Lecture 22 Flashcards
What are the two fundamental processes in ecosystems?
1) Energy flow
2) Nutrient Cycling
How does energy enter ecosystems?
Energy enters ecosystems as radiant energy, primarily from the SUN.
What happens to radiant energy once it enters an ecosystem? (2)
converted into chemical energy and
stored in the bonds of organic molecules
Name an organic molecule and what processes it?
Glucose (processed by photosynthesis)
Is energy transfer in ecosystems 100% efficient?
No, energy transfer in ecosystems is never 100% efficient.
What is nutrient cycling?
process where nutrients cycle from the abiotic (non-living) to the biotic (living) components of ecosystems
How do energy flow and nutrient cycling relate in ecosystems?
While energy flows through ecosystems, matter cycles within them through nutrient cycling.
How does energy flow through an ecosystem?
by entering as light, usually from the sun, and exiting as heat.
Describe the flow of energy from primary producers to consumers.
primary producers (autotrophs) -> primary consumers (herbivores) -> secondary consumers (carnivores)
What role does decomposition play in ecosystems?
- connects all trophic levels in ecosystems by recycling essential chemical elements.
What are considered to be decomposers? (2)
Fungi and bacteria
What do decomposers do?
they recycle essential chemical elements
How do they recycle essential chemical elements?
By decomposing organic material and returning elements to inorganic reservoirs
What would happen if decomposition stopped?
all life on Earth would CEASE!!
What defines heterotrophic organisms?
Heterotrophic organisms obtain energy from food intake.
Name 2 examples of heterotrophs
animals & fungi
What are autotrophs known as?
organisms capable of making their own nutrients from simple inorganic compounds, such as CO2.
How do autotrophs produce nutrients?
plants produce the glucose needed for energy from CO2, H2O and sunlight (photoautotrophs)
What is the difference between autotrophs and heterotrophs in terms of nutrient acquisition?
Autotrophs -> produce their nutrients from simple inorganic compounds,
Heterotrophs -> rely on consuming other organisms or organic matter for their nutrient intake.
What is the source of energy for ecosystems?
SUN = primary source of energy
What organisms occupy the first trophic level?
Producers
Give examples of producers (those who occupy the first trophic level)
green plants
Who are the primary consumers in ecosystems?
herbivores (second trophic level)
What do herbivores eat?
They eat producers
Who are the secondary consumers in ecosystems?
Carnivores (occupy third trophic level)
What is the role of tertiary consumers in ecosystems?
They eat secondary consumers and occupy the fourth trophic level.
What function do decomposers serve in ecosystems?
Decomposers, or saprotrophs, break down dead organic material, returning nutrients to the environment
What happens to the energy content of food as it moves through the food chain?
As energy moves through the food chain, some of it is used for growth and metabolic processes
How is most of the energy lost as?
most of it is lost as heat, requiring a continual input of energy from the sun.
What does a community consist of at each trophic level?
A community consists of many species at each trophic level, including primary producers, herbivores, and carnivores.
How does energy pass through the trophic structure of a community?
Energy passes through the trophic structure of a community from producers to consumers.
Describe a simple food chain scenario.
a plant (producer) is consumed by a single grazer (primary consumer), which is then eaten by a single carnivore (secondary consumer)
Are simple food chains relatively common or rare in nature
relatively RARE
If food chains don’t accurately represent our food distribution, what is better?
a FOOD WEB
How do animals in most communities feed?
animals do not feed in a specialized manner but may eat many types of plants
How do carnivores typically feed at the next trophic level?
Carnivores tend to eat several different prey.
How are food chains related to food webs?
How are food chains related to food webs?
What is a food web?
A food web is a complex network of interconnected food chains within a community.
Why are food webs more representative of natural communities than food chains?
because they illustrate the multiple feeding relationships and interactions among different species in a community.
What is primary production?
the amount of light energy converted to chemical energy
Who performs primary production in an ecosystem?
Autotrophs, such as plants
What sets the spending limit for the energy budget of the entire ecosystem?
the extent of photosynthetic production
What is total primary production in an ecosystem called?
the ecosystem’s gross primary production (GPP).
Is all of the GPP stored as organic material in plants?
No, not all of the GPP is stored as organic material in the growing plants.
What does NPP stand for?
Net primary production
What is NPP?
NPP = GPP minus the energy used by the primary producers for cellular respiration.
What is the main equation then?
NPP = GPP -R
What is R in the equation?
R is the energy used by PRIMARY producers for respiration
What portion of primary production is available to consumers?
Only NPP is available to consumers.
Productivity of terrestrial environments is limited by what?
is limited by a combination of temperature, availability of water & sunlight
Primary production is positively correlated with WHAT?
evapotranspiration
What is evapotranspiration?
= amount of water transpired by plants & evaporated from landscape
Primary production increases with 2 things, name them:
- amount of precipitation
- solar energy
How come these factors help increase primary production? (what do they drive?)
these factors drive evaporation & transpiration
Which terrestrial ecosystem is the most productive?
Tropical rain forests
What conditions contribute to the high productivity of tropical rainforests? (2)
warm + wet conditions
Which ecosystems are generally low in productivity?
Deserts and arctic tundra
What are the typical conditions in low-productivity ecosystems?
Low-productivity ecosystems are typically dry (deserts) or dry and cold (arctic tundra).
What is actual evapotranspiration?
amount of water annually transpired by plants and evaporated from a landscape
To ecologists, what is hte key measurement?
net primary production
Why is net primary production (NPP) important to ecologists?
NPP is important because it represents the storage of chemical energy that is available to consumers in the ecosystem.
What does NPP represent in an ecosystem?
NPP represents the storage of chemical energy available to consumers.
What is secondary production in an ecosystem?
Secondary production is the amount of chemical energy in consumers’ food that is converted to their own new biomass during a given time period.
How is secondary production different from NPP?
Secondary production refers to the energy converted into new biomass by consumers, while NPP refers to the energy stored by primary producers that is available to consumers.
How much of the energy in a plant leaf is used for secondary production when a caterpillar feeds on it?
one-sixth of the energy in the leaf is used
What happens to the energy contained in the caterpillar’s feces?
The energy in the feces remains in the ecosystem temporarily
Most of the energy is lost as what?
mostly lost as heat after the feces are consumed by detritivores.
What portion of the caterpillar’s energy is available to secondary consumers?
Only the chemical energy stored herbivore (caterpillar) biomass
What is an example of a secondary consumer in this context?
Other organisms that will eat the caterpillar act as secondary consumers.
Complete the sentence, _______ of energy with each transfer in a _____ _______
LOSS of energy with each transfer in a FOOD CHAIN
What is the average trophic efficiency b/w trophic levels?
10%
Why is much of the NPP unavailable to herbivores?
because it resides as indigestible substances
Give an example of an indigestible substance:
like lignin
How is most of the chemical energy stored in carbon compounds lost?
it’s lost as heat (when metabolized or used to keep the consumer alive)
Is all the energy ingested by secondary consumers converted to biomass?
(yes/no + why?)
NO, some lost as heat or used to stay alive & capture prey
Are all herbivores eaten by secondary consumers?
no, not all
Why is not all energy at each trophic level used for growth or reproduction?
because it is also metabolized for maintenance and lost as heat
How do toxic substances enter the food chain?
Through accumulation in the environment.
What happens if an organism does not metabolize a toxin?
It gets stored in the body.
Define bioaccumulation.
The build-up of toxins in an organism’s body.
What is biomagnification?
Increase in toxin concentration across trophic levels.
Why do toxins become more concentrated at higher trophic levels?
Each predator consumes multiple prey, accumulating toxins.
How do nutrients cycle through an ecosystem?
They cycle through biotic and abiotic forms.
Why must nutrients cycle between the biotic and abiotic parts of an ecosystem?
To ensure continuous availability for living organisms.
Where do nutrient pools exist in an ecosystem?
In the air, soil, rocks, sediments, and water.
What are biogeochemical cycles?
They are cycles where nutrients move between living organisms and the abiotic environment.
Give an example of nutrient cycling in an ecosystem.
Nutrients move from one organism to another and back to the abiotic environment, completing the cycle.
Why is nitrogen (N) essential?
for proteins, nucleic acids (DNA, RNA), and other biomolecules.
Where are large reservoirs of nitrogen found?
in the atmosphere
The air comprises of how much Nitrogen? (%)
comprising 78% of the air
What is the role of bacteria in the nitrogen cycle?
microbial transformations within the nitrogen cycle
What is nitrogen fixation?
for converting atmospheric nitrogen into biologically useful forms
Is it carried out by prokaryotes or eukaryotes?
PROkaryotes
What does Nitrogen fixation involve?
the use of nitrogenase
What is nitrogenase?
an enzyme that works in the absence of oxygen
Why is nitrogenase important in nitrogen fixation?
it converts atmospheric nitrogen into ammonia or related compounds.
SO, What is nitrogen fixation?
conversion of atmospheric nitrogen (N2) into ammonia (NH3) and ammonium (NH4+)
What are the 2 types of nitrogen fixers?
Free-living nitrogen fixers & Mutualistic prokaryotic nitrogen fixers
What are some examples of mutualistic prokaryotic nitrogen fixers?
- Rhizobium/legume symbiosis
- Frankia symbiosis with woody plants
- lichen symbioses involving Cyanobacteria such as Nostoc
Where do Rhizobium bacteria typically fix nitrogen?
found in legume plants
How do nitrogen-fixing cyanobacteria adapt to aquatic environments?
In aquatic environments, nitrogen-fixing cyanobacteria have specialized cells called heterocysts
What are the 5 steps in the nitrogen cycle?
1) Nitrogen fixation
2) Nitrifcation
3) Assimilation
4) Ammonification
5) Dentifrication
Which one involves Bacteria?
ALL of them but Assimilation
(therefore, BACTERIA is very important)
1) What is nitrogen fixation?
Bacteria convert atmospheric nitrogen (N2) into forms that plants can use, such as ammonium (NH4+) or ammonia (NH3).
N2 -> NH4+ or NH3
2) What is Nitrification?
Bacteria convert some of the products of nitrogen fixation into nitrates (NO3-) and nitrites.
ex.: NH4+ or NH3 -> NO3-
3) What is assimilation?
Plant roots absorb organic forms of nitrogen from the soil.
4) What is Ammonification?
Bacteria decompose organic nitrogen into ammonium (NH4+).
5) What is Denitrification?
Bacteria convert organic nitrogen back into atmospheric nitrogen (N2) gas.
Show the path from nitrogen fixation to denitrification of chemicals:
Nitrogen Fixation (N2) –> Ammonium (NH4+) or Ammonia (NH3) –> Nitrification (NH4+ or NH3 to NO3-) –> Assimilation (Absorption by roots) –> Ammonification (Organic nitrogen to NH4+)
What other chemical is important?
C = Carbon
What biomolecules rely on carbon as an essential component? (4 main)
Proteins, nucleic acids, carbohydrates, lipids, etc.
What role does carbon dioxide play in the carbon cycle?
It serves as an important gas in the carbon cycle
Where is carbon dioxide found in the environment?
It is found in the ocean, freshwater, and rocks. + AIR
What % does Carbon hold in air?
approximately 0.04%
How do plants acquire carbon?
during photosynthesis
What processes return carbon dioxide to the environment?
cellular respiration, combustion, and erosion
What does the water cycle renew?
renews the supply of water on Earth
What are the key components involved in the water cycle exchange? (4)
land, ocean, atmosphere, and organisms
How does water enter the atmosphere? (2)
- through evaporation from bodies of water
- transpiration from plants
Describe the steps involved in the water cycle from the atmosphere to the land. (3 first steps)
Step 1: Precipitation (from atmosphere to land)
Step 2: Evaporation (from land to atmosphere)
Step 3: Transpiration (loss of water from plants to the atmosphere)
How does water return to the ocean in the water cycle? (2)
through runoff and percolation through soil into groundwater.
What strongly regulates nutrient cycling?
vegetation
How does internal cycling within a terrestrial ecosystem impact mineral nutrients?
It conserves most of the mineral nutrients.
Describe the experiment conducted at Hubbard Brook Experimental Forest.
Some areas were completely logged and then sprayed with herbicides for three years to prevent re-growth of plants. All the original plant material was left in place to decompose.
What were the effects of the experiment on nutrient cycling?
loss of nutrient cycling
How did the treatment of logged areas affect nutrient cycling?
It disrupted nutrient cycling.
How did deforestation impact water runoff? (due to what? (2))
due to the absence of plants to absorb and transpire water from the soil
Water runoff increased by __-__%
30-40%
What were the consequences of increased water runoff?
increased loss of minerals
Name 3 types of minerals
Calcium (Ca) & Potassium (K) & Nitrate
What does the study demonstrate about nutrient control in intact forest ecosystems?
the amount of nutrients leaving an intact forest ecosystem is controlled by the plants.
What insights did the study provide regarding human activities and ecosystem processes?
human activities (deforestation) affect ecosystem processes
How are humans skilled at disrupting nutrient cycles?
By adding new materials, often toxic, to ecosystems and moving nutrients around the biosphere.
How do humans intentionally and unintentionally change nutrient distribution?
intentional actions = agriculture
unintentional events = soil runoff (causing eutrophication)
What environmental impacts result from burning fossil fuels?
releases compounds like carbon, sulfur oxides, and nitrogen oxides,
How do these releases of chemicals affect our planet?
atmospheric warming, climate change, ozone depletion, and acid precipitation.
How can humans aid in the recovery of damaged ecosystems?
By initiating/accelerating ecological succession.
What is bioremediation?
It involves using living organisms, like prokaryotes, fungi, or plants, to detoxify or remove toxins from polluted ecosystems.
Provide an example of bioremediation.
Using lichen to absorb uranium, a toxic substance, from polluted environments.
What is biological augmentation?
It involves reintroducing living organisms to restore essential materials to ecosystems.
Name a few living organisms that help restore essential materials to ecosystems:
like bacteria, archaea, or plants
Offer an example of biological augmentation.
Colonizing former pastureland with the original tropical forest in Costa Rica.
