2.2 Improved

Energy

The ability to do work. In ecosystems, it flows from one location to another (e.g., in food chains) and is transformed between forms (e.g., light to chemical).

Matter

The physical substance of an ecosystem, composed of organic (carbon-based) and inorganic nutrients. It is continuously cycled and transformed via chemical reactions.

1st Law of Thermodynamics

The principle that energy can be transformed from one form to another but cannot be created or destroyed. Also known as the Law of Conservation of Energy.

2nd Law of Thermodynamics

The principle that in any energy conversion, some energy is lost to a less useful form (usually heat), increasing the system's entropy (disorder). This explains why energy transfers in ecosystems are inefficient.

Photosynthesis

The process by which autotrophs use sunlight to convert carbon dioxide and water into chemical energy as glucose. Light energy is converted to chemical energy.

Cellular Respiration

The process in all organisms that releases stored chemical energy from glucose to power life functions. A significant amount of energy is lost as heat during this process.

Autotroph

An organism that produces its own food from inorganic sources, usually via photosynthesis. Examples include plants, algae, and photosynthetic bacteria.

Consumer

A heterotrophic organism that obtains energy by feeding on other organisms, transferring energy through trophic levels and regulating populations.

Herbivore

An animal that consumes plants for energy. Example: Deer eating grass.

Predator

An animal that hunts, kills, and consumes other animals. Example: Lions hunting zebras.

Parasite

An organism that lives on or in a host, deriving nutrients at the host's expense. Example: Tapeworms.

Scavenger

An animal that consumes dead organisms that it did not kill. Example: Vultures.

Detritivore

An organism that consumes dead organic material and breaks it into smaller particles. Example: Earthworms.

Saprotroph

An organism that feeds on nonliving organic matter by secreting digestive enzymes and absorbing the nutrients. Example: Fungi.

Decomposer

A microorganism that breaks down dead organic material into simpler substances, recycling nutrients back into the ecosystem. Example: Bacteria.

Trophic Level

The position an organism occupies in a food chain. Producers are Level 1, herbivores are Level 2, and so on.

Food Chain

A simple, linear model showing the flow of matter and energy from one organism to the next. Example: Phytoplankton → Zooplankton → Small Fish → Large Fish.

Food Web

A complex model of interconnected feeding relationships in a community. Their complexity increases an ecosystem's resilience.

Biomass

The total mass of dry organic matter of an organism or population in a given area, typically measured in g/m².

Productivity

The rate at which biomass is generated in an area over time, measured in units like kJ/m²/year or g/m²/year. High rates indicate more available energy.

Gross Productivity (GP)

The total amount of biomass gained by an organism or trophic level before any deductions.

Net Productivity (NP)

The amount of biomass remaining after losses from respiration (R). This is the energy available to the next trophic level. Formula: NP = GP - R.

Energy Loss Between Trophic Levels

Energy transfer is inefficient (~10% rule). Losses occur because not all biomass is consumed; not all consumed matter is absorbed (lost as waste); and a large portion is lost as heat from cellular respiration.

Maximum Sustainable Yield (MSY)

The largest yield that can be taken from a species' stock over time without depleting it. It is equivalent to the net productivity of that population.

Pyramid of Numbers

A diagram showing the total count of individual organisms at each trophic level. Its limitation is that it can be inverted when the producer is very large (e.g., one oak tree), making it misleading.

Pyramid of Biomass

A diagram showing the total dry mass (standing crop) at each trophic level. Its limitation is that it's a snapshot in time and can be inverted in certain aquatic ecosystems.

Pyramid of Energy

A diagram showing the rate of energy flow through each trophic level over time. It is measured in units like kJ m⁻² yr⁻¹ and is always upright due to the 2nd Law of Thermodynamics.

Pollutant

A substance or energy introduced into the environment that has undesired effects. Can be biodegradable or non-biodegradable.

Bioaccumulation

The build-up of a persistent, non-biodegradable toxin within the tissues of a single organism over its lifetime.

Biomagnification

The increasing concentration of a persistent, non-biodegradable toxin at successively higher levels in a food chain.

Microplastics

Tiny plastic particles (<5mm) that can act as vectors for non-biodegradable pollutants by absorbing them and transporting them into organisms that ingest the plastic.

Human Impacts on Energy/Matter Flows

Activities like burning fossil fuels, deforestation, and agriculture disrupt natural cycles. They can lead to loss of biomass, disrupt food webs, and reduce an ecosystem's capacity for photosynthesis.

The greenhouse effect

A natural process where solar energy warms Earth's surface, and certain atmospheric gases (CO₂, CH₄, water vapor) trap some re-emitted heat. Without this, Earth's temperature would be about –18°C.