13. Energy Flows and Dissipates Flashcards
What is ecosystem ecology?
ecosystem: biological community and its interactions with the abiotic world
energy flow and nutrient cycling
What is the second law of thermodynamics?
entropy (disorder) is always increasing
What are some implications of the second law of thermodynamics?
usable energy is always decreasing in every chemical reaction
nothing is 100% efficient, everything eventually loses energy
What is the ecological relevance of the second law of thermodynamics?
ecological interactions are essentially just chemical reactions, they also follow energy loss and gain
What is an EXAMPLE of the ecological relevance of the second law of thermodynamics?
humans are fuelled by food, but it flows through us through excrements
we’re made inefficient since if people are eating the right amount we ‘lose’ the energy (don’t gain weight, just maintain)
What are ecosystem dynamics?
energy flows and dissipates
flows from the sun to primary producers, then primary consumers (herbivores), then secondary consumers (carnivores) WHILE they are producing excrement and heat (these are the tropic levels??)
What is the fate of all energy?
it’s heat
where does the heat go? -> it dissipated on earth and gets re-radiated to space
Describe the pyramid of energy
there always has to be more energy in the primary consumers than the others (since they are the first to access the most energy dense food)
pyramid: law of physics
What is the 10% rule of thumb?
10% biomass/energy is passed up a trophic level, the other 90% of energy is lost as heat in the transfer
Which animal has the highest efficiency of transferring prey biomass into their biomass?
young animals have higher efficiencies than adult ones
What groups of animals have the most effective transfer efficiencies?
herbivores: 10% (ish)
ectothermic carnivores: 5-15%
(ex. crickets)
What groups of animals have the least effective transfer efficiencies?
humans: 0%
plants capturing light: 1-2%
endothermic carnivores: 1-5%
(ex. mammals)
How does the second law of thermodynamics apply to larger mammals?
larger mammals move better, but they need more energy
they have larger home ranges (reason for the increased moving)
How does the second law of thermodynamics apply to conservation biology?
larger animals (carnivores) need larger parks
thus are at a greater risk of extinction because parks are getting smaller and smaller
From an ecocentric point of view, what is the fundamental reason that we should eat less meat?
because we’d be eating from a lower tropic level where there is more food available
reduce you ecological footprint by eating lower on the food chain
this minimizes the losses to entropy
less space is required to produce your food → leaves more space for nature
