ECOLOGY & ECOSYSTEMS PT.2 Flashcards
(28 cards)
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 + 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
- oversimplified - reality = food webs
whats a trophic cascade
occur when predators in a food web alters prey - releases 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
– 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
– gross growth efficiency / trophic level efficiency = % of energy that a trophic level consumes that is converted to biomass (and made available to higher trophic levels) - 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 of organic matter production 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 site undergoes a series of changes due to disturbance eliminating all / most of the species
- primary succession = communities 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
