Earth's Spheres and Ecosystems Overview

Earth's Spheres

• Earth has four main spheres: lithosphere, atmosphere, hydrosphere, and biosphere.
• Lithosphere: The solid outer layer of Earth, consisting of the crust and upper mantle.
• Atmosphere: The layer of air surrounding Earth, regulating temperature and protecting from radiation.
• Hydrosphere: All of Earth's water, including oceans, rivers, lakes, and ice.
• Biosphere: The realm of all living things on Earth.
• These spheres are interconnected and rely on each other for survival.

Ecosystems

• An ecosystem is all living organisms in a region interacting with each other and their non-living environment.
• Biotic factors: Living things, their remains, products, and wastes (e.g., animals, plants, nests).
• Abiotic factors: Non-living things (e.g., temperature, wind, water, air, minerals).
• Ecosystems contain different levels of organization:
  • Organism: Individual living thing
  • Population: All members of the same species in an area
  • Community: All populations in an area
  • Ecosystem: All living and non-living things in an area

Ecological Niches

• An ecological niche is the function a species serves in its ecosystem, including what it eats, what eats it, and how it behaves.
• Each species occupies a unique niche.
• Common consumer types and examples include:
  • Herbivore: Eats only producers (e.g., plants)
  • Carnivore: Eats only consumers (e.g., animals)
  • Omnivore: Eats both producers and consumers
  • Scavenger: Eats dead remains (e.g., vultures)
  • Decomposer: Feeds on dead decaying organisms (e.g., fungi)

Food Chains and Webs

• Food chain: A sequence of organisms, each feeding on the next, showing energy transfer.
• Food web: A representation of feeding relationships within a community (a more complex depiction than a food chain).
• Trophic level: The feeding level of an organism in a food chain or web.

Ecological Pyramids

• Biomass pyramids: Show total mass of organisms at each trophic level.
• Types of pyramids also include Energy and Numbers pyramids.

Biogeochemical Cycles (Carbon and Nitrogen)

• Carbon cycle: Carbon moves from the atmosphere to plants through photosynthesis, then to animals through consumption, and returns to the atmosphere after an organism dies. Decomposers play a significant role.
• Nitrogen cycle: After plants absorb nitrogen, it moves through the food chain. After organisms die, decomposers release nitrogen into the environment.

Limiting Factors

• Limiting factors are factors that restrict population size.
• These can be biotic (e.g., food availability) or abiotic (e.g., water availability).
• Limiting factors affect the tolerance range of a species—the upper and lower limits of their survival and reproduction.

Species Interactions

• Competition: Organisms vying for limited resources
• Parasitism: One organism (parasite) benefits at the expense of another (host).
• Commensalism: One organism benefits, while the other is neither harmed nor helped.
• Mutualism: Both organisms benefit.
• Predation: One organism (predator) kills and eats another (prey).

Carrying Capacity

• Carrying capacity is the maximum population size an environment can support.
• Sustainability is linked to carrying capacity as exceeding carrying capacity can harm the environment and the organisms within.