Topic 6: Ecosystems Flashcards
What 2 types of judgements are required for solving environmental issues?
- Technical judgements.
- Value judgements.
What is Ecology?
The science used to understand the environment and how it works.
What is a species population?
A group of the same species that occurs in the same place at the same time.
What is a community?
A number of different species populations.
What is an ecosystem?
All the living organisms in a community as well as the abiotic factors they interact with.
What are the levels of organisation of species?
- Biosphere.
- Ecosystem.
- Community.
- Population.
- Organism.
What are the 5 types of ecology?
- Organismal ecology.
- Population ecology.
- Community ecology.
- Ecosystem ecology.
- Biosphere ecology.
What are living components of an ecosystem?
Biotic.
What are nonliving components of an ecosystem?
Abiotic.
What is the interaction between abiotic and biotic ecosystem components?
Abiotic components influence biotic components.
Biotic components influence abiotic components.
What is energy flow?
The way energy is passed through a system.
What does an ecological systems approach aim to understand?
Energy flow and the cycling of nutrients.
What is characteristic of energy flow?
Unidirectional. Does not cycle.
Requires continuous input of energy into an ecosystem.
What is the basic energy flow order?
Energy source -> autotrophs -> heterotrophs
What are autotrophs?
Organisms capable of synthesising all their required organic molecules from simple inorganic substances and an energy source.
What are heterotrophs?
Organisms that cannot synthesis complex organic molecules and must feed on organic material formed by other organisms to obtain energy and necessary molecular building blocks for metabolism and growth.
How does material cycle in basic terms?
Chemical materials are cycled from the abiotic environment, through living organisms, and back to the abiotic environment.
What is the ultimate energy source for the biosphere?
Sunlight.
What percentage of organic matter in the biosphere is autotrophic?
99%
What percentage of visibility light is converted to chemical energy?
1%
What are trophic levels?
The feeding levels in an ecosystem.
What are producers?
Organisms that convert solar energy to chemical energy via photosynthesis.
Mostly plants and phytoplankton
What do primary consumers feed on?
Producers.
Primary consumers are mostly herbivores
What do secondary consumers feed on?
Primary consumers.
What do tertiary consumers feed on?
Secondary consumers.
What are the 3 types of degraders?
- Scavengers.
- Detritivores.
- Decomposers.
What do scavengers eat?
Dead organisms.
What do detritivores eat?
Organic litter or detritus.
What are decomposers?
Fungi and bacteria that cause chemical decay of organic matter from all trophic levels.
What is metabolic energy lost as?
Heat.
How is energy obtained?
The breakdown of complex molecules, such as carbohydrates, releases chemical energy.
At each trophic level, energy is used for what 3 things?
- Growth.
- Reproduction.
- Metabolism.
What is primary productivity?
The rate at which solar radiation is converted into chemical energy.
What is the energy fixed in photosynthesis?
The Gross Primary Productivity (GPP)
What is the energy fixed in photo synthesis minus the energy used in respiration?
Net Primary Productivity (NPP)
On average, how much is the NPP of the GPP?
50%
NPP describes the what of biomass?
The rate of biomass production.
Not the total biomass of the system.
What is biomass?
The weight of living tissue per until area.
e.g. kg/ha
What are the 4 main factors that limit primary productivity?
- Light.
- Water.
- Temperature.
- Nutrients.
What are estuaries?
Partially enclosed coastal bodies of water where a freshwater river or stream meets the ocean.
What are the 3 types of ecological pyramids?
- Pyramids by numbers.
- Pyramids by biomass.
- Pyramids by energy.
How much energy is converted between levels into biomass?
Between 2% to 15%
What is the appropriate percentage loss of energy between trophic levels?
90%
What 2 reasons are there for the decrease in productivity between trophic levels?
- Organisms at one level do not consume all organic matter available at the lower level.
- Not all energy transferred is used for growth (increase in biomass).
Why are there so few large carnivores?
Loss of energy through the trophic levels limits number of tertiary consumers.
What are the 2 types of food chains?
- Grazing food chains. Directly dependent on green plants as primary food base.
- Detritus food chains. Primary food is detritus.
What is detritus?
Dead and decaying organic matter.
What is detritus?
Dead and decaying organic matter.
What are 3 characteristics of detritus food chains?
- Occur in all ecosystems, in parallel with grazing food chains.
- Much of the primary production (plant material) is not directly consumed but dies and enters the detritus pool.
- Contributes to the recycling of materials as well as to the flow of energy.
How long are typical food chains?
3 or 4 trophic levels for grazing pathways.
Rarely more than 5 levels.
Why are complete food chains/food webs more common?
- Several consumers usually feed on the same plant.
- Each consumer may eat many types of plants.
- Some consumers feed at different levels
- Omnivores eat producers as well as consumers.
