Intro to Ecology: Climate & Biomes

Ecology: Interactions and Environmental Limits

Definition and Scope

• Ecology is the study of interactions between organisms and their environment, which ultimately limit the distribution of species.

• The structure and distribution of terrestrial biomes are controlled mainly by climate.

Key Points

• Climate varies systematically across the planet and is affected by ocean currents, mountains/elevation, and continentality (location on continent).

• Solar radiation drives variation in climate, influenced by latitude (zones), seasons, and air circulation (including the Coriolis effect).

• Climatic variation shapes broad-scale vegetation patterns and the distribution of organisms.

Climate: Patterns and Influences

Weather vs. Climate

• Weather: Short-term atmospheric conditions (minutes to days).

• Climate: Long-term prevailing weather conditions in an area (typically over 30 years).

• Major abiotic components of climate: Temperature, Precipitation, Sunlight, Wind.

Determinants of Global Climate Patterns

• Solar energy and Earth's movement in space are primary drivers.

Latitudinal Variation in Sunlight Intensity

Sunlight and Temperature Gradients

• The angle at which sunlight hits Earth affects its intensity (amount of heat/light).

• Intensity is strongest at the tropics (direct sunlight), weakest at the poles (oblique angle).

• This variation causes temperature gradients, which drive atmospheric and oceanic circulation.

Example:

• Equator receives more solar energy per unit area than the poles, resulting in warmer climates.

Atmospheric Circulation

Large-Scale Air Movement

• Air moves, rises, falls, warms, cools, and changes humidity, affecting pressure and climate.

• Major circulation cells (Hadley, Ferrel, Polar) create predictable wind and precipitation patterns.

Coriolis Effect

• Earth's rotation causes winds to bend (right in the Northern Hemisphere, left in the Southern Hemisphere).

• This effect influences global wind patterns and ocean currents.

Other Factors Affecting Climate

Ocean Currents

• Ocean currents redistribute heat, moderating coastal climates (e.g., North Atlantic Drift keeps Europe warmer).

• Large water bodies moderate temperature extremes of nearby terrestrial environments.

Continentality

• Inland locations have larger temperature ranges and drier conditions than maritime locations.

• Land heats and cools quickly; water moderates temperature changes.

Mountains and Elevation

• Higher elevation = colder temperatures (approx. 6°C drop per 1,000 m increase in altitude).

• Mountains force air to rise, cool, and lose moisture as precipitation (rain shadow effect on leeward side).

Structure & Distribution of Terrestrial Biomes

Definition of Biomes

• Biomes are major life zones characterized by vegetation type (terrestrial) or physical environment (aquatic).

• Climate (rainfall and temperature) is crucial in determining biome distribution.

Vegetation Layers & Plant Types

• Biomes are often named for their dominant vegetation and climate factors.

• Vegetation layers in forests include:

  • Forest floor: Soil, dead plants, decomposers, small plants.

  • Understory: Seedlings, saplings, shrubs, grasses, forbs; shade-tolerant species.

  • Canopy: Mature tree crowns forming the upper habitat zone.

Examples of Biomes

Biome	Climate	Vegetation	Location Example
Tropical Rainforest	High rainfall, warm temperatures year-round	High plant diversity, vertically layered	Bilagua, Costa Rica
Desert	Low rainfall, highly variable temperatures	Drought-adapted plants (succulents, shrubs)	Southwestern USA
Temperate Deciduous Forest	Moderate rainfall, distinct seasons	Deciduous trees, layered vegetation	Eastern North America
Temperate Grassland	Highly seasonal precipitation, hot summers, cold winters	Grasses, few trees	Prairies of North America
Boreal Forest (Taiga)	Variable rainfall, long cold winters	Coniferous trees, limited layers	Canada, Russia
Tundra	Low precipitation, cold temperatures	Mosses, lichens, low shrubs	Arctic regions

Climographs

How to Read a Climograph

• Climographs display average temperature (line graph) and precipitation (bar graph) for each month of the year.

• Useful for describing climates and ecological conditions of different biomes.

Example:

• Tropical Wet: High, consistent rainfall and temperature.

• Tropical Dry: Seasonal rainfall, more variable temperature.

Ecology and Species Distribution

Determinants of Species Distribution

• Species distributions result from ecological (short-term) and evolutionary (long-term) interactions with the environment.

• Dispersal: Movement of individuals or gametes away from their origin, contributing to global distribution.

Abiotic and Biotic Factors

• Abiotic factors: Temperature, water, oxygen, salinity, sunlight, wind, rocks, soil.

• Biotic factors: Predation, herbivory, competition, mutualism, parasitism.

Example:

• Abiotic: Cactus distribution limited by temperature and water availability.

• Biotic: Competition between plant species for sunlight in a forest.

Summary Table: Factors Affecting Climate

Factor	Effect on Climate
Sun (Latitude/Seasons)	Drives temperature gradients and seasonal variation
Air Circulation	Distributes heat and moisture globally
Ocean Currents	Moderate coastal climates, redistribute heat
Mountains/Elevation	Influence temperature, precipitation patterns (rain shadow)
Continentality	Inland areas have greater temperature extremes

Learning Objectives

• Define ecology and distinguish between weather and climate.

• Describe factors influencing climate (latitude, sunlight, wind, ocean currents, mountains, continentality).

• Explain what biomes are and what determines their distribution.

• Identify vegetation layers and plant types in different biomes.

• Describe characteristics of six major biome types.

• Discuss factors affecting species distribution, including abiotic and biotic examples.