Earth Science Fundamentals: Biomes, Atmosphere, and Cycles

Posted on Jan 10, 2026 in Geology

Earth’s Geography and Sustainability

There are seven continents: Africa, Antarctica, Asia, Europe, North America, South America, and Australia.

There are five major oceans: Pacific Ocean, Atlantic Ocean, Indian Ocean, Southern Ocean, and Arctic Ocean.

Economic Classifications (Income Levels)

  • Low-Income Economies (LICs): Less than $1,036 GNI per capita.
  • Middle-Income Economies (MICs): $1,036 to $12,535 GNI per capita.
  • High-Income Economies (HICs): Greater than $12,535 GNI per capita.

Sustainability refers to meeting the needs of the present without compromising the ability of future generations to meet their own needs.

Why Sustainable Resource Management is Necessary

We need sustainable management of resources to ensure long-term availability of natural resources, protect ecosystems, reduce pollution, and support economic and social development.

The Water Cycle and Its Importance

1. Describe the Water Cycle

The water cycle is the continuous movement of water through the atmosphere, land, and oceans. It is vital for regulating climate, supporting life, and replenishing freshwater.

Components of the Water Cycle (Limited Scope)

Be able to interpret and draw diagrams representing the water cycle, including:

  • Evaporation: Water turns into vapor.
  • Transpiration: Water vapor released from plants.
  • Condensation: Vapor forms clouds.
  • Precipitation: Rain, snow, sleet, or hail.
  • Interception: Water caught by vegetation.
  • Infiltration: Water enters the soil.
  • Surface Run-off: Water flows over the land surface.
  • Through-flow: Water moves through the soil layer.
  • Groundwater Flow: Water moves through underground aquifers.

Earth’s Atmosphere Structure

Major Components of the Atmosphere (Elements)

  • Nitrogen (78%)
  • Oxygen (21%)
  • Argon (0.93%)
  • Carbon Dioxide (0.04%)

Structure of the Atmosphere

Describe the structure of the Earth’s atmosphere, distances from Earth, and temperature changes:

  • Troposphere (0–12 km): Where weather occurs; temperature generally decreases with altitude.
  • Stratosphere (12–50 km): Contains the ozone layer; temperature increases with altitude due to ozone absorption.
  • Mesosphere (50–85 km): The coldest layer; temperature decreases with altitude.
  • Thermosphere (85–600 km): Temperature increases significantly due to absorption of solar radiation.
  • Exosphere (600+ km): Merges into outer space.

The Ozone Layer

The ozone layer is located in the stratosphere, typically between 15 and 35 km above Earth.

It absorbs harmful ultraviolet (UV) radiation, protecting living organisms from its damaging effects.

The Greenhouse Effect

The process by which certain gases in the atmosphere trap heat:

  1. Step 1: Solar radiation reaches the atmosphere; some is reflected back into space.
  2. Step 2: The remaining solar energy is absorbed by the land and oceans, heating the Earth.
  3. Step 3: Heat radiates from Earth toward space.
  4. Step 4: Some of this heat is trapped by greenhouse gases, keeping the Earth warm enough to sustain life.
  5. Step 5: Human activities (fossil fuel burning, agriculture, land clearing) increase greenhouse gas concentrations.
  6. Step 6: This traps extra heat, causing the Earth’s temperature to rise (global warming).

The order of atmospheric layers from Earth outward is: Troposphere, Stratosphere, Mesosphere, Thermosphere, Exosphere.

Ecosystem Components and Interactions

Key Ecological Definitions

  • Biome: Large geographical area characterized by specific climate and dominant life forms.
  • Ecosystem: A community of living organisms interacting with their non-living environment.
  • Population: A group of individuals of the same species living in the same area.
  • Community: All the different populations that live and interact in an area.
  • Habitat: The natural home or environment of an organism.
  • Niche: The specific role an organism plays within its ecosystem.

Trophic Levels and Components

  • Producers: Organisms that create their own food (e.g., Plants).
  • Consumers: Organisms that obtain energy by feeding on others:
    • Primary: Herbivores (eat producers).
    • Secondary: Carnivores (eat primary consumers).
    • Tertiary: Top predators (eat secondary consumers).
  • Decomposers: Organisms (fungi, bacteria) that break down dead organic matter.
  • Abiotic Components: Non-living factors such as temperature, humidity, water, oxygen, salinity, light, and pH.

Biotic factors (predation, competition, symbiosis, and disease) significantly influence the number and diversity of organisms found within an ecosystem.

Photosynthesis

The process by which plants use sunlight, $\text{CO}_2$, and water to produce glucose and oxygen:

$$6 \text{CO}_2 + 6\text{H}_2\text{O} \rightarrow \text{C}_6\text{H}_{12}\text{O}_6 + 6 \text{O}_2$$

Summary of Components and Energy Flow

Components Review

  • Biotic Components: Producers, Consumers (primary, secondary, tertiary), and Decomposers.
  • Abiotic Components: Temperature, humidity, water, oxygen, salinity, light, pH.
  • Greenhouse Gases include: $\text{CO}_2$, $\text{CH}_4$, $\text{N}_2\text{O}$, $\text{H}_2\text{O}$ vapor, $\text{O}_3$ (ozone).

Energy Loss in Food Chains

Approximately 90% of energy is lost between trophic levels. The three main ways energy is lost are:

  • Heat loss to the environment.
  • Energy used for movement and metabolic processes.
  • Energy contained in waste (undigested material).

9. Photosynthesis and the Carbon Cycle

Photosynthesis on land and in the oceans is vital to the carbon cycle because it removes $\text{CO}_2$ from the air, stores carbon in biomass, and supports all food chains.

10. Defining Trophic Roles

  • Producer: Makes its own food (autotroph).
  • Primary Consumer: Eats producers (herbivore).
  • Secondary Consumer: Eats primary consumers.
  • Tertiary Consumer: Eats secondary consumers.
  • Decomposer: Breaks down dead matter, returning nutrients to the environment.

11. Trophic Levels and Energy Transfer

Trophic Levels: The levels in a food chain that show the flow of energy.

Energy is transferred from producers to consumers; this energy decreases significantly at each successive level.

14. Energy Loss Explanation: Energy is lost due to heat generation, energy expended for movement, and undigested material passed as waste.

15. Food Chains and Webs: Construct simple food chains and food webs using arrows to show the direction of energy flow.

Respiration and the Carbon Cycle

16. Aerobic Respiration Definition

The process of energy production within cells that requires oxygen.

17. Aerobic Respiration Equations

  • Word Equation: Glucose + Oxygen $\rightarrow$ Carbon Dioxide + Water + Energy
  • Chemical Equation: $\text{C}_6\text{H}_{12}\text{O}_6 + 6\text{O}_2 \rightarrow 6\text{CO}_2 + 6\text{H}_2\text{O} + \text{ATP}$ (This is the opposite reaction to photosynthesis).

18. The Carbon Cycle Description

Carbon moves through the environment via photosynthesis, respiration, decomposition, and combustion (burning of fossil fuels).

19. What is Carbon?

Carbon is an element essential for life, characterized by having 6 protons (6 atoms). It is found in many organic compounds, including:

  • Glucose
  • Fossil fuels
  • Proteins
  • Fats
  • Organic matter