ESS Energy, Biomass and Ecosystems

Trophic levels

• an organism's role in the flow of energy within an ecosystem, signifying a stage in the transfer of energy and nutrients throughout the ecosystem.

Autotrophs/Primary producers

• synthesise their carbon compound from inorganic sources of carbon and other elements

Consumers

• Organisms that gain chemical energy from carbon (organic) compounds obtained from other organisms. 

Herbivores

• consumers that feed primarily on plants and other photosynthetic organisms.

Detritivores

• consumers that feed on dead organic matter, particularly plant detritus and perfom internal digestion

Predators

• consumers that hunt, capture, and kill other animals for food.

Parasites

• consumers that live on or inside a host organism, deriving nutrients at the host's expense.

Saprotrophs

• organisms that feed on decaying organic matter by secreting digestive enzymes and absorbing the resulting nutrients (external digestion)

Scavengers

• consumers that feed on carrion and decomposing organic matter, playing a vital role in cleaning the environment and recycling nutrients.

Decomposers

• Break down dead organic material into simpler organic substances

Food chain

• illustrates the sequential transfer of energy and nutrients among organisms within an ecosystem according to their feeding interactions.

Heterotrophs

• organisms that cannot synthesize their own carbon compounds from inorganic sources. 

Photoautotrophs

• organisms use light energy to drive the process of photosynthesis

Chemoautotrophs

• organisms obtain energy from the oxidation of inorganic molecules, such as hydrogen sulfide (H₂S) or ammonia (NH₃), to synthesize organic compounds.

First Law of Thermodynamics

• energy can be transformed but not created or destroyed.

Second Law of Thermodynamics

• when energy is transformed from one form to another, some of it must be degraded into a less useful form, such as heat and the total entropy of a system and its surroundings always increases.

Photosynthesis

• process that supports life on Earth by transforming light energy from the Sun into chemical energy in the form of glucose. 

Cellular Respiration

• process by which organisms break down glucose to release the stored chemical energy for cellular activities.

Entropy

• measure of the amount of disorder or randomness in a system

Food webs

• show the complexity of trophic relationships in communities and the interconnectedness between food chains

Trophic Efficiency

• percentage of energy that is transferred from one trophic level to the next.

Biomass

• Total mass of the living material present in a particular place or in particular organisms within a given trophic level

Pyramid of Numbers

• diagrammatic representation of the numbers of different organisms at each trophic level in an ecosystem at any one time.

Pyramid of Biomass

• represent the biomass (number of individuals x mass of each individual at each trophic level) at any one time.

Pyramid of Energy or Productivity

• represent the rate of flow of energy through each trophic level of an ecosystem during a fixed time period

Gross Productivity

• total gain in biomass by an organism or trophic level over a specific period. It represents the total amount of energy captured through processes like photosynthesis in producers or the total food intake in consumers.

Net Productivity

• amount of biomass remaining after accounting for losses due to cellular respiration. It represents the energy available for growth, reproduction, and consumption by higher trophic levels.

Primary Productivity

• rate at which primary producers convert inorganic carbon (CO₂) and other elements into organic compounds using an external energy source.

Gross Primary Productivity

• rate at which solar energy is captured in sugar molecules during photosynthesis (energy captured per unit area per unit time).

Net Primary Productivity

• amount of biomass remaining after energy losses due to cellular respiration in primary producers.

Secondary Productivity

• rate at which consumers convert the chemical energy in their food into their biomass. 

Gross Secondary Productivity

• the amount of biomass assimilated or biomass eaten after fecal loss

Net Secondary Productivity

• rate at which consumers produce biomass or energy per unit area per unit time remaining after accounting for respiratory losses​

Maximum Sustainable Yields

• largest yield (catch or harvest) that can be taken from a species' stock over an indefinite period under constant environmental conditions.

Ecological Efficiency

• ratio of energy transferred from one trophic level to the next relative to the energy received by the lower trophic level

Non-Biodegradable Polluants

• substances that do not break down naturally in the environment. They resist decomposition by natural processes and, as a result, can persist for long periods. Cause significant ecological harm through the processes of bioaccumulation and biomagnification 

Polychlorinated Biphenyls (PCBs)

• Industrial chemicals used in electrical equipment, which are highly persistent and toxic.

Bioaccumulation

• gradual build-up of non-biodegradable pollutants in an organism or trophic level over time. This occurs because these pollutants are absorbed faster than they are excreted or metabolized. As a result, their concentration increases within the individual organism.

Biomagnification

• non-biodegradable pollutants accumulating in organisms over time – a process, leading to higher concentrations in the predator's body.

Microplastics

• tiny plastic fragments or particles less than 5 millimeters in diameter.