Pre-IB Bio Chapter 54

Ecosystems, Energy, and Matter

Ecosystem

All of the organisms living in a community as well as the abiotic factors in which they interact

Ecosystems can range from a _________, such as an aquarium to a _________ area such as a lake or forest

Microcosm, large

Two main processes in an ecosystem regardless of size:

Energy flow, chemical/nutrient/matter cycling

Energy _______ through ecosystems

Flows

Main 4 nutrients that cycle covered in class

Nitrogen, Phosphorus, Carbon, Water

Ecosystem ecologists view ecosystems as ________ of energy and ________ of matter

Transformers, processors

The laws of physics and chemistry apply to ecosystems particularly in regard to…

The flow of energy

Energy conversions are not completely efficient because…

Energy is “lost” as heat, and due to cellular respiration (Breaks down sugars to make Adenosine Triphosphate aka ATP).

All organisms (not including viruses) undergo

Cellular respiration

Energy is never lost, instead it’s…

Transformed

Trophic relationship represents when…

Energy and nutrients pass from primary producers (autotrophs) to primary consumers (herbivores) and then to secondary consumers (carnivores) that eat other carnivores (tertiary consumers).

Two kinds of decomposers

Detritivores and saprotrophs

Decomposers are consumers that obtain their energy from…

Detritus

Examples of detritus (DOM)

Remains of dead organisms, feces, fallen leaves, wood.

Detritivores:

Ingests (internal) then digests non-living organic matter, has a mouth. (Think the two i’s in the word represent ingest and internal).

Examples of detritivore

Worms, dung beatles, slugs, etc.

Saprotrophs:

Heterotrophs that obtain organic nutrients from dead organisms via external ingestion/digestion (S=Saprotroph=Secrete)

Examples of saprotrophs

Mushrooms, bacteria, etc.

Decomposers form a link between…

Primary producers and consumers in an ecosystem

How many trophic levels do decomposers connect?

All

Real job of decomposers

Cycle nutrients

Detritovores decompose ___________ matater and transfer _________ elements in _________ forms to ______________ reservoirs such as soil, ________, and air

Organic, chemical, inorganic, abiotic, water

Decomposers play a key role in _________ ___________ within an ecosystem

Nutrient cycling

Primary production in an ecosystem is…

The amount of light energy converted to chemical energy by autotrophs during a given time period

Ecosystem energy budgets:

The extent of photosynthetic production sets the sending limit for the energy budget of the entire ecosystem

The global energy budget:

The amount of solar radiation reaching the surface of the Earth limits the photosynthetic output of ecosystems

Gross Primary Production (GGP)

The amount of light energy that is converted to chemical energy by photosynthesis.

GPP=NPP+R, where NPP=Net Primary Production, and R=Respiration (E used for Cellular respiration)

Not all of the energy is stored as organic material…

Some is used for plants own metabolic reactions — Cellular Respiration

Net Primary Production (NPP)

Gross Primary Production minus the energy used by primary producers for cellular respiration.

NPP=GPP-R where GPP=Gross Primary Production and R=Respiration (E used for cellular respiration)

Net Primary Production represents…

The storage of chemical energy available to consumers in the ecosystem

Ecosystems vary considerably in their NPP contribution to…

The total NPP on Earth.

Terrestrial ecosystems contribute about __________ of global NPP and marine ecosystems about ____________

2/3, 1/3

In marine and freshwater ecosystems, both _______ and __________ are important in controlling primary production.

Light, nutrients

The depth of light penetration affects production throughout the _________ zone of an ocean or lake

Photic

What limits primary production more than light in ecosystems?

Nutrients

Limit nutrient

The element that must be added in order for production to increase in a particular area

Nutrients that most often limit marine production:

Nitrogen and phosphorus

Why do we need Nitrogen?

Necessary to make amino acids (Proteins)

Necessary to make nucleic acids (Makes up DNA and RNA)

Necessary for many metabolic processes (Photosynthesis)

All organisms are made up of proteins, DNA, and RNA

Why do we need Phosphorus?

Major component of Nucleic acids (Makes up DNA and RNA)

Makes up the phospholipid bilayer (Plasma membrane → surrounds cells and mitigates what enters and exits the cell)

Component of ATP (Energy currency)

Addition of large amounts of ________ to lakes has a wide range of ecological impacts

Nitrogen

In some areas chemical runoff has caused _____________ of lakes, which can lead to the eventual loss of most fish species from the lakes

Eutrophication

Eutrophication:

Nutrients (phosphorus and nitrogen) become highly concentrated in a body of water leading to high growth of organisms (algae)

The two kinds of eutrophication

Oligotrophic and Eutrophic

Characteristics of Oligotrophic:

Lots of Oxygen, few nutrients, clear water

Characteristics of Eutrophic:

Low oxygen, lots of nutrients, murky green lake — Think chemical runoff leads to Eutrophication, leads to murky green water

Cultural Eutrophication:

Caused by humans (sewage) or addition to fertilizer

If eutrophic lakes have lots of photosynthetic algae in them (produced by Oxygen) — why does the lake have low oxygen?

Decomposers (saprotrophic bacteria) perform abiotic respiration to break down algae

In terrestrial and aquatic ecosystems, climatic factors such as temperature and moisture affect _________ ___________ on a large geographic scale

Primary productivity

Measurement of contrast between wet and dry climate

Actual evapotranspiration

Actual evapotranspiration:

Amount of water that annually changes from liquid to water vapor in a landscape.

Actual evapotranspiration is related to…

Net Primary Production (NPP)

On a local scale, _______ are often the limiting factor in primary production

Nutrients

Only about _______ of the energy in a leaf is used for _________ production

1/6, secondary

Production efficiency of an organism

The fraction of energy stored in food that is not used for respiration

Trophic efficiency

The percentage of production transferred from one trophic level to the next — Usually ranges from 5%-20%, in this class 10%

Loss of energy with each transfer in a food chain can be represented by

A pyramid of net production

Ecological consequence of low trophic efficiencies can be represented in a…

Biomass pyramid

Most biomass pyramids show a sharp ________ at successively _________ trophic levels

Decrease, higher

A pyramid of numbers represents the number of…

Individual organisms in each trophic level

Eating meat is a relatively _______ way of tapping photosynthetic production

Inefficient

Worldwide agriculture could successfully feed many more people if all humans ate only ______ _______ (Would help our carbon footprint)

Plant material

According to the green world hypothesis, terrestrial ________ consume relatively _______ plant biomass because they are held in check by a variety of factors

Herbivores, little

Most terrestrial ecosystems have _______ standing crops despite the large numbers of _________

Large, herbivores

Factors that keep herbivores in check according to the green world hypothesis

Plants have defenses against herbivores

Nutrients (not energy supply) usually limit herbivores

Abiotic factors limit herbivores

Infraspecific competition can limit herbivore numbers

Interspecific interactions check herbivore densities

Predation keeps herbivores in check

Life on Earth depends on the ______ of essential chemical elements

Recycling

Nutrient circuits that cycle matter through an ecosystem involve both biotic and abiotic components and are often called…

Biogeochemical cycles

All main nutrients cycle globally via gaseous forms except for…

Phosphorus — cycles on a local level

All elements cycle between…

Organic and inorganic reservoirs

Another word for the water cycle

Hydrologic cycle

The water cycle is driven by…

Solar energy

Why do we need water?

Necessary for metabolic processes such as photosynthesis and cellular respiration

The carbon cycle reflects the reciprocal processes of…

Photosynthesis and cellular respiration

Photosynthesis

Plants take in CO2 to make saccharides (sugars)

Organisms put CO2 out into the atmosphere via

Respiration

Why do we need carbon?

Necessary building block for organic molecules — Can form 4 covalent bonds, is in most organic molecules, forms long chains.

Are all molecules that contain carbon organic?

No, carbon alone isn’t organic

Equation for Photosynthesis

6CO2+6H2O →(Sunlight) C6H12O6+O2, think Devil=666

Equation for Cellular Respiration

C6H12O6+6O2 → 6CO2+6H2O+38ATP

Sink

Any process that absorbs carbon from atmosphere more than it releases

Source

Any process that releases more carbon than it absorbs

Flux

Process by which carbon in cycled

Egestion

Act of discharging undigested or waste material from a cell or organism

What percentage of the atmosphere is Nitrogen?

78%

The nitrogen cycle involves local cycles between organisms and…

Soil or water

Some plants (EX: Soybeans) have a ________ relationship with bacteria

Symbiotic

How is a Nitrogen relationship symbiotic?

Bacteria gets a home in plant root system and plants get Nitrogen that is fixed by bacteria

Nitrogen fixation

Conversion of nitrogen gas (N2) into nitrate (NO3) — Bacteria are responsible

Ammonification

When plants and animals excrete waste or die, bacteria convert nitrogen into ammonia

Nitrification

Bacteria convert Nitrogen into Nitrite (Two step process, 1. Some bacteria convert ammonia into nitrites, 2. Then others convert nitrites into nitrates)

Denitrification

Some bacteria convert ammonia, nitrite and nitrates back into nitrogen gas (Denitrification), this returns nitrogen gas to the atmosphere

Why is the phosphorus cycle localized?

No phosphorus in the atmosphere

Short term phosphorus cycle

Soil → Producers → Consumers, when organisms die or produce waste decomposers return phosphorus to soil

Long term phosphorus cycle

Weathering of rock and soil that contains phosphorus will slowly add phosphorus to the soil

What decomposers play a key role in the general pattern of chemical recycling?

Saprotrophs (fungi)

Rates at which nutrients cycle in different ecosystems are extremely __________, mostly as a result of differences in rates of _____________

Variable, decomposers

In addition to transporting nutrients from one location to another, ________ have added entirely new materials, some of them ____________ to ecosystems.

Humans, toxic

Agriculture constantly removes _______ from ecosystems that would ordinarily be _______ back into the soil

Nutrients, cycled

___________ is the main nutrient lost through agriculture

Nitrogen

Industrially produced fertilizer is typically used to replace lost __________

Nitrogen

Critical load:

Maximum amount of nutrient or pollutant an ecosystem can receive without harmful effects