Adaptations to Abiotic Factors
Abiotic factors
- Abiotic factors are non-living factors that affect organisms within their habitat e.g.
- Light intensity and wavelength
- Temperature
- Turbidity, or cloudiness, of water
- Humidity
- Soil or water pH
- Soil or water salinity
- Soil composition
- Oxygen or carbon dioxide concentration
Adaptions to abiotic factors: sand dune grass species
- Marram grass is commonly found on sand dunes, a habitat where abiotic factors include:
- Low water availability
- High salinity
- Low nutrient levels
- Marram is an example of a xerophyte, a group of plants that are adapted to survive in dry conditions; xerophytes need to deal with the following challenges
- Dry air means that there is a steep concentration gradient between the inside of leaves and the surrounding air; this means that water evaporates quickly from the surface of cells in the leaf and is lost to the surrounding environment
- Soil water availability is low, meaning that any water lost by evaporation may not be easily replaced
- Some marram grass leaf adaptations raise the humidity of the air surrounding the leaf, reducing the steep concentration gradient and so reducing water loss by evaporation
- Leaves are rolled up to reduce the exposure of surfaces to the wind; this traps water vapour inside the rolled leaf
- The stomata are sunken in pits to trap water vapour
- The inner surface of the leaf is covered in tiny hairs which trap water vapour
- Marram grass leaves also have a thick waxy cuticle on their outer surface to reduce evaporation
Marram grass adaptation diagram
Marram grass is an example of a xerophyte, and has adaptations that reduce water loss by evaporation
Adaptions to abiotic factors: mangrove tree species
- Mangrove swamps are tropical, coastal habitats that are frequently submerged in sea water, so abiotic factors include:
- High salinity
- Low fresh water availability
- Low oxygen availability (due to being underwater)
- Mangrove trees grow with their roots submerged in sea water, so they face challenges such as:
- The cells of the roots that are underwater are unable to take in oxygen for respiration
- The surrounding salty water means that the availability of fresh water is low
- The surrounding sea water has a higher solute concentration than the contents of the mangrove root cells, so there is a risk of the mangrove roots losing water from its submerged roots by osmosis
- Mangroves are adapted to deal with low oxygen levels by having some form of aerial root system; the parts of the roots that are above the water take in oxygen for respiration
- Red mangroves have prop roots
- These roots also provide stability in unstable soil
- Prop roots are partially under the water, and these underwater networks of roots provide crucial shelter for marine animals
- Black mangroves have structures known as pneumatophores that grow vertically upwards out of the water-logged soil
- Red mangroves have prop roots
- Mangrove trees also have different methods of dealing with low fresh water and high salinity levels
- Red mangroves have cells that do not allow the entry of salt into their water-transport systems, allowing the trees to take up fresh water
- These cells also prevent the outward movement of water, so prevent water loss by osmosis
- Black mangroves take salt water into their cells and excrete excess salt through salt glands in their leaves
- Red mangroves have cells that do not allow the entry of salt into their water-transport systems, allowing the trees to take up fresh water
Mangrove adaptations diagram
Mangroves have adaptations that allow them to survive in environments with low oxygen levels and high salinity