Chapter 52 | Ecology and the Biosphere

Ecology

The study of the interactions that living organisms have with the living and nonliving components of their environment

Organismal Ecology

Individual organisms and their interactions with the environment and other organisms

Population Ecology

Studies how individuals of the same species interact with each other and their environment, including factors like population size

Community Ecology

Examines all populations of different species in a given area and their interspecies relationships and interactions

Ecosystem Ecology

The interactions between living organisms and nonliving components in an environment, combining community dynamics with physical factors

Landscape Ecology

Mosaic of ecosystems

Global Ecology

The biosphere - sum of all the planet’s ecosystems and landscapes

Terrestrial organisms & their environment

Depend on climate

Climate

Long-term weather conditions in a particular area

Weather

Sunlight & temperature, air circulation, precipitation, ocean currents

Latitudinal variation

At higher latitudes, there’s less sunlight. Most sunlight is at the equator (0°), with a 23.5° tilt. Near the poles, the sun's angle is lower, resulting in less sunlight

Tropic of Cancer

23.5 degrees North

Tropic of Capricorn

23.5 degrees South

Seasonal variation

Caused by the tilt of the Earth

March/September Equinox (spring/autumn)

The sun hits the equator directly

June solstice (summer)

The sun directly hits the Tropic of Cancer (23.5°N), bringing increased sunlight and temperature to the Northern Hemisphere

December solstice (winter)

The sun directly hits the Tropic of Capricorn (23.5°S), bringing increased light and temperature to the Southern Hemisphere

Wind patterns

• Trade Winds: E → W

• Westerlies: W → E

Precipitation patterns

Most occurs at the equator. At 30°N & 30°S, dry air results in very little rain

Ocean currents

• Affect only coasts, moderating temperatures

• Near the equator (E → W), east coasts get warmer ocean temperatures

• Near poles (W → E), west coasts get cooler ocean temperatures

Regional effects

Mountain ranges disrupt air circulation, creating a rain shadow—precipitation falls on one side, leaving the other dry

Deforestation

Loss of vegetation leading to reduced photosynthesis and higher temperatures

Microclimates

Focused, specific localized climate

Climate change

A long-term change in climate (over 30+ years) that impacts the distribution of organisms

Biomes

Major life zones characterized by vegetation (land biomes) or physical factors like temperature and water (aquatic biomes)

Characteristics of terrestrial biomes

• Each biome has a climate range shown by climographs

• Ecotones

• Many biomes, especially forests, have vertical layers

• Organisms share characteristics due to convergent evolution

• Disturbances (fires, hurricanes, landslides) are common

Climate range

The temperature and precipitation conditions typical for each biome

Climograph

Graph showing the average/mean temperature vs precipitation

Ecotones

Gradations that exist between each biome

Vertical layering in forests

1. Canopy - tree tops

2. Understory - lower trees & shrubs

3. Floor

Tropical forest

• Located at the equator with consistent warm temperatures (25-29°C)

• The wettest biome (200-400cm rain/year)

• High biodiversity and competition for resources

• Has multiple layers, including emergent and midstory

• Most competition occurs on the nutrient-poor forest floor

Desert

• Less than 30cm of precipitation per year

• Found near 30°N or 30°S

• Variable temperatures (-30°C to 50°C) often seasonal or daily

• Organisms are adapted to dryness and drought, with many being nocturnal

Savanna

• Consistently warm (24-30°C)

• Dry season (~9 months)

• Wet season (30-50cm rain)

• Organisms are adapted to drought and fire, with grasses and scattered trees

Chaparral

• Wet winters (~10°C, 30-50cm rain)

• Dry, hot summers (30-40°C)

• Organisms are adapted to drought and fire

Grassland

• Dry, cold winters (-10°C, snow/ice)

• Wet, hot summers (30°C, 50-100cm rain)

• Dominated by grasses and grazers, often converted into farmland

Temperate broadleaf forest

• Summer: 30-35°C

• Winter: 0-10°C

• Consistent precipitation (70-200cm/year)

• Organisms go dormant or migrate in winter

• Features vertical layers: canopy, understory, shrubs, and floor

Northern coniferous forest

• The largest terrestrial biome

• Cold winters (-50°C)

• Snowy precipitation

• Summers are warmer (10-20°C)

• Variable precipitation supports conifers that resist cold or go dormant in winter

Tundra

• The coldest biome with short, wet summers and long, dry winters

• Permafrost (permanent ice layer)

• Mostly herbaceous plants

Aquatic biomes

• Oceanic pelagic zone

• Marine benthic zone

• Freshwater biomes

Zonation

The distribution of plants or animals into specific zones

Aquatic layering

• Pelagic zone:

  • Photic zone

  • Aphotic zone

• Benthic zone

• Abyssal zone (only in oceans)

Pelagic zone

Photic zone & aphotic zone

Benthic zone

The ocean floor

Lakes from the shore

• Littoral Zone: Shallow, rich in life near the shore

• Limnetic Zone: Open water, farther from shore, with less life

Oceans from the shore

• Intertidal Zone: Organisms adapted to tides

• Neritic Zone: Rich in life, close to shore

• Oceanic Zone: Deep water, less life, more open

Thermocline

Gradual decrease in temperature due to increasing in depth

Oceanic pelagic zone

• Covers ~70% of Earth; largest biome

• Most life is in the photic zone (phytoplankton & zooplankton), with mixing from ocean currents

Hydrothermal vents

Hot spots due to Earth’s core heat, fostering chemoautotrophs and creatures that feed on them

Coral reefs

• Found in the neritic and benthic zones

• High biodiversity and thrive in waters between 20-30°C

Intertidal zone

Area that’s submerged in water part of the time, with organisms adapted to both water and air

Freshwater biomes

Lakes:

• Eutrophic

• Oligotrophic

• Wetlands

• Estruaries

• Streams & Rivers

Eutrophic lakes

Lakes with high nutrients, much life, and low oxygen levels

Oligotrophic lakes

Lakes with low nutrients, little life, and high oxygen levels

Wetlands

Areas that are waterlogged for part of each day

Estruaries

Where freshwater mixes with salty seawater, creating a unique, brackish environment

Streams & rivers

Flowing water that starts fast and narrow (headwaters) and becomes wider and slower downstream

Altitudinal biomes

Biomes that mimic the latitudinal biomes based on altitude