Ecosystems

  • Definition: An ecosystem is the combination of all living (biotic) and non-living (abiotic) factors interacting in a habitat.

  • The environment within an ecosystem comprises all biotic and abiotic factors.

  • The distribution of different ecosystems is due to variation in biotic and abiotic factors found within each area.

Types of Ecosystems

  • In both terrestrial and aquatic systems, biotic and abiotic components significantly influence species diversity.

  • Terrestrial environments include desert, grassland, shrubland, woodland, temperate forest and tropical rainforest.

  • Aquatic environments are either marine (saltwater) or freshwater.

  • Two main aquatic environments: saltwater/marine (e.g., coral reefs) and freshwater (e.g., lakes).

  • The main factors influencing organisms in aquatic environments include salinity, light availability, and pressure; the level of water salinity influences the main types of organisms found.

Specific Terrestrial Descriptions

  • Desert or arid zone

  • Shrubland

  • Open woodland

  • Sclerophyll forest

  • Temperate rainforest

  • Tropical rainforest

Selection Pressures in an Ecosystem

  • Abiotic factors: temperature, light, water availability; additional abiotic aspects include rainfall and gas concentrations in water.

  • Biotic factors: competition for resources, predators, and availability of prey/food, mates, disease-causing organisms.

  • Selection pressures drive natural selection: those with traits that help them survive and reproduce are favoured.

  • If trait variation has a genetic basis, these variations are passed to offspring, leading to generation-to-generation changes.

  • Over several generations, the surviving population becomes adapted to the environment.

Abiotic vs Biotic Selection Pressures (Overview)

  • Abiotic selection pressures include non-living factors such as temperature, light, water availability, rainfall, salinity, and gas concentrations in water.

  • Biotic selection pressures include living factors such as availability of food, number of competitors, number of mates, number of predators, and the diversity of disease-causing organisms.

Abundance & Distribution of a Species

  • Population size is a key feature affecting survival and adaptation.

  • Distribution describes where a species is found; abundance indicates how many individuals exist across the ecosystem.

  • Abiotic and biotic pressures influence distribution and abundance by causing fluctuations or movement; populations may occupy certain areas and not others due to available resources.

How Environment Affects Abundance/Distribution (Key Points)

  • Abiotic factors in terrestrial settings commonly affect abundance/distribution: temperature range, light, and water availability.

  • In aquatic settings, salinity is a key abiotic pressure.

  • Biotic pressures include food availability, competitors, mates, predators, and disease-causing organisms.

Summary of Ecosystem Types

  • Terrestrial examples: desert, grassland, shrubland, woodland, temperate forest, tropical rainforest.

  • Aquatic examples: coral reefs, rivers, lakes, oceans.

  • Abiotic selection pressures: non-living components (e.g., temperature, salinity, dissolved gases).

  • Biotic selection pressures: living components (e.g., availability of food, mates, predators, competitors).

Inquiry Question (From Learning Intention)

  • How do environmental pressures promote a change in species diversity and abundance?

Revision/Practice Questions

  • What is meant by selection pressure?

  • Give examples of a biotic selection pressure in an ecosystem.

  • Explain how adaptations are passed from one generation to the next.

  • Predict which factors may act as selection pressures in the future.

Relationships to Prior Learning and Real-World Relevance

  • Connects to foundational ideas: ecosystems consist of interacting biotic/abiotic components, resources create competition, natural selection drives adaptation, and population dynamics govern biodiversity.

  • Real-world relevance: understanding how environmental pressures shape biodiversity informs conservation, habitat management, and responses to climate change.

Note: The transcript mentions "Stock.co" and some formatting from the PowerPoint; such items are not essential to the conceptual notes, but are acknowledged as part of the source material.

No numerical values or explicit formulas are provided in the transcript. If needed, numerical analysis could be added later when data is provided.