Environmental Systems and Societies: Key Concepts

Posted on Mar 19, 2025 in Biology

Definitions: Test 1

  • Open system: A system that exchanges energy and matter with its surroundings.
  • Closed system: A system that exchanges only energy with its surroundings.
  • Isolated system: A system that doesn’t exchange anything with its surroundings.
  • Transfer: Movement of energy or matter from one place to another.
  • Transformation: When energy changes from one form to another.
  • 1st Law of Thermodynamics: Energy cannot be created or destroyed, only transformed.
  • 2nd Law of Thermodynamics: Entropy increases in isolated systems.
  • Unstable equilibrium: Once the equilibrium is lost, it is very difficult to return to the initial position.
  • Steady-state equilibrium: It is very difficult to destabilize.
  • Negative feedback: Brings the system back to equilibrium.
  • Neutral equilibrium: Nearly impossible to destabilize.
  • Negative feedback loop: Tends to bring a system back to equilibrium.
  • Positive feedback loop: Amplifies change, moving a system away from its equilibrium.
  • Tipping point: The point where equilibrium is lost.
  • Technocentrism: The belief that technology can provide solutions to all environmental problems.
  • Ecocentrism: Puts ecology and nature as equal to humanity.
  • Anthropocentrism: The belief that humans should sustainably manage the global system.
  • Sustainability: The use and management of resources that allows full natural replacement of the resources exploited and full recovery of the ecosystems.
  • Sustainable development: Development that meets the needs of the present population without compromising the ability of future generations to meet their own needs.
  • Natural capital: Resources that are managed to provide a sustainable natural income from goods and services.
  • Natural income: The portion of natural capital produced.
  • Modern Environmental Movement: Seeks sustainable development through changes in policy and individual behavior.
  • Model: A simplification of reality in order to understand how systems work and how they respond to changes.

Model Strengths

  • Allows us to preview changes.
  • Simplifies complex systems for easy understanding.

Model Weaknesses

  • May oversimplify a complex system, leading to inaccurate conclusions.
  • Subjective point of view.

Pollution

The addition of a substance or an agent to the environment through human activity.

Types of Pollution

  • Organic/Inorganic (e.g., pesticides)
  • Light, sound
  • Invasive species: Non-native species that have been introduced.

Types of Origins

  • Point source: Single and identifiable source (e.g., water pollution) – easy to stop.
  • Non-Point source: No identifiable source (e.g., runoff from agriculture).

Environmental Impact Assessment (EIA)

An EIA is needed when a change in an environment is proposed. It considers the environmental effects.

Quantitative Factors

  • Biodiversity: The higher the biodiversity, the higher the probability that the environment will be changed.
  • Pollution
  • Climate Change

EIA: A process of evaluating the likely environmental impacts of a proposed project or development, taking into account inter-related socio-economic, cultural, and human-health impacts.

Baseline studies are conducted before a development project is undertaken.

Pros of EIA

  • Legally obligatory.
  • Necessary to know the impacts on the environment.
  • Also considers the effect on humans.

Cons of EIA

  • No rule on which impact needs to be included, which can be manipulated.
  • Lack of information on the effects in the future.

Interactions Between Organisms

  • Herbivory: Primary consumers feed only on plant materials.
  • Predation: A consumer kills and eats another consumer. Predators have evolved to kill their prey.

Photosynthesis

The process by which green plants and some other organisms use sunlight to synthesize nutrients from carbon dioxide and water.

Photosynthesis as an Open System

  • Inputs:
    • Water
    • Carbon dioxide
    • Light
  • Outputs:
    • Oxygen
    • Chemicals
    • Heat
    • Glucose

Definitions: Chapter 2

  • Ecological footprint: A measure of the amount of land that would be needed to provide the resources and assimilate the waste of one person.
  • Organism: An individual living thing that can exist on its own.
  • Population: A group of organisms of the same species living in the same area at the same time and capable of interbreeding.
  • Species: A group of organisms capable of interbreeding and producing fertile young. Animals coming from two different species are infertile.
  • Population density: The number of individuals in an area.
  • Carrying capacity: The maximum number of individuals that an ecosystem can support.
  • Photosynthesis: The process by which plants transform light energy into chemical energy.
  • Respiration: A process in living organisms involving the production of energy, with the intake of oxygen and release of carbon dioxide from the breakdown of complex organic substances.
  • Ecology: The scientific study of interactions between organisms and their environments, focusing on energy transfer.
  • Symbiosis: A close and often long-term relationship between two or more species.
    • Parasitism: A relationship between species, where one organism, the parasite, lives on or in another organism.
    • Mutualism: An interaction between individuals of different species, the result of which is beneficial.
  • Biotic factors: Resulting from living organisms (e.g., disease agents, predation, competition).
  • Abiotic factors: Non-living factors of the environment that affect living organisms and the functioning of ecosystems (e.g., sunlight, water, pH, wind).
  • Habitat: The natural environment of an organism.
  • Niche: The role and position a species has in its environment.
    • Fundamental Niche: The full range of conditions and resources in which a species could survive and reproduce.
    • Realized niche: The actual conditions and resources in which a species exists due to biotic interactions.

Factors that Affect Population Growth

  • Food
  • Predators
  • Disease
  • Natality
  • Exponential population growth: When resources are unlimited – J-shaped curve.
  • Logistic growth: Population expansion decreases as resources become scarce, resulting in an S-shaped curve.
  • Competition: The activity or condition of striving to gain or win something by defeating or establishing superiority over others.
  • Community: All the populations of different species that live in the same place at the same time.
  • Ecosystem: A biological community of interacting organisms and their physical environment.
  • Trophic level: The position that an organism or a group of organisms occupies in a food chain.
  • Autotroph: Typically plants or algae, produce their own food using photosynthesis and form the first trophic level in the food chain.
    • Phototrophs: Organisms that use energy from sunlight to synthesize organic compounds for nutrition.
    • Chemoautotrophs: Bacteria which make their own food from other simple compounds.
  • Heterotrophs: Cannot produce their own food directly from sunlight. They require energy stored in complex molecules.
    • Herbivore
    • Carnivore
    • Omnivore

Food Chains

A sequence that shows how each individual feeds on the organism below it in the chain.

  • They always start with a producer.
  • The source of energy is always the sun.
  • Consumers eat plants, animals, etc.

Ranking Consumers

  • Producers: Make their own food.
  • Secondary consumers: Eat primary consumers.
  • Tertiary consumers: Eat secondary consumers.

Food Web

The natural interconnection of food chains and a graphical representation of what-eats-what in an ecological community.

Ecological Pyramids

Differences between the amounts of living materials stored at each trophic level of a food chain. They give an idea of what feeds what.

Pyramid of Numbers

Shows the number of organisms at each trophic level of the food chain at one time. The length of each bar gives a measure of the relative numbers. Producers are at the bottom, with the greatest number.

Advantages
  • Simple, easy method of giving an overview.
  • Good for comparing changes in population over time.
Disadvantages
  • Numbers can be too great to represent accurately.
  • Some pyramids are inverted.

Biomass

The total dry mass of organic matter in organisms or ecosystems. We can see how productive an ecosystem is and compare it with others.

How Biomass is Collected

  1. Collect samples and estimate the number of species in the ecosystem.
  2. Sort into trophic levels.
  3. Dry.
  4. Measure the mass of each trophic level.

Pyramids of Biomass

Represents the storage of each trophic level.

Disadvantages
  • Impossible to measure biomass exactly.
  • Organisms must be killed to measure dry mass.
  • Time of year affects the results.

Pyramid of Productivity

Shows the actual transfers and allows for the rate of production. Pyramids are not inverted; energy from solar radiation can be added.

Disadvantages
  • Difficult to collect energy data.
  • Difficult to assign species to a particular trophic level (omnivores).
  • Bioaccumulation: The accumulation of a pollutant within an organism or trophic level because it cannot be broken down.
  • Biomagnification: An increase in the concentration of a pollutant along a food chain.
  • Producers: Organisms capable of producing complex organic compounds from simple inorganic molecules through the process of photosynthesis (using light energy) or through chemical energy. They are the first level in the food chain.