tags: 
  - bio
topic: Biodiversity
date: 2023-11-20

Introduction

key concepts

The primary source of energy is sunlight, from the sun.
Primary level producers (otherwise known as plants) are capable of taking in sunlight, converting it to usable chemical energy in photosynthesis for the rest of the ecosystem.
Trophic level:: The position of an organism in the food chain.
Only about 10% of the energy originating from a trophic level is transferred to the next one.
While energy moves through trophic levels and eventually dissipates as heat, biogeochemical cycles refer to the movement of actual chemical elements.
- Examples of biogeochemical cycles:: Water, carbon, nitrogen and phosphorus.

Energy Transfer Between Organisms

Trophic 'pyramids' are shown with the primary producers on the bottom, and the highest predator at the top.
Each trophic level receives required energy from the level below it; however, a considerable amount is lost between levels.
- It is estimated that only 10% of energy from the previous trophic level is received by the next one up.
- This is attributed to natural loss of energy as per maintenance of life processes; e.g aerobic respiration, body heat.
  - Only 1% of energy that is received by the Earth is ever used by plants.

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Matter in ecosystems typically cycles through the biotic environment (organisms) to the abiotic environment (non-living parts of an ecosystem).
Organisms take in inorganic nutrients from the environment, using them to create organic molecules (as part of photosynthesis) and hence new biomass. Once they die and decompose, organic material is broken down into inorganic substances ready to be taken in again.

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Water is taken in by plants from soil and ingested by animals from surface sources.
Evaporation - water from surface sources forms into water vapour.
Transpiration - subset of evaporation, but from plant leaves.
Condensation - water vapour cools to form actual water.
Precipitation - water falls as rain, hail or snow.
Melting - snow and ice melt into liquid water.
Run-off water flows through rivers/creeks etc to the ocean.
Leaching - water that has entered soil 'leaches' underground.

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Carbon is exchanged through the four spheres (air, ground, water, living things)
Atmosphere - (air); present as carbon dioxide as a byproduct of cellular respiration.
Hydrosphere - (water); present as bicarbonates and calcium carbonate in corals and shells.
Biosphere - (living things); present as carbohydrates, lipids, and other organic carbon compounds.
Lithosphere - (ground); detritus (dead organic material).

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Nitrogen gas, which composes about 78% of the Earth's atmosphere, is chemically inert and has to be processed by nitrogen fixing bacteria before being used.

Nitrogen fixation: nitrogen gas is fixed by bacteria, converting it into ammonia.
Ammonification: alternatively, decomposers break down organic organisms to also release ammonia.
Nitrification: converts the ammonia (either from atmosphere or decomposers) into nitrogen dioxide.
Nitrification: and eventually to nitrogen trioxide, where it can be assimilated by plants
Denitrification: or denitrified, returning it to atmospheric nitrogen (inert nitrogen gas).

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As a primary component in energy storage (ATP) and membranes (e.g phospholipids), a phosphorous cycle does exist for transmission between living and dead organisms.
Phosphorous compounds are typically solid; erosion is what returns this phosphate to the environment.
Phosphates are typically used as fertiliser; hence, excess fertiliser usage can result in runoff in water sources.
This eventually forms sediment.
Additionally, decomposers can also release phosphates (as well as nitrogen and carbon dioxide)