T10.3 - Changes In Ecosystems Flashcards
State what is meant by the term colonisation
The process in which a species spreads to new areas.
State what is meant by the term succession
The process by which the communities of organisms colonizing an area change over time.
State what is meant by primary succession
The establishment and development of an ecosystem in an area that was previously uninhabited.
What are pioneer species?
The first species to colonise an area
What is a climax community?
A self-sustaining, stable community with constant biodiversity and species range
Give examples of pioneer species
Mosses, lichens, algae, small annual plants; grasses, herbs
Describe the process of primary succession
● Bare rock is colonised by pioneer species, which break up the rock
● When they die they add humus/organic matter to the ground as they decompose; this provides mineral ions, water and anchorage for higher plant species.
● When these plants die they add more humus so soil becomes deeper
● this holds onto more water and minerals which can support herbaceous plants/ shrubs / trees.
● until eventually a climax community is established.
State what is meant by secondary succession
The recovery of a damaged ecosystem (flood, fire, human activity) in an area where the soil was left intact
Describe the process of secondary succession
● As soil is more developed more complex pioneer plant species colonise.
● When these plants die they add more humus so soil becomes deeper;
● this holds onto more water and minerals which can support shrubs / trees,
● until eventually the climax community is restored
What are the differences between primary and secondary succession?
● Primary succession starts on bare ground / rock, whereas secondary succession starts on disturbed ground / soil which was previously colonised.
● In primary succession pioneer species are simple species like algae / moss / lichen which get succeeded, whereas in secondary succession pioneer species are more complex species like fast growing grasses / small shrubs.
● In primary succession a climax community is established for the first time, whereas in secondary the climax community is restored;
● Primary succession takes hundreds of years, whereas secondary succession takes approx 50-150 years.
What are biotic factors?
Living factors that affect an ecosystem
Give examples of biotic factors
Predation, competition, herbivory, parastism, disease, food supply, availability of mates, pollination
How does predation affect population sizes?
Predator numbers always less than prey.
Predator numbers track peaks and troughs of prey numbers later in time.
What is intraspecific competition?
Competition between individuals of the same species
How does intraspecific competition affect population sizes?
Stabilises population size as numbers limited by availability of resources
What is interspecific competition?
Competition between individuals of different species.
How does interspecific competition affect population sizes?
Competitive exclusion - one species can out compete others and exclude from habitat.
Resource partitioning / niche differentiation- competition can affect distribution, with species found in different areas to avoid competition.
How does availability of mates affect population size?
Inability to find mate reduces abundance as no reproduction.
If lots of mates available then abundance increases as more reproduction.
How does disease / parasitism affect population size?
Disease reduces abundance but populations recover.
Parasites usually tolerated at specific levels.
How does food supply affect population size?
Food shortage reduces abundance.
Good food availability increases abundance.
How does pollination affect population size?
Higher number of pollinators will increases abundance.
Reduction in pollinators will reduce plant species abundance as not able to reproduce.
What are abiotic factors?
Non-living factors in an ecosystem
Give examples of abiotic factors
Light intensity/wavelength, temperature, wind speed, pH, salinity, edaphic factors, water availability
What are soil edaphic factors?
Soil structure and mineral content
Explain how light intensity affects population size and distribution of plant species
Plant growth increases in higher light areas;
light is required for LDRs of photosynthesis;
photons excite electrons from chlorophyll during photoactivation,
which leads to production of NADPH and ATP via
Chemiosomosis;
low light reduces production of NADPH and ATP for LIRs.
Explain how high temperatures affects population size in plants
Reduces population due to;
denaturing enzymes such as RUBISCO,
which reduces rate of LIRs e.g. reduces carbon fixation, reducing photosynthesis and therefore plant growth.
Increases rate of transpiration which may cause plasmolysis of plant cells
Explain how low temperatures affects population size in plants
Reduces poulation size due to:
slow plant growth;
as slow rate of enzyme-controlled reactions
e.g. carbon fixation slow;
so slow rate of photosynthesis
Explain how wind speed affects population size
High wind speed reduces population size due to;
increased evaporation,
cooling effect so organisms live where wind speed is low.
Increases transpiration
Explain how water availability affects population size
Chemical reactions happen in solution - so organisms found where water is available unless specially adapted.
Explain how oxygen availability affects population size
Oxygen required for aerobic respiration - terminal electron acceptor during oxidative phosphorylation- organisms found where O2 levels are high
