Download Assignment1ACoRe - Unit1Area2FunctioningOrganisms

Exchange of Gas
What you intend the students to learn about this idea?
1/ Gases are exchanged across surfaces to enable survival of organisms
 Organisms cannot survive without gas exchange
 Oxygen and carbon dioxide are needed for energy-transforming processescellular respiration and photosynthesis.
 Cellular respiration produces energy (uses oxygen and produces carbon
dioxide) whereas respiration is the movement of gases between the
environment and the cell
 Diffusion is the process which carbon dioxide (waste product of respiration) is
expelled and oxygen is obtained. This process is passive and depends on the
concentration gradient.
 Gas exchange in organisms can occur in different ways: Animals- special
surfaces in their respiratory system, Mammals – respiratory surfaces in their
lungs, Fish – gas exchange surfaces in their gills, Insects – air-filled tubes
(trachea) send oxygen to respiratory surfaces
 Aerobic organisms are oxygen dependent – the amount of oxygen effects
amount of energy.
 Anaerobic organisms are not oxygen dependant.
2/ The respiration of mammals occurs across well developed respiratory structures
 There is plenty of oxygen in atmospheric air (21%). While it also consists of
carbon dioxide the majority of air is nitrogen.
 Larger animals which have high metabolic rates need lots of oxygen.
 Animals have well developed respiratory mechanisms linked closely to the
circulatory system.
 Lungs are internally expanded respiratory structures & must remain moist.
 Breathing air uses less energy than water.
 Mammalian respiratory system consists of the pharynx, trachea, bronchi,
bronchioles and alveoli
 Gas exchange occurs at the alveoli were capillaries facilitate diffusion.
 Haemoglobin (respiratory pigment) carries large amounts of O2 in the blood.
 Inspiration occurs when the diaphragm and muscles contract to draw air into
lungs. Expiration occurs when they relax and air is forced out of the lungs.
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 Adequate gas exchange requires a large moist surface area, thin membrane
and enough supply of substances
 What can hinder respiration and how? Emphysema and asthma.
3/ Organisms can breathe in water using gas exchange surfaces in gills
 The amount of oxygen dissolved in water is very low and depends on
temperature, salinity and depth.
 Organisms living in water do not have a high demand of oxygen because they
use less energy
 Gills allow exchange of gases in water & are expanded respiratory surfaces
 Water passes over gills in one direction and small amounts of oxygen are
efficiently gained because of the counter-current flow of blood and water
 Gas exchange occurs across membranes in the gills called lamellae.
4/ Smaller organisms and plants exchange gas directly with their environment.
 Small organisms need little oxygen especially inactive organisms
 Small organisms have a high surface area to volume ratio so exchange of gas
occurs directly with their environment. This occurs with plants however they
can regulate this process.
 Plants use up carbon dioxide produced by cellular respiration as well as
additional carbon dioxide from the environment during the day in
photosynthesis which produces oxygen.
 Flowering plants don’t have specialised organs for gas exchange but have
openings called stomata which allow passage of oxygen and carbon dioxide
 Insect have a network of fine internal air-filled tubes (tracheae) along its body
with openings (spiracles). Air moves along these tubes.
 Insect blood usually plays no part in gas exchange. Gas is diffused straight to
the body cells.
Why is it important for students to know this?
1/ In facilitating knowledge of the world students need to understand that all
organisms require gas exchange and do this in different ways. Respiration is
interlinked with how other systems function and understanding gas exchange will
assist with learning about bodily function as a whole.
2/ Students need to understand why we need to obtain oxygen/carbon dioxide to
survive and how this process occurs. Understanding respiration, the effects of
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asthma and the implications of smoking will inform student so they can make wiser
life choices. Students need to understand that the body’s absorption of oxygen can
be hindered by not meeting the body’s iron requirements.
3/ In facilitating knowledge of the world students need to understand how
organisms are able to breathe in aquatic environments. Understanding the
requirements of gas exchange in fish will assist in students providing appropriate
care for aquatic pets.
4/ Understanding the requirements of gas exchange in plants and small organisms
will assist in students providing appropriate care for plants and other pets. Having
an understanding of plant respiration will assist students in thinking about global
warming. Understanding flowering plants use of stomata for gas exchange will help
students understand differences when looking at plants in different habitats.
What else you know about this idea (that you don’t intend students to know yet)?
1/ Regulation of respiration. Respiration physiology in detail. Details of the
anaerobic process as well as cellular respiration.
2/ How inspiration works in detail. Detailed knowledge of respiratory diseases. The
development of the respiratory system in young.
3/ How pollution can affect the ability of marine life to breathe. Details of the
process of gas exchange in swim bladders.
4/ The effect of air pollution on the respiration of plants and insects. Detailed
knowledge of how plant respiration could work to reduce global warming.
Knowledge about students’ thinking/difficulties connected with teaching this idea
1/ Vernacular misconception - ‘respiration’ is different from ‘cellular respiration’
2/ Tidal volume can be perceived to be fixed and that it cannot increase with
breathing frequency. All air in the lung is expelled in exhalation. Dependency of gas
exchange on concentration gradients
3/ Gills are the only structure involved in gas exchange of fish (swim
bladder/cutaneous respiration).
4/ Gas exchange in plants occurs at night. Insect blood has a major role in gas
exchange like mammals and fish
Teaching procedures (& particular reasons for using these to engage with this idea)
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 Build a spirometer– by building spirometers using plastics tubes and bottles
in buckets of water students can measure how much air can fit into their
lungs and the amount they would normally inhale and exhale. This can be very
useful in allowing students to visualise tidal volume and the capacity of lungs
which can often be confused.
 Dissection of fish – students are shown how water flows across the gills and
get to see the gill structure. This can be helpful to students as they get to
visualise the gill structure with their own eyes instead of relying on textbook
diagrams. Students will be able to investigate the gill structure and identify
different components.
 Models of fish versus human respiration– Students build paper models of fish
and human respiratory systems showing tissues, blood flow and gas
exchange. This highlights the differences in respiratory structures and how
they function. It also can assist kinetic and visual learners to better
understand how these systems are put together and how they function.
 Concept map – By allowing student to construct concept maps their
understanding of the concept is show. This can enable any misconceptions to
be addressed. It will also help student to visualise the different aspect and
how they link together to form a functioning system.
Specific ways of ascertaining students’ understanding or confusion around this
idea (include likely range of responses)
Firstly students’ misconceptions can be determined through worksheets, quizzes or
class discussions. Then teaching approaches to gas exchange can be focused on
carefully addressing any aspects which may lead to confusion. Assessment of
understandings can be achieved through worksheets, activities, quizzes, class
discussion, predict observe and explain, concept maps and probing understanding.
Common misconceptions of gas exchange are:
1/ Vernacular misconception of the term ‘respiration’
2/ Tidal volume is fixed. All air in the lungs is expelled in exhalation. The dependency
of gas exchange on concentration gradients
3/ Gills are the only structure involved with respiration of fish (swim
bladder/cutaneous respiration)
4/ Gas exchange in plants occurs at night. Insect blood is involved with respiration.
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