C4.2 Transfer of energy and matter

An ecosystem is a biological community of interacting organisms and their physical environment. It includes both the living (biotic) components, such as plants and animals, and the nonliving (abiotic) components. It is an open system - exchange matter through processes

Closed systems only permit the transfer of energy into and out of them

Open systems like ecosystems exchange matter through processes like nutrient cycling, and energy through photosynthesis and respiration.

Sunlight is the primary energy source for most ecosystems because it is converted into chemical energy by photosynthetic organisms (producers) through the process of photosynthesis

deep-ocean hydrothermal vents, where organisms use chemosynthesis instead of photosynthesis to produce energy from chemical compounds like hydrogen sulfide. Another example is cave ecosystems, which often depend on organic matter (detritus) that washes in or on chemosynthetic bacteria harnessing energy from chemical reactions.

a hierarchical series of organisms each dependent on the next as a source of food.

A producer is an organism that creates its own food or energy. A consumer is an organism that gets its energy by eating plants or animals.

An apex predator, also known as a top predator, is a predator at the top of a food chain, without natural predators of its own.

the flow of energy

See slide 17

A food web illustrates how food chains intertwine in an ecosystem.

Food webs also demonstrate that most organisms consume or are consumed by more than one species, which food chains often do not show.

decomposers and detritivores can then make use of the energy (though they aren't typically included in food chains) that is left over from other species in the food chain for example:

- biomass that is not eaten (e.g. squirrels don't eat the outer coat of an acorn)

- Incomplete digestion-the feces still contain some useful nutrients that aren't digested and absorbed

Detrivores: earthworms, millipedes, and dung beetles
Saprotrophs: Mushroom, fungi that breed on the ground or the dead material.

Organisms that make their own organic carbon compounds from inorganic carbon.

the process where organisms convert inorganic carbon dioxide into organic molecules, such as glucose

Autotrophs must "fix" carbon to convert inorganic atmospheric carbon (like carbon dioxide) into organic molecules, such as glucose, which serve as their own source of energy and building materials

The two ways in which autotrophs produce carbohydrates are photosynthesis and chemosynthesis

Photoautotrophs acquire energy by processing sunlight with nutrients through photosynthesis.

Chemoautotrophs synthesize energy by converting inorganic substances through a chemical reaction called chemosynthesis. Chemoautotrophs get energy from inorganic molecules, such as sulfur or iron, by oxidizing them.

plants, algae, and cyanobacteria.

iron-oxidizing bacteria, sulfur-oxidizing bacteria, and nitrogen-oxidizing bacteria

In iron-oxidizing bacteria, the energy required for carbon fixation is provided by the conversion of (ferrous)Fe2+ into (ferric)Fe3+. These ions are naturally present in some mineral deposits, and when these deposits are exposed to the atmosphere (by mining or natural erosion), they can be used by iron-oxidizing bacteria to produce food.
The energy and electrons released by this reaction power the light-independent reactions (just like in photosynthesis, but without the light-dependent reactions).

Heterotrophs are organisms that obtain their energy and biomass by digesting and absorbing the organic molecules in another organism.

digestion breaks down large organic molecules into smaller, absorbable monomers. Assimilation is the process of absorbing these digested molecules and using them to build or replace the heterotroph's own complex molecules. Synthesis is the creation of new complex carbon compounds (like DNA, lipids, and proteins) using the absorbed monomers, a process that requires energy.

heterotrophs and autotrophs obtain their energy from different sources, but use that energy in oxidizing carbon compounds during cell respiration.

a process used by all organisms to release energy from food molecules, converting it into adenosine triphosphate (ATP), which cells use to power their activities

The level at which a species exists in a food chain

determined by its source of energy. It is identified as a producer (level 1) that makes its own food, a primary consumer (level 2) that eats producers, a secondary consumer (level 3) that eats primary consumers, and so on, with tertiary consumers (level 4) and apex predators at the top

an organism can occupy multiple trophic levels in different food chains, which creates a more complex and stable food web. This is because the organism's position depends on what it eats in a particular chain, and it can be both a primary consumer (herbivore) and a secondary or tertiary consumer (carnivore or omnivore)

The energy in each trophic level of a food chain is communicated using units of energy per unit area per unit time, such as kilojoules per square meter per year ( kJ m-2 yr-1)

An energy pyramid is a graphical depiction of energy flow in a community. The different levels represent different trophic levels, with producers at the bottom. The energy pyramid shape shows how the amount of useful energy that enters each trophic level — chemical energy in the form of food — decreases as it is used by the organisms in that level.

The top trophic level is the smallest because only part of the energy in one trophic level will become part of the next trophic level.

See slide 18

Respiration: Organisms use energy for metabolic processes like movement, growth, and maintaining body temperature. This energy is lost to the environment as heat during cellular respiration, making it unavailable to the next trophic level.

Incomplete consumption and digestion: Not all parts of an organism are eaten, and some parts may be indigestible (like cellulose in plant matter). The energy contained in these parts is not transferred to the consumer and is either egested as waste or broken down by decomposers.

Death and decomposition: Many organisms die from causes other than predation. The energy stored in their biomass is not transferred to the consumer level and is instead utilized by decomposers, such as fungi and bacteria.

10%

The biggest reason for energy losses is that ATP production by cell respiration is only around 40% efficient, so 60% of the energy in glucose is simply lost as heat.

ATP use also involves some heat loss-when ATP is used, most of the energy is captured by the protein to do work, but some is (again) lost as heat.

the amount of energy decreases significantly (by approximately 90%), while matter is transferred but continuously recycled within the ecosystem

Metabolic processes: Organisms use energy for life functions like movement, growth, and reproduction. During this process, energy is released as heat, which cannot be used by the next trophic level.

Incomplete consumption: Not every part of an organism is consumed by the next level, so some energy stored in that material is not transferred.

Incomplete digestion: Organisms can't digest all of the matter they consume, so some energy is lost in waste products.

approximately 10% of the energy from one trophic level is transferred to the next.

the mass of carbon compounds in living organisms. (The weight of organisms, minus the water found in them.)

Gross primary production: the total amount of primary production during a given time period

Net primary production: the stored chemical energy available to consumers

g m-2 yr-1 (grams per square meter per year)

Climatic conditions, such as the amount of sunlight absorbed at different latitudes, temperature, and precipitation.

The accumulation of biomass in heterotrophs by digestion and absorption of organic matter.

Energy is used for metabolic processes: When primary consumers eat producers, they use the energy for their own life functions, such as movement, growth, and reproduction.
Energy is released as heat: A large amount of this energy is lost as heat during cellular respiration, making it unavailable to the next trophic level.
Biomass is not fully transferred: Not all of the ingested organic matter is converted into new biomass; some is respired away and some may not be digested and assimilated, further reducing the amount of energy available for the next level.
The "10% rule": This energy loss is often summarized by the "10% rule," which states that only about 10% of the energy from one trophic level is transferred to the next, with the rest being lost.

a pool is a reservoir or storage location for carbon, such as the atmosphere, oceans, or living organisms.

A sink is a pool that absorbs more carbon than it releases, like plants during photosynthesis.

Flux is the rate and direction of carbon transfer between pools, for example, from the atmosphere to plants via photosynthesis

See slide 19

If Photosynthesis > Cellular Respiration, then the ecosystem acts as a carbon sink (net uptake of carbon)

If Photosynthesis < Cellular Respiration, then the ecosystem acts as a carbon source (net release of carbon)

Carbon sequestration is the process of capturing and storing atmospheric carbon dioxide. It is one method of reducing the amount of carbon dioxide in the atmosphere with the goal of reducing global climate change.

Rapid oxidation of a substance, accompanied by the production of heat and light.

coal, oil, natural gas, wood, peat.

When peat is compressed under sediment, high pressure and heat force out moisture, turning peat into coal.

Oil and natural gas form from the decay of marine organisms on the ocean floor. Sediments deposit on top, creating anoxic conditions that compact and heat the organic matter, forming oil and gas.

See slide 20

The annual fluctuations in the Keeling Curve reflect the balance of photosynthesis and cell respiration through the seasons.
When the curve is rising, CR > PS, and when the curve is falling, PS > CR.

Two major phenomena can be observed in this curve:
Annual fluctuations by season
Long-term increase year-after-year

The overall rise is due to increasing combustion.

using the closed chamber technique, bottomless containers are used to cover the surface and measure changes in CO2 concentration over a given time frame, allowing to quantify surface fluxes.

Chemical elements can be recycled but energy cannot.

Biogeochemical cycles important to living organisms include the water, carbon, nitrogen, phosphorus, and sulfur cycles.

it involves the uptake of inorganic nutrients by autotrophs, transfer to heterotrophs, and finally, nutrient recycling by decomposers.

they break down dead organic matter into simpler inorganic compounds that can be reused by plants and other organisms.