into its mouth
and across the gills. Oxygen diffuses out of the water into the blood vessels of the gill, while
carbon dioxide leaves the blood vessels and enters the water passing by the gills.
https://www.cliffsnotes.com/study-guides/biology/biology/gas-exchange/mechanisms-for-gasexchange#:~:text=In%20animals%2C%20gas%20exchange%20follows,occurs%20directly%20with%
20the%20environment.&text=Hemoglobin%20binds%20loosely%20to%20oxygen%20and%20carries
%20it%20through%20the%20animal's%20bloodstream.
What’s I’ve learned
MULTIPLE CHOICE. Choose the letter of the correct answer.
1. Which of these is the correct equation for photosynthesis?
a. carbon dioxide + water → glucose + oxygen
b. glucose + oxygen → carbon dioxide + water
c. carbon dioxide + glucose → water + oxygen
2. Which gas is released when plant cells respire aerobically?
a. Oxygen
b. Carbon dioxide
c. Nitrogen
3. When does respiration happen in plants?
a. All the time
b. Only during the day
c. Only during the night
4. There is an overall uptake of carbon dioxide and release of oxygen by a plant under certain
conditions. Which statement about such a plant is correct?
a. Respiration is happening faster than photosynthesis
b. Photosynthesis and respiration are happening at the same rate
c. Photosynthesis is happening faster than respiration
13
5. How do plants obtain the carbon dioxide they need for photosynthesis?
a. By osmosis
b. By diffusion
c. By active transport.
6. Which of these is an adaptation of leaves for efficient gas exchange?
a. Tightly packed spongy mesophyll cells
b. A waxy cuticle on the upper surface of the leaf
c. Tiny pores, called stomata, in the lower epidermis
7. What happens to stomata in the light?
a. Their guard cells absorb water by osmosis, become turgid and the stomata open
b. Their guard cells absorb water by osmosis, become flaccid and the stomata close
c. Their guard cells lose water by osmosis, become turgid and the stomata open
8. When is the movement of carbon dioxide, oxygen and water vapour at the surface of the
leaf likely to be greatest?
a. When the stomata are open
b. When the stomata are closed
c. When it is cool and humid
9. What colour would hydrogencarbonate indicator be at high concentrations of carbon
dioxide?
a. Purple
b. Red
c. Yellow
10. Net gas exchange from a leaf can be investigated using hydrogencarbonate indicator in a
stoppered tube. Why might one of the test leaves be boiled first?
a. To see if high temperatures increase the rate of photosynthesis and respiration
b. To show that a leaf has to be alive for it to affect the amount of carbon dioxide in the
tube
c. To remove the waxy cuticle so that gas exchange can happen more quickly
14
Lesson
Transport and Circulation
4
What I need to know
Learning Competency
The learners compare and contrast transport and circulation in plants and animals
(STEM_BIO11/12-IVa-h-1)
Specific Learning Outcomes
At the end of the lesson, the learners will be able to:
•
•
•
explain the functions of structures in animal circulation; and
trace the path of blood in the systemic and the pulmonary circulation
describe the transport of substances in xylem and phloem;
What I know
PRIOR KNOWLEDGE: Define the following words.
1. Xylem
2. Phloem
3. Diffusion
4. Cell transport
5. Circulation
6. Arteries
7. Veins
8. Valves
9. Systemic Circulation
10. Pulmonary Circulation
What’s new
PRE ACTIVITY:
1. What are the functions of xylem and phloem?
15
What’s is it
INTRODUCTION:
Plants have two systems for the transportation of substances, by using two different
types of transport tissue. Water and solutes are transported by the xylem from the roots to the
leaves, while food is transported by the phloem from the leaves to the rest of the plant.
Transpiration is the process by which water evaporates from the leaves, therefore causing
more water to be drawn up from the roots. Plants have adaptations to reduce the excessive
loss of water.
Xylem and phloem
There are two transport systems present in the plant to move food, water and minerals
through their roots, stems and leaves. These systems make use continuous tubes called the
xylem and phloem which are also known as vascular bundles.
Water on the surface of spongy and
palisade cells (inside the leaf)
evaporates and then diffuses out of the
leaf. This is called transpiration.
Reference: https://sites.google.com/site/biopt14operationplant/plant-transportsystem#:~:text=There%20are%20two%20transport%20systems,also%20known%20as%20vascular%
20bundles.
16
Transport systems are crucial to survival. Unicellular organisms rely on simple
diffusion for transport of nutrients and removal of waste. Multicellular organisms have
developed more complex circulatory systems.
There are two types of circulatory systems found in animals: open and closed
circulatory systems.
Open circulatory systems
In an open circulatory system, blood vessels transport all fluids into a cavity. When the
animal moves, the blood inside the cavity moves freely around the body in all directions. The
blood bathes the organs directly, thus supplying oxygen and removing waste from the organs.
Blood flows at a very slow speed due to the absence of smooth muscles, which, as you learnt
previously, are responsible for contraction of blood vessels. Most invertebrates (crabs, insects,
snails etc.) have an open circulatory system
The human circulatory system involves the pulmonary and systemic circulatory
systems. The pulmonary circulatory system consists of blood vessels that transport
deoxygenated blood from the heart to the lungs and return oxygenated blood from the lungs
to the heart. In the systemic circulatory system, blood vessels transport oxygenated blood from
the heart to various organs in the body and return deoxygenated blood to the heart.
Pulmonary circulation system
In the pulmonary circulation system, deoxygenated blood leaves the heart through the
right ventricle and is transported to the lungs via the pulmonary artery. The pulmonary artery
is the only artery that carries deoxygenated blood. It carries blood to the capillaries where
carbon dioxide diffuses out of the blood into the alveoli (lung cells) and then into the lungs,
where it is exhaled. At the same time, oxygen diffuses into the alveoli, and then enters the
blood and is returned to the left atrium of the heart via the pulmonary vein.
Systemic circulation
Systemic circulation refers to the part of the circulation system that leaves the heart,
carrying oxygenated blood to the body's cells, and returning deoxygenated blood to the heart.
Blood leaves through the left ventricle into the aorta, the body's largest artery. The aorta leads
to smaller arteries that supply all organs of the body. These arteries finally branch into
capillaries. In the capillaries, oxygen diffuses from the blood into the cells, and waste and
carbon dioxide diffuse out of cells and into blood. Deoxygenated blood in capillaries then
moves into venules that merge into veins, and the blood is transported back to the heart.
These veins merge into two major veins, namely the superior vena cava and the inferior vena
cava (figure: double circulation). The movement of blood is indicated by arrows on the
diagram. The deoxygenated blood enters the right atrium via the the superior vena cava. Major
17
arteries supply blood to the brain, small intestine, liver and kidneys. However, systemic
circulation also reaches the other organs, including the muscles and skin
Pulmonary circulation system
The systemic circulatory system supplies blood to the entire body.
18
Lesson
Regulation of Body Fluids
5
What I need to know
Learning Competency
The learners shall be able to describe excretory systems in animals especially the
human urinary system and their functions in homeostasis. (STEM_BIO11/12-IVa-h-1)
Specific Learning Outcomes
At the end of the lesson, the learners will be able to:
• define some key terms related to osmoregulation;
• describe different types of animals based on the osmolarity of their body
• fluids in relation to the environment;
• enumerate the three types of nitrogenous wastes in animals;
• enumerate and describe excretory systems in invertebrates;
• characterize the mammalian urinary system and the role of nephrons; and
• analyze the role of the kidneys in the body’s acid-base balance.
What I know
PRIOR KNOWLEDGE: Definition of Terms
1. Internal Environment
6. Osmoregulators
2. Osmolarity
7. Ammonia
3. Osmosis
8. Urea
4. Osmoregulation
9. Uric acid
5. Osmoconformers
10. Filtration
What’s new
PRE ACTIVITY: Answer the following questions briefly.
1. What are the possible consequences should there be a failure in the ability of the body
to dispose or eliminate toxic metabolic wastes?
2. What are the two types of animals based on the osmolarity of their body fluids in relation to
the environment?
3. Identify the three types of nitrogenous wastes excreted by animals.
19
What’s is it
INTRODUCTION:
Osmosis is the movement of solvent molecules through a semipermeable membrane
into an area that has a higher solute concentration. Osmotic pressure is the external pressure
needed to prevent the solvent from crossing the membrane. Osmotic pressure depends on
the concentration of solute particles. In an organism, the solvent is water and the solute
particles are mainly dissolved salts and other ions, since larger molecules (proteins and
polysaccharides) and nonpolar or hydrophobic molecules (dissolved gases, lipids) don't cross
a semipermeable membrane. To maintain the water and electrolyte balance, organisms
excrete excess water, solute molecules, and wastes.
Osmoregulation Strategies of Different Organisms
Bacteria - When osmolarity increases around bacteria, they may use transport
mechanisms to absorb electrolytes or small organic molecules. The osmotic stress activates
genes in certain bacteria that lead to the synthesis of osmoprotectant molecules.
Protozoa - Protists use contractile vacuoles to transport ammonia and other excretory
wastes from the cytoplasm to the cell membrane, where the vacuole opens to the environment.
Osmotic pressure forces water into the cytoplasm, while diffusion and active transport control
the flow of water and electrolytes.
Plants - Higher plants use the stomata on the underside of leaves to control water loss.
Plant cells rely on vacuoles to regulate cytoplasm osmolarity. Plants that live in hydrated soil
(mesophytes) easily compensate for water lost from transpiration by absorbing more water.
The leaves and stem of the plants may be protected from excessive water loss by a waxy
outer coating called the cuticle. Plants that live in dry habitats (xerophytes) store water in
vacuoles, have thick cuticles, and may have structural modifications (i.e., needle-shaped
leaves, protected stomata) to protect against water loss. Plants that live in salty environments
(halophytes) have to regulate not only water intake/loss but also the effect on osmotic pressure
by salt. Some species store salts in their roots so the low water potential will draw the solvent
in via osmosis. Salt may be excreted onto leaves to trap water molecules for absorption by
leaf cells. Plants that live in water or damp environments (hydrophytes) can absorb water
across their entire surface.
Animals - Animals utilize an excretory system to control the amount of water that is lost
to the environment and maintain osmotic pressure. Protein metabolism also generates waste
molecules which could disrupt osmotic pressure. The organs that are responsible for
osmoregulation depend on the species.
Osmoregulation in Humans
In humans, the primary organ that regulates water is the kidney. Water, glucose, and
amino acids may be reabsorbed from the glomerular filtrate in the kidneys or it may continue
through the ureters to the bladder for excretion in urine. In this way, the kidneys maintain the
electrolyte balance of the blood and also regulate blood pressure. Absorption is controlled by
20
the hormones aldosterone, antidiuretic hormone (ADH), and angiotensin II. Humans also lose
water and electrolytes via perspiration.
Osmoreceptors in the hypothalamus of the brain monitor changes in water potential,
controlling thirst and secreting ADH. ADH is stored in the pituitary gland. When it is released,
it targets the endothelial cells in the nephrons of the kidneys. These cells are unique because
they have aquaporins. Water can pass through aquaporins directly rather than having to
navigate through the lipid bilayer of the cell membrane. ADH opens the water channels of the
aquaporins, allowing water to flow. The kidneys continue to absorb water, returning it to the
bloodstream, until the pituitary gland stops releasing ADH.
Reference:https://www.thoughtco.com/osmoregulation-definition-and-explanation4125135#:~:text=Plants%20%2D%20Higher%20plants%20use%20the,vacuoles%20to%20regulate%
20cytoplasm%20osmolarity.&text=Animals%20%2D%20Animals%20utilize%20an%20excretory,envir
onment%20and%20maintain%20osmotic%20pressure .
What’s more
ACTIVITY:
1. Identify the structures and functions of the Kidney.
21
Lesson
6
Immune Systems
What I need to know
Learning Competency
The learners shall be able to explain how immune systems work. (STEM_BIO11/12IVa-h-1)
Specific Learning Outcomes
At the end of the lesson, the learners will be able to:
•
•
•
•
•
•
•
compare innate and adaptive immune responses;
define the term “antibody”;
name the different kinds of antibodies produced by humans; and
explain the function of each type of antibody.
explain where T cells come from;
identify the different types of T cells and
describe the functions of T cells
What I know
PRIOR KNOWLEDGE: Definition of Terms
1. Innate immune Response
5. Cell mediated response
2. Adaptive immune response
6. antibodies
3. Immunity
7. antigen
4. Humoral Response
8. infection
What’s new
PRE-ACTIVITY:
1. What are the different types of Immunity?
22
What’s is it
The immune system is typically divided into two categories--innate and adaptive-although these distinctions are not mutually exclusive.
Innate immunity
Innate immunity refers to nonspecific defense mechanisms that come into play
immediately or within hours of an antigen's appearance in the body. These mechanisms
include physical barriers such as skin, chemicals in the blood, and immune system cells that
attack foreign cells in the body. The innate immune response is activated by chemical
properties of the antigen.
Adaptive immunity
Adaptive immunity refers to antigen-specific immune response. The adaptive immune
response is more complex than the innate. The antigen first must be processed and
recognized. Once an antigen has been recognized, the adaptive immune system creates an
army of immune cells specifically designed to attack that antigen. Adaptive immunity also
includes a "memory" that makes future responses against a specific antigen more efficient.
Reference: http://www.biology.arizona.edu/immunology/tutorials/immunology/page3.html
Human antibodies are classified into five isotypes (IgM, IgD, IgG, IgA, and IgE)
according to their H chains, which provide each isotype with distinct characteristics and roles.
Fig. 6-1. List of common Antibodies. Reference: https://tinyurl.com/y2pf24j5
23
IgG
IgG is the most abundant antibody isotype in the blood (plasma), accounting for 7075% of human immunoglobulins (antibodies). IgG detoxifies harmful substances and is
important in the recognition of antigen-antibody complexes by leukocytes and macrophages.
IgG is transferred to the fetus through the placenta and protects the infant until its own immune
system is functional.
IgM
IgM usually circulates in the blood, accounting for about 10% of human
immunoglobulins. IgM has a pentameric structure in which five basic Y-shaped molecules are
linked together. B cells produce IgM first in response to microbial infection/antigen invasion.
Although IgM has a lower affinity for antigens than IgG, it has higher avidity for antigens
because of its pentameric/hexameric structure. IgM, by binding to the cell surface receptor,
also activates cell signaling pathways.
IgA
IgA is abundant in serum, nasal mucus, saliva, breast milk, and intestinal fluid,
accounting for 10-15% of human immunoglobulins. IgA forms dimers (i.e., two IgA monomers
joined together). IgA in breast milk protects the gastrointestinal tract of neonates from
pathogens.
IgE
IgE is present in minute amounts, accounting for no more than 0.001% of human
immunoglobulins. Its original role is to protect against parasites. In regions where parasitic
infection is rare, IgE is primarily involved in allergy.
IgD
IgD accounts for less than 1% of human immunoglobulins. IgD may be involved in the
induction of antibody production in B cells, but its exact function remains unknown.
Reference: https://tinyurl.com/y2pf24j5
T cell: A type of white blood cell that is of key importance to the immune system and
is at the core of adaptive immunity, the system that tailors the body's immune response to
specific pathogens. The T cells are like soldiers who search out and destroy the targeted
invaders.
Immature T cells (termed T-stem cells) migrate to the thymus gland in the neck,
where they mature and differentiate into various types of mature T cells and become active in
the immune system in response to a hormone called thymosin and other factors. T-cells that
are potentially activated against the body's own tissues are normally killed or changed ("downregulated") during this maturational process.
Reference: https://www.medicinenet.com/script/main/art.asp?articlekey=11300
There are 3 main types of T cells: cytotoxic, helper, and regulatory. Each of them has
a different role in the immune response.
Cytotoxic T cells (CD8+)
Cytotoxic T cells (Tc cells) have a co-receptor called CD8 on their cell surface. CD8
partners with the T cell receptor and with MHC class I molecules, acting as a sort of bridge.
This bridge allows cytotoxic T cells to recognize normal cells that are infected by a pathogen.
When the cytotoxic T cell recognizes the infected cell, it becomes activated and produces
molecules that kill the infected cell, destroying the pathogen in the process.
24
Fig. 6-2. Cytotoxic T cells (CD8+) mediatory response on infected cells.
Reference: https://tinyurl.com/y4kop6z7
Helper T cells (CD4+)
Helper T cells (Th cells) have a different co-receptor called CD4 on their cell surface.
CD4 also partners with the T cell receptor but interacts with MHC class II molecules instead
of MHC class I molecules. This allows helper T cells to recognize pathogen peptides that have
been displayed by antigen presenting cells. When helper T cells recognize a peptide on an
antigen presenting cell, they become activated and begin to produce molecules called
cytokines that signal to other immune cells.
Fig. 6-3. Helper T cells (CD4+) mediatory response on antigen presenting cells.
Reference: https://tinyurl.com/y4kop6z7
Regulatory T cells (T reg cells) also have CD4 on their surface, but they do not activate
the immune system like helper T cells do. Instead, regulatory T cells play a protective role by
shutting off the immune response when it is no longer needed. This prevents excessive
damage to the normal cells and tissues in the body. Regulatory T cells suppress the immune
response in several ways, including:
25
•
•
•
Producing anti-inflammatory cytokines that suppress the immune response
Releasing molecules that kill activated immune cells
Changing the way dendritic cells behave so they can't activate T cells
Reference: https://tinyurl.com/y4kop6z7
What’s more
ACTIVITY:
Answer the following questions on a separate sheet of paper:
a. Describe when inflammation is good and when it is bad.
b. What are the five hallmarks of inflammation?
c. What is the importance of inflammation in the immune response?
26
Lesson
7
Chemical and Nervous
Control
What I need to know
Learning Competency
The learners compare and contrast chemical and nervous control in plants and animals
(STEM_BIO11/12-IVa-h-1)
Specific Learning Outcomes
At the end of the lesson, the learners will be able to:
•
•
•
•
explain how animals respond to environmental stimuli;
describe the mechanisms of chemical and nervous control in animals;
explain how plants respond to environmental stimuli; and
describe the mechanisms of chemical control in plants.
What I know
PRIOR KNOWLEDGE: Definition of Terms
1.
2.
3.
4.
5.
6.
7.
8.
Nervous System
Peripheral Nervous System
Central Nervous System
Brain
Spinal Cord
Motor Neurons
Sensory Neurons
Somatic Nervous System
9. Autonomic Nervous System
10. Axon
11. Myelin Sheath
12. Neurons
13. Hypothalamus
14. Tropisms
15. Thermoreceptors
16. Pain receptors
What’s new
PRE-ACTIVITY: Write your answers in a separate sheet of paper.
1. How animals respond to environmental stimuli?
2. How plants respond to environmental stimuli?
27
What’s is it
INTRODUCTION
Animal behavior is controlled by a nervous system, which is comprised of special nerve
cells called neurons. The nervous system operates according to the same general principles
in all types of animals.
The nervous system is stimulated from the environment, through sensory receptors. A
stimulus is any form of energy that can be detected by the body. A signal is the physical coding
of information (e.g., a message) capable of transmission through environment.
Sensory processing includes all central acts of information processing, which link the
initial stages of sensory reception with the creation of subjective sensory perception. Animals
normally only respond to stimuli which they select; they filter out certain stimuli that surround
them and react to others they choose to accept.
TYPES OF STIMULI
Stimuli can be of many types:
•
•
•
•
Visual - what the animal sees
Auditory -what the animal hears
Tactile - what the animal feels
Chemical - what the animal smells or tastes.
Table 7-1. Types of sensory receptors and their corresponding functions.
Types of sensory receptors
Example of function
Mechanoreceptors
-Corpuscles in the deep layers of skin
-Sense deep touching
-Stretch receptors in skeletal muscles
-Maintaining posture
-Hair cells of vestibular apparatus and -Senses of hearing and balance
cochlea of inner ear
Thermoreceptors
-Ends of sensory neurons in skin
-Monitor external temperature
-Neurons in hypothalamus
-Monitor internal temperature
Chemoreceptors
-Receptor cells in arteries
-Taste bud receptors
-Sensor cells in surface layers of the nose
-Monitor blood oxygen level
-Sense taste
-Sense smell
Photoreceptors
-Rod cells in retina
-Cone cells in retina
-Sense low light vision
-Sense bright light and color
Pain Receptors
-Ends of sensory neurons
-Awareness of tissue damage
28
Mechanoreceptors
Mechanoreceptors are those which detect movement. Sound is generally detected
through mechanoreceptors which detect vibrations in air or water. Sound waves cause
vibrations in air or water particles, which are then detected by mechanisms such as vibration
sensitive hairs (in the limb joints of many arthropods) or sensitive membranes in the ears of
mammals.
Thermoreception
This refers to the sensitivity of nerve endings to temperature. The mechanism is similar
to chemoreception; but has not been studied and understood as extensively as
chemoreception. Birds are thought to have relatively few thermo-receptors compared with
mammals. Birds do have thermo-receptors on their beak & tongue though. Many reptiles have
well developed thermo-receptors, both on the skin, and even in their brain. Some snakes hunt
their prey using body heat. Heat travels through the atmosphere as infra-red (long wavelength)
electromagnetic radiation and is detected by cells sensitive to changes in temperature. Heat
receptors are generally deeper in the body than cold receptors.
Chemoreception
This is the ability to identify and detect concentrations of chemical substances. Virtually
every nerve cell is a “chemoreceptor” (i.e. it reacts to specific substances released by other
nerve cells, in a specific way). There are two types of chemo receptors:
·
Exteroceptors – which detect chemicals in the external environment (ie. outside the
animal);
·
Interoceptors – which detect chemicals within the animal’s body (eg. in the blood, digestive
system, etc.
a. Pheromones
These are chemicals excreted by one animal in order to cause a response in another
animal.
Example: The silkworm moth produces a polyalcohol chemical (known as bombykol) from its
abdominal gland, which attracts males of the species from as much as several kilometers
away.
Research has found that the organic chemical for each pheromone varies
tremendously depending on what signal it entails.
b. Taste
Mammals in general can detect four basic tastes: sour, bitter, salty and sweet. In a
human, different parts of the tongue are affected by different tastes. The flavor of food depends
upon both taste and smell.
Examples of Chemical Stimulation:
·
·
·
·
Some clams will try to escape when placed in water that has had starfish in it.
A cat becomes alert and flees when it smells a dog.
When injured certain fish release a type of pheromone that alerts other fish to danger.
Many animals release sex pheromones to attract a mate.
29
Photo Receptors - Sight
Vision in primitive animals might be little more than the simple discrimination of light or
darkness. In more complex animals, vision is however increasingly complex, allowing
identification, formation and resolution of images and colors.
Sensory judgement in more complex animals (e.g. mammals) depends upon not only
differentiating perceived images, but also the ability to be selective in what is seen (i.e.
separating the signal from noise).
Reference: https://tinyurl.com/y3xxt7fz
Plant Responses
Like all organisms, plants detect and respond to stimuli in their environment. Unlike
animals, plants can’t run, fly, or swim toward food or away from danger. They are usually
rooted to the soil. Instead, a plant’s primary means of response is to change how it is growing.
Plants also don’t have a nervous system to control their responses. Instead, their responses
are generally controlled by hormones, which are chemical messenger molecules.
Plant Tropisms
Plant roots always grow downward because specialized cells in root caps detect and
respond to gravity. This is an example of a tropism. A tropism is a turning toward or away from
a stimulus in the environment. Growing toward gravity is called geotropism.
Fig. 7-1. Illustration of geotropism.
Reference: http://biology-igcse.weebly.com/auxins.html
30
Plants also exhibit phototropism, or growing toward a light source. This response is
controlled by a plant growth hormone called auxin. Auxin stimulates cells on the dark side of
a plant to grow longer. This causes the plant to bend toward the light.
Fig. 7-2. Illustration of phototropism.
Reference: https://phototropism2011.wordpress.com/about/
Daily and Seasonal Responses
Plants also detect and respond to the daily cycle of light and darkness. For example,
some plants open their leaves during the day to collect sunlight and then close their leaves at
night to prevent water loss. Environmental stimuli that indicate changing seasons trigger other
responses. Many plants respond to the days growing shorter in the fall by going dormant. They
suspend growth and development in order to survive the extreme cold and dryness of winter.
Dormancy ensures that seeds will germinate and plants will grow only when conditions are
favorable.
Responses to Disease
Plants don’t have immune systems, but they do respond to disease. Typically, their
first line of defense is the death of cells surrounding infected tissue. This prevents the infection
from spreading. Many plants also produce hormones and toxins to fight pathogens. For
example, willow trees produce salicylic acid to kill bacteria. The same compound is used in
many acne products for the same reason. Exciting new research suggests that plants may
even produce chemicals that warn other plants of threats to their health, allowing the plants to
prepare for their own defense. As these and other responses show, plants may be rooted in
place, but they are far from helpless.
Reference: https://tinyurl.com/yypqcrve
31
What’s more
ACTIVITY:
1. What are the divisions of the nervous system?
2. Differentiate the functions of the endocrine and the nervous system
32
Lesson Sensory and Motor
8
Mechanisms
What I need to know
Learning Competency
The learners should be able to describe the structures involved in major animal
senses. (STEM_BIO11/12-IVa-h-1)
Specific Learning Outcomes
At the end of the lesson, the learners will be able to:
•
•
•
•
•
•
•
•
describe the five types of sensory receptors;
illustrate the three types of eyes in animals;
explain how vision occurs in humans;
differentiate the parts of the human ear and describe the functions of each
discuss how the senses of smell and taste detect chemicals.
describe diverse means of animal locomotion;
differentiate the three types of skeletal systems: hydrostatic, exoskeleton and
endoskeleton
explain how a muscle contracts.
What I know
PRIOR KNOWLEDGE: Definition of Terms
1. Photoreceptors
8. Conjunctiva
2. Mechanoreceptors
9. Retina
3. Chemoreceptors
10. Optic Nerve
4. Thermoreceptors
11. Eustachian tube
5. Pain receptors
12. Hydrostatic Skeleton
6. Sclera
13. Endoskeleton
7. Cornea
14. Appendicular skeleton
33
What’s new
PRE-ACTIVITY:
1. How different animals sense their environment. Examples: dogs sniffing chemicals.
Animals
Sensory response to the environment
1.
2.
3.
4.
5.
What’s is it
INTRODUCTION
A major role of sensory receptors is to help us learn about the environment around us,
or about the state of our internal environment. Different types of stimuli from varying sources
are received and changed into the electrochemical signals of the nervous system. This
process is called sensory transduction.
Sensation is the activation of sensory receptors at the level of the stimulus. Perception
is the central processing of sensory stimuli into a meaningful pattern involving awareness.
Perception is dependent on sensation, but not all sensations are perceived.
Structural Receptor Types
The cells in the retina that respond to light stimuli are an example of a specialized
receptor cell, a photoreceptor.
An exteroceptor is a receptor that is located near a stimulus in the external
environment, such as the somatosensory receptors that are located in the skin.
An interoceptor is one that interprets stimuli from internal organs and tissues, such as
the receptors that sense the increase in blood pressure in the aorta or carotid sinus.
A proprioceptor is a receptor located near a moving part of the body, such as a muscle
or joint capsule, that interprets the positions of the tissues as they move.
34
Functional Receptor Types
Chemical stimuli can be detected by a chemoreceptors that detect chemical stimuli,
such as a chemicals that lead to the sense of smell.
Physical stimuli, such as pressure and vibration, as well as the sensation of sound and
body position (balance), are interpreted through a mechanoreceptor.
Another physical stimulus that has its own type of receptor is temperature, which is
sensed through a thermoreceptor that is either sensitive to temperatures above (heat) or
below (cold) normal body temperature.
Reference: https://open.oregonstate.education/aandp/chapter/13-1-sensory-receptors/
The three types of eyes that have evolved in the animal kingdom are:
I. Eye cups in flatworms and other invertebrates
II. Compound eyes in insects and arthropods
III. Single lens eyes in squid
THE HUMAN EYE
Fig. 8-1. Anatomy of the Human Eye.
Reference http://jyssbio5158.weebly.com/the-human-eye.html
35
How hearing is possible in the human ear?
The outer ear lobes catch sound waves and channel them to the eardrums. From the
eardrum, the middle ear amplifies the sound wave vibrations to three small bones – the
hammer, anvil and stirrup. The sound waves travel to the oval window.
The Eustachian tube equalizes air pressure in the middle ear and outer ear. The
hearing organ is in the inner ear, composed of several channels of fluid wrapped in a spiral
cochlea. This is encased in the bones of the skull. Vibrations in the oval window produce
pressure waves. These waves travel through the upper canal to the tip of the cochlea, enter
the lower canal and fade away.
Pressure waves of the upper canal push down to the middle canal and the membrane
below this canal vibrates. These vibrations stimulate hair cells attached to the membrane by
moving them against the overlying tissue. The hair cells are able to develop receptor potentials
causing release of neurotransmitters that induce action potentials in the auditory neurons.
The Three Types of Skeleton
I. Hydrostatic skeleton occurs in a body compartment in which a volume of fluid is held under
pressure. This is common in aquatic and burrowing animals. An example is the Hydra and
other invertebrates with a semi-enclosed body cavity made of a few layers of cells. There is
no solid “bone” but the animal under aquatic pressure can stay upright and move. Earthworms
have smooth muscles and fluid-filled body compartments.
II. Rigid, armor-like coverings characterize an exoskeleton. Muscles are attached inside.
Joints are thin and flexible. The best examples are found in arthropods (insects, crustaceans).
When insects grow, they shed off their old “armor” and grow a new one. Cite other examples
such as those in clams and
snails.
III. An endoskeleton consists of rigid but flexible support made of bones, cartilage surrounded
by masses of muscles. In sponges, cells are supported on spicules. The endoskeleton of
echinoderms is made from calcium plates underneath the skin.
What’s more
ACTIVITY: Answer in a separate sheet of paper.
1. Explain echolocation in bats.
2. Discuss the evolution of the vertebrate eye.
3. Draw the differences among striated or skeletal muscle, smooth muscle and cardiac
muscle.
36
Lesson
Feedback Mechanisms
9
What I need to know
Learning Competency
The learners should be able to explain how some organisms can maintain steady
internal conditions (STEM_BIO11/12-IVi-j-2)
Specific Learning Outcomes
At the end of the lesson, the learners will be able to:
•
•
•
•
explain the need for homeostasis; and
describe how various organs systems enable homeostasis
differentiate positive and negative feedback mechanisms
outline the homeostatic control of temperature regulation, osmotic balance and
glucose level regulation
What I know
PRIOR KNOWLEDGE: Define the following terms:
1. Homeostasis
2. Positive feedback mechanism
3. Negative feedback mechanism
What’s new
PRE-ACTIVITY: Answer the following questions.
1. Explain why homeostasis is important to organisms.
2. Identify five (5) hormones that are responsible for maintaining homeostasis in the
human body. Explain their functions and normal mechanisms.
37
What’s is it
INTRODUCTION
Animal organs and organ systems constantly adjust to internal and external changes
through a process called homeostasis (“steady state”). Homeostasis means to maintain
dynamic equilibrium in the body. It is dynamic because it is constantly adjusting to the changes
that the body’s systems encounter. It is equilibrium because body functions are kept within
specific ranges. Even an animal that is apparently inactive is maintaining this homeostatic
equilibrium.
Homeostatic Process
The goal of homeostasis is the maintenance of equilibrium around a point or value
called a set point. While there are normal fluctuations from the set point, the body’s systems
will usually attempt to go back to this point. A change in the internal or external environment
is called a stimulus and is detected by a receptor; the response of the system is to adjust the
deviation parameter toward the set point. For instance, if the body becomes too warm,
adjustments are made to cool the animal. If the blood’s glucose rises after a meal, adjustments
are made to lower the blood glucose level by getting the nutrient into tissues that need it or to
store it for later use.
Negative Feedback Mechanisms
Any homeostatic process that changes the direction of the stimulus is a negative
feedback loop. It may either increase or decrease the stimulus, but the stimulus is not allowed
to continue as it did before the receptor sensed it. In other words, if a level is too high, the
body does something to bring it down, and conversely, if a level is too low, the body does
something to make it go up. Hence the term negative feedback.
An example is animal maintenance of blood glucose levels. When an animal has
eaten, blood glucose levels rise. This is sensed by the nervous system. Specialized cells in
the pancreas sense this, and the hormone insulin is released by the endocrine system. Insulin
causes blood glucose levels to decrease, as would be expected in a negative feedback system
Positive Feedback Loop
A positive feedback loop maintains the direction of the stimulus, possibly accelerating
it. Few examples of positive feedback loops exist in animal bodies, but one is found in the
cascade of chemical reactions that result in blood clotting, or coagulation. As one clotting
factor is activated, it activates the next factor in sequence until a fibrin clot is achieved. The
direction is maintained, not changed, so this is positive feedback. Another example of positive
feedback is uterine contractions during childbirth
Reference: https://tinyurl.com/y6n8gmzb
38
Fig. 9-1. Homeostatic Mechanism of the Body’s Thermoregulation
What’s more
ACTIVITY: Answer in a separate sheet of paper.
1. Identify and describe 10 disorders that result from the disruption of homeostasis.
2. Identify and explain five (3) positive feedback and five (3) negative feedback
mechanisms present in the human body.
39
References
Manuals/Modules/Lesson Exemplar
The Commission on Higher Education. Teaching Guide for Senior High School
General Biology 2
Department of Education Central Office. Most Essential Learning Competencies
( MELCs). 2020.
Websites
Canva. Accessed on November 5, 2020. https://www.canva.com/education
https://www.macmillanhighered.com/BrainHoney/Resource/6716/digital_first_content/trunk/t
est/hillis2e/hillis2e_ch14_2.html
https://www.evolvingsciences.com/Photosynthesis%20worksheet%20.html
https://www.s-cool.co.uk/a-level/biology/gas-exchange/revise-it/gas-exchange-inplants#:~:text=Plants%20obtain%20the%20gases%20they,underside%20of%20the%20leaf
%20%2D%20stomata.
https://www.s-cool.co.uk/a-level/biology/gas-exchange/revise-it/gas-exchange-inplants#:~:text=Plants%20obtain%20the%20gases%20they,underside%20of%20the
%20leaf%20%2D%
http://jyssbio5158.weebly.com/the-human-eye.html
https://open.oregonstate.education/aandp/chapter/13-1-sensory-receptors/
40