Gas Exchange (WIP - need to do insects + fish) Flashcards
What are the adaptations of the alveoli?
- Large surface area: volume ratio
- Fluid lined enabling gas to dissolve
- Surrounded by capillaries
- Surfactant (complex substance that reduces surface tension by interrupting hydrogen bonds of water molecules)
- Elastic tissue / can recoil
- Alveolus / capillary wall are both 1 cell thick
- Both walls consist of squamous epithelial cell
- Capillaries have narrow lumen so erythrocytes squeeze against capillary wall
What is the role of cartilage in the trachea and bronchi?
- Rings of cartilage in the walls of trachea and bronchi provide support
- Strong but flexible
- Stop the trachea and bronchi collapsing when pressure drops
What are the intercostal muscles and what is their role?
- Muscles positioned between the ribs
- Contraction of the external intercostal muscles elevates the ribs and spreads them apart
- Contraction of the internal intercostal muscles depresses the ribs and pulls them closer together
- Antagonistic muscles (when one contracts, the other relaxes)
What are other words for “breathing out”?
Expiration / exhalation
What are other words for “breathing in”?
Inspiration / inhalation
What happens during inhalation?
External intercostal muscles contract, internal intercostal muscles relax. Diaphragm flattens. Increased volume means lower pressure in the chest. Atmospheric air at higher pressure drawn in.
What happens during exhalation?
Internal intercostal muscles contract, external intercostal muscles relax. Ribs fall, diaphragm moves up. Decreases volume means increased pressure in chest. Pressure in chest is higher than in air so is exhaled.
What is a spirometer?
A piece of apparatus that measures the gas exchange in the lungs.
What is a dicotyledonous plant?
A type of flowering plant with 2 seed leaves.
What is a xerophytic plant?
A plant that is adapted to reduced their water loss so it can survive in very dry conditions.
What are the stomata?
Tiny openings on the underside of the leaf which have guard cells on either side.
What happens to the stomata during the day?
The guard cells on either side are filled with fluid, which makes them turgid. This causes the stomata to open, allowing carbon dioxide to enter for photosynthesis and oxygen to diffuse out.
What happens to the stomata at night?
During the night, the guard cells on either side empty of fluid. This makes them flaccid and causes the stomata to close. As a result, carbon dioxide and oxygen cannot be exchanged. However, on the plus side, less water vapour is lost due to evaporation.
What happens if a plant loses too much water?
The plant cells will lose turgidity, may undergo plasmolysis and the plant will eventually die.
What is plasmolysis?
The detachment of plasma membranes from cell walls as cytoplasm shrinks.
Water loss is unavoidable due to stomata being open during the day. How are plants adapted to minimise water loss?
- Waxy cuticle reduces loss due to evaporation through epidermis
- Stomata often on under surface of leaf to minimise evaporation due to sunlight
- Stomata closed at night
- Deciduous plant lose leaves in water ~ temperature too low for photosynthesis
What are the features of xerophytes?
- Thick cuticles
- Small / needle shaped leaves
- Few stomata
- Stomata shrunk into pits in epidermis
- Hairs around stomata and over leaf surface
How does having a thick cuticle help xerophytic plants reduce water loss?
Stops uncontrollable evaporation through leaf cell.
How does having a small leaf surface area help xerophytic plants reduce water loss?
Less surface area for evaporation.
How does having a low stomata density help xerophytic plants reduce water loss?
Smaller surface area for diffusion.
How does having sunken stomata help xerophytic plants reduce water loss?
It maintains humid air around stomata, reducing diffusion of water vapour out.
How does having stomatal hairs (trichores) help xerophytic plants reduce water loss?
It maintains humid air around stomata, reducing diffusion of water vapour out.
How does having rolled leaves help xerophytic plants reduce water loss?
It maintains humid air around stomata, reducing diffusion of water vapour out.
How does having extensive roots help xerophytic plants reduce water loss?
It maximises water uptake.
