lecture 10 - how do organisms acquire energy? heterotrophs Flashcards
heterotrophy
use organic sources of carbon synthesized by others to derive energy (eat other organisms/organic material)
which organismal group can heterotrophy be found in
all organismal groups
herbivores
organisms that eat plants
carnivores
organisms that eat animals
detritivores
organisms that eat dead organic matter (it used to be alive but is no longer living)
food economics
heterotrophs need to balance ease of getting food and food quality
ecological stoichiometry
the balance of these five elements in ecological interations
what are the five elements for ecological stoichiometry
carbon, oxygen, hydrogen, nitrogen, phosphorous
carbon (food stoich)
provides structure to organisms
oxygen (food stoich)
part of water molecules (organisms mostly made of water)
hydrogen (food stoich)
other part of water molecules
nitrogen (food stoich)
part of amino and nucleic acids
phosphorous (food stoich)
essential for cellular processes such as ATP energy transfer
what is the C:N abundance in plants
high carbon and nitrogen ratio (lots of carbon to build up structure)
what is the C:N abundance in animals, fungi, and bacteria
low carbon and nitrogen ratio (structural components are less carbon rich)
what does the carbon and nitrogen ratio dictate
what and how much each type of heterotroph needs to eat
what is the ease balance of herbivory
getting food is easy but the quality of the food is low
nutritional chemistry
high C:N ratio means plants (particularly those high with lots of cellulose and lignin) are difficult to ingest and digest
there are adaptations to teeth and digestive systems though
plant defence
plants fight back with adaptations to deter herbivory
physical (thorns and spines) and/or chemical (alkaloids, cyanide, tannins)
how does herbivory compensate
compensates for low nutritional quality by eating A LOT
what is the ease balance for carnivory
ease of getting the food is low and the quality of the food is high
what are the pros to carnivory
a predator can use multiple prey species and get the same nutrition
strong selection to efficiently capture and consume prey (adaptations and natural selection)
what are the cons to carnivory
little variation in C:N ratio across animal species
eating animals is one of the easiest ways to meet nutritional needs as long as the animal can catch them
what is the ease balance for detritivores
ease of getting the food is plus or minus to the quality of the food
how do decomposers consume food
they do not ingest but can directly absorb nutrients through chemical and biological processes (not all of them ingest + digest food)
how do detritivores consume food
must ingest and digest dead organic matter via internal processes
what elements are dead plants rich in
rich in carbon and energy but low in nitrogen
what are detritivores limited by
abiotic factors and the chemical composition of the detritus
mixotrophy/omnivore
mixotrophs can gain energy from photosynthesis (inorganic) and from consuming organic matter. omnivores gain energy from both plant and animal matter
how to measure energy limits in plants
photosynthesis reaches a plateau above Isat (max ability to photosynthesize)
how to measure energy limits in animals
food intake saturates at a certain level of food density
what is the relationship between good density and feeding rate
functional response curves (i-iii)
