Unit 11 - Community & Ecosystem Ecology Flashcards
(58 cards)
Species Diversity
- diverse communities have increased productivity (biomass production)
- diverse communities are better able to withstand and recover from distiurbances
***it’s better to be a diverse community
Comparing Diverse vs. Non-diverse Habitats `
ex: the non-diverse (homogenous) community could only tolerate warm tempature conditions
- the other non-diverse community could only tolerate cold temps
- the diverse community could withstand both cold and warm temps (the differences in species can fill different ecological niches)
Biomass
biomass = the total mass of all organisms in a habitat
Trophic Level
organisms that share the same function in the same food chain
Food Webs
say food webs instead of food chains because it’s more complex than a food chain
- not all organisms fit into certain trophic levels (omnivores, detritivores, mixotrophy don’t fit into certain trophic levels)
Dominant Species
dominant species = the species in a community that is the most abundant or has the highest biomass
how a species becomes dominant:
- they’re most competitive in getting resources (they outcompete everyone else for resources)
- they’re best at avoiding disease or predation
Keystone Species
keystone species = species that have a big effect on the community or ecosystem (they are important and how the ecosystem together - without them the ecosystem would fall apart)
- the keystone species isn’t always abundant
- they have strong control on the community (bc they’re needed so the community doesn’t fall apart)
ex: The sea otter is the keystone species bc they eat the sea urchins who eat all of the kelp
- without the otters, the urchins would eat all of the kelp which would destroy the kelp and the other animals that need the kelp
Ecosystem Engineers
they influence the structure of the community by physically changing the environment
ex: Beavers
- they chomp down branches and build a dam which blocks water (physically changing the environment)
Community Structure
the ways that trophic levels affect each other is helpful to describe the community organization
- communities can either be bottom-up or top-down controlled
**all organisms have to consume energy to survive and grow
Bottom-Up Control
the food availability at lower trophic levels controls how many individuals (abundance) there are at each trophic levels above
- to get more biomass, you have to add resources to the bottom of the food chain so the upper levels get the resource (or become more abundant)
***community structure is driven by resource availability
Top-Down Control
the amount of consumers (abundance) at higher trophic levels controls the amount of individuals at each trophic level below it
ex: if you add more kelp to the bottom of the food chain, it won’t increase the amount of otters because the kelp doesn’t limit the number of otters do (since kelp is at the bottom) — instead, the orchas (at the top) limit the amount of organsisms at lower trophic levels
***community structure is driven by abundance of consumers
Examples of Top-Down Control
original:
- there’s a lot of fish so there’s few zooplankton (bc the fish are eating them) which means there’s a lot of kelp because there’s not enough zooplankton to eat all of the kelp
later: they removed a lot of the fish
- now there’s few fish which means there’s a lot of zooplankton (bc the fish aren’t eating them) so there’s not a lot of kelp bc there’s so many zooplankton eating them and not a lot of fish eating the zooplankton
- keystone species here = fish
Trophic Cascades
changes to the top trophic level cause changes in lower trophic levels
*can be the addition or removal of a top trophic level
ex: if you add a new trophic level to the top (something that eats fish) there will be less fish and more zooplankton (bc the top trophic level is now eating the fish) so there’s not a lot of kelp bc there’s more zooplankton available
- sometimes just the presence of the predator is enough to change it’s prey’s behavior (ex: sharks prey on turtles and the presence of the shark changes the turtle’s behavior so they won’t eat the kelp)
Heterotrophs
they have to ingest (consume) food to get energy (every consumer is a heterotroph other than primary producers)
Autotrophs
they have to make their own food thru photosynthesis (every autotroph is a primary producer)
- they create their own energy for biomass
- get energy from chemicals (light)
Conservation of Energy
energy is the common currency of all organisms
- energy is never created or destoryed (but it can change forms)
***energy is flowing in and out of systems
Energy Flow
Energy flows into the system as sunlight
- energy flows out of the system as heat
- the chemical energy (light from the sun) comes into the primary producer who uses the light to convert it and make chemical energy
- from here —- either the primary producer uses the chemical energy to grow OR it uses the energy for consumption (other trophic levels higher up eat the primary producer, and then the secondary producer eats the primary consumer etc…)
Primary Production
the production of biomass of chemical energy in organic compounds by living organisms
- primary producers are the autotrophs (plants, algae, microbes)
production (P) = rate of generation of new biomass
Limiting Production Factors - Abiotic
abiotic factors limit production
- sunlight (no sunlight limits growth of primary producers)
- nutrients
- water
**rate affects production
Limiting Biomass Factors - Biotic
biotic factors
- losses (mortality/consumption) and decomposition
**amount of mass of species within the food web effects biomass
Why We’re Interested in Biomass
we’re interested in biomass bc it’s easier to measure than production (the growth rate)
- we don’t know if biomass is high or low because of high or low production (we can’t determine biomass based on production)
Production doesn’t equal Biomass
production and biomass aren’t the same thing
biomass can be low and production can be high or biomass can be high and production can be low or any of the possibilities
***think of a bank account
- the money in the bank account = the biomass
- we don’t know how much someone spent or how much someone makes (production) based on the money in their bank account
Food Chain Length
food chain length is usually short is most ecosystems
- usually ecosystems have between 5-7 trophic levels
Autotrophs Undergo Photosynthesis
primary producers undergo photosynthesis because they have to use the light energy and convert it into chemical energy
primary production = the amount of light energy converted into chemical energy
- available for the plants to grow but also helps the primary consumers eat the primary producers
chemical energy is available for:
- plants to carry out their activities (50%)
- adds biomass to the plants
