Topic 6 - Exchange Flashcards
What are the two main ways insects reduce water loss?
- Their exchange system has a large surface area:volume ratio / small surface area.
The internal SA is large but the external (where they lose water) is small. - (Waxy) cuticle over their rigid exoskeleton.
How are the spiracles adapted to help maintain the humidity around the opening?
They are able to open and close where water can evaporate / not evaporate. Have hairs around the opening.
How does the presence of spiracle hairs help to reduce the rate of water loss from the insect?
Hairs reduce rate of air movement and humid air gets trapped around spiracles. The concentration gradient decreases.
How does abdominal pumping move gases into the tracheal system of a locust?
It pushes air in the tracheae out to allow fresher, oxygen rich air to enter the locust when it pushes back in.
What is a function of the rings of chitin that support the larger trachea of an insect?
It stops the larger trachea from collapsing / closing up.
What is the problem of water for respiration?
Oxygen is not very concentrated in water. Warm water has less dissolved oxygen than cold.
What is the structure of fish gills?
- Water taken in through mouth and passed over the gills and out of the operculum.
- Gills comprise of filaments stacked up in a pile, which increases surface area for gas exchange.
- Sprouting upwards from the filaments are the lamellae, they increase the SA.
- Flat plates with very thin surfaces.
- Thin epithelium and good blood supply help maintain a concentration gradient.
Why is the countercurrent flow (what fish have) more efficient than if they had parallel flow?
Parallel flow = diffusion gradient only at first part of filament. Equilibrium is met at 50%.
Countercurrent flow = concentration of oxygen in water is always slightly more than the concentration in the blood - diffusion gradient is maintained across the entire width of the gill lamellae. Around 80% of oxygen from the water can be absorbed into blood.
Why do fish die when they are taken from the water?
Gills are designed for water. Gill surface are covered in water and they stick together when taken out of the water, which decreases the surface area. Gills can also dehydrate.
What are some adaptations xerophytes have evolved to live in areas where water is in short supply?
- Extra thick waxy cuticle (more impermeable).
- Less overall surface area than normal plant leaves = less evaporation.
- Low stomatal density = fewer stomata = less water escapes.
- Sunken stomata (in epidermis) that shelters them from conditions that increase transpiration.
- Stomatal hairs = trap water vapour as it leaves the stomata and creates humid air around stomata. Decreases water potential gradient = decreased rate of transpiration.
What is the trachea? Function?
- A flexible airway supported by C shaped rings of cartilage.
- Can collapse slightly to allow food to pass down to oesophagus.
- Walls are made from muscle with ciliated epithelial cells and goblet cells. Goblet cells produce mucus.
What are the bronchi? Function?
- Two divisions of the trachea, each leading to one lung.
- Have goblet and epithelial cells and cartilage, but the amount is reduced as the bronchi get smaller.
What are the bronchioles? Function?
- A series of branching subdivisions of the bronchi.
- Walls made from smooth muscle lined with epithelial cells. Smooth muscle allows them to constrict so they can control air flow at alveoli.
What are the alveoli? Function?
- Minute air-sacs located at the end of the bronchioles.
- Contain collagen and elastic fibres and are made from a single layer of flattened epithelial cells.
- Elastic fibres allow them to stretch as they fill with air when breathing in and then recoil when breathing out.
What direction do gases move?
From an area of high pressure to an area of low pressure.
