C.2 Communities and Ecosystems Flashcards
What is a trophic level?
The position an organism occupies within a feeding sequence
What always occupies the first trophic level in a feeding sequence?
Producers
Why do primary consumers occupy the second trophic level?
Because they feed on producers
What may occupy subsequent trophic levels?
Further consumers
What does a food chain show?
The linear feeding relationships between species in a community?
What do arrows represent in a food chain?
The transfer of energy and matter as one organism is eaten by another
In food chain, what direction does the arrow point in?
The direction of energy flow
What is the first organism in a food chain?
A producer
What follows producers in a food chain?
Consumers
What will most species feeding requirements consist of?
Multiple food chains
In most species feeding requirements what will organisms occupy?
Different trophic levels
What is a food web?
A diagram that shows how food chains are linked together into more complex interrelated feeding relationships
Why is a food web more representative of actual feeding pathways within an ecosystem? (2)
- organisms can have more than one food source
- organisms can have more than one predator
What can organisms do in a food web but not in a food chain?
Occupy more than one trophic level
What does ecological production refer to?
The rate of generation of biomass in an ecosystem
How is ecological production usually expressed?
In units of mass per area per time
What is biomass?
The total dry weight of organic matter in organisms or ecosystems
What is essentially the entirety of all biologically produced organic matter?
Biomass
What is the percentage of energy that is converted into biomass dependent on?
- energy lost as inedible materials
- energy lost via excretion of undigested and unabsorbed materials
- energy is lost as heat from cellular respiration
What is primary production?
The production of chemical energy in organic compounds by producers
What is the main source of energy for primary production?
Sunlight
What is a second source of energy for primary production?
Chemosynthesis
What are the two categories of primary production?
Gross primary production
Net primary production
What is gross primary production?
The amount of chemical energy as biomass that a producer creates in a given length of time
What is net primary production?
The amount of chemical energy that is not consumed by respiration
What is secondary production?
The generation of biomass by consumers
What is the biomass generation in secondary production driven by?
The transfer of organic compounds between trophic levels via feeding
How may secondary production be categorised as?
Gross and net amounts of biomass
What is gross?
Total
What is net?
Usable
What does the feed conversion ratios measure?
The efficiency of an animal in converting the food provided into a desired output
What is the equation for FCR?
mass of feed/ mass of desired output
What does the lower the feed conversion ratio mean?
The more efficient the method of food production
How is a low feed conversion ratio obtained?
By minimising the potential losses of energy for the animal stock
What are three ways to obtain a low feed conversion ratio?
- restricting animal movement
- optimising feeding practices
- slaughtering animals at a young age
What is the problem with efficient food production practices?
There are ethical issues involved
Why will restricting animal movement lower FCR?
It reduces energy lost to cell respiration
Why would you optimise feeding practices?
So that food is ingested and digested more effectively
Why would you slaughter animals at a young age?
Older animals tend to grow more slowly and have a higher FCR
What are the two ways to describe an ecosystem?
Open or closed
What does a closed ecosystem exchange with its surroundings?
Energy but not matter
Is an open or closed ecosystem self-contained?
A closed ecosystem
What does an open ecosystem exchange with surrounding environments?
Both energy and matter
What is an ecosystem?
The interaction of living and non-living things within an area
What will emerge in a given geographical area according to climate conditions?
Particular types of stable ecosystems
What is a biome?
A geographical area that has a particular climate and sustains a specific community of plants and animals
What are the two main factors that affect the distribution of biomes?
Temperature and rainfall
What will temperature and rainfall vary in accordance to?
Latitude and longitude
Altitude
Proximity to the ocean
What is a tropical rainforest?
Hot and humid environments near the equator with dense vegetation and high biodiversity
What is taiga?
Coniferous forests near the poles that have cold temperatures and little precipitation
What are deserts?
Dry and arid environments that display extreme temperature conditions
What is a climograph?
A graphical representation of basic climatic parameters at a given geographical location
What do climographs combine?
Temperature and precipitation
What can climographs be used to identify?
Seasonal patterns and changes
What did Robert whittaker do?
Developed a holistic climograph that allowed for the classifying of nine biomes
What do deserts typically have?
High temperatures and low precipitation
What do rainforests typically have?
High temperature and high precipitation
What do taigas typically have?
Low temperatures and low precipitation
What do pyramids of energy show?
The flow of energy between trophic levels
How are pyramids of energy measured?
In units of energy per area per time
What shape are pyramids of energy?
Triangular
Why are pyramids of energy never inverted?
90% of energy is lost between trophic levels
Why will pyramids of energy differ between ecosystems?
Due to the effect of climate on primary productivity
What will warmer temperatures speed up?
Enzyme reactions needed for photosynthesis
Why will high precipitation increase photosynthesis?
The photolysis of water is essential for non-cyclic photophosphorylation
Describe tropical rainforests level of net primary productivity?
High
Describe deserts level of net primary production?
Low
Why can ecosystems with high productivity be able to support more trophic levels?
As they will be able to supply more energy to consumers
What will affect how efficiently energy is transferred between trophic levels?
The types of species within a particular biome
What do gersmehl diagrams show?
The differences in nutrient flow and storage between different types of ecosystems
What are the three ways nutrients are stored in nutrient sinks?
Biomass
Litter
Soil
What is litter?
Any organic matter in and on the soil
What is soil?
The top layer of earth that is composed of disintegrated rock particles
What can nutrients be transferred between?
Nutrient sinks
How are nutrients cycled?
Via environmental inputs and outputs
What is fallout?
Nutrients being transferred from biomass to litter
What is decay?
Litter to soil
What is uptake?
Soil to biomass
How can litter additionally gain nutrients?
Via precipitation
How can litter also lose nutrients?
Surface runoff
How can soil gain nutrients from the erosion of rocks?
Via weathering
How can soil also lose nutrients?
Via leaching
What will climatic factors affect the interrelationships between?
Nutrient stores and flows
How are most nutrients stored as in tropical rainforests?
Biomass
Describe the rate of transfer of nutrients between stores in tropical rainforests?
Fast
Why is biomass where most nutrients are stored in tropical rainforest?
Litter is rapidly decomposed and vast roots quickly draw nutrients from soil
How are most nutrients stored in taiga?
As litter
Why is litter the most common place for nutrients to be stored in taiga?
Low temperatures slow decomposition which delays nutrient transfer to soil and biomass
Why is there little nutrient gain from precipitation or weathering in the taiga?
Due to low levels of rainfall
What may be high if the snow melts?
Surface runoff
How are most nutrients stored in desert?
In soil
Why is soil the most common storage for desert?
Few plants exist to store nutrients as biomass or produce litter
Why is there little nutrient gain from precipitation and little nutrient loss via runoff?
Due to very low levels of rainfall
What is negligible in the desert?
The amount of weathering and leaching
What does ecological succession describe?
The process of how a sequence of increasingly complex communities develop over time
When has the climax community been reached?
When succession has ended and the community has all of its characteristics
When does primary succession occue?
When communities develop on entirely new land without any established soil
What are examples of where primary succession might happen? (4)
River deltas
Glaciers
Sand dunes
Exposed rock
What are pioneer species?
The organisms which first colonise the region
What are pioneer species typically?
Lichen or moss
What happens when the lichen and moss die?
They decompose which creates the first organic soil capable of sustaining plant growth
What happens as plant species colonise the area?
The litter produced by their growth and their decomposing remains will cause changes
What are the five changes to soil and rock when plant species colonise the area?
Soil depth will increase
soil pH will become altered
Soil mineral content will increase
Soil will became aerated and water retention is increased
Rocks will be broken down by the roots
What will the changes in soil allow for?
The growth of larger plants
What does the growth of larger plants help reduce?
Erosion through the binding action of their roots
What will happen between larger and smaller plants?
Larger plants will outcompete smaller shade intolerant plants
How can a primary succession be identified?
According to the distribution of plants at a site of ecological nascency
What is a site of ecological nasency?
Any location where a new community may emerge from uninhabitable land
Why do regions further from the glacier have more time to develop life?
As glacial retreat exposes bare rock for colonisation
What can environmental disturbances cause?
Fluctuations to the structure and rate of change within ecosystems
What may a natural environmental disturbance give rise to?
Secondary succession
What is secondary successs?
Where one ecosystem is replaced by another
When does secondary succession occur?
When succession starts on existing soil following the upheaval of a pre-existing ecosystem
What is removed so a new ecosystem can develop on the site of the old?
Biota
Why is dominance usually achieved by the fastest growing plants in secondary succession?
Because soil is already developed
What triggers a secondary succession?
An environmental disturbance destroys the pre-existing climax community
What is first to grow back in secondary succession?
Grasses and herbaceous plants
What is not required in secondary succession?
Pioneer species
In secondary succession, what will develop to their fullest?
Fast growing trees
In secondary succession, what will develop in the understory?
Shade tolerant trees
in secondary succession what may happen as the ecosystem reverts to its prior state?
The fast growing trees may be overtaken by larger, slower growing trees as the ecosystem reverts to its prior state
What is deforestation?
The permanent destruction of a forest via the removal or clearance of trees
How does deforestation disturb the normal nutrient cycle?
- less evapotranspiration = less rainfall
- less litter = reduced humus
- loss of nutrients from leaching
- soil becomes acidic and thin
- infertile soil reducing biodiversity
- alters distribution of plant species
What causes environmental distrubances?
Natural or artificial disruptions to a normal ecosystem
What are six ways the effect of an environmental disturbance on an ecosystem can be measured?
- population density
- species diversity and richness
- presence of indicator species
- canopy coverage/light intensity
- biomass
- edaphic factors
Why must measurements taken from a disturbed area need to be compared against measurements taken from an undisturbed control?
To statistically calculate both the effect and magnitude of the environmental disturbance
