Ecology Lesson 4 Flashcards
Ecosystem function
Species interactions. Energy and nutrient flows. It is how an ecosystem ‘works’. Humans are altering ecosystem function. It’s responsible for the ability of the earth to support life. Can be viewed as how energy passes through and the cycling of nutrients.
Components of an ecosystem
Embedded within the physical environment (climate, geology, oceanography, etc.). Living and non-living components:
* Living organisms
* Dead organisms
* Physical environment
Layers of ecosystem
Primary produces are autotrophs (first layer that turns light into energy). Then primary consumers eat them, and secondary consumer eats primary. Then detritus is dead organisms, and decomposers break down dead materials to cycle back.
What are heterotrophs in the cycle
Primary and secondary consumers. Decomposers.
This is to ensure the ecosystems are sustainable we must what?
Turn dead organisms into nutrients.
Living components
Group of organisms that process energy and nutrients in similar ways (aka feed the same way).
How are the components connected?
Organisms to organisms (energy flow) and Organisms to the physical environment (nutrients flow)
What is the ecosystem function characterized by?
the connections between components and the flow of energy and nutrients.
The ecosystem energetics
Ecosystems (and life) are powered by the sun (the energy that it releases. Radiant energy to photosynthesis to chemical energy.
What do primary producers do?
Capture radiant energy (photosynthesis) and store chemical energy (molecular bonds in organic compounds like carbs, sugars, ATP, and it’s stored in the organism as chemical energy). It takes the light and turns it into their physical structure.
What do ecosystems transfer?
Transfer chemical energy through consumption (transfer to consumers) and death (transfer to detritus).
Detritus
A pool of energy. The producers and consumers die and their body on ground becomes detritus.
What do ecosystems lose?
Ecosystems lose heat energy through respiration. Each level does respiration.
What must the ecosystem have?
Continuous energy in from the sun.
Decomposers
Bacteria that eat detritus. They help the flow of energy. Invertebrates, fungi, bacteria. Obtain chemical energy and nutrients from detritus (dead
organisms) then recycle it to keep the flow going.
Return some nutrients to physical environment.
One way energy flow in ecosystems?
enters as radiant energy, stored and transferred as chemical energy, leaves as heat energy.
How much energy is lost during each tropic level?
10% of the energy is lost. This can be because the consumer doesn’t eat the whole thing.
How can we compare ecosystem energy flows?
Amount of energy reaching ecosystem
Efficiency of energy capture
Transfer rates
Rates of energy loss
Circular flow of nutrients?
Nutrients mostly retained. Cycle between organisms and physical environment. The nutrients in the environment goes back into the primary producers.
Carbon cycle
Plants get CO 2 from atmosphere and convert to organic carbon (Org C). Org C transferred among components. CO 2 returned to atmosphere through respiration, then back into the plants.
How can we compare ecosystem nutrient cycles?
Nutrient stores in physical environment.
Efficiency of nutrient uptake (some organisms evolved to flourish in low nutrient environments).
Transfer rates (how fast are the nutrients moving around).
Retention of nutrients in the environment.
Ecosystem Health
An ecosystem processes and transfers energy and
nutrients
* Fueled by energy from outside the ecosystem.
* Cycle and recycle nutrients from and to the
physical environment.
An ecosystem might be ‘unhealthy’ if it is less
able to what?
Obtain or transfer energy (ie. not enough producers)
Cycle or retain nutrients (not enough species)
Rate of primary production
Rate that primary producer biomass is built. How effective is sunlight being turned into primary produce of biomass. Energy capture and nutrient
uptake. Death rates. Plant respiration (heat loss). Use satellites to measure how much chlorophyll is in the plant (the productivity of the plant).
Rate of secondary production
Rate that consumer biomass is built. Supported by primary producers. How much do they depend on the primary producers. Energy and nutrient transfer. Death rates. Respiration.
Rate of decomposition
Rate that inorganic nutrients are released from detritus. How effective are the decomposers in releasing nutrients from detritus.
Measures of ecosystem function?
Rate of primary production
Rate of secondary production
Rate of decomposition
Reasons to care about ecosystem health and
function?
Feeding ourselves
Natural ecosystems
We are changing the rates
Feeding ourselves
- Primary production – how fast can we grow food? (agriculture)
- Secondary production – how fast can we turn plants
into animals? - Decomposition – nutrient supply for growing plants.
Natural ecosystems
- Primary production – plant/tree abundance and
recovery after damage. How fast ecosystems recover. - Secondary production – animal diversity and abundance.
- Decomposition – nutrient supply that animals rely on.
We are changing the rates
- Deforestation (less primary producers).
- Use of fertilizers (modifying nitrogen cycle by packing it up and using it to grow plants for human food).
- Greenhouse gas emissions & climate change (affects nitrogen cycle).
Net primary production (NPP)
Plant growth rate (energy accumulated as biomass). Balance of energy coming in minus the energy that’s lost. Rate that plant biomass increases in an ecosystem. Synthesizes many rates.
Biomass
amount (mass) of organic matter present in an ecosystem.
NPP equation
NPP = GPP - Ra
Gross primary production (GPP)
Total light energy captured by plants
Autotrophic Respiration (Ra)
Energy lost due to plant respiration
Units of NPP and GPP
Energy (joules)/time
Biomass (kg)/time
Net Ecosystem Production (NEP)
Energy (biomass) accumulated in all ecosystem
components (per unit time). Understanding the contribution of that ecosystem in terms of locking up carbon. Related to natural carbon solution.
* Plants capture energy
* Energy stored as biomass in all components
* Heat energy lost from all components
Total Respiration (RT)
Heat (biomass) lost from all components
NEP equation
NEP = GPP - RT
Positive NEP
Ecosystem biomass is increasing.
Ecosystem absorbs more CO 2 than it releases.
Helps lower atmospheric CO 2 (climate change).
Negative NEP
Ecosystem biomass is decreasing.
Ecosystem releases more CO 2 than it absorbs.
Contributes to increasing atmospheric CO 2.
What are NEP and NPP?
They are large scale measures of ecosystem productivity.
What limits NPP in terrestrial ecosystems?
- Temperature (+ light)
Latitude (how close you are to the poles)
Elevation (how high up you are) - Moisture
- Soil nutrients (adding fertilizers we can overcome those limitations and increase plant growth).
- Limiting nutrient: Nitrogen
Why is nitrogen important?
Forms of organic nitrogen: DNA, proteins. They make bodies. It’s crucial at limiting the total productivity.
Bacteria driven nitrogen cycle?
In the atmosphere as N2 gas. In this form it’s inert so because to can’t be used by organisms. Then the nitrogen-fixing bacteria turn N2 into NH4+ which is found in the soil. Then the nitrifying bacteria turns it into NO3-. Both of these are in the soli and can be used by the plant. Then the denitrification bacteria turn it back into N2 and release it back into the atmosphere.
NH4+ does what?
Some have formed a symbiosis relationship with rhizobium (bacteria that live in the root of plants).
Plants in nitrogen cycle
Decomposition: Trees turns organic N into NH4+. The nitrogen is locked up in their tissues then broken down by decomposers the nitrogen goes into the soil water.
Assimilation: Turning NH4+ → Organic N or NO3- → Organic N.
Trees use nutrients. to build biomass.
How do humans get there DNA?
By consuming plants and animals.
Global nitrogen fixation
Pristine (85 Tg/yr) this is the natural nitrogen cycle.
lighting is 5 (they break apart the atoms in nitrogen gas and fix them into other forms).
N-fixing bacteria is 80
Human Input (220 Tg/yr) the cycle is now dominated by humans
Agriculture is 195 (using fertilizers all by grazing plants)
Buring fossil fuels is 25
Agriculture increases rates of N-fixation by what ?
- Growing legumes (soybeans, peas, beans). (60 Tg/hr).
- Manufacturing fertilizer. 135 Tg/yr. Used to increase productivity of our fields.
Soybeans do what?
Symbiosis
Root nodules contain N-fixing
bacteria (Rhizobium)
Consequences of applying N fertilizer
Long term impacts of excessive
nitrogen inputs:
* High nitrate (NO 3- ) levels in soil
water – can be toxic
* Loss of nutrients from soil (e.g.
calcium)
* Pollution of aquatic ecosystems
What limits NPP in marine ecosystems?
- Light (Depth)
- Nutrients
Eutrophication
Excessive primary production due to overload
of nutrients. Too much nitrogen.
Phytoplankton
Multiply quickly then they die and sink to the bottom where decomposers decompose it and use up oxygen in doing so.
Decomposition of algae leads to what?
oxygen (O 2 ) depletion. aka Dead zone: low O 2 , fish and others die.
Fertilizer summary
- Fertilizer converts N2 to forms that
plants can use (NH 4+ and NO 3- ) - Overuse leads to increased NO 3- levels
in soil water - Excess nitrogen ends up in aquatic
ecosystems - Eutrophication and oxygen-depletion
in freshwater and coastal habitats
Fossil fuel use
- Burning fossil fuels adds nitrogen to atmosphere
- Nitrogen deposited back into ecosystems
Humans in adding nitrogen
Through the application of fertilizer and burning fossil fuels, humans have hugely increased the amount
of available nitrogen.
Legume crops: N2 → NH 4+
Fertilizer: N2 → NH 4+ + NO 3-
Fossil fuels: Org N → NO 3-
