INTERACTIONS BETWEEN EARTH’S SYSTEMS AND LIVING THINGS – EARTH AND SPACE SCIENCE

Cycles in Nature

Life on Earth depends on essential substances such as oxygen, nitrogen, carbon dioxide, and water. You might wonder: Will these vital resources ever run out? Thankfully, the answer is no, because they are constantly recycled through natural cycles in Earth’s systems.

Below, we will explore four major cycles that keep these substances moving through ecosystems.

Nitrogen Cycle   

Nitrogen is an essential nutrient for all living things. Although nitrogen gas (N₂) makes up about 78% of Earth’s atmosphere, most organisms cannot use it in this form.

     Key steps to Nitrogen Cycle

• Fixation: Nitrogen-fixing bacteria in soil or plant roots convert atmospheric nitrogen into nitrates.
• Assimilation: Plants absorb nitrates from the soil to build proteins and other compounds.
• Consumption: Herbivores (primary consumers) eat the plants, and nitrogen moves up the food chain.
• Decomposition: When plants and animals die, decomposers break them down, returning nitrogen compounds to the soil.
• Denitrification: Denitrifying bacteria convert nitrates back to nitrogen gas, releasing it into the atmosphere.

Nitrogen cycles continuously between the air, soil, living organisms, and back to the air.

Carbon Cycle

Carbon is a fundamental building block of life. It cycles between the atmosphere, living organisms, oceans, and Earth’s crust.

Key steps of the carbon cycle

• Photosynthesis: Producers (plants, algae) absorb carbon dioxide (CO₂) from the air and convert it into carbohydrates using sunlight.
• Consumption: Herbivores and other consumers eat plants, transferring carbon through the food web.
• Respiration: All living things release carbon dioxide back into the air when they break down food for energy.
• Decomposition: Dead organisms are broken down by decomposers, releasing carbon into the soil and atmosphere.
• Fossil Fuels: Over millions of years, buried organic matter becomes coal, oil, or natural gas. Burning these fuels releases stored carbon back into the atmosphere.

Impact: Burning fossil fuels adds extra CO₂ to the atmosphere, contributing to the greenhouse effect and climate change.

Oxygen Cycle

Oxygen is essential for respiration in most living things. The oxygen cycle describes how oxygen moves through the atmosphere, living organisms, and Earth’s crust.

Key steps of the oxygen cycle:

• Photosynthesis: Plants use sunlight to convert CO₂ and water into glucose and oxygen. This releases oxygen into the atmosphere.
• Respiration: Animals and plants use oxygen to break down glucose for energy, releasing CO₂ back into the air.
• Decomposition: Decomposers also use oxygen when breaking down dead material.
• Weathering: Oxygen reacts with minerals in rocks (oxidation).

Oxygen levels in the atmosphere remain balanced through these processes.

Water Cycle

Water is vital for all life on Earth. The water cycle describes the continuous movement of water between Earth’s surface and atmosphere.

Key steps of the water cycle:

• Evaporation: Water from oceans, lakes, and rivers turns into water vapor due to the sun’s heat.
• Transpiration: Plants release water vapor through their leaves.
• Condensation: Water vapor cools and forms clouds.
• Precipitation: Water falls as rain, snow, sleet, or hail. Runoff and Infiltration: Water returns to oceans and lakes, or soaks into the ground to replenish groundwater.

 Water is continuously cycled and purified naturally, supporting all life on Earth.

Natural Hazards

Nature doesn’t only sustain life—it can also pose serious threats. A natural hazard is a natural event that has the potential to cause damage, including loss of life and destruction of property.

There must be a risk of harm to people, ecosystems, or property. The severity and location determine how much damage a hazard might cause. Human actions—like poor farming or construction—can make natural hazards worse.

Types of Natural Hazards: Hazard, Type, and Description

• Earthquakes    Sudden shaking of Earth’s surface due to tectonic activity.
• Volcanoes       Eruptions of molten rock, gases, and ash from beneath Earth’s surface.
• Floods.            Overflow of water onto normally dry land, often after heavy rainfall.
• Droughts         Long periods of very little or no rainfall, leading to water shortages.

Areas near tectonic plate boundaries are more likely to experience earthquakes and volcanoes. Coastal regions are at greater risk of hurricanes and flooding. Deforestation and poor land use increase risks of landslides and floods. Urbanization near rivers can worsen flood damage.

Hazard Probability (≥10 deaths/year)     Probability (≥1000 deaths/year)

Flood.                                      86%                                       0.4%

Earthquake.                55%                                      1.2%

Drought                               33%                                          0.8%

Volcano                              12%                                           0.2%

Floods are very frequent, but often less deadly. Earthquakes are less frequent but can be extremely deadly, especially in vulnerable regions.

 Effects of Natural Hazards

Short-term Effects: Loss of life, Injuries and displacement, Damage to homes and infrastructure

Long-term Effects: Economic disruption, Food and water shortages, Environmental damage, Increased poverty in affected regions

 Why Some Countries Suffer More

          Reason.                                         Explanation

• Poor infrastructure                             Buildings and roads are more likely to collapse or be damaged.
• Inadequate emergency services          Slower response means more lives lost.
• Limited public awareness.                   People may not know how to protect themselves.
• Poor communication systems Slower spread of warnings and evacuation notices
• High population density in hazard zones         More people are affected when disaster strikes.
• Economic limitations  Fewer resources available for recovery and rebuilding.

Short- and Long-Term Effects of Natural Hazards

Natural hazards do not affect all regions equally. The impact often depends on the development level of the area.

 Short-term effects can include: Loss of power and communications, Damage to water and sewage systems, Infrastructure damage (roads, bridges, buildings), Financial losses, Injuries and sickness, Death

Long-term effects are often worse in less developed regions: Economic collapse, Prolonged homelessness and displacement, Disease outbreaks, Limited ability to recover and rebuild

More developed areas usually have resources to avoid or minimize long-term effects. Less developed areas may see short-term disasters turn into long-term crises.

 Hazard Mitigation

Mitigation means taking steps to reduce the damage that disasters cause. It aims to save lives and protect property.

• Structural Mitigation: Dams, dikes, levees, containment ponds: Control or hold back floodwaters

Storm shelters: Protect people during tornadoes and severe storms

• Nonstructural Mitigation: Building codes: Rules about construction materials and methods to improve safety (e.g., earthquake-resistant designs)

Zoning ordinances: Decide where buildings can be built to reduce risk

Land-use planning: Avoid building in high-risk areas like floodplains or fault lines

Example: San Francisco, near a major fault, has strict earthquake-resistant building codes.

Natural Resources

 Materials or energy sources found in nature that humans use for survival and development.

 Types of Resources:

• Renewable Resources: These can naturally replenish or be managed sustainably. Examples: Wind, Sunlight, Waves, Air, Forests, Soil, Water, Fish, Wildlife. Require proper management to remain sustainable.
•  Nonrenewable Resources: These exist in limited quantities and take millions of years to form. Once used, they cannot be quickly replaced. Examples: Minerals (iron ore, diamonds), Fossil fuels (oil, coal, natural gas), Nuclear fuel minerals (uranium, plutonium)

 Extraction: Mining: Removes minerals from rocks.

Drilling and hydraulic fracturing: Used to extract oil and natural gas from porous rocks like sandstone and limestone.

 Fossil Fuels

Created over millions of years from the remains of plants and animals. Pressure and heat transformed this organic matter into oil, coal, and natural gas. Main energy sources for transportation, heating, and electricity. Oil may run out in ~50 years. Coal reserves may last ~300 years. Likewise extraction can harm the environment.

Sustainability of Resources

As nonrenewable resources become harder to find and use, we must focus on sustainability. sustainability is using resources in ways that meet our needs without preventing future generations from meeting theirs.

 Steps for Sustainability:

• Improve fuel efficiency.
• Reduce reliance on nonrenewable energy.
• Invest in renewable energy sources.
• Carefully manage renewable resources (e.g., sustainable forestry, fisheries).
• Reduce waste and pollution.

It’s up to individuals, communities, businesses, and governments to ensure resources last for future generations.