Topic 7: Succession Flashcards
Succession definition
The changes over time, in the species that occupy a particular area
Ecosystems
All of the interaction, biotic and abiotic factors in a specific area
Humus
Dead and decaying organic matter
It improves the water-holding capacity of the soil, soil depth and nutrients
Abiotic factors
Physical conditions of the environment
E.g. temperature,PH,rainfall and humidity
Biotic factors
The living parts of the environment
E.g. competition,food availability,predation
Community
The populations of different species living in the same habitat at a particular time, all part of a food web
Lichen
An organism that consists of a fungus and an algae
Annual
A plant that completes its lifecycle within a single growing season
Biennial
A plant that lives for/flowers every 2 years
Perennial
A plant that lives for more than 2 seasons
Herbaceous
A plant that is a perennial but has leaves that die back to the ground at the end of each season
Shrub
A woody plant that branches near ground level
tree
A woody plant with a single main stem-the trunk
Primary succession
The change in species composition over time in a habitat that has not previously been inhabited
Happens on newly formed/exposed land
There is no soil or organic matter to start
3 examples of primary succession
A glacier retreating and exposing rock
Sand being piled in dunes by wind and sea
Volcanoes erupting and depositing lava
First stage of primary succession
The colonisation of an inhospitable environment by organisms called pioneer species
What is the pioneer species in the colonisation of rock and why ?
Lichen, they can grow in these areas because they are adapted to cope with the harsh conditions
Role of lichen in the colonisation of bare rock
When they die, they decompose and release sufficient nutrients to support a community of small plants,
They change the abiotic environment by forming soil and nutrients
What happens after the role of lichen in the colonisation of bare rock?
Mosses are often in the next stage, followed by ferns. The plants decompose which adds more humus to the solution. This improves the water holding capacity of the soil.
Different species gradually replace these plants and increase soil nutrients, which allows tree seedlings to become established and grow
Trees will out-compete plants that aren’t shade tolerant
What features may pioneer species have
Produce large numbers of seeds
Rapid seed germination
Ability to photosynthesise
Ability to fix atmospheric nitrogen
Tolerant to extreme conditions
Why may pioneer species need to produce a large amount of wind dispersed seeds or spores
To reach isolated situation
Why do pioneer species have a rapid germination of seeds
They dont need a period of dormancy to germinate
Climax community
It is the final stage of succession
It is a stable state
It has a balanced equilibrium of many plant and animal species
E.g. generally deciduous oak woodland, Britain
Animals and succession
Animal species change as succession progresses because there is a greater variety of habitats and breeding sites, and food and niches
So biodiversity increases
Exam question, Describe and explain how succession occurs
- Colonisation by pioneer species
- Leads to a change in environment
- E.g. more humus
4.enables other species to colonise and survive
5.larger herbaceous plants can grow in deeper and more nutrient rich soil
6.this leads to an increse in biodiversity
7.stability increases, less hostile environment - A climax community is established
Severe abiotic factors
Harsher environment=fewer adapted species, so less survive and there is less species diversity
There is then a smaller number of food chains/more simple food webs
Lower stability, communities are more likely to fail
In this environment,generally the abiotic factors determine the species present
Humans can make them worse
Less harsh abiotic factors
The less harsh environment, the more species, the greater the species diversity
In this environment, it is the biotic factors e.g competition, that determine whether particular species survive
When does secondary succession occur ?
It occurs when land that already sustains life is suddenly altered,this could be due to land clearance for agriculture or a forest fire
Any natural disaster or human activity
Secondary succession
The stages to return to a climax community are the same bit,occur more quickly
There is soil and seeds & spores may already be present
Some of the species in the new climax community may be different because land has been altered
There are no pioneer species in secondary
Conservation
Is the management of earths natural resources so that the maximum use of them can be made in the future
Conservation of habitats frequently involves management of succession
Main reasons for conservation
Ethical
Economical
Cultural
Aesthetic
Ethical reasons for conservation
We share the planet and co-exist with other species
Economic reasons for conservation
We need to maintain ecosystems because there are a lot of substances we find useful from living organisms
cultural and aesthetic reasons for conservation
Habitats and organisms enrich our lives-variety=interest and creativity for humans
