B3.2  Transport

Theme:  Form and Function

All biological transport systems demonstrate form-function relationships where vessel architecture, tissue organization, and cellular adaptations directly serve the functional requirements of moving materials efficiently throughout organisms.​​

• Capillary structure maximizes exchange through thin walls, narrow diameters creating large surface area, and fenestrations where rapid exchange is needed. Artery structure withstands high pressure through thick muscular and elastic walls that maintain blood flow. Vein structure enables return flow through valves preventing backflow and flexible walls allowing muscle compression.
• Tissue fluid exchange occurs through pressure filtration systems where capillary structure creates the pressure differences needed for fluid movement and lymphatic drainage.
• Mammalian heart adaptations include cardiac muscle for powerful contractions, specialized pacemaker cells for rhythm control, separate chambers for efficient pumping, valves ensuring unidirectional flow, and coronary vessels supplying the heart muscle itself.
• Xylem vessel structure enables water transport through hollow tubes with lignified walls resisting tension, absent end walls allowing unimpeded flow, and pits for water entry and exit. Transpiration-cohesion mechanism works because xylem structure maintains continuous water columns under tension.
• Phloem structure optimizes nutrient transport through sieve tubes with reduced cellular contents for easy flow, companion cells packed with mitochondria for active loading, and plasmodesmata connecting the transport partnership.
• Root pressure generation uses active transport structures to create positive pressure when transpiration is insufficient.
• Stem and root tissue distribution positions vascular bundles strategically for efficient transport between organs, with xylem and phloem arranged to serve their specific directional transport functions.

Guiding Questions:  
Guiding questions help students view the content of the syllabus through the conceptual lenses of both the themes and the levels of biological organization.

• What are the differences and similarities between transport in animals and plants?
• What adaptations facilitate transport of fluids in animals and plants?

​​Linking Questions:  
Linking questions strengthen students’ understanding by making connections between topics.  The ideal outcome of the linking questions is networked knowledge.

• How do pressure differences contribute to the movement of materials in an organism?
• What processes happen in cycles at each level of biological organization?

Key Terms to Know: * higher level only

Arteriole*
Artery
Atria (Heart)*
Atrioventricular Valve*
Backflow
Blood
Blood Pressure
Bony Fish*
Capillaries
Capillary Action
Cardiac Cycle*
Cardiac Muscle Cell*
Carotid Pulse
Causation
Cell Wall
Cohesion
Companion Cell*
Compression
Coronary Artery
Coronary Heart Disease
Correlation
Correlation Coefficient
Cortex (of stem and/or root)
Deciduous Plant*
Diameter
Diastolic Blood Pressure*
Dicotyledon
Double Circulation*

Elastin
Epidemiology
Epidermis
External Environment
Fenestration
Flexibility
Heart Rate
Humidity*
Hypothesis
Incidence
Internal Environment
Leaf
Lignin
Lumen
Lymph*
Lymph Duct*
Mammal*
Micrograph
Muscle Tissue
Negative Pressure Potential
Occlusion
Pacemaker (Sinoatrial Node)*
Phloem
Phloem Sap*
Plasma*
Plasmodesmata*
Positive Pressure Potential*
Pressure Filtration*

Pulse
Radial Pulse
Root (Plant)
Root Pressure*
Semilunar Valve*
Septum*
Sieve Plant*
Sieve Tube Cell*
Single Circulation*
Sink*
Source (Plant)*
Stem (Plant)
Surface Area
Systolic Blood Pressure*
Tissue Fluid*
Transpiration
Transverse Cross-Section
Valve
Variables
Vascular Bundle
Vein (Mammal)
Ventricle (Heart)*
Venule*
Vessel
Xylem
Xylem Pit

B3.2.1— Adaptations of capillaries for exchange of materials between blood and the internal or external environment.

• Describe how the structures of capillaries are adapted to capillary function.  Include lumen diameter, branching, wall thickness, and fenestrations. 

B3.2.2— Structure of arteries and veins.

• Compare the diameter, relative wall thickness, lumen size, number of wall layers, abundance of muscle and elastic fibers and presence of valves in arteries and veins.
• Given a micrograph, identify a blood vessel as an artery or vein.​

B3.2.3— Adaptations of arteries for the transport of blood away from the heart.

• State the function of arteries.
• Describe the structures and functions of the three layers of the artery wall. 
• Discuss how the wall thickness, lumen size, and muscle and elastic allow arteries to withstand and maintain high blood pressures.  ​

B3.2.4— Measurement of pulse rates.

• State the unit of measurement of the pulse rate. 
• Outline two methods for determining heart rate.​

B3.2.5— Adaptations of veins for the return of blood to the heart.

• State the function of veins.
• Discuss how pocket valves, thin walls and skeletal muscles maintain the flow of blood through a vein.​

B3.2.6- Causes and consequences of occlusion of the coronary arteries.

• State the function of the coronary arteries. 
• Outline the cause and consequence of a coronary occlusion.
• Evaluate correlations between diet and lifestyle variables and risk of coronary heart disease.
• List factors that are correlated with an increased risk of coronary occlusion and heart attack.

B3.2.7—  Transport of water from roots to leaves during transpiration.

• State that xylem tissue is used to transport water from roots to leaves in plants.
• Outline the role of cellulose in the transport of water via capillary action.
• Describe the cause and consequence of transpiration pull. 
• State why transport of water relies on cohesion between water molecules.
• State that transpiration is a passive process.

B3.2.8- Adaptations of xylem vessels for transport of water.

• Describe how the structure of xylem vessels are adapted for the transport of water under low pressure. 
• Outline how xylem is able to maintain rigidity even under low pressure or mechanical disturbance.

B3.2.9-  Distribution of tissues in a transverse section of the stem of a dicotyledonous plant.  

• Draw a plan diagram to show the distribution of tissues in a stem, including vascular bundles, xylem, phloem, cambium, cortex, pith and epidermis.
• Outline the function of tissues in a stem, including vascular bundles, xylem, phloem, cambium, cortex, pith and epidermis.
• State two ways xylem and phloem can be differentiated in cross sections of stem.

B3.2.10- Distribution of tissues in a transverse section of the root of a dicotyledonous plant.

• Draw a plan diagram to show the distribution of tissues in a root, including vascular bundles, xylem, phloem, cortex and epidermis.
• Outline the function of tissues in a root, including vascular bundles, xylem, phloem, cortex and epidermis.
• State two ways xylem and phloem can be differentiated in cross sections of root.

AHL ​B3.2.11- Release and reuptake of tissue fluid in capillaries.

• List components of blood plasma.
• Define tissue fluid.
• Describe the cause and effect of bulk transport of fluid into and out of a capillary network from tissue fluid.
  

AHL B3.2.12- Exchange of substances between tissue fluid and cells in tissues.

• ​Outline the direction and mechanism of transport of substances that are exchanged between tissue fluid and cells in the tissues.

AHL B3.2.13- Drainage of excess tissue fluid into lymph ducts.

• Outline why there is a need to drain excess tissue fluid into lymph ducts.
• Outline the structure and function of lymph ducts. 
• State how lymph is returned to the blood circulation.

AHL B3.2.14- Differences between the single circulation of bony fish and the double circulation of mammals.

• State the function of the heart and lungs/gills in the circulation of blood.
• Draw a diagram to illustrate the double circulation system in mammals.
• Draw a diagram to illustrate the single circulation system in fish.
• Explain why the mammalian heart must function as a double pump.

AHL B3.2.15- Adaptations of the mammalian heart for delivering pressurized blood to the arteries.

• Label a diagram of the heart with the following structure names:  superior vena cava, inferior vena cava, pulmonary semilunar valve, aorta, pulmonary artery, pulmonary veins, aortic semilunar valve, left atrioventricular valve, left ventricle, septum, right ventricle, left atrium, right atrium, and right atrioventricular valve.
• Outline how the following structures allow the heart to function in delivering pressurized blood to arteries: cardiac muscle cells, atria, ventricles, atrioventricular and semilunar valves, septum, arteries, veins and coronary vessels. ​

AHL B3.2.16- Stages in the cardiac cycle.

• Define myogenic contraction.
• Define cardiac cycle.
• Outline the role of the pacemaker cells in the sinoatrial node.
• Describe the propagation of the electrical signal from the sinoatrial node through the atria and ventricles.
• Explain the flow of blood during atrial and ventricular systole and diastole.
• Define systolic and diastolic blood pressure. 
• State the cause of systolic and diastolic blood pressure.
• Interpret systolic and diastolic blood pressure measurements from data and graphs.

AHL B3.2.17- Generation of root pressure in xylem vessels by active transport of mineral ions.

• List conditions in which a plant may generate root pressure to transport water. 
• Outline the mechanism by which roots maintain a positive pressure potential when evaporation from leaves is insufficient to move water through a plant.​

AHL B3.2.18- Adaptations of phloem sieve tubes and companion cells for translocation of sap.

• Define translocation, phloem sap, source and sink.
• List example source and sink tissues.
• State that phloem transport is bidirectional.
• Outline the stages of phloem translocation including loading of carbohydrates at a source, transport of carbohydrates through the plant, and unloading of carbohydrates at a sink.
• Outline the structure and function of sieve tube elements, with specific mention of the rigid cell wall, reduced cytoplasm and organelles, no nucleus and sieve plates. 
• Outline the structure and function of companion cells, with specific mention of mitochondria and plasmodesmata.