Energy And Food Webs Flashcards
What are the two laws of thermodynamics?
- Energy cannot be created or destroyed; it can change from one form to another.
- When energy is converted from one form to another, some of it is lost in the form of heat and the entropy increases.
Define ecosystem
Biological community Together with the abiotic environment in which it is set
Define standing crop
The bodies of living organisms within the unit area
Define biomass
Mass of organisms per unit area of ground (of water). Usually expressed as joules per metre squared or dry matter. Dead organisms are not regarded as biomass (dead organic matter)
What does entropy mean?
Thermal energy cannot be converted to mechanical energy as the degree of disorder increases
How does the flow of energy start?
The flow of energy starts by harnessing the Sun by autotroph’s which are mainly plants.
What are autotroph’s?
Organisms that produce their own food
What is the equation for photosynthesis?
6CO2 + 12H2O + radiant energy —> C6H12O6 + 6H2O + 6O2
What are lithotrophs?
Organisms that are use inorganic substrates as energy
What type of environments do lithotrophs like to live in?
Extreme areas as they’re extremophiles (e.g deep trenches)
Why are lithotrophs Important?
They are important in the formation of soil and in biogeochemical cycling
What two things can lithotrophs be?
Bacteria or archea
Define primary productivity
The rate at which light energy is converted by photosynthesis to biomass or area
What are the two types of productivity?
Gross primary productivity GPP
Net primary productivity NPP
Define gross primary productivity
The total amount of energy that plants capture and assimilate in a given period of time (total rate of photosynthesis)
Define net primary productivity
Plant growth per unit area per time. It represents the rate of production of new biomass
How do you find net primary productivity, give an equation
NPP=GPP - Cellular respiration (R)
What is cellular respiration?
Chemical energy captured in photosynthesis it’s released within cells of plants and animals.
What can be used to measure the net production?
Harvesting of carbohydrates from the plant
How can the carbon dioxide uptake be measured?
It can be measured by a decrease in carbon dioxide concentration in a close chamber or by the uptake of carbon-14 labelled CO2.
What three things influence primary productivity?
Water
Temperature
Nutrient availability
These are make up the climate around the plant
How does primary productivity vary among ecosystems?
There is a high net primary production in the equator and the coast but there is a low net primary productivity on the poles and the deserts, this is because there is no water in the desert so plants cannot grow and the temperature is too low in the poles.
How does net primary production vary amongst oceans?
Shallow coast means high productivity as there is a higher temperature and high in nutrients in shallow water. There is a greater transport of nutrients from the bottom sediments to the top waters which is aided by waves.
Inputs from nutrients are also from terrestrial ecosystems
How much carbon is made in terrestrial ecosystems?
56.4 pg of C12 per year
How much carbon is made in marine ecosystems?
48.3 pg of C12 per year
How much land-based net primary productivity do humans use?
32%
How much do humans make up of land based biomass?
0.5%
What happens as a result of this over use of land-based net primary production?
It causes extinction to occur and threatens planets availability to support everyone
Describe the energy flow from producers onwards
Produces
Primary consumers
Secondary consumers et cetera
Decomposes
Why are secondary composers usually carnivores?
As carnivores don’t eat each other as there is little energy to gain from this so they must eat primary consumers which eat plants
What is the link in a food chain called?
A trophic level
Define ecological efficiency
The percentage of energy transferred from one trophic level to another
Who created the universal model of energy flow through ecosystems?
E.P. Odum
Three reasons why there is less energy at the next trophic level
Respiration and excretion and heat loss
What are the three types of ecological pyramids?
Pyramid of energy
Pyramid of numbers
Pyramid of biomass
What important feature do all three types of ecological pyramid share?
They all have a loss of energy as heat
What does a pyramid of energy show?
How much energy is present at each level and how much is transferred onto the next trophic level
What does the pyramid of numbers show?
The number of organisms at each level. Usually there are more organisms at the bottom
What does the pyramid of biomass show?
Total biomass at each successive tropic level. Biomass indicates the amount of fixed energy at a given time
What do the links in food web show?
Feeding connections
What type of change can affect the diet available to a predator in a food chain?
Temporal or seasonal change
Give an example of an animal that’s diet changes with temporal change
Great tits
In winter eats beech seeds and moss capsules and in summer it eats animals and small organisms.
What type of change can affect a food chain the most?
If an apex predator is removed. This causes trophic cascades
How do you find the connectance of a food web?
Connectance = (Actual number of interspecific interactions) Divided by (Potential number of interspecific interactions)
What is the general trend for connectance?
As the number of species increases connectance decreases
Give an example of trophic cascades
Wolves in Yellowstone National Park
The Wolves used to eat the elk which is a herbivore it used to eat the aspen and willow trees in the park. When the wolves were removed the elks ate too many plants and ruined the ecosystem so wolves were reintroduced to hunt the elk.
