Republic of the Philippines
Department of Education
REGION I
SCHOOLS DIVISION OF CANDON CITY
Candon City, Ilocos Sur
GENERAL BIOLOGY 2
Quarter 4 – Week 3 – Module 3
Prepared by: Elsa B. Biswelan
Lesson
1
I.
Plants and Animals: Gas
Exchange
OBJECTIVES:
1.
2.
3.
4.
Compare breathing mechanisms in vertebrates.
Describe respiratory surfaces or organs in invertebrates and vertebrates.
Describe the structures of gas exchange of plants.
Compare and contrast the following processes in plants and animals: Gas exchange
(STEM_BIO11/12IVa-h-1)
II. GUIDE QUESTIONS:
1.
2.
3.
4.
How do we compare breathing mechanisms in vertebrates?
How do we describe respiratory surfaces or organs in invertebrates and vertebrates?
How do we describe the structures of gas exchange of plants?
How do we compare the following processes in plants and animals: Gas exchange?
III. DISCUSSION
Gas exchange is the uptake of molecular oxygen from the environment and the discharge
of carbon dioxide to the environment. It is often called respiratory exchange or respiration,
but it should not be confused with cellular respiration. Oxygen is needed in tissues for aerobic
cellular respiration to occur and extract ATP from food. Carbon dioxide must be released to
prevent physiological pH in tissues from being very acidic. In plants, however, the carbon
dioxide that is released as a by-product of cellular respiration may again be taken up for the
process of photosynthesis.
Structures for gas exchange in plants
1. Stomates found in leaves - The exchange of oxygen and carbon dioxide in the leaf (as
well as the loss of water vapor in transpiration) occurs through pores called stomata
(singular = stoma).
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2. Stems' lenticels – It permits the exchange of gases between the environment and the
internal tissue spaces of the organs (stems and some fruits). They permit the entrance
of oxygen and simultaneously the output of carbon dioxide and water vapor.
3. Aerial root hairs - The exchange of gases in the roots of a plant takes place by the
process of diffusion. During diffusion, oxygen diffuses into the root hairs and passes
into the root cells, from where the carbon dioxide moves out into the soil.
4. Pneumatophores or the lateral roots of mangroves- The “breathing roots” known as
pneumatophores. These portions of the root grow upward until they project some
centimeters above the low-tide level. They have small openings called lenticels in their
bark so that air can reach the rest of the plant’s root system. Another feature of most
mangroves is aerial.
Respiratory organs or surfaces in invertebrates:
A. Cell surface or cell membrane – especially used in unicellular organisms
B. Integumentary exchange – refers to the general body surface or skin used by animals
with a high surface-to-volume ratio, e.g., flatworm and earthworm. Amphibians also
use their skin in addition to their lungs as a gas exchange surface.
C. External Gills – used by invertebrates that live in aquatic habitats; gills are highly
folded, thin-walled, vascularized epidermis that project outward from the body, e.g.,
crayfish, lobster, sea star, nudibranch.
D. The tracheal system in arthropods – utilizes fine air-conducting tubules to provide
gaseous exchange at the cellular level; it is not dependent on a circulatory system, e.g.,
insects, spiders.
Respiratory surfaces in vertebrates:
A. External Gills – Thin, vascularized epidermis that project from the body surface of a
few amphibians, e.g., larval salamander
B. Internal Gills – Rows of slits or pockets in adult fishes positioned at the back of the
mouth such that water that enters the mouth can flow over them as it exits just behind
the head. Water flows over the gills and blood circulates through them in opposite
directions. This mechanism, called countercurrent flow, is highly efficient in
extracting oxygen from water, whose oxygen content is lower than air.
C. Lungs – internal respiratory surfaces shaped like a cavity or sac; lungs provide a
membrane for gaseous exchange; since they are not in direct contact with all other parts
of the body, lungs require a circulatory system to transport gases to the rest of the body;
found in birds, reptiles, and mammal.
a. Air moves by bulk flow into and out of the lung.
b. Gases diffuse across the inner respiratory surfaces of the lungs.
c. Pulmonary circulation allows the diffusion of dissolved gases across lung
capillaries
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d. In body tissues, oxygen diffuses from blood → interstitial fluid → cells; the
pathway of carbon dioxide is in reverse
e. All lungs receive deoxygenated blood from the heart and return oxygenated blood
to the heart.
Compare breathing mechanisms in vertebrates:
A. Amphibians ventilate their lungs by positive pressure breathing which forces air down
the trachea.
B. Birds use a system of air sacs as a blower to keep air flowing through the lungs in one
direction only, preventing the mixing of incoming and outgoing air.
C. Mammals ventilate their lungs by negative pressure breathing which pulls air into the
lungs when the volume of the lungs expands as the rib muscles and diaphragm contract.
However, the incoming and outgoing air mix decreases the efficiency of ventilation.
IV. EXAMPLES:
Plant and Animals Nutrition-The comparison
Gas exchange of the plant
https://www.google.com/search?q=structures+for+gas+exchange+in+plants
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Respiratory organs of or surfaces in invertebrates
https://www.britannica.com/science/respiratory-system
Respiratory organs of or surfaces in invertebrates
https://www.google.com/search?q=Respiratory+organs+of+surfaces+in+vertebrates
General Biology 2 - Page 4 of 6
V. GENERALIZATION
Gas exchange is a process that occurs when oxygen and carbon dioxide diffuse across a
surface or membrane in opposite directions. It is needed to provide cells with enough oxygen
for cellular respiration, and to remove the carbon dioxide that the cells produce.
Gaseous exchange occurs in the root hair of young terrestrial plants. Oxygen in the air
spaces in the soil dissolves in the film of moisture surrounding soil particles and diffuses into
the root hair along a concentration gradient. It diffuses from root hair cells into the cortex where
it is used for respiration.
VI. EXERCISES:
Activity 1
DIRECTIONS: Fill out the table by classifying each word from the box if it relates to plants
or animals. Write on a separate sheet of paper.
Stomates
Lungs
Aerial root hairs
Deoxygenated blood
PLANTS
Oxygenated blood
Stems' lenticels
ANIMALS
Activity 2
DIRECTIONS: Compare your breathing rates range from 12-25 times per minute. In this
activity, you will compare your breathing rate at rest to your breathing rate
after exercise. Follow the procedure, write your observations, and answer the
questions correctly. Write your answer on a separate sheet of paper.
Observations
Activity
Resting
After 30 s exercise
After 1 min of exercise
Rate
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Analysis
1. How did exercise affect your breathing rate?
2. Can you think of a reason for your answer to question 1?
3. What other factors besides exercise might influence your normal breathing rate?
4. Did you notice any other way your breathing changed with exercise? Give a possible
reason for this change.
VII. REFERENCES:
Tiamson, M.E. (2016). General Biology (Philippine Edition). Vibal Group
Reece JB, Urry LA, Cain ML, Wasseman SA, Minorsky PV, and RB Jackson. Campbell
Biology. Tenth Edition. Boston, USA: Pearson Education, Inc. 1279p.
Starr C and R Taggart. 2011. BIOLOGY: The Unity and Diversity of Life. Tenth Edition.
Australia: Thomson – Brooks/Cole. 933p.
Barrion AA, Tudor MFVA, Colle MCD, Reamillo MCS, and MAP Robles. 2000. BIOLOGY
II
Laboratory Manual: An Investigative Approach.
VIII. ANSWER KEY:
Activity 2
Answers May Vary
Activity 1
PLANTS
Stomates
Stem’s lenticels
Aerial root Hairs
ANIMALS
lungs
Deoxygenated blood
Oxygenated blood
ADDITIONAL ACTIVITY
General Biology 2 - Page 6 of 6