Transcript Ch 6 Distributing Materials 2

Chapter 6
Distributing Materials
Internal transport systems: Why have one?
In single-celled and very thin multicellular organisms, direct exchange
with the environment may be sufficient to meet the requirements of all
cells, provided that:
 the surface area to volume ratio of the organism is high
 the distances to be covered are short – no cell is very far from the
external environment.
 there are low requirements for oxygen
Liverworts
Flatworms
Algae
Transport in larger organisms
Diffusion is inadequate or too slow to meet cellular needs.
To meet these needs:
• most animal species have specialised circulatory systems
• most land plants also have specialised transport systems
Transport occurs across specialised exchange organs:
• leaves and roots in plants
• gills, lungs, digestive systems in animals
What needs to be transported?
 Nutrients
 Respiratory gases
 Wastes
 Hormones (for coordination)
 Heat
How are they transported?
 In mammals and birds, heat is transported by:
 the blood throughout the body
 between the external surface and interior of the body
in order to maintain a reasonably uniform body temperature.
 Blood cells are involved in:
 gas transport
 defence
 immunity
 blood clotting
 Circulated fluids carry materials between exchange surfaces and
sites of production, use and storage.
Influences on transport systems
 The demands placed on a transport system are due to factors
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as body size
energy and nutrient requirements
source of oxygen (air or water)
climate
level of activity
reproductive condition
 Transport is normally regulated to conserve energy.
 Organisms with high energy and nutrient requirements, such
as mammals and birds, have high demands and must have
very effective transport systems.
Features of effective transport systems
 Large surface areas available for exchange both with
the environment and internally.
 Reliable and responsive means of moving fluid around
the body.
 Fluid that maximises the amount of material that can
be transported (good carrying capacity)
 Control mechanisms that regulate the transport
according to need.
Types of fluid
Intracellular fluid: the cytosol – fluid inside cells.
Extracellular fluid: all other fluid in the body.
Blood: contains both intracellular fluid (in blood cells) and extracellular fluid (plasma).
Interstitial fluid: portion of extracellular fluid located in the spaces between cells in
tissues.
Exchange of substances between blood and body tissues occurs between
plasma and interstitial fluid.
Composition of fluid in an average human
(Total ~ 40 L)
Types of transport systems in animals
Open circulatory systems:
 common to molluscs and arthropods (eg insects).
Closed circulatory systems:
 evolved in echinoderms and vertebrates.
 common in active animals (vertebrates, squid)
Open circulatory systems
Usually have:
• very low pressures
• long circuit times (time taken for fluid to pass from the heart, out to
the tissues and back to the heart)
• weak pumps
• fluid that does not return directly to the heart
Dorsal longitudinal vessel (the ‘heart’)
contracts.
Fluid is forced out at the anterior end
This fluid flows through tissue spaces
Re-enters the dorsal vessel through a series of
openings.
mollusc
earthworm
Closed circulatory systems
• Blood is enclosed within vessels of different size and
wall thickness.
• Blood is pumped by a muscular heart through vessels
(arteries, veins, capillaries).
• Blood can be returned to the heart very rapidly.
• Higher blood pressures are possible - providing a
reliable blood supply that can used in different ways
for many functions at the same time.
• Blood is separated from the interstitial fluid by vessel
walls - allowing blood to have different, highly
specialised properties for transport and defence.
• Carrying capacity for oxygen is greatly increased by
haemoglobin molecules.
Mammalian transport systems
• Mammals have two transport systems - a closed blood circulatory
system and an open lymphatic drainage system.
• Components of the mammalian circulatory system are a muscular
heart, pulmonary and systemic veins and arteries, thin walled
capillaries and highly specialised blood.
• The four chambers of the mammalian heart contract in coordinated
way to propel blood into the pulmonary and systemic arteries.
• Blood pressure is caused by the contraction of the ventricles.
• Exchange occurs across capillary walls and blood returns to the heart
in veins.
Human heart: anatomy
• Located under the ribcage in the centre of the chest between
the right and left lung.
• Shaped like an upside-down pear.
• Muscular walls beat, or contract, pumping blood
continuously to all parts of the body.
• The size of the heart varies depending on age, size, or the
condition of the heart.
• A normal, healthy, adult heart is the size of an average
clenched adult fist.
• Some diseases of the heart can cause it to become larger.
Heart chambers
4 chambers:
• right and left atria (AY-tree-uh)
• right and left ventricles (VEN-trih-kuls)
Right ventricle:
• pumps blood from the heart to the lungs
• oxygen added to the blood
• carbon dioxide is passed from blood, to blood vessels to lungs
and is removed from the body when you breathe out.
Left atrium:
• receives oxygen-rich blood from the lungs
• pumping action of the left ventricle sends oxygen-rich blood
through the aorta (a main artery) to the rest of the body
Right side of the heart
Superior and inferior vena cavae (largest veins in the body)
Carry deoxygenated blood from upper and lower parts of the body
To the right atrium
To the right ventricle
Through the pulmonary artery to the lungs
Oxygen is picked up through capillaries
Oxygen-rich blood passes from lungs, to heart through pulmonary veins
The left side of the heart
Oxygen-rich blood from the lungs passes through the pulmonary veins
Enters the left atrium and is pumped into the left ventricle
To the rest of the body through the aorta
Heart + all organs need blood rich with oxygen
Oxygen is supplied to heart through the coronary arteries
Coronary arteries are located on heart’s surface at the beginning of the aorta.
Aorta carries oxygen-rich blood to all parts of the heart.
Human heart: exterior
Front surface of the heart, including the coronary arteries and major blood vessels.
Human heart: interior
Cross-section of a healthy heart and its inside structures.
Internal structure of the heart
Septum
• Internal wall of tissue
• Divides right and left sides of the heart
Chambers
• Four chambers.
• Two upper chambers are the atria - receive and collect blood.
• Two lower chambers are the ventricles - pump blood out of the heart into the circulatory
system to other parts of the body.
Valves
• Control flow of blood.
• Open and close in coordination with the pumping action of the atria and ventricles.
• Each valve has a set of flaps (cusps) which seal or open the valves.
• One way - allow pumped blood to pass through the chambers and into arteries without backing
up or flowing backward
• Four types
o aortic (ay-OR-tik)
o tricuspid (tri-CUSS-pid)
o pulmonary
o mitral (MI-trul)
Mammalian Heart in Action
The animation shows how the heart pumps blood.
http://www.nhlbi.nih.gov/health/dci/Diseases/hhw/hhw_pumping.html
Blood pressure
Systolic and diastolic pressure fluctuate in arteries and arterioles; almost zero through the capillaries.
Blood pressure is lower in pulmonary arteries than in systemic arteries.
The right ventricle has a thinner muscle wall and lower pumping pressure than the left ventricle.
Blood pressure: Giraffe facts!
• In a fully grown 5 m tall giraffe, the head
is about 1.5 m above the heart.
• The heart must develop a high pressure
to push a column of blood against gravity
up the arteries to the brain.
• The mean blood pressure in the giraffe’s
aorta is about 200 mmHg - about twice
that of many mammals, including
humans.
• To produce such a pressure, the walls of
the giraffe’s left ventricle are extremely
thick!
Heartbeat
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"lub-DUB" sound.
Between the "lub" and "DUB," blood is pumped through the heart and circulatory system.
Complicated series of very precise and coordinated events.
Each side of the heart uses an inlet valve to help move blood between the atrium and ventricle:
• tricuspid valve between the right atrium and ventricle.
• mitral valve between the left atrium and ventricle.
The "lub" is the sound of the mitral and tricuspid valves closing.
Each of the heart’s ventricles has an outlet valve:
• right ventricle uses the pulmonary valve to move blood into the pulmonary arteries.
• left ventricle uses the aortic valve to move blood into the aorta.
The "DUB" is the sound of the aortic and pulmonary valves closing.
Each heartbeat has two basic parts:
• diastole (relaxation)
• systole (contraction) - atrial and ventricular
During diastole, the atria and ventricles of the heart relax and begin to fill with blood.
At the end of diastole, the heart's atria contract (atrial systole) and pump blood into the
ventricles.
The atria then begin to relax.
Next the heart's ventricles contract (ventricular systole) and pump blood out of the heart.
Blood components
Blood vessels
Main blood vessels:
• Arteries
• Veins
• Capillaries
Name that part!
Check your knowledge!
‘Blue’ babies: hole in the heart
In human embryos, blood bypasses the lungs
by two means:
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by flowing through the foramen ovale between the
right and left atria
through the ductus arteriosus between the
pulmonary artery and aorta (remnant of the
original sixth aortic arch.
Sometimes one or both connections do not close over
completely.
Both can be surgically repaired, leaving a perfectly
healthy heart.
Blood is not completely oxygenated - continues to
bypass the lungs.
Deoxygenated haemoglobin is a darker bluish-red
and gives the skin (particularly the lips) a bluish tinge.
Lymphatic system
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Extensive network of vessels
Open system
Drains fluid from body; returns it to the blood circulation
Fine, blind-ending lymphatic capillaries in tissues join to
form increasingly larger vessels that eventually empty into
the large veins near the heart.
Returning interstitial fluid is called lymph.
Contains proteins that leak out of the capillaries
Larger lymph vessels contract
Most lymph flow results from external compression of
lymph vessels by muscular activity (eg during movement and
breathing).
Lymph fluid is forced in one direction because of numerous
one-way valves, like those in veins, located along the vessels.
Build up of lymph causes swelling (oedema).
What do you know? - Plant transport systems
Without referring to your text, explain the difference between:
1. vascular and non-vascular plants
2. phloem and xylem
3. transpiration and translocation
Use labelled and annotated diagrams to support your ideas.
Now use your text to check your ideas.
Transport systems in plants
Plants need water, carbon dioxide and light for photosynthesis.
Vascular land plants:
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ferns, cycads, conifers and flowering plants
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absorb water through roots and carbon dioxide through leaves
Non-vascular land plants (bryophytes):
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liverworts, mosses and hornworts
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absorb water directly from the environment into their body tissue
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water is moved throughout these plants by the slow processes of
diffusion, capillary action and cytoplasmic streaming
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lack the vascular tissue that provides support in larger plants usually sprawl horizontally (most only 1-2 cm)
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Dawsonia superba:
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largest non-vascular plant
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grows in moist mountain ash forests
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reaches 30 - 40 cm in height.
Selection of bryophytes: moss,
liverworts, hornworts.
Dawsonia superba (largest moss)
Vascular plants
Have a transport system that:
• is continuous through roots, stems and leaves.
• carries water and inorganic nutrients obtained from the soil by the roots throughout the plant.
• transports the sugars made in leaves to other parts of the plant.
• vascular tissues - xylem and phloem - tubular pathways through which fluids flow.
Plant transport systems
Xylem: transport water and inorganic nutrients up the plant from the soil.
Phloem: transport sugars (in solution) produced by photosynthesis throughout the
plant.
Vascular tissue:
• composed of phloem and xylem
• tubular pathways through which fluids flow
• continuous through roots, stems and leaves
• found in ferns, cycads, conifers and flowering plants
• easily visible in leaves as:
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parallel veins in grasses
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branching veins in many other leaves
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stringy parts of celery and silver beet leaf stalks
• extend from roots to the very ends of leaves, into developing buds and fruit
• few cells in plants are far from vascular tissue
Vascular bundles
 The arrangement of xylem and phloem tissues in roots and stems is
distinctive.
 In roots, xylem and phloem tissues are located alternately around a
central core of xylem.
 In stems, xylem and phloem tissue form ‘vascular bundles’ in
which the phloem lies outside the xylem on the same radius.
 Extend into the leaves.
Xylem
In flowering plants, the xylem includes:
• tracheids
• vessel elements
• parenchyma - only living cells in mature, functioning xylem
• sclerenchyma cells (supporting fibres).
Mature xylem vessel:
• long, water-filled tube
• cylindrical skeletons of dead cells joined end to end
• as they mature, the primary cell wall of cellulose is strengthened with lignin
• becomes a stronger and more rigid secondary cell wall
• cytoplasm and nucleus disintegrate
• at each end the cell walls are perforated or completely open
• fluid can flow directly through them (like a pipe)
• pits (unthickened areas) and perforations in the sidewalls of the xylem vessels allow
sideways movement of substances between neighbouring vessels.
Xylem elements
Vessels:
• found in flowering plants
• joined end-to-end
• form a long channel
Tracheids:
• present in all vascular plants
• exist singly
Tracheids
Tracheids of the primary xylem:
• mature first
• stretched during development
• walls are rings or spirals
Tracheids of secondary xylem:
• walls develop after all length-wise growth has ceased
• not stretched during development
• more continuous
• connected to one another by numerous pits
• pits may occur anywhere on the cell wall
• particularly numerous on the tapered end of the cell
where it abuts with the adjacent cell.
• water and dissolved substances move upwards from the
tracheid through the pits
bordered pits (pine)
Tracheids
• Single large, tapering water-filled cells
• Many pits in their lignified cell walls
• Mature tracheids are dead
• no nucleus or cytoplasm
• not connected end to end
• Water transfers from tracheid to tracheid through the pits.
• In conifers (eg pines), xylem contains:
• tracheids
• no xylem vessels
• wood is softer (referred to as softwoods)
Xylem parenchyma cells
• living cells
• store starch manufactured in one growing season for use at the beginning
of the next
• scattered as packing tissue between the xylem vessels
• pith (innermost region of a stem) - involved in starch storage in plants (eg
sago and sugar cane)
• lateral (sideways) movement of water and nutrients through woody stems
occurs along horizontally arranged rays - specialised xylem parenchyma
cells orientated radially
• structural pattern of xylem vessels, fibres and rays is characteristic for
different species of trees
• xylem forms the inner woody parts of stems and trunks
• central heartwood has no living cells
Phloem
Mature sieve tubes:
• living cells
• no nucleus
• non-lignified cell walls
• linear rows of elongated cells
• cell walls at each end perforated by a number of holes (like a sieve)
• strands of cytoplasm pass through the perforations, connecting cells together
• usually associated with one or more companion cells
• connected to the companion cells by very thin cytoplasmic strands
(plasmodesmata)
Companion cells:
• keep their nucleus
• active in moving sugars into and out of sieve tubes
• like sieve tube cells, have thin cell walls
Supportive fibres:
• similar to those of xylem tissue
Phloem
• involved in the transport of
sugars
• composed of:
• sieve tubes
• parenchyma cells
• companion cells
• supportive fibres
• in woody stems, located
outside xylem and forms
the inner part of bark.
• ring barking severs phloem
tissue causing the tree’s
death
Phloem: sieve tube cells and companion cells.
Transport of sucrose
Sucrose is moved into the sieve
cells against a concentration
gradient.
This causes water to move
from the xylem by osmosis
into the sieve cells.
Transpiration
 Loss of water vapour from leaves.
 Involves the xylem.
 Driven by radiant energy of the sun
 As water evaporates from the cell walls, the leaf draws water
from nearby xylem vessels to replace the lost water.
 Thousands of leaf cells, each drawing water from xylem,
create a suction that pulls water up xylem vessels from roots.
 Movement of xylem sap from roots to leaves is driven by
transpiration and, to some extent, by root pressure.
Transpiration
The movement of fluid through xylem
vessels is caused largely by transpiration.
Root pressure
Under some circumstances, internal
fluid pressure (root pressure) in the
roots of some plants causes fluid to rise
up through xylem vessels.
Guttation
• Loss of liquid water from leaves - visible consequence of root pressure.
• In relatively small plants, root pressure forces droplets of water from
specialised pores at the tips of principal leaf veins.
• Occurs
• at night, when air is moist
• when the soil is very wet (eg over-watered pot plant)
• Assists the survival of plants - ensures continual upward movement of
sap, transporting essential nutrients from the soil to the leaves - in
tropical conditions, where humidity in the surrounding air is so high that
little transpiration occurs,
Transpiration Facts
 The pull of transpiration, plus the cohesion of water, can be
strong enough to draw water 100 m up a tree trunk.
 Transpiration does not require an intact root system. It
continues
 when cut flowers and leafy shoots are put in a vase of water.
 if the stem is killed with poison or heat.
Factors affecting transpiration
 Dependent on factors that affect the rate of evaporation:
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temperature, wind, available surface area and humidity.
Water vapour is largely lost from leaves through open stomata.
Transpiration rate is low at night because conditions are cooler,
more humid and stomata are usually closed.
Evaporation is reduced when there is a high level of water vapour
in the air (decreases the water concentration gradient between leaf
spaces and air).
Air currents increase the rate of transpiration because they reduce
the humidity in the vicinity of the leaf surface by moving water
vapour away from the leaf.
Hairs create a layer of relatively undisturbed air over the leaf
surface, reducing the rate of evaporation of water.
Translocation
• Movement of fluid through phloem
• Result of active pumping of sugars,
with water following along an
osmotic gradient.
• Sugars and water enter phloem sieve
tubes in leaves and are translocated
throughout the plant.
• Sugars are actively unloaded from
sieve tubes at sites where they are
required.
Translocation
 Transport of organic materials through phloem.
 Occurs through the sieve tubes.
 Involves both active transport and passive movement of fluid.
 Two principal types of organic molecules are transported:
 soluble carbohydrates (sucrose)
 nitrogenous compounds (eg amino acids)
 Photosynthetic cells in leaves are the ‘source’ of carbohydrates for the entire plant.
 Once carbohydrates have been made:
 converted to sucrose
 transported to ‘sinks’
 used or converted to complex carbohydrates (starch) and stored for future use.
 Storage organs are:
 sinks when carbohydrates are being stored
 sources when carbohydrates are released again as sucrose for growing tissues
Translocation: Direction
 Translocation is often in a downward direction:
 leaves are the major site of production of sugars
 roots are a major site of consumption
 Can take place upwards - sucrose is translocated to growing shoots and to
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developing fruits for storage
Roots take up inorganic nitrogenous ions (nitrates and ammonium) from
soil and transport them through xylem to leaves.
The cells in leaves contain enzymes that catalyse the formation of amino
acids from these inorganic nitrogenous substances.
Amino acids are then transported throughout the plant through the
phloem.
Amino acids are the basic building blocks for proteins and are required for
the synthesis of enzymes, ATP and nucleic acids.
Ring barking
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Removal of a complete ring of bark.
Disrupts a plant’s transport systems.
Phloem is cut.
Simple way of killing trees.
After being ring barked:
• Trees still take up plenty of water from the soil (in xylem).
• New shoots may form above the damaged bark (short while only).
• Sugars made in the leaves (photosynthesis) can not get down to the roots.
• Root cells eventually die - lack food to provide energy for maintenance.
• As roots die, nutrient and water uptake from the soil gradually stops;
plant dies.