Energy Flow Flashcards
What is the 1st law of thermodynamics?
energy can neither be created nor destroyed, only transformed.
What is the 2nd law of thermodynamics?
all systems in the universe tend to move towards a state of greater disorder (entropy). During energy conversions, some energy is always lost
What is a photoautotroph?
An organism that uses pigment to trap light energy and convert it to chemical energy (i.e: photosynthesis)
What does an autotroph do?
Produces its own food/ energy from inorganic substances
What is the name for an organism that consumes other organisms for energy?
Heterotrophs
What does a heterotroph do?
Consumes other organisms to obtain organic molecules for energy
What is the Euglena genus an example of?
a mixotroph
What are the 4 main types of heterotroph?
Carnivores
Omnivores
Herbivores
Scavengers
What is the difference between carnivores and scavengers?
Scavengers are a specialised type of carnivore that mostly feeds on dead and decaying animal matter rather than killing and eating it fresh
What are the 2 main types of decomposers and what do they do?
Detritivores - obtain nutrients by consuming non-living organic sources (like detritus and humus)
Saprotrophs - live in/ on non-living organic matter, secrete digestive enzymes and absorb the products of digestion externally
Give an example of a detritivore and a saprotroph
Detritivore - earthworm, dung beetle
Saprotroph -bacteria, fungi
Are saprotrophs consumers?
No - because they don’t ingest food, they ingest the products of external digestion
What does a consumer do?
Ingests organic matter which is living or recently killed
What are 2 issues with trophic level models?
Simplistic - some omnivores are opportunistic and will feed and multiple trophic levels
Mixotrophs - fit into both producer and primary consumer levels
What is the primary production?
the amount of energy converted by autotrophs to organic molecules over a time period - it represents the starting point of energy flow in an ecosystem
what is secondary production?
amount of chemical energy converted into new biomass (growth and reproduction) by consumers
What are 3 reasons energy transfer is inefficient?
Toxic waste is excreted
Some ingested material is not absorbed
Some organic material remains uneaten (i.e: bones, fur)
Most energy is lost as heat/ thermal energy
How do you calculate production efficiency?
(Net secondary production X 100) / absorption of primary production
What % of energy is transferred to each trophic level?
10%
Why is there often only 4 trophic levels?
Because the rule of tenths means only 10% of energy is transferred from each trophic level to the next - there wouldn’t be enough food for the 5th trophic level to consume to sustain life
Where is the other 90% of energy lost to per trophic level?
- not eaten
- not digested
- excreted
- lost as heat
What unit are pyramids of energy measured in?
KJ m-2 y-1
energy KJ per area per time
In a pyramid of energy, which level is the biggest?
The bottom (producers)
Why are food webs better models than pyramids of biomass
Pyramids only show a simplified food chain, whereas food webs show more complex ecological interactions between multiple food chains
Name 3 limitations of food web models?
Still too simplistic
Trophic interactions can change over time
Doesn’t account for migratory animals
Micro-organisms are not accounted for
The strength of relationships cannot be measured
Doesn’t recognise mutualistic relationships
Often difficult to interpret
