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Abiotic
and
Biotic
Factors
What are Abiotic and Biotic factors?
Abiotic factors are non-living factors (environmental) which
affect the survival of living organisms.
Biotic factors relate to other living organisms in the environment
which can affect the survival of other organisms.
Abiotic Factors
Biotic Factors
Habitat
Parasites
Temperature
Predators
Rainfall
Competition
Snow
Finding a mate
Hurricanes
Disease causing agents
Cyclones
Shelter
Oxygen Levels
Carbon dioxide levels
Water Availability
Salinity
Nest Sites
Soil
Abiotic Factors:
Water
Salinity
pH
Temperature
Surviving Extreme Conditions:
One extreme condition faced by many plants in Australia is fire.
Trees like Eucalypts have adaptations which help them to survive
and regenerate after fire. These include:
- Having thick bark which protects the inner cambium layer
which is the tissue which produces new growth of bark and
stem tissue needed for survival
- Thick bark also protects the epicormic buds which lie under the
bark and is responsible for sprouting and regrowth.
Epicormic buds are kept dormant by apical dominance and it is
only during fire when the apical dominance is removed by the loss
of the top of the tree in fire.
Another survival mechanism for plants is having lignotubers. A
lignotuber is a swelling at the base of a plant which holds dormant
buds. These are usually found under the ground and are only
activated when fire destroys the aerial portion of the plant.
Plant Adaptations to Arid Conditions:
Xerophytes are lovers of dryness.
To increase water uptake these plants increase their root length
to find water. They either:
- extend out and around or
- Extend out and down
To reduce water loss these plants:
- Have a thick cuticle which is waxy and impenetrable to water
which help to minimise water loss to the environment.
- They reduce the size and number of stomata to reduce
transpiration rates and restrict opening times for water loss.
- They also have the stomata not on the surface of the leaf but
on in sunken pits which also aids in reducing the amount of
water loss.
- They have small leaves reducing the surface area for water
loss.
- Produce drought resistant seeds which remain dormant until
heavy rain arrives.
Plant Adaptations to Aquatic Environments:
Abiotic Factors which affect aquatic environments:
Marine
Freshwater
Salinity
Rate of current flow
Temperature
pH of water
Dissolved oxygen levels
Temperature
Dissolved carbon dioxide
levels
Dissolved oxygen levels
Dissolved nutrients
Dissolved carbon dioxide
levels
Tidal movements
Dissolved nutrients
Wave action
Frequency of flooding
Clarity of water
Input of waste water
How does temperature, pH and light affect plant survival?
Temperature:
Water absorbs and releases large amounts heat with very little temperature
change.
Water tends to have a layered effect with hot water closer to the top whilst
the coldest water is on the bottom. This layered effect creates multiple
different environments for organisms to occupy.
pH:
pH is determined largely by the amount od dissolved carbon dioxide which
forms carbonic acid in water.
An increase in carbon dioxide will increase photosynthesis but as a result of
the increase in pH many other organisms will die (such as fish)
Light:
Transparent water permits light to reach photosynthetic organisms
Cloudy water prevents light reaching these organisms and could result in
the death of the plants which in turn will affect the food supply for many
other organisms in the food chain.
Hydrophytes:
A hydrophyte (water lover) is a plant that grows in or on water.
The adaptation these plants have include:
- Air filled spaces in their tissue through which air can move from
aerial parts of the plant to submerged parts
- Stomata are located on the upper surface of leaves that float
on top of the water as the underside is only exposed to water.
In plants that are entirely submerged :
- Diffusion occurs across the leaf surface which has a large
surface area with very few stomata.
- Spongy in the leaves and stems store oxygen produce by
photosynthesis and this oxygen can then be used for cellular
respiration.
Plant Adaptation to Salty Conditions:
Halophytes are lovers of salt.
Plants survive salinity by regulating the concentration of salt in
the shoots. Plants do this by:
- Having a higher osmotic pressure in their cytoplasm than
other species
- Control salt levels by:
- excluding salt form the leaves
- return salt to the roots
- diluting incoming salt by increased growth of
shoot
- shedding salt-laden leaves
- excreting salt through salt glands
Glossary Terms
Abiotic Factors
Biotic Factors
Limiting Factors
Tolerance range
Distribution
Adaptation
Adapt to
Hydrophyte
Pneumatophores
Hibernation
Torpor
Xerophytes
Halophytes
Lignotuber
Epicormic buds
Complete the following:
Key Questions:
7,10,11,12,13
Chapter Review Questions:
1,2,3,4,5,8,10