19.6 Succession Flashcards
What is succession
Give some examples
Ecosystems are dynamic so change day to day as populations fluctuate, sometimes slowly and sometimes very rapidly
Succession describes these changes over time
For example
. Sand being piled onto dunes
. Volcanoes erupting and depositing lava
. Lakes or ponds created by land subsiding
How does succession change the biodiversity in an area
At each stage, a new species colonise the area, and these may change the environment
In a way that makes it:
. Less suitable for the existing species, so as a result the new species out-competes the existing one and so take over a given area
. More suitable for other species with different adaptations, so that species will be out competed by better adapted new ones
So these alterations can lead to a less hostile environment which make it easier for other species to survive in it
What is a pioneer species
What features do they have that suit them to colonisation
Give 6 features
. They make up the first stage of succession
- Asexual reproduction so a single organism can rapidly multiply to build up a population
- The production of vast quantities of wind dispersed seeds so they can easily reach isolated areas eg volcanic islands
- Rapid germination of seeds on arrival so they don’t require a period of dormancy
- The ability to photosynthesise, as light is normally available but other food is not
- The ability to fix nitrogen from the atmosphere as if there is soil, there will not be nutrients in it
. Tolerance to extreme conditions
Describe the 4 stages of succession
. Pioneer species colonise the area
. They change the environment by making soil/sand
. Environment becomes less hostile to new species
. Biodiversity increases
Describe the process of succession from an area of bare rock
. Lichens are one of the few organisms that can survive on bare rock
. Over time, they weather down the rock to produce sand or soil, although this itself can’t support other plants
. As lichens die, they decompose to release sufficient nutrients to support a community of small plants
. Then moss, then ferns
. With the constant erosion of rock, and the increasing amount of organic matter available from the death of these plants, a thicker layer of soil is built up
. The organic material holds water making it easier for other plants to grow , so these change the abiotic environment , making it less hostile, so more suitable for the organisms that follow eg flowers, shrubs and trees
. These species provide sources of food, so more food chains develop into food webs which will lead to more stable communities
What is the ultimate community in the UK
What is the name for a final community
Deciduous oak woodland
This state comprises a balanced equilibrium of species with few, if any, new species replacing those that have become established
This is called a climax community which will remain stable over long periods of time
How have animals undergone a similar series of successional changes
. These changes are determined by the plant types available for food and habitats
. Dead lichens provide food for animals eg mites
The growth of moss and grass provide food for insects, worms etc
These are then followed by secondary consumers eg centipedes which feed on these organisms
When trees and flowers grow, they support communities of reptiles, mammals and birds
What are 5 common features that always occur during succession
- The abiotic environment becomes less hostile:
Eg if soil forms which can retain water, there are more nutrients, so more plants
. This leads to: - More habitats and niches form
which in turn will produce - Increased biodiversity as different species occupy these habitats , and this is particularly evident in the early stages, reaching a peak in mid-succession, because it eventually decreases during the climax community as dominant species out compete pioneer and other species
- This leads to more complex food webs, leading to..
- Increased biomass
What determines the dominant species of a community
- Abiotic factors eg climate determine the dominant species
- In a climax community, they are in a stable equilibrium
In other climates in the world, the climax community is tundra, rain forest etc
What is secondary succession
When would it occur
- When land that has already sustained life is suddenly altered
Eg by clearing land for agriculture, or a fire burning down all the trees
. The ecosystem will return to almost its original, but occurs more rapidly than from scratch
. Because soil already exists with spores and seeds which may remain alive, and there are some animals entering by migration, and plants entering by seed dispersal from the surrounding area
. However some species in the climax community will be different
Two characteristics of a climax community
. Stable community over a long time
. Abiotic factors constant over time
. Population is stable around carrying capacity
