Succession Flashcards
What is the word used to describe Ecosystems ?
Dynamic
What are Abiotic factors ?
The physical conditions of the environment e.g temperature
What are Biotic factors ?
Relating to the living part of the environment
Define Succession
The change in a community over time, either due to a change in abiotic factors, or due to the species present.
What is primary Succession ?
Primary succession is the process that occurs when newly formed or newly exposed land (with no species present) is gradually colonised (inhabited) by an increasing number of species
Describe primary succession in a series of stages.
Firstly, seeds and spores that are carried by the wind land on the exposed rock and begin to grow
These are the pioneer species.
As these pioneer species die and decompose, the dead organic matter (humus) forms a basic soil
Seeds of small plants and grasses, sometimes also carried in the wind or sometimes transported other ways (e.g bird faeces) land on this basic soil and begin to grow (these smaller plants are adapted to survive in shallow, relatively nutrient-poor soils)The roots of these small plants and shrubs also form a network that helps to hold the soil in place and prevent it from being washed away.
As these small plants and shrubs die and decompose, the new soil becomes deeper and more nutrient-rich
Larger plants and shrubs, as well as small trees, that require deeper, more nutrient-rich soil, can now begin to grow
As the soil deepens further and trees are able to grow, they may then out-compete certain shrubs and other smaller plant species, which may no longer be able to grow beneath the trees due to a lack of light
Finally, the soil is sufficiently deep, contains enough nutrients and can hold enough water to support the growth of large trees
These final species to colonise the new land become the dominant species of the now relatively complex ecosystem.
A climax community is formed.
What is a climax community ?
The final community formed, containing all the different plant and animal species that have now colonised the new land, is known as the climax community
What is a pioneer species ?
a species that can colonise bare rock or ground
What is often the pioneer species on bare rock ?
Lichen (an organism which consists of a fungus and an alga)
How can newly formed or newly uninhabited land be formed ?
The magma from erupting volcanoes cools and often leads to the formation of new rock surfaces or even new rocky islands in the sea
Another way new land can be exposed is by sea-level dropping or the drying up of a lake, leaving areas of bare rock
Changes in the enviroment occur at each stage in succession. Why does this happen?
At each stage in succession, there are certain species that gradually change the local environment so that it becomes less hostile and more suitable for the new species (with different adaptations)
These species are then better adapted and can outcompete the pioneer species
Often, these new colonising species then change the environment in such a way that it becomes less suitable for the previous species
What is humus ?
Humus is the dead organic matter formed when the pioneer organisms die and decompose.
Animal species will also change as succession progresses. Why is this ?
There are a greater variety of habitats
Greater variety of food
so a wider variety of available niches.
What is an example of Primary succession ?
Sand dune succession
Sand dunes in coastal areas (marram grasses are the pioneer species in these environments as they have deep roots to access water that other plants can’t reach and are able to tolerate the salty environment i.e. the high concentrations of sodium and calcium ions caused by sea spray)
What features would you expect in a climax community ?
same species present over a long time/ stable community over a long time
Abiotic factors are more or less CONSTANT
populations are stable
