Unit 1: The Living World

1.1 Ecosystems

Objectives and Essential Knowledge

• Learning Objective: Explain how the availability of resources influences species interactions.

  • ERT-1.A.1: In a predator-prey relationship, the predator is an organism that eats another organism (the prey).

  • ERT-1.A.2: Symbiosis is a close and long-term interaction between two species in an ecosystem

    • Types of symbiosis:

      • Mutualism: both organisms benefit.

      • Commensalism: one organism benefits, the other is neither helped nor harmed.

      • Parasitism: one organism benefits at the expense of the other.

  • ERT-1.A.3: Competition occurs within or between species due to limited resources. Resource partitioning can help reduce competitive pressure.

Ecosystem Basics

• Definitions:

  • Individual: one organism (e.g., elk).

  • Population (Pop.): group of individuals of the same species (e.g., elk herd).

  • Community: all living organisms in a specific area.

  • Ecosystem: all living and nonliving components in an area (plants, animals, rocks, soil, water, air).

  • Biome: regional group of ecosystems defined by climate.

1.2 Terrestrial Biomes

Objectives and Essential Knowledge

• ERT-1.B: Describe global distribution and environmental aspects of terrestrial biomes.

  • Includes major biomes: taiga, temperate rainforests, temperate seasonal forests, tropical rainforests, shrubland, temperate grassland, savanna, desert, tundra.

  • Factors affecting distribution include climate, geography, latitude, altitude, nutrient availability, and soil.

Characteristics of Biomes

• Biomes are uniquely adapted communities based on annual temperature and precipitation patterns. Examples include:

  • Deserts: plants adapted for water retention (e.g., camels, cacti).

  • Grasslands: plants have energy-storing roots for quick recovery from fires.

1.3 Aquatic Biomes

Objectives and Essential Knowledge

• ERT-1.C: Describe distribution and environmental aspects of aquatic biomes.

  • Freshwater biomes: streams, rivers, ponds, lakes (vital for drinking water).

  • Marine biomes: oceans, coral reefs, marshes, estuaries (important for oxygen production).

Characteristics of Aquatic Biomes

• Key factors influencing ecosystem dynamics:

  • Depth, temperature, salinity, and flow of water.

  • Freshwater rivers have high oxygen levels due to flow, while lakes have stratified zones (littoral, limnetic, profundal, benthic).

  • Wetlands: areas with water-saturated soil support unique plant communities and help mitigate floods, recharge groundwater, and filter pollutants.

1.4 Carbon Cycle

Objectives and Essential Knowledge

• ERT-1.D: Explain interactions in the carbon cycle.

  • Carbon cycles through various reservoirs (oceans, plants, soil, atmosphere).

  • Carbon sources (release carbon) include fossil fuel combustion; sinks (store carbon) include oceans and forests.

Key Processes

• Photosynthesis and cellular respiration transfer carbon between living organisms and the atmosphere. Organic matter decomposition stores carbon over time, while fossil fuel combustion releases previously stored carbon rapidly.

1.5 Nitrogen Cycle

Objectives and Essential Knowledge

• ERT-1.E: Explain interactions in the nitrogen cycle.

  • Nitrogen fixation converts atmospheric nitrogen into ammonia, usable by plants.

  • Major reservoirs include the atmosphere, soil, and living organisms.

Key Processes

• Key roles of soil bacteria in processes like nitrification, ammonification, assimilation, and denitrification. Human impacts, particularly from fertilizers, can lead to eutrophication and pollution.

1.6 Phosphorus Cycle

Objectives and Essential Knowledge

• ERT-1.F: Explain phosphorus cycle interactions.

  • Major reservoirs include rocks and sediments, and phosphorus does not have a gas phase.

  • Phosphorus is a limiting nutrient, affecting ecosystem productivity.

1.7 Hydrologic Cycle

Objectives and Essential Knowledge

• ERT-1.G: Explain the hydrologic cycle's processes.

  • Powered by solar energy, the cycle includes evaporation, precipitation, transpiration, runoff, and infiltration.

1.8 Primary Productivity

Objectives and Essential Knowledge

• ENG-1.A: Explain solar energy acquisition and transfer.

  • Gross Primary Productivity (GPP): total rate of photosynthesis.

  • Net Primary Productivity (NPP): energy available for consumers after plant respiration.

1.9 & 1.10 Trophic Levels & The 10% Rule

Objectives and Essential Knowledge

• ENG-1.B / ENG-1.C: Explain energy transfer and matter cycling through ecosystems.

  • The 10% rule states that only 10% of energy is passed from one trophic level to the next due to energy loss during metabolic processes.

Trophic Levels

• Producers convert sunlight to chemical energy.

• Consumers are categorized into primary (herbivores), secondary (carnivores), and tertiary (top predators).

1.11 Food Chains and Food Webs

Objectives and Essential Knowledge

• ENG-1.D: Describe food chains and food webs.

  • Food webs demonstrate intricate interrelationships in the flow of energy and nutrients, showing how changes in one species can affect the whole ecosystem.