LEC 20 Flashcards
Trophic interactions are feeding relationships that link organisms in an ecosystem based on _________________________
What they eat and what eats them
Each trophic level, or feeding category, is based on the number of steps by which it is separated from the _________ in the ecosystem
Autotrophs
The first (basal) trophic level consists of _____________
Autotrophs (primary producers)
The first trophic level generates __________ using sunlight (photosynthesis) or inorganic molecules (chemosynthesis)
Chemical energy (NPP)
All other trophic levels consists of
Heterotrophs (consumers)
The second trophic level includes _______ that feed on _______-
Herbivores, autotrophs
The third trophic level includes __________ that feed on ___________-
Carnivores, herbivores
The fourth (and higher) trophic levels include _________ that feed on _______________
Carnivores, other carnivores
There are ______________
Levels within levels
Some organisms do not fit conveniently into trophic levels
Omnivores feed at multiple levels:
Coyotes are examples of omnivores, consuming:
- Autotrophs (fruits, berries)
- Herbivores (Grasshoppers)
- Carnivores
- Old leather boots
All organisms in an ecosystem are either __________________ or ________________________
Consumed by other organisms, enter the pool of dead organic matter (detritus)
In any ecosystem, only a small portion of NPP is _________, while most ends up as ________-
Consumed, detritus
Dead plant, animal, and microbial matter (detritus), as well as wastes (feces), are consumed by ___________________ during the process of ____________
Decomposers (detritivores), decomposition
Detritus is considered part of the _______ trophic level, so ___________ are included with the ______ level
First, detritivores, second
Understand that detritus does NOT have any NPP, but still can be considered on the first trophic level
A ___________ is a graphical representation of __________________ with respect to trophic relationships
Trophic pyramids, energy or biomass
Because a proportion of the energy at each trophic level is _____ during transfer to the next trophic level, _____________ may never be ________-
Lost, energy pyramids, inverted
It is possible for ___________ to be _________ (more biomass at higher trophic levels)
Biomass pyramids, inverted
Examples are usually ______________
Aquatic (marine, specifically)
-Large baleen whales feeding on tiny phyto- or zooplankton with short lifespans and high turnover
Only ________ of energy from the first trophic level makes it to the next trophic level
~10%
Trophic efficiency is a measure of how much energy from one trophic level makes it to the next trophic level. Trophic efficiency consists of three components:
1) Consumption efficiency
2) Assimilation efficiency
3) Production efficiency
Consumption efficiency
Measures how much energy at one trophic level is consumed by the next trophic level
Ranges from ~5% to ~50% in different ecosystems
The rest of the energy is simply not eaten
All autotrophic energy may not be consumed by herbivores due to:
- The autotrohp’s chemical (screenplay compounds) and physical (spines and thorns) defenses
- Nutrient-poor components (wood) compared to nutrient-rich components (leaves)
Assimilation efficiency
Measures how much energy from one trophic level is incorporated into the next trophic level by digestion and used for maintenance and defense
Ranges from ~20% to ~80%
The energy that is not assimilated is lost as wastes (feces)
Assimilation efficiency is __________ in carnivores than herbivores because:
GREATER;
Plant matter contains much indigestible material, such as cellulose and lignin
Animals have similar carbon to nitrogen ratios as the carnivores consuming them, so they can more easily be assimilated
Production efficiency
Measures how much energy from one trophic level goes into the production of new biomass for the next trophic level (in the form of growth and reproduction)
Ranges from ~1% to ~50%
The rest of the energy is lost as heat during cellular respiration
Production efficiency is ___________ in ectotherms than in endotherms because endotherms ___________________ during metabolism
GREATER; produce much more heat
Ectotherms gain heat from surroundings, not food
Trophic efficiency =
Consumption efficiency x assimilation efficiency x production efficiency
Trophic efficiency ranges from ~1% to ~20%
Average trophic efficiency is 10%
There are usually no more than _______ trophic levels in any ecosystem
four or five
QWith ________- of the energy lost at each trophic level, there is not enough energy (NPP) remaining to support any additional levels
90%
Predation (as well as competition, mutualism, etc.) are _____________ between two species
direct interaction
Indirect interations occur when the relationship between two species is mediated by a ___________ species
Third (or more)
Trophic cascades are _________ involving multiple predator and prey species
Indirect interactions
In the simplest type of trophic cascade, predation by a carnivore (_____ trophic level) ______ the number of herbivores (____ trophic level), which in turn _______ the number of autotrophs (____ trophic level)
third, decreases, second, increases, first
A food web is a conceptual diagram of the ________ among organisms in an ecosystem
trophic interactions
A food web shows ________ how energy flows from one member of an ecosystem to another
Qualitatively
As _____ increases in food web diagrams, so does ___________
Realism, complexity
Considering ________________ together reveals keystone species and dominant species
Trophic pyramids, indirect effects, and food webs
Keystone species are those species that have a greater influence on energy flow and ecosystem composition than ______________________
their abundance or biomass might suggest
Tend to be HIGHER trophic level
____________ 1966 intertidal study was the first to introduce the concept of keystone species
Robert Paine’s
Keystone species tend to be _______________ (leading to the common term ________________)
Top carnivores; keystone predator
__________ were determined to be keystone species in the intertidal
Sea stars
Dominant species (AKA foundation species) are those species that have large effects on energy flow and ecosystem composition due to their _____________________
High abundance or biomass
Dominant species tend to be autotrophs
-Tend to be first trophic level
