Organisms and their environment

Define the key ecological terms: habitat, population, community, ecosystem, and niche.
Explain how both living (biotic) organisms and the non-living (abiotic) environment influence each other within an ecosystem.
Define bioaccumulation and biomagnification.

Habitat: An organism's home or specific living place (e.g., a woodland for a squirrel).
Population: All members of one species living in a particular habitat (e.g., all robins in a garden).
Community: All the different populations of organisms (various species) living and interacting in the same habitat.
Ecosystem: The community of organisms and the non-living (abiotic) parts of their environment (like soil, water, sunlight), including all their interactions.
Niche: An organism's specific role or "job" within its ecosystem, including what it eats, what eats it, and how it uses resources.

Organisms Affect Their Environment:
- Living (biotic) things actively change their surroundings.
- For instance, plants release oxygen, their roots stabilise soil, and their decomposing leaves enrich it.
- Animals like earthworms aerate soil, while beavers build dams, creating new wetland habitats.
- Human activities, such as farming and building, also cause significant environmental changes.
Environment Affects Organisms:
- The non-living (abiotic) environment strongly influences organisms.
- Temperature: Affects activity levels and survival.
- Water Availability: Essential for life, dictating which species can thrive.
- Light Intensity: Crucial for plants (photosynthesis) and influences animal behaviour.
- Soil Factors: pH and nutrient content determine plant growth, which in turn supports animal life.

Human activities can release harmful toxic materials (pollutants like pesticides or heavy metals like mercury) into ecosystems.
These can become increasingly dangerous as they move through food chains.
- Bioaccumulation: This is when a toxin builds up in an individual organism's body over its lifetime because it's absorbed faster than it can be removed or broken down.
- Biomagnification: This describes how the concentration of these toxins increases at each level of a food chain.
  - Producers (e.g., algae) might absorb small amounts of a toxin.
  - Primary consumers (e.g., small fish) eat many producers, concentrating the toxin in their bodies.
  - This concentration continues to increase up the food chain, so top predators (like large birds or mammals, including humans) can accumulate very high, harmful levels of the toxin.
A well-known example is the pesticide DDT:
- Low environmental levels of DDT biomagnified up food chains, causing birds of prey to lay thin-shelled eggs, which led to population declines.

Habitat: The specific place or environment where an organism lives.
Population: All the individuals of a single species living together in a particular habitat.
Community: All the different populations of organisms (different species) living and interacting with each other in a habitat.
Ecosystem: All the living organisms (the community) interacting with the non-living (abiotic) parts of their environment.
Niche: The specific role or position an organism has within its ecosystem, including how it uses resources and interacts with others.
Biotic: Relating to living organisms.
Abiotic: Relating to the non-living parts of the environment (e.g., temperature, water, light, soil).
Bioaccumulation: The buildup of a toxic substance in the tissues of an individual organism over its lifetime.
Biomagnification: The increasing concentration of a toxic substance in organisms at successively higher levels in a food chain.

Investigate a local ecosystem (such as a garden, park, pond, or woodland) and attempt to identify different populations, describe the community, the habitat, and list key biotic and abiotic factors you observe.
Research current environmental issues related to biomagnification, such as mercury contamination in fish or the movement of microplastics through marine food chains, and discuss their impact on wildlife.