2.3 Adaptations for Transport Flashcards
What makes up an earthworm’s circulatory system?
Closed circulatory system
Blood under pressure
Organs not in direct contact with blood
Respiratory gasses transported in blood
What makes up the mammalian circulatory system?
Heart with two aorta and two ventricles
Closed, double circulatory system
What makes up an insect’s circulatory system?
Fluid-filled blood cavity (haemocoel)
Open circulatory system
Dorsal tube-shaped heart
What are the major blood vessels of the heart?
Vena Cava Aorta Pulmonary vein Pulmonary artery Coronary arteries
What makes up the human heart?
Cardiac muscle
Valves
Varying thickness of walls
Own blood supply
What are the layers of large blood vessels like arteries?
Tough collagen
Elastic muscle to sustain pressure
Smooth endothelium to reduce friction
What makes up a vein?
Thinner muscle layer than arteries
Semi-lunar valves to prevent back flow of blood
Why do arteries have thick walls?
To resist pressure
How do arterioles adjust blood supply?
They adjust their diameter
Describe capillaries.
Small diameter
Walls only one cell thick
Friction with walls slows blood flow
There are many capillaries in a capillary bed meaning they have a large total cross-sectional surface area which slows blood flow
Low velocity and thin walls make it very easy to exchange materials with tissue fluid
What is the cardiac cycle?
Sinoatrial node is spontaneously active
Excitation makes the atria contract
Connective tissue stops excitation reaching the ventricles
The excitation travels along the atrioventricular node to the Bundle of His / His Bundle and along the Purkinje fibres in the ventricle walls
Excitation makes ventricles contract /after/ the atria
Changes in pressure withing the atria and ventricles causes the valves to open and close
When the blood leaves the heart, where is the highest pressure?
In the aorta and main arteries
What causes pressure changes inarterioles
Friction
Large total surface area and narrow bore
If they are contracted or dilated
How can blood pressure be increased when returning to the heart?
By the massaging effect of muscles
How is oxygen carried in the blood?
As oxyhaemoglobin in the haemoglobin
How can the functioning of different types of haemoglobin be demonstrated?
Plot an oxygen dissociation curve of mammalian haemoglobin against foetal haemoglobin
Draw an oxygen dissociation curve for mammalian, foetal, lugworm and llama haemoglobin.
Llama and lugworm are highest, foetal is in the middle and mammalian is the lowest.
Name a physiological adaptation for life in oxygen depleted conditions.
Myoglobin found in skeletal muscles
It increases haemoglobin’s affinity for oxygen
It holds oxygen in the muscles until it is needed
What is the Bohr effect?
Lowered pH caused by dissolved CO2 reduces the oxygen affinity of haemoglobin
Oxygen is released only when and where it is most required
The oxygen dissociation curve shifts to the right
What (aside from respiratory gasses) is transported in the blood?
Protein Digested food materials Hormones Ions Antibodies
How do water and small solutes pass into and out of capillaries?
Pass through the endothelium at the beginning of the capillary beds where the hydrostatic pressure (forcing liquid out) is greater than the osmosis pressure (drawing water in)
At the end of the capillary bed the hydrostatic pressure is lower and the water potential gradient causes an inward flow.
99% of the fluid that leaves the blood at the arteriole end of the capillary bed returns at the venous end.
The rest is returned via the lymphatic system.
Draw the structure of a dicotyledon root.
.
What are the root hairs for?
Absorption of water
- Provide a large surface area
- Freely permeable
What is the apoplast route?
Soil solution soaks into the walls of epidermal cells
Travels across the cortex through cell walls or through spaces between cells
Drawn by the transpiration stream
Water can also cross the plasma membrane by osmosis
What is the symplast route?
Soil solution soaks into the walls of the epidermal cells
Travels across cortex cell walls or between cells
Moves through the cytoplasm of cells via the plasmodesmata.
What is the vacuolar pathway?
Water travels through the cell vacuoles.
What is the endodermis?
A layer of cells which surround the pericycle within which lies the vascular tissue (stele)
What is the Casparian band?
A band that blocks the endodermis apoplast route, located tangentially in the cell wall.
It’s made of water-proof suberin
When it reaches the Casparian strip, water passes across the plasma membrane and continues along the symplast route.
How does nitrogen enter a plant?
As nitrate ions/ammonium ions.
Diffuse along the concentration gradient into the apoplast stream.
Enter symplast by active transport against the concentration gradient.
Flows via the plasmodesmata in the cytoplasmic stream.
What happens to ions when the reach the endodermis?
They have to be actively taken up to pass the Casparian strip so the plant can selectively take up ions.
This causes the water potential in the xylem to drop, drawing water through the endodermis.
Positive hydrostatic pressure inside xylem = water forced upwards (root pressure!)
Draw the structure of a stem.
.
What is the xylem?
Dead, lignified tracheids and vessels with pits, supporting fibres and living parenchyma.
What are the tracheids and vessels in the xylem for?
They form a continuous system of channels for water transport.
What is the simple journey of water through a plant?
It passes through the root to the xylem, up through the stem to the leaves where most evaporates.
How are the columns of water in the xylem held up?
By the cohesive force between water molecules and the adhesive forces between the water molecules and the hydrophilic lining of the xylem vessels.
What is transpiration?
The loss of water from the leaves which gives rise to the transpiration stream.
The continued removal of water from the top of the xylem vessels results in a tension causing a pull on the xylem column.
What environmental factors can effect the rate of transpiration?
Temperature
Humidity
Air movement
What change can the plant make to alter water loss through transpiration?
Open or close the stomata
What are the classifications of plants based on the structure in relation to water supply?
Hydrophytes
Mesophytes
Xerophytes
What are hydrophytes?
eg water lily
Live on or within an aquatic environment
Little need for support or transport tissues
Little or no cuticle
Stomata only on the upper surface of their leaves
Large air spaces in the stem and leaf tissues
What are xerophytes?
eg Marram grass
Live under conditions of low water availability
Modified structures to prevent water loss
Eg sunken stomata, thick cuticle, hairs (all to revent water loss
What are mesophytes?
Live in temperate regions
Flourish in habitats with adequate water supply
Shed their leaves for winter
What are phloem?
Sieve tubes and companion cells linked by plasmodesma with fibres and parenchyma
How are the products of photosynthesis transported in a plant?
In soluble form (sucrose) to all parts of the plant in the phloem
How was early evidence about translocation of solutes in plants obtained?
Ringing experiments
We found it is a rapid process through the technique of radioactive tracing combined with using aphid mouthparts
What part of the plant is a source of sugar where the growing tissues act as a sink?
The leaves
What is the mass flow hypothesis?
There is a passive flow of sucrose from source to sink
It doesn’t account for all observations eg movement in opposite directions at the same time & at different rates
