6.5: Limiting water loss Flashcards
The features that make a good gas exchange system are the same features that do what?
The features that make a good gas exchange system are the same features that increase water loss
The features that make a good gas exchange system are the same features that increase water loss.
In order to survive, what does terrestrial organisms do?
In order to survive, terrestrial organisms must limit their water loss without compromising the efficiency of their gas exchange systems
Examples of terrestrial organisms
Examples of terrestrial organisms are:
- Insects
- Plants
Most insects are terrestrial (do what)?
Most insects are terrestrial (live on land)
Most insects are terrestrial (live on land).
The problem for all terrestrial organisms is that water easily evaporates from the surface of their bodies and they can become dehydrated.
They have evolved adaptations to conserve water.
However, efficient gas exchange requires a thin, permeable surface with a large area.
What do these features conflict with?
These features conflict with the need to conserve water
Insects have evolved the following adaptations that reduce water loss, what?
Insects have evolved the following adaptations that reduce water loss:
- A small SA:V ratio
- Waterproof coverings over their body surfaces
- Spiracles
Insects have evolved the following adaptations that reduce water loss - A small SA:V ratio, waterproof coverings over the body surfaces and spiracles.
1. A small SA:V ratio to do what?
A small SA:V ratio to minimise the area over which water is lost
Insects have evolved the following adaptations that reduce water loss - A small SA:V ratio, waterproof coverings over the body surfaces and spiracles.
1. A small SA:V ratio to minimise the area over which water is lost.
2. Waterproof coverings over their body surfaces.
In the case of insects, what is this covering?
In the case of insects, this covering is a rigid outer skeleton of chitin
Insects have evolved the following adaptations that reduce water loss - A small SA:V ratio, waterproof coverings over the body surfaces and spiracles.
1. A small SA:V ratio to minimise the area over which water is lost.
2. Waterproof coverings over their body surfaces.
In the case of insects, this covering is a rigid outer skeleton of chitin that is covered with what?
In the case of insects, this covering is a rigid outer skeleton of chitin that is covered with a waterproof cuticle
Insects have evolved the following adaptations that reduce water loss - A small SA:V ratio, waterproof coverings over the body surfaces and spiracles.
1. A small SA:V ratio to minimise the area over which water is lost.
2. Waterproof coverings over their body surfaces.
In the case of insects, this covering is a rigid outer skeleton of chitin that is covered with a waterproof cuticle.
3. Spiracles are the openings of the tracheae at the body surface and these can be closed to reduce water loss.
What does this conflict with?
This conflicts with the need for oxygen
Insects have evolved the following adaptations that reduce water loss - A small SA:V ratio, waterproof coverings over the body surfaces and spiracles.
1. A small SA:V ratio to minimise the area over which water is lost.
2. Waterproof coverings over their body surfaces.
In the case of insects, this covering is a rigid outer skeleton of chitin that is covered with a waterproof cuticle.
3. Spiracles are the openings of the tracheae at the body surface and these can be closed to reduce water loss.
This conflicts with the need for oxygen and so largely occurs when?
This:
- Conflicts with the need for oxygen
- So largely occurs when the insect is at rest
Insects have evolved the following adaptations that reduce water loss - A small SA:V ratio, waterproof coverings over the body surfaces and spiracles.
1. A small SA:V ratio to minimise the area over which water is lost.
2. Waterproof coverings over their body surfaces.
In the case of insects, this covering is a rigid outer skeleton of chitin that is covered with a waterproof cuticle.
3. Spiracles are the openings of the tracheae at the body surface and these can be closed to reduce water loss.
This conflicts with the need for oxygen and so largely occurs when the insect is at rest.
These features mean that insects cannot use the body surface to diffuse respiratory gases in the way a single-celled organism does.
Instead, they have an internal network of tubes called tracheae that carry air containing oxygen directly to what?
Instead, they have an internal network of tubes called tracheae that carry air containing oxygen directly to the muscle tissues
While plants also have waterproof coverings, they cannot have a small SA:V ratio.
Why is this?
This is because:
- Plants photosynthesise
- Photosynthesis requires a large leaf surface area for the capture of light and for the exchange of gases
Xerophytes
Xerophytes are plants that are adapted to living in:
- Hot and dry environments
- Areas where water is in short supply
Xerophytes are plants that are adapted to living in hot and dry environments and in areas where water is in short supply.
Without these adaptations, what would happen to these plants?
Without these adaptations, these plants would:
- Become desiccated
- Die