• Shuffle
    Toggle On
    Toggle Off
  • Alphabetize
    Toggle On
    Toggle Off
  • Front First
    Toggle On
    Toggle Off
  • Both Sides
    Toggle On
    Toggle Off
  • Read
    Toggle On
    Toggle Off
Reading...
Front

Card Range To Study

through

image

Play button

image

Play button

image

Progress

1/40

Click to flip

Use LEFT and RIGHT arrow keys to navigate between flashcards;

Use UP and DOWN arrow keys to flip the card;

H to show hint;

A reads text to speech;

40 Cards in this Set

  • Front
  • Back
As the cell size increases what happens to the surface: volume ratio?

It decreases


- The diffusion pathway is longer and therefore diffusion would be slower.

What is gas exchange?
The process by which oxygen reaches cells & carbon dioxide is removed from them.
Talk about Unicellular Organisms (Amoeba)...

- Small Size = Extremely large SA:V


- Gas exchange across the whole body surface.


- Permeable membrane allows diffusion of gases.


- Aquatic organism = moist surface allows gases to dissolve and diffuse.


- Specialised exchange organs not needed.



Talk about Simple Multicellular Organisms (Flatworm)...

- Small size


- Evolved a flattened shape to overcome the problem of increase in size.


= Large SA:V, no cell is too far from the surface (short diffusion pathway) = no need for specialised pathway organs.


- Permeable surface


- Aquatic - moist surfaces allow gases to dissolve and diffuse.

Talk about Earthworms...

- Multicellular organism


- Terrestrial organism but has developed tube shape


- Lives in damp conditions


- Secretes mucus = surface is moist so gases can easily difuse


- Elongated shape = large SA:V


- Blood vessels close to the body surface so gases can easily diffuse in/out.


- Blood circulates in vessels = maintains concentration gradient for diffusion of oxygen in/ carbon dioxide out.

Why do large multicellular organisms require a specialised gas exchange surface?

1. As size of organism increases = decrease in SA:V.


2. Diffusion across body surface is insufficient to provide enough oxygen.


3. Larger organisms are more metabolically active = higher oxygen demand.#


4. Diffusion pathway is too large = slower.


5. So need a specialised exchange surface between organism & external environment.


6. Need method of transport to distribute gases around body.


7. Have toughened body surface so have internal gas exchange surfaces.

In order to achieve the max. rate of diffusion, all respiratory surfaces must be...


1. Permeable


2. Moist


3. Thin


4. Large SA:V


5. Maintenance of a concentration gradient.


What type of gas exchange surfaces to amphibians (frog) have?


- Larvae/tadpole live in water = gills


- Adults are terrestrial = skin- when inactive & skin & lungs- when active.


Describe the structure of an amphibian lung?

- Simple


- Little infolding of the gas exchange tissues.



What is a benefit of having internal lungs?

- Reduce heat loss.


- Reduce water loss


- Protection by ribcage or exoskeleton



Give 2 functions of the reptile ribs?

1. Provide support & protection of organs


2. Enable ventilation of lung

How does the structure of the reptile lungs differ from that of amphibian lungs?
Reptile lungs have more complex internal structure, w/ in-folded tissue to increase the surface area for more efficient gas exchange while amphibians' are more simple with little infolding.

The respiratory system of birds...


- More efficient that other vertebrates.


- Ventilation is assisted by a system of air sacs connected to the lungs.


- Air sacs act as bellows.


- Fresh air passes through respiratory system in one direction = ensures no residual stale air is left in lungs.


- First - fresh air to posterior sacs, into lungs, then anterior sacs, then exits through trachea.


- Ventilation is brought by the movement of the ribs.


- Contraction of flight muscles ventilates the lungs.


Respiratory system for insects...

- Do not use blood to transport gases.


- Air diffuses into insects through holes called spiracles.


- Spiracles lead to a system of branched chitin lined air tubes called tracheae.


-Spiracles open & close.


- During periods of activity, movements of the abdomen ventilate the tracheae.

Why is it important the spiracles can open & close like valves?

- To allow exchange of gases.


- To reduce water loss.

What structural feature ensures that the tracheae remain open?
Chitin lines the tracheae keeping it open.

Advantages of tracheal system:


- No respiratory pigment needed = less energy need to produce it & move it.


- Oxygen alone moves faster than oxygen in blood.


- Reduces water loss


- Oxygen is supplied directly to tissues.


Problems caused by living in water?

- Water contains less oxygen.


- Rate of diffusion is slower in water.


- Water is a dense medium so doesn't flow as freely .

Discuss Cartilaginous Fish...


E.g. Sharks


- Skeleton made entirely of cartilage


- On each side of its head has 5 gill clefts which open @ gill slits.


- Water is taken in & forced through gill when floor of the mouth is raised.


- Use parallel flow.


Explain parallel flow.

- Gill capillaries on the same direction of the water.


- Efficient at first b/c has a very steep concentration gradient.


- But halfway along the gill lamellae equilibrium is reached & diffusion of oxygen & carbon dioxide is no longer possible.

Bony Fish


E.G Salmon

- Have an internal skeleton made of bone.


- Gills are covered w/ a flap called the operculum.


- Use counter current flow.

Explain Counter Current flow.


- Water flows in opposite direction to blood flow.


- Blood always meets water w/ a higher oxygen concentration.


- Concentration gradient is maintained over the whole length of the gill lamellae.


- Counter current flow is more efficient than parallel flow as it results in a higher blood saturation level.


How many gills on each side does a head of a bony fish?
4
How does water pass through the gills in a fish?

-Water is taken in through the mouth, passes over the gills & is expelled via the operculum.


- Movements of the buccal cavity floor & operculum allow a one-way current of water to flow through the gills for the exchange of gases.



Ventilation Mechanism in Fish...

Water flows in


- Mouth - open


- Operculum - Closes


- Floor of Buccal Cavity - Lowers


- Volume - Increases


- Pressure - Decreases


Water flows out = opposite.

The structure of gills of a bony fish...

- Gill arch - thin filaments - gill lamellae.


- Gill lamellae has large SA for gas exchange.


- Blood circulates through capillaries in the gill plates.

What will happens if the gills were dry?

- Shrink so smaller SA= less efficient


- Not moist so hard for gases to diffuse easily.

What is the reason for 'C' shaped cartilage in the trachea?
- Allows for expansion & stops it from collapsong

What is the name of the airtight compartment of the body that encloses the lungs?


Thorax.


Explain how ventilation occurs in the human lungs.

Inspiration


- External Intercostal Muscles = Contract


- Ribs = Out & Up


- Diaphragm = contracts & flattens


- Volume of the Thorax = Increases


- Pressure in the Thorax = Decreases


- Outside Air Pressure = Higher than in the lung




Expiration = Opposite

Why are alveoli suitable for gas exchange?

- Large number = large SA for diffusion of gases.


- Moist - Gases dissolve easily


- Permeable


- Walls are 1 cell thick - short diffusion distance.


- Each alveolus has an extensive capillary network - circulation of blood maintains the concentration gradient.



What is a surfactant and why is it important?

- Chemical substance that covers surface of alveoli


- Reduces surface tension & prevents the alveoli from sticking together & collapsing when breathing out.

What is the function of the plural membrane?
Lubricates & causes cohesion in the lungs.
What is the use of a respiratory pigment?
To increase the oxygen carrying capacity of the blood (haemoglobin)

How are leaves adapted for gas exchange?


- Mesophyll layer is covered in water = moist


- Flat leaf blade = large SA:V


- Stomatal Pores = Permeable


- Air spaces in space in spongy mesophyll rapid diffusion = short diffusion distance


How is leaf adapted for photosynthesis?


- Large SA:V to absorb as much light as possible.


- Leaves can orientate themselves towards the sun.


- Leaves are thin to allow light to penetrate lower layers.


- Cuticle & epidermis are transparent to allow light to pass through to the mesophyll below.


- Palisade cells are elongated and densely packed together & contain many chloroplast.


- Chloroplast can rotate & more within the mesophyll cells to maximise light absorption.


- Intercellular air spaces allow carbon dioxide to diffuse into cells, oxygen & water vapour to diffuse away.


Info about the stomata...

- Found in the wax cuticle on the underside of the leaf.


- They allow carbon dioxide to enter & oxygen to leave.


- 2 Guard cells surround each stomata.



What is unusual about guard cells?

- They are only epidermal cells that contain chloroplast.


- They have unevenly thickened cell walls.

What happens to the guard cells when the open & close?


Open


- Inner cell wall is thick & outer wall thin = turgid



Close


- Guard cells become flaccid the pores close.


The Mechanism for Stomatal Opening...

- Potassium ions are actively transported from the epidermal cells into guard cells.

- Stored starch (insoluble) in guard cells is converted into malate (soluble) by enzymes in cytoplasm.


- Water potential in GC is lowered so water enters by osmosis.


- GC become turgid & curve apart b/c the outer cell walls are thinner than the inner cell walls.