Lecture 23

Question 1

WHat is an ecosystem?

Answer 1

• all organisms living in a community as well as all the abiotic factors with which they interact
• can be small or large

Question 2

WHat are the 4 key componenets of an exosystem?

Answer 2

• primary producers
• consumers
• decomposers
• abiotic environemnt

Question 3

What is energy flor?

Answer 3

• it enters ecosystem mostly as solar radiation and is lost as heat

Question 4

What happens to most of the solar energy that enters Earth’s atmosphere and what happens to the rest?

Answer 4

• 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

Question 5

explain composting and heat production

Answer 5

• 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

Question 6

Why are decomposers important?

Answer 6

• rate of nutrient recycling depends on decomposer activity

Question 7

What are some examples of decomposers?

Answer 7

• 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

Question 8

What differs between a productive wet tropical and coniferous rainforests with high Gross Primary Productivity (GPP) compared to low productivity tundra and desert?

Answer 8

• climate (energy inputs), water and nutrient availabilities differ

Question 9

What is GPP used for?

Answer 9

• gross primary productivity
• it is used to promote growth and maintenance (mostly respiration

GPP produces growth (NPP) + maintenance
(100%) (45%) (55%)

Question 10

What is NPP and what can it be measured as?

Answer 10

• 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)

Question 11

What limits primary production?

Answer 11

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

Question 12

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Question 13

How are nutrients a limiting factor?

Answer 13

• when light and moisture are available, production is limited by nutrients

Question 14

What’s a limiting nutrient? give the most common limiting nutrients as well

Answer 14

• 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

Question 15

why are large predators rare?

Answer 15

• available energy cannot support high numbers of large predators at the top of food chains or energy pyramids

Question 16

How can we increase N in an ecosystem?

Answer 16

• plant crops with N2-fixing symbiotic bacteria (legumes)
• add chemical fertilizer

ex. Root nodules with N2 fixing bacteria

Question 17

What if we add N to an ecosystem?

Answer 17

• if N is a limiting nutrient, NPP will increase
• Nitrate Nitrogen (NO3-) is highly mobile in water
• some N will escape in ground water and run off into streams, rivers, lakes, ocean, often along with phosphorous (a key aquatic nutrient)

Question 18

What are the 5 biological effects of climate change?

Answer 18

1. geographic range shift - pine beetles move north, bad for pine forests
2. Phenology shifts - change in surrounding, white winter coats in hares when the snow melted
3. Evolutionary Adaptation - change in allele frequencies
4. Extinction - die and cant reproduce due to new physical or biological condition
5. Acidification - ocean+CO2 = acidic