Ecosystems (Ecology) Flashcards
The Earth is a relatively closed system with respect to _________. However, it is an open system in terms of ________.
1) Chemicals
2)Energy
Why is Earth an open system in terms of energy?
It receives energy from the Sun and steadily emits thermal energy to outer space
What is an ecosystem?
-Includes all the organisms that live in a particular place, plus the abiotic environment in which they live and interact.
Ecosystems are intrinsically dynamic in a number of ways… give 2.
-Their processing of matter
-Their processing of energy
True or false? The Earth has an essentially fixed number of each of the types of atoms of biological importance and those atoms are endlessly recycled.
True! This means that each organism assembles its body from atoms that previously were in the soil, the atmosphere and other parts of the abiotic environment or other organisms
What are biogeochemical cycles?
-Chemicals moving through ecosystems
-Those cycles include biological processes (biotic) and also geological (abiotic) processes.
-Occur at different spatial scales, from cellular to planetary, and timescales, from seconds (biochemical reactions) to millennia (weathering of rocks).
What are the main biogeochemical cycles?
1) Water cycle
2) Carbon cycle
3) Nitrogen cycle
4) Phosphorous cycle
Why is water essential for life?
-medium in which all living bio chemistry occur
-Water dissolves nutrients and distributes them to cells, regulates body temperature, and removes waste products
What % of the Earth’s surface is covered by water?
71%
What percentage of water i salty and located in the ocean and what percentage is fresh water?
Salt: 97%
Fresh: 3%
However, most fresh water is inaccessible under ice cap, glacier and ground water.
What percentage of fresh water is easily accessible?
Only 1% of the 3% of fresh water on the surface of water (therefore 0.03%)
What are the 5 steps to the water cycle?
1) Evaporation from ocean, lake, river and soil
2) Transpiration from the vegetation
3) Condensation in cloud
4) Precipitation (rain, snow, etc.)
5) Recharge the aquifers, lakes and rivers and eventually returning to the ocean
How much carbon is in an adult human (percentage per body weight)
18% carbon per body weight
In which ways can carbon be transformed?
-Carbon fixation
-Aerobic respiration
-Methanogenesis
What is carbon fixation?
Metabolic reactions transform gas into matter (ex.: photosynthesis)
What is aerobic respiration?
Metabolic reactions transform matter into gas
What is methanogenesis?
Production of methane (CH4) by anaerobic cellular respiration
How are humans contributing to climate change (in regards to the carbon cycle)?
-Humans are creating an imbalance in the carbon cycle by burning fossil fuels
-Fossil fuels were mainly ancient photosynthetic organisms that capture CO2 from the atmosphere millions of years ago and sequester this carbon in the ground when they died
-However, humans are now freeing large amounts of carbon that was sequestered for millions of years in less than 200 years
What major event caused the instability of levels of CO2 and CH4 (which was originally stable for the past 10,000 years)?
The Industrial Revolution
The excess of greenhouse gases in the atmosphere… do what?
Block heat from escaping the Earth’s atmosphere
What is the importance of Nitrogen (Nitrogen cycle)?
-Nitrogen is the main gas in our atmosphere
-Nitrogen is essential for life, being a component of nucleic acids and amino acids (proteins).
What is Nitrogen availability?
-Even though nitrogen is abundant in the atmosphere (78%), the plants and animals cannot use it under this form of nitrogen gas (N2).
-For plants and algae nitrogen need to be under inorganic form, such as ammonia (NH3) or nitrate (NO3-)
-For animals, nitrogen uptake is done by eating organic compounds (plants and other animals) containing nitrogen atom (nucleic acids, amino acids, etc.)
What is nitrogen fixation?
It is the synthesis of ammonia from N2 by nitrogen fixing bacteria (Rhizobium)
Where are nitrogen fixing bacteria found?
In soil,or in symbiosis with certain plants such as legumes
In water, most nitrogen is fixed by…
Cyanobacteria
What are the main sources of nitrogen fixation?
Most natural = nitrogen fixing bacteria
Second natural = lightning
What is ammonification?
Bacteria and related microorganisms derive metabolically useful energy from the oxidation of organic nitrogen to ammonium
What is nitrification?
A two step process which ammonium (NH4+) is first oxidized to nitrite (NO2-) and then nitrate (NO3-) in the respiration process of nitrifying bacteria
What are the conditions for nitrification to occur?
1) Under aerobic condition (O2) an ecosystem of nitrifying bacteria oxidize ammonium
What is a bacteria that oxidizes ammonium ions (NH4+) to nitrites (NO2)
Nitrosomonas bacteria
What is a bacteria that oxidizes nitrites (NO2) into nitrates (NO3)?
Nitrobacter bacteria
Both processes of nitrification are carried out by….
Microbes (free or living on plant roots)
What is denitrification?
Facultative anaerobic bacteria respiration process where nitrate (NO3-) is reduced to molecular nitrogen (N2)
What is assimilation?
Plants can only uptake nitrogen under ammonium (NH4+) or nitrate (NO3-)
Why have humans doubled the rate of transfer of N2 in usable forms into soils and water?
One of the main reasons is the artificial fixation of nitrogen to make fertilizer
What does nitrogen have to do with the agricultural revolution?
-Before the agriculture revolution, nitrogen fertilizer only came from organic sources such as manure and compost
-Organic fertilizer is limited, since for example: you first need nitrogen fixing bacteria to fix N2 into NH4+ that can be assimilated by plats and then the plant nitrogen would be eaten by animals to produce manure
-The use of organic fertilizer is not adapted to industrial farming so a new source of fertilizer is needed to fuel the increase in human population
What is the Haber process?
Invented by Fritz Haber, it is an industrial nitrogen fixation process that takes nitrogen from the atmosphere (N2) and makes it into ammonia (NH3)
What did the Haber process permit?
-The production of chemical nitrogen fertilizer which was in part responsible for the agricultural revolution and growth of the human population
-Haber-Bosch process was used to make explosives which fueled WW1.
Who made chemical weapons with chlorine gas?
Fritz Haber
What is the importance of Phosphorous in the Phosphorous cycle?
-Phosphorous is required by all organisms
-Occurs in nucleic acids, ATP and phospholipids of membranes
-Exists mainly under the inorganic form of phosphate (PO4^3-) or under organic matter in the ecosystems
How do autotroph (ex: plants and algae) use free inorganic phosphate PO4^3-?
They use them in the soil or water for synthesizing their phosphorous-containing organic compounds
How do heterotroph (such as animas) build their own phosphorus compounds?
They use the organic phosphorus of plants or algae
Why does free PO4^3- only exist in low concentrations in soil?
-Combines with other soil constituents to form insoluble compounds
-Tends to be washed away by streams and rivers
-Weathering of many sorts of rocks releases new PO4^3- into terrestrial systems, but then rivers carry the PO4^3- into the ocean basins. There is a large one-way flux of PO4^3- from terrestrial rocks to deep-sea sediments
Which countries overapply nitrogen and phosphorous?
Singapore, New Zealand, Japan, South Korea, and Belgium
Describe the effects of phosphates and fertilizers?
-Phosphates as fertilizers
-Human activities have greatly modified the global phosphorus cycle since the advent of crop fertilization.
-PO4^3- fertilizers is typically derived from crushed phosphate-rich rocks and bones
-PO4^3- fertilizers is a non renewable resource. When the phosphate mine will become depleted, there will be no more fertilizers to sustain modern agriculture
Does phosphorous have a gas form?
NO
What is eutrophication?
Excessive growth of algae due to surplus in nutrients (Nitrogen and Phosphorous)
-It causes oxygen depletion of the water after the bacterial degradation of the dead algae
-Some Cyanobacteria produce toxins that can cause serious sickness or death. It can also contaminate sea food
What is the first law of thermodynamics?
Energy can be neither created nor destroyed, but only change form
What are examples of energy?
-light
-chemical-bond
-motion
-heat
True or false? Organisms can convert heat to any other forms of energy?
False. If an organism converts chemical-bond or light to heat, this energy is lost
What is the second law of thermodynamics?
Whenever organisms use energy under the form of light or chemical-bond some of this energy is converted to heat (entropy)
Does part of the thermal energy radiate back to space?
Yes
What is causing climate change (thermal equilibrium)?
Since the Industrial Revolution, humans have produced a large amount of greenhouse gases, which threaten the thermal equilibrium between the sun input of energy and the amount that is radiated back to space.
Almost all living organisms on Earth use the energy of the ___ in a direct and indirect way
Sun
What are autotrophs?
‘’Self-feeders’’ synthesize the organic compounds of their bodies from inorganic precursors
What are photoautotrophs?
Organisms that can make their own energy using sun light and CO2 (Carbon fixation) via photosynthesis (ex.: plants, algae, Cyanobacteria).
What are chemoautotrophs?
Create their own energy and biological materials from inorganic chemicals (rare)
Ex: prokaryote that uses hydrogen sulfide available in deep water vent
What are heterotrophs?
Organisms that cannot produce their own food using inorganic compounds (carbon fixation) and therefore derives their energy by breaking the chemical bond of organic matter, from plants and/or animals.
What are tropic levels?
Level at which an organism ‘’feeds’’
What are primary producers
All the autotrophs in the system
What are the consumers in order?
Heterotrophs
1) Herbivores
2) Primary carnivores
3) Secondary carnivores
Tropic levels 2, 3 and 4 are…
Consumers
What is productivity?
The rate at which the organisms in the tropic level collectively synthesize new organic matter (biomass)
What is Gross Primary Productivity (GPP):
productivity of the primary producers (biomass)
What is respiration?
Primary producers break down organic compounds to make ATP
What is net primary productivity (NPP)?
It’s the GPP less (-) the respiration of the primary producers
What is secondary productivity?
The productivity of a heterotroph trophic level is termed secondary productivity.
-For instance, the rate at which new organic matter is made by means of individual growth and reproduction in all the herbivores in an ecosystem is the secondary productivity of the herbivores trophic level
Each heterotroph trophic level has its own ________ productivity
Secondary
How much (%) of incoming solar energy is captured by producers per year?
1%
How do primary producers store solar energy?
In chemical bonds
What happens to the chemical-bonds stored by primary producers?
-some of this chemical energy is used during the primary producer respiration
-Some of the energy released by the chemical bonds is lost to heat
True or false? From the initial amount of sun energy captured by the producer (plants). Most of it goes into the biomass of the herbivore (grasshopper)
False!
Only a small amount goes into the biomass of the herbivore
What happens to the rest of the chemical-bond energy of the plants (for herbivores/animals)?
The rest of the chemical-bond energy of the plant is lost through the animal respiration and heat, n addition part of the matter is lost through undigested food (feces)
How much (%) of the initial sun energy is left in the biomass of the grasshopper for the bird to use (after loss through respiration, head and feces)?
17%
What is the amount of chemical-bond energy available to a trophic level over time?
About 10%
Why are there limits on top carnivores?
There is an exponential decline of energy left (chemical energy). This limits the lengths of trophic chains and the numbers of top carnivores and ecosystem can support
Approximately how much energy captured by photosynthesis passes all the way through to secondary carnivores?
Approximately 1/1000
Can the pyramid of biomass ever be inverted?
Yes
Ex: in aquatic systems here algae is the primary produces and copepods is the primary consumer (herbivore) the pyramid can be inverted.
This can be explained by the fact that phytoplankton (algae) reproduce very quickly but have much shorter individual lives
What are detritivores?
Heterotrophs that eat decaying matter
What are decomposers?
Microbes/fungi (heterotrophs) that break up dead matter
