The Bioshphere and Ecosystems

Levels of Ecological Organization

The hierarchy of biological organization from smallest to largest: organism → population → community → ecosystem → biome → biosphere, showing increasing levels of complexity and interaction

Organism

One individual living thing

Population

Group of individuals of the same species living in the same area

Community

All populations of different species living and interacting in the same area

Ecosystem

A community of organisms plus all abiotic (nonliving) factors in their environment interacting together

Biome

Large geographic region defined by climate and characteristic ecosystems (ex: desert, tundra, rainforest)

Biosphere

All ecosystems on Earth combined; the zone of life on Earth

Interdependence

The idea that organisms rely on each other and on their environment for survival

Abiotic Factors

Nonliving parts of an ecosystem that affect organisms (ex: water, sunlight, temperature)

Biotic Factors

Living parts of an ecosystem (ex: plants, animals, bacteria)

Niche

The role of an organism in its ecosystem, including its habitat, food source, and interactions with other organisms

Habitat

The physical place where an organism lives

Food Chain

A linear sequence showing energy flow from one organism to another

Food Web

A network of interconnected food chains showing multiple energy pathways in an ecosystem

Effects of Disturbing a Food Web

Can cause population increases or decreases, loss of biodiversity, and overall ecosystem imbalance

Energy Flow

The movement of energy through an ecosystem from producers to consumers and decomposers

Nutrient Cycles

The recycling of essential elements (like carbon, nitrogen, water, phosphorus) through living and nonliving parts of ecosystems

Trophic Levels

Levels in a food chain: producers → primary consumers → secondary consumers → tertiary consumers

Producers (Autotrophs)

Organisms that make their own food using sunlight (photosynthesis) or chemical energy (chemosynthesis)

Consumers (Heterotrophs)

Organisms that obtain energy by eating other organisms

Herbivore

Consumer that eats only plants

Carnivore

Consumer that eats only animals

Omnivore

Consumer that eats both plants and animals

Decomposers

Organisms (like bacteria and fungi) that break down dead matter and recycle nutrients back into the ecosystem

10% Rule

Only about 10% of energy is transferred from one trophic level to the next; the rest is lost as heat

Chemosynthesis

Process where organisms produce food using chemical energy instead of sunlight

Photosynthesis

Process used by plants and other autotrophs to convert sunlight, CO₂, and water into glucose and oxygen: 6CO₂ + 6H₂O + light → C₆H₁₂O₆ + 6O₂

Water Cycle

The movement of water through evaporation, condensation, precipitation, and runoff in the environment

Carbon Cycle

The movement of carbon through living organisms, atmosphere, oceans, and soil via processes like respiration, photosynthesis, and decomposition

Nitrogen Cycle

The movement of nitrogen through the atmosphere, soil, and organisms, including nitrogen fixation and decomposition

Phosphorus Cycle

The movement of phosphorus through rocks, soil, water, and living organisms, important for DNA and ATP

Greenhouse Effect

Process where greenhouse gases trap heat in Earth’s atmosphere, keeping the planet warm enough for life

Global Warming

Long-term increase in Earth’s average temperature due to increased greenhouse gases like CO₂ and methane

Estuary

Coastal area where freshwater from rivers mixes with saltwater from the ocean; highly productive ecosystem

Limiting Nutrient

A nutrient that is in the shortest supply and restricts ecosystem growth (ex: nitrogen or phosphorus)