Adaptations for Gas Exchange- Unit 2.2 Flashcards
What do gill rakers do?
Remove debris
Describe what is meant by diffusion.
The net movement of molecules from a higher concentration to a lower concentration. It occurs passively. (without energy)
What is the capillary endothelium?
The single layer of cells of the capillary wall.
Why do multicellular organisms need a specialised gas exchange mechanism?
They have a lower surface area to volume ratio so cells are further away from the surface, meaning diffusion has to occur over a greater distance.
Why does the amoeba have adequate gas exchange?
- Large surface area to volume ratio
- Thin so short diffusion pathway
- Small
How does a continuous supply of oxygen reach all tissues of an earthworm?
- Large surface area
- Skin is the respiratory surface which is moist
- Tubular structure
What does the cartilage do in the lungs?
Keeps the trachea open as it’s made from rings of strong, bendy cartilage.
What do goblet cells do?
Produce mucus to trap inhaled dust.
What are cilia and what do they do?
Hairs on cells in the trachea, bronchi and bronchioles. They move to push mucus with trapped particles upwards. (away from lungs)
What do elastic fibres do and where are they located?
Between the alveoli. They stretch lungs when inhaling, recoil when exhaling to push air out.
What is and where is the pleural membrane?
Protective lining on the lungs.
What is the alveolar epithelium?
The single layer of cells lining the alveoli.
Describe the path that oxygen take across the alveoli.
- oxygen diffuses out of alveoli
- across alveolar epithelium
- across capillary endothelium
- then into haemoglobin in blood
Describe the path of carbon dioxide across alveoli.
- Diffuses into alveoli from blood
- Then breathed out through lungs
- To trachea
- Then out of mouth and nose
What liquid does alveoli secrete?
Surfactant
What is an alveoli?
A microscopic air sac.
What does surfactant of the alveoli do?
Stops alveoli collapsing by lowering surface tension of water layer lining alveoli.
Name four adaptations the alveoli have to speed up the rate of diffusion.
- Thin exchange surfaces (alveolar epithelium)
- Short diffusion pathways (alveolar epithelium one cell thick)
- Large surface area to volume ratio
- Steep concentration gradient (between alveoli and capillaries)
How does oxygen enter and travel though fish?
•Oxygenated water enters gills in one-way current that continually flows by pumping mechanisms.
What are lamellae?
Thin plates in the gills that create a large surface area. They have lots of capillaries and a thin surface layer.
What is counter-current flow?
Blood flowing over the lamellae in one direction with water flowing over in the opposite direction.
Why is a counter-current flow beneficial?
A concentration gradient is maintained between water and blood. (as much oxygen as possible diffuses from water into blood)
What is metabolic rate?
The rate of energy expenditure by the body.
What are gill filaments?
Specialised respiratory area. Water is forced over them by a ventilating mechanism.
How is ventilation in a bony fish achieved?
Pressure changes in the buccal and opercular cavities.
What is the buccal in a fish?
The mouth.
What are the opercular cavities in a fish?
The gills.
Describe stage 1 of the ventilation mechanism of a bony fish. (4)
- Mouth opens & floor of buccal cavity lowers
- Volume of buccal cavity increases & pressure decreases
- Operculum remains closed
- Water pulled into buccal cavity from outside due to pressure change
Describe stage 2 of the ventilation mechanism in a bony fish. (3)
- Mouth closes
- Buccal cavity contracts, raising floor of cavity
- Water forced across gills
Describe stage 3 of the ventilation mechanism of a bony fish. (2)
- Pressure in gill cavity increases & forces operculum open
* Water leaves via operculum
What is the operculum?
The gill slit.
Fish have haemoglobin and a circulatory system to do what?
Carry oxygen throughout the fish.
How do insects reduce water loss?
Have evolved a rigid waterproof exoskeleton covered by a cuticle.
How does gas exchange occur in insects?
Through paired holes (spiracles) which lead into a system of branched, chitin lined air tubes (tracheae)
What are the ends of the tracheae called in an insect?
Tracheoles
Name 4 labels on an insect.
- Head
- Thorax
- Spiracle
- Abdomen
What ventilates the tracheal system in an insect?
Compression and expansion of the abdomen.
When the abdomen expands in an insect, the thorax spiracles are… and the abdominal spiracles are…
Open
Closed
As the abdomen is compressed in an insect, the thorax spiracles… and the abdominal spiracles…
Close
Open
Does oxygen enter or exit the thorax spiracles in an insect?
Enter
Does oxygen enter or exit the abdominal spiracles in an insect?
Exit
What is a thorax in a human?
An airtight compartment.
Order the path that oxygen takes from entering the body to the site of gas exchange in a human.
1• Trachea
2• Bronchi
3• Bronchioles
4• Alveoli
Describe inspiration.
- Intercostal muscles contract, raising ribcage upwards and outwards.
- Diaphragm contracts and flattens.
- Volume of thorax increases and pressure decreases.
- Air enters and lungs expand.
Describe expiration.
- Intercostal muscles relax, moving ribcage inward and downward.
- Diaphragm relaxes and curves upwards.
- Volume of thorax decreases and pressure increases.
- Air forced out of lungs.
Why are surfactants often given to premature babies?
It prevents the alveoli of their immature lungs from sticking together.
Why do plants need to exchange gases?
For respiration and photosynthesis.
What is the main gas exchange surface on a plant?
Leaf.
How is a leaf adapted for gas exchange?
- Thin
- Flat
- Large surface area
- Short diffusion pathway
Order each part of a flowering plants leaf from top to bottom.
1• Waxy cuticle 2• Upper epidermis 3• Palisade mesophyll 4• Spongy mesophyll 5• Vascular bundle 6• Guard cell 7• Stomata
Name the function of the waxy cuticle in a leaf.
Reduces water loss from leaf surface by evaporation.
Name function of upper epidermis in a leaf. What are they?
Transparent cells which allow light to pass through mesophyll tissue. They synthesise and secrete the waxy cuticle.
What does the palisade mesophyll do in a leaf? What do they contain?
Contain many chloroplasts for photosynthesis. This layer is the main photosynthetic tissue.
What do the spongy mesophyll and air spaces do in a leaf?
Spongy palisade cells photosynthesise. Air spaces between cells allow for circulation of gases.
Two examples of vascular bundles:
Xylem and phloem.
What do the vascular bundles do in a plant?
Xylem- water and mineral transport.
Phloem- transport of products of photosynthesis. (sucrose and amino acids)
Function of guard cells in a leaf:
They become turgid and flaccid due to changes in water potential. This opens and closes stomata pore.
What does the stomata do in a plant?
Allows gas exchange.
Why can chloroplasts rotate and move in mesophyll cells in a leaf?
To allow arrangement of the best possible position for light absorption.
How many guards cells bound a pore/stoma in a leaf?
2
Describe the structure of a guard cell in a leaf. (4)
- Have chloroplasts.
- Thick inner wall and thin outer wall.
- Thick inner wall causes cell to become curved when swelled, opening the stomatal pore.
- Can change shape to open/close stomata, helping control gas exchange and water loss.
Why are stomata found on the lower leaf surface?
To reduce water loss from evaporation. (sun hits top of leaf so being at the top would result in leaf becoming flaccid)
Do most stomata close or open at night?
Close
During the day when light intensity is sufficient, the stomata is…
Open
How does water enter/exit the guard cells in a leaf?
Osmosis
When the stomata closes, water potential…
Increases
When the stomata opens, water potential…
Decreases
What is parallel flow in a fish?
Blood and water flow in the same direction.
