Lecture 4 - Air, water and chemicals Flashcards
Give some examples of plants and animals which are very sensitive to moisture loss.
Examples:
- nematodes - mosses
- molluscs - earthworms
Give some examples of plants or animals which are very tolerant of moisture stress.
Examples:
- arthropods
- desert vertebrates
- cacti
Why is water important?
- Life originated in the sea
- Biochemical and physiological processes take place in solution within the cell
Give an example of an organism which is adapted to water loss.
Case study: Drosophila subobscura
- is active just after dawn and before dusk when temperature is at its lowest and relative humidity high in order to avoid water loss from the spiracles
Why do plants have stomata which are able to open and close?
Plants need to open their stomata in order to gain CO2 for the light-independent reaction however they cant have them open too long as they also lose water via their stomata so they need to close them to avoid drying out.
Why does the film of water in soil need to be thin?
The thin film allows oxygen to diffuse and if the film is too thick then anaerobic conditions are created.
Why do different plant species grow better in different soil types and give examples.
Different soils contain different proportions of minerals and different plant species require different proportions of minerals.
Case study 1: Oak trees prefer deep heavy fertile soil
Case study 2: Beech trees prefer lime-rich or fertile sandy soils.
Why is it advantageous for a plant to be adapted to a low nitrogen environment?
Nitrogen is an essential resource for plants however it is very limiting.
Case study: legumes are able to fix their own nitrogen due to their mutualistic relationship with nitrogen-fixing bacteria.
In which environments are the greatest stresses due to salinity?
Salt marshes and estuaries.
