The Water Cycle
What term describes the process where water vapor condenses and returns to Earth's surface?
Precipitation. This includes rainfall, snow, sleet, and hail.
What economic measure is used to rank countries by wealth?
GDP per capita (the total economic output divided by population).
Name the four main layers of the atmosphere from bottom to top.
troposphere, Stratosphere, Mesosphere, Thermosphere.
What are biotic and abiotic components of ecosystems?
Biotic components are living things (plants, animals, fungi, bacteria). Abiotic components are non-living factors (water, soil, sunlight, temperature).
Name two places carbon is stored and two ways it moves between them.
Carbon is stored in oceans, atmosphere, forests, soil, and fossil fuels. It moves through photosynthesis, respiration, decomposition, and ocean absorption.
Explain the difference between infiltration and percolation in the water cycle.
Infiltration is the movement of water from the surface into soil, while percolation is the downward movement of water through soil layers and rock toward groundwater stores.
What's the difference between LEDCs and MEDCs?
What are the four main gases in our atmosphere?
Nitrogen (78%), Oxygen (21%), Argon (0.9%), Carbon dioxide (0.04%).
Why are food webs better than food chains for showing ecosystem relationships?
Food chains show simple straight lines of who eats whom (grass → rabbit → fox). Food webs show the reality that most organisms eat multiple things and are eaten by multiple predators, creating a complex network of feeding relationships.
What's the difference between the fast and slow carbon cycles?
The fast (biological) carbon cycle works over days to decades through photosynthesis, respiration, and decomposition. The slow (geological) cycle works over millions of years through rock formation, weathering, and volcanic activity.
How does deforestation affect the water cycle in a watershed?
Deforestation reduces evapotranspiration (water release from plants), increases surface runoff, reduces infiltration, increases erosion, leads to faster peak discharge in rivers, heightens flood risk, and can reduce local rainfall patterns.
What is the Human Development Index (HDI)?
HDI measures development using three factors: health (life expectancy), education (years of schooling), and living standards (income). Countries are ranked as having very high, high, medium, or low development.
Why does temperature increase with height in the stratosphere?
Temperature increases with height in the stratosphere because ozone absorbs ultraviolet radiation from the sun and converts this energy to heat. This creates a temperature inversion and helps protect Earth from harmful UV rays.
What's the difference between primary and secondary succession?
Primary succession starts on bare land with no soil (like after volcanoes or glaciers), beginning with lichens and mosses. Secondary succession happens where soil already exists after a disturbance (like fires or abandoned farms), starting with weeds and grasses. Both gradually change until reaching a stable community.
How do oceans absorb carbon dioxide and what problems does this cause?
Oceans absorb CO₂ when it dissolves in seawater and when marine plants use it for photosynthesis. This leads to ocean acidification, making it harder for coral, shellfish, and some plankton to build their shells and skeletons, threatening marine ecosystems.
Describe how urbanization alters the hydrological cycle and explain two mitigation strategies.
Urbanization increases impermeable surfaces, reducing infiltration and increasing runoff speed and volume. This leads to faster peak discharge, increased flooding, reduced groundwater recharge, and polluted waterways. Mitigation strategies include permeable paving, green roofs, bioswales, retention ponds, and urban forests/green spaces.
How do the Brandt Line and North-South divide classify countries, and what are their problems?
Both divide the world into rich "North" and poor "South" regions. Problems include: they're too simple, don't account for rising economies like China, reflect colonial thinking, ignore inequality within countries, and use outdated rich-poor divisions.
How are the troposphere and mesosphere different?
The troposphere (lowest layer) gets colder with height, contains most weather and air pollution, and is where we live. The mesosphere (third layer up) also gets colder with height, is very thin, has the coldest temperatures in the atmosphere, and is where meteors burn up.
Why is energy lost between each level in a food chain?
About 90% of energy is lost between each level because energy escapes as heat during respiration, movement, and through undigested waste. This is why food chains rarely have more than 4-5 links and why there are fewer animals at higher levels (like wolves) than lower levels (like rabbits).
How have humans changed the carbon cycle in the last 200 years?
humans release about 12-13 billion tons of carbon yearly, mainly from burning fossil fuels (9-10 billion tons) and deforestation (1-2 billion tons). About 55% stays in the atmosphere, 25% goes into oceans causing acidification, and 20% is absorbed by land plants. This has increased atmospheric CO₂ from 280 to over 420 parts per million.
Evaluate how climate change is projected to impact the global water cycle and the implications for water security.
Climate change is projected to intensify the water cycle with more extreme precipitation events, longer droughts, increased evaporation rates, and altered rainfall patterns. Rising sea levels will cause saltwater intrusion into coastal aquifers. This creates water security challenges including increased flooding and drought risks, reduced reliability of water supplies, and competition for diminishing resources. Regional impacts vary dramatically, with many already water-stressed regions facing greater challenges.
How do different ways of measuring development (GDP, HDI, Gini, Happy Planet Index) show different pictures?
Different measures reveal different priorities: GDP shows economic output but misses wellbeing (Qatar is rich but has labor issues); HDI adds health and education (Norway ranks high); Gini shows inequality (South Africa has high inequality despite moderate GDP); and Happy Planet Index measures sustainable happiness (Costa Rica outperforms many wealthy nations despite lower income).
How have human activities changed different layers of the atmosphere?
Humans have increased greenhouse gases in the troposphere causing warming, while CFCs damaged the ozone layer in the stratosphere. These changes create feedback loops: Arctic ice melting absorbs more heat; warming releases more water vapor (a greenhouse gas); and thawing permafrost releases methane, further increasing warming.
How is climate change affecting ecosystems worldwide?
Climate change is disrupting ecosystems through warming temperatures and changing rainfall. Coral reefs are bleaching, deserts are expanding, and polar habitats are shrinking. Species timing is getting mismatched (like pollinators arriving before flowers bloom), and some areas may reach tipping points where ecosystems completely transform, like Amazon rainforest potentially becoming savanna.
What are the pros and cons of different ways to remove carbon from the atmosphere?
Natural methods like reforestation are cheaper ($10-50/ton) but can be reversed by fires and need lots of land. Technological solutions like direct air capture could remove unlimited carbon but are expensive ($100-600/ton) and energy-intensive. Soil carbon enhancement is promising but hard to measure, while ocean-based approaches risk ecological damage. The best strategy combines approaches, but none replace the need to reduce emissions.