Ecosystems Flashcards
Ecosystem
A community of interacting organisms and the environment they live in and interact with.
Community + abiotic factors = ecosystem
Population
Organisms of the same species who live in a particular area
Community
Populations of different species who live in a particular area
A feature of a community
Organisms in a community are interdependent
Niche
The role an organism plays in the ecosystem
* involves both physical and environmental conditions it needs
Factors that can affect a community
Abiotic
&
Biotic
Abiotic Factors
- Moisture levels
- temp
- 02 levels
- light intensity
- Soil pH & mineral content
- wind intensity & direction
Biotic factors
- New pathogens
- New predators
- Decomposers
- Availability of food
Cyclic changes
Changes that repeat themselves
* e.g. predator and prey cycles
Dynamic ecosystems
A feature of ecosystems
* they are constantly changing and balancing
Directional Changes
Changes that go in one direction
* e.g. erosion of coastlines
Unpredictable/erractic changes
No pattern of direction of change
* e.g. natural disasters/hurricanes
Biomass
The biomass of an organism (or of a sample of tissue) is:
* The mass of living material
* The chemical energy that is stored within the organism or tissue
Trophic level
The level at which an organism feeds in a food chain
Only a small amount of energy is passed
How is energy lost through trophic levels?
As heat
How is materials lost through trophic levels?
- CO2
- H2O
- Indigestible material
- Unconsumed waste
Pyramid of numbers
shows the no. of organisms
Pyramid of biomass
shows the dry weight of th organisms
Gross primary productivity
The rate plants convert light energy ointo chemical energy
How can you maximise productivity?
GPP
Using:
* light banks
* greenhouses
* pesticides/fungicides
Net primary productivity
GPP(Gross primary productivity) - Respiration
How is energy (from the sun) lost?
- only 40%of light enters the light-dependent stage
- 2/3 of glucose used for growth of plant
- respiration
- 1-8% of energy from the sun enters the food chain
Secondary productivity
Transfer of biomass between trophic levels
How can you maximise productivity?
SECONDARY
BY:
* Harvesting animals before adulthood
* selective breeding for rapid production
* antibiotics to reduce loss of energy to pathogens
* minimising time to find food
What are Sapotrophs?
Organisms that get their nourishment from dead materials. They also release materials back into the atmosphere.
How do Sapotrophs absorb their food?
They secrete digestive enzymes on to the dead enzymes then take it in.
Examples of sapotrophs
Decomposers: bacteria & fungi
What is Nitrogen fixation?
When nitrogen gas in the atmosphere is converted to ammonia.
Can be caused by lightning
Nitrogen fixation- BACTERIA
Mutualistic bacteria- Rhizobium :
Lives root nodules of leguminous plants
Free-living bacteria- Azobacter:
Found in the soil
Ammonification
The process where nitrogen compounds from dead organisms (or waste) are turned into ammonia by decomposers/sapotrophs.
Nitrification
The process where ammonium ions are converted to nitrogen compounds by nitrifying bacteria.
Denitrification
What is succession?
The change in an ecological community over time.
What is a seral stage?
Stage that is noticeably different from before.
What is a climax community?
The final stable community that is not subject to further succession.
