Lecture 23 Flashcards
WHat is an ecosystem?
- all organisms living in a community as well as all the abiotic factors with which they interact
- can be small or large
WHat are the 4 key componenets of an exosystem?
- primary producers
- consumers
- decomposers
- abiotic environemnt
What is energy flor?
- it enters ecosystem mostly as solar radiation and is lost as heat
What happens to most of the solar energy that enters Earth’s atmosphere and what happens to the rest?
- most is absorbed or reflected by non-photosynthetic surfaces (water, rock, soil, ice)
- only a small amount of incoming solar energy is fixed by primary producers as gross primary productivity (0.8%) (carbohydrates)
- but it powers ecosystems, and the nergy is ultimately lost back to space as HEAT
- energy dissipates as it flows through ecosystems
explain composting and heat production
- metabolic heat production by bacteria and fungi
- spontaneous fires may result!
- a bed may take 3-5 days to heat up and reach temp of 60-70 degC
- managers strive to keep the compost below 69 degC because hotter temps cause the beneficial microbes to die off
- if the bed gets too hot, water sprays and turning will help to dissipate the heat.
- Most of energy entering decomposer food chains is also lost as heat
Why are decomposers important?
- rate of nutrient recycling depends on decomposer activity
What are some examples of decomposers?
- insects, worms, bacteria and archaea, fungi
- the waste products, corpses from the consumers goes to the decomposer and goes back to the producers as nutrients
What differs between a productive wet tropical and coniferous rainforests with high Gross Primary Productivity (GPP) compared to low productivity tundra and desert?
- climate (energy inputs), water and nutrient availabilities differ
What is GPP used for?
- gross primary productivity
- it is used to promote growth and maintenance (mostly respiration
GPP produces growth (NPP) + maintenance
(100%) (45%) (55%)
What is NPP and what can it be measured as?
- Net Primary Productitivity
- new growth (ex. on a tree, leaves, wood, roots, reproduction)
- GPP produces growth NPP
- can be measured as energy used for new growth (kJ/m^2/year)
OR - BIOMASS production (grams/m^2/year) of wood growth, leaves, seeds, and other tissues, in forestry or agriculture applications is of great interest to human populations
ex. on a tree, the rings in a cross-section shows new growth (NPP)
What limits primary production?
Globally,
- NPP is greater in terrestrial habitats than in open oceans
- NPP is greater near the equator than the poles (high energy & water availability - rain)
Locally,
- NPP is limited by nutrient availability
ewde adddd
How are nutrients a limiting factor?
- when light and moisture are available, production is limited by nutrients
What’s a limiting nutrient? give the most common limiting nutrients as well
- the nutrient that must be added for production to increase
the most limiting nutrients are available:
- nitrogen (N) - terrestrial
- phosphorous (P) - freshwater
- iron (Fe) - oceans
why are large predators rare?
- available energy cannot support high numbers of large predators at the top of food chains or energy pyramids
