ECOLOGY & ECOSYSTEMS PT.2 Flashcards
what’s a trophic level
Number of feeding levels away from original source
of energy
First trophic level characteristics
- Primary producers - Make their own organic matter from an energy source and inorganic compounds
– Use energy from the sun and co2 from the air to photosynthesize
– Green plants, algae and certain bacterial
– Called autotrophs
Second trophic level characteristics
- Primary consumers
– Herbivores
– Organisms that feed on autotrophs
– Heterotrophs
– Cannot make their own organic compounds and must feed on other living things
third trophic level characteristics
– Feed directly on herbivores
– Carnivores (“meat-eaters”)
– Secondary consumers
fourth trophic level characteristics
– Feed on third-level carnivores
– Tertiary consumers
what are decomposers
- Feed on waste and dead organisms of all trophic levels
– Trophic level may vary based on the structure of the ecosystem
– Includes scavengers, fungi, microorganisms, termites, etc
what are food chains
– Linkage of who feeds on whom
– Energy, chemicals and some compounds are transferred from creature to creature along food
chains
- oversimplified - reality = food webs
whats a trophic cascade
occur when predators in a food web suppress the abundance or alter the behavior of their prey, thereby releasing the next lower trophic level from predation (or herbivory if the intermediate trophic level is a herbivore)
2 types of trophic cascades
- Top Down Cascade: food chain or food web is disrupted by the removal of a top predator
- Bottom up cascade: when a primary producer,
or primary consumer is removed
whats biomass
organic matter derived from living or recently
living organisms
– the energy in living organisms
how is energy and biomass transferred through an ecosystem
- Organisms at each trophic level transform a
fraction of what they eat into biomass
– This biomass is then available to higher trophic
levels
– The percentage of energy that a trophic level
consumes that is converted to biomass (and made
available to higher trophic levels) is known as its gross growth efficiency / trophic level efficiency - Typically each trophic level contains about 10% of the trophic level below
whats the Second law of thermodynamics
– No use of energy is ever 100% efficient
– Energy is lost as heat
whats Gross Production
Increase in stored energy before any is used
- respiration + heat losses + net production
whats net production
Change in biomass over a given time
Three measures used for biological production
Biomass, Energy stored, Carbon stored
whats Biological production
amount and rate of organic matter production which
occur in a given ecosystem
- can be expressed in 2 ways:
- dry matter produced per area per time (net production)
- energy produced per area per time (gross production = respiration + heat losses + net production)
whats an ecosystem
biological community of interacting organisms and their physical and non living environment
whats a keystone predator/species
plays a unique and crucial role in the way an ecosystem functions e.g. removing sea otters will increase the number of urchins and decrease the amount of kelp
2 ways communities can respond to disturbance
– Resistance – a community that resists changes
– Resilience – community changes in response to
disturbance , but later returns to its original state
*A community may be modified by disturbance
and never return to its original state
what is succession and its 2 types
When a disturbance is severe enough to
eliminate all or most of the species, the affected
site may undergo a series of changes
- primary succession = communities are built from
scratch
- secondary succession = Reestablishment of an ecosystem following disturbance - occurs after disturbance where not all life has been destroyed e.g. hurricane
what general patterns do dunes successions follow
– Sand dunes are continually formed along sandy
shores
* Breached and destroyed by storms
– After dune forms
* Grasses established
* Grass runners stabilize dunes
* Other species seeds may germinate and become
established
– Early succession plant characteristics
* Small size
* Grow well in bright light
* Withstand harshness of environment
– Over time larger plants can become established
* Eastern red cedar, eastern white pine
* Beech and maple
what general patterns do Abandoned farm fields successions follow
– Land cleared for farming in the 18th and 19th
centuries
* Now allowed to return to forest
– Succession
* Small plants adapted to harsh and variable conditions
* Larger trees grow (sugar maple, beech, yellow birch,
etc.)
General patterns of succession
– An initial kind of autotroph specially adapted to the
unstable conditions
– A second stage of autotrophs
– larger autotrophs, including trees, enter and begin to dominate the site
– the mature ecosystem develops
what happens to Biomass and biological diversity In early stages of succession
increase
what happens to Storage of chemical elements during progression from early to middle stages of succession
increases
- Increased storage in organic matter
- Increased rate of uptake (nitrogen fixation)
- Decreased rate of loss (presence of live and dead
organic matter slows erosion)
whats a Pioneer species
the first to colonize previously disrupted or
damaged ecosystems, beginning a chain of ecological
succession that ultimately leads to a more biodiverse steady-state ecosystem
what 3 ways does Earlier-successional species affect what happens later in succession
- Facilitation - prepare the way for other species
- Interference - interfere with the entrance of other species
- Life history differences -
what are biomes
regions of the world with similar climate (weather,
temperature) animals and plants
- There are terrestrial biomes and aquatic biomes, both freshwater and marine
