Lecture 10: Trophy Flashcards
What are the three types of heterotroph?
Herbivores (plants), carnivores (animals), and detritivores (dead organic material)
What is the difference between autotrophs and heterotrophs?
Autotrophs get their carbon and energy from inorganic sources (photosynthesis, and chemosynthesis), and heterotrophs use organic sources of carbon and energy (things that are or were alive)
What is the main trade-off that has the be balanced by heterotrophs?
The ease of getting food and the quality of food
What is ecological stoichiometry? What are the 5 elements?
The balance of 5 elements in ecological interactions/systems
Carbon (structure)
Nitrogen (amino and nucleic acids)
Phosphorus (cellular processes, ATP)
Hydrogen (part of water)
Oxygen (part of water)
What is the main concern when it comes to food quality? How do plants and animal food sources differ in this aspect?
The main concern for food quality is the relative abundance of carbon and nitrogen or the C:N ratio of the food source.
Plants have a relatively high C:N ratio (lots of carbon as they need to grow tall and stiff, integral for structure)
Animals have a relatively low C:N ratio (their structural components are less carbon rich, and have more nitrogen)
The C:N ratio dictates what and how much of each food the heterotroph needs to eat
What is the trade-off that is present for herbivores? What are some adaptations to overcome this?
Food is very easy to get but the quality of the food is low, not enough nitrogen. Plants are also difficult to digest as they are extremely high in carbon therefore also high in cellulose.
Overcome via adaptations to the teeth and digestive system, such as mandibles/palps that allow for slicing and manipulation of plant material, continuously growing incisors, complex digestive systems and repeated chewing that allows for maximal nutrient advantage
What are some challenges to herbivory? How do herbivores overcome this?
Plants fight back with adaptations such as physical things (thorns, spines), and chemical (alkaloids, cyanide, tannins)
To overcome this, herbivores have become tolerant to some glycosides (via amino acid changes),or long necks/tongues to maneuver around thorns/spines, or attacking the plant in groups to overcome defences
How do herbivores compensate for their low nutritional quality?
They eat a lot (maybe sleep a lot too, because this is energetically expensive)
What is the trade-off that is present for carnivores?
Their ease of getting food is lower (handling times are increased), but the quality of the food is higher (more N).
There is very little variation in the C:N ratio across animal species, therefore carnivores can use multiple prey species and get the same nutrition, they need few digestive adaptations, they experience strong selection for traits that allow efficient capture and consumption of prey
What are some adaptations that enable carnivores to overcome their difficulty to catch food?
Sharp claws for grabbing prey, being extremely fast, teeth for tearing and efficiently consuming prey
What is the evolutionary trade off for detritivores?
It is easy to obtain food, however the quality of the food is highly variable
Is a detritivore a decomposer? Are they all decomposers?
A detritivore is one group that falls under the heading of decomposer, but not all decomposers are detritivores (many different groups of decomposers
What is the difference between decomposers and detritivores?
Detritivores must INGEST and DIGEST organic matter via internal processes
Decomposers do NOT INGEST but can directly absorb nutrients through chemical and biological processes
What is the main obstacle that detritivores face?
Dead plants are rich in carbon and energy but they are low in nitrogen, this is because living plants are also low in nitrogen and thus they have increased nitrogen use efficiency and the reabsorb nitrogen before dropping their leaves and because of this, dead plants are lower in N than living ones
What are limiting factors for detritivores?
Abiotic factors such as chemical composition of the detritus composition (nitrogen concentration mostly), as well as soil moisture (too wet they drown and too dry they dessicate)
