Chapter 49: Introduction to Ecology – Study Notes

Introduction to Ecology

Major Goals and Areas of Ecology

Ecology is the scientific study of the interactions between organisms and their environment. The primary goal of ecology is to understand the distribution and abundance of organisms. Ecological research is divided into five broad areas:

• Organismal Ecology: Examines how individuals interact with their environment, including physiological and behavioral adaptations. Example: Studying how desert animals conserve water.

• Population Ecology: Focuses on groups of individuals of the same species and how their numbers change over time. Example: Investigating factors that regulate deer populations in a forest.

• Community Ecology: Studies interactions among different species living in the same area. Example: Analyzing predator-prey relationships in a savanna.

• Ecosystem Ecology: Explores energy flow and nutrient cycling among organisms and their physical environment. Example: Measuring carbon cycling in a wetland ecosystem.

• Global Ecology (Biosphere Ecology): Examines ecological phenomena at the planetary scale, including global climate change. Example: Assessing the impact of deforestation on atmospheric CO2 levels.

Distribution and Abundance of Species

Limiting Factors

The distribution and abundance of aquatic and terrestrial species are influenced by several factors:

• Abiotic Factors: Non-living components such as temperature, water, sunlight, soil, and nutrients. These factors vary with ecosystem type. Example: Temperature limits the range of polar bears to Arctic regions.

• Biotic Factors: Living components including competition, predation, disease, and symbiosis. Example: The presence of predators can restrict prey populations.

• Historical Factors: Past events such as continental drift, glaciation, and evolutionary history can influence current distributions.

Human Influence on Species Distributions

Native, Exotic, and Invasive Species

• Native Species: Species that occur naturally in a region.

• Exotic Species: Species introduced to a region where they are not native, often by human activity.

• Invasive Species: Exotic species that spread rapidly and negatively impact native species and ecosystems.

Humans influence species distributions through habitat destruction, introduction of exotic species, pollution, and climate change.

Climate and Its Variation

Global Climate Patterns

• Why does climate vary around the globe? The Earth's curvature causes uneven heating, with the equator receiving more direct sunlight than the poles.

• Why are some parts of the world warmer and wetter? Warm, moist air rises at the equator, cools, and releases precipitation, creating tropical rainforests. Dry air descends at about 30° latitude, forming deserts.

• Why do seasons exist? The tilt of the Earth's axis causes different regions to receive varying amounts of sunlight throughout the year.

Biomes

Definition and Distribution

A biome is a large terrestrial or aquatic region characterized by distinct climate, vegetation, and organisms. The distribution of terrestrial biomes is primarily determined by abiotic factors such as temperature and precipitation.

• Terrestrial Biomes: Include tropical rainforests, deserts, temperate forests, tundra, etc.

• Abiotic Factors: Temperature, rainfall, sunlight, and soil type are key determinants.

Interpreting Climate Maps

• Regions with high rainfall and warm temperatures support dense vegetation (e.g., tropical forests).

• Areas with low rainfall and high temperatures are typically deserts.

• Seasonal variation in temperature and precipitation influences the type of vegetation present.

Aquatic Biomes

Important Abiotic Factors

• Salinity: Salt concentration affects organism distribution (e.g., freshwater vs. marine species).

• Water Depth: Influences light penetration and photosynthesis (photic vs. aphotic zones).

• Water Flow: Affects nutrient availability and organism movement.

• Nutrient Availability: Determines productivity and species diversity.

Productivity in Aquatic Ecosystems

• Coastal Runoff: Delivers nutrients from land to aquatic systems, enhancing productivity.

• Ocean Upwelling: Deep, nutrient-rich water rises to the surface, supporting high primary productivity.

• Lake Turnover: Seasonal mixing of water layers redistributes nutrients and oxygen.

Climate Change and Human Impacts

Changing Climate

• Global temperatures are rising due to increased greenhouse gas emissions.

• Changes in precipitation patterns, more extreme weather events, and shifting biomes are observed.

• Organisms may shift their ranges, adapt, or face extinction.

Human Impacts on Biomes

• Terrestrial Biomes: Deforestation, urbanization, agriculture, and pollution alter habitats and reduce biodiversity.

• Aquatic Biomes: Overfishing, pollution, damming, and introduction of invasive species disrupt aquatic ecosystems.

Key Terms and Definitions

Term	Definition
Population	Group of individuals of the same species living in a specific area
Community	All populations of different species living and interacting in an area
Biosphere	The global sum of all ecosystems
Biogeography	Study of the distribution of species and ecosystems in geographic space and through geological time
Biotic Factor	Living component of an ecosystem
Abiotic Factor	Non-living component of an ecosystem
Biological Niche	The role and position a species has in its environment
Dispersal	Movement of individuals or gametes away from their origin or from centers of high population density
Exotic Species	Species introduced to an area where they are not native
Invasive Species	Exotic species that spread rapidly and cause harm to native species or ecosystems
Climate	Long-term patterns of temperature, precipitation, and other atmospheric conditions
Weather	Short-term atmospheric conditions in a specific place at a specific time
Hadley Cell	Large-scale atmospheric convection cell in which air rises at the equator and sinks at medium latitudes
Temperate Region	Area of the Earth between the tropics and the polar circles
Tropical Region	Area of the Earth near the equator, characterized by warm temperatures year-round
Biome	Major ecological community type defined by climate and dominant vegetation
Net Primary Productivity	The rate at which plants convert solar energy to biomass, minus the energy used for respiration
Deciduous	Plants that shed their leaves seasonally
Evergreen	Plants that retain their leaves year-round
Photic Zone	Upper layer of a body of water that receives enough sunlight for photosynthesis
Aphotic Zone	Deeper layer of water where sunlight does not penetrate
Coastal Runoff	Movement of water and nutrients from land to coastal waters
Ocean Upwelling	Process by which deep, nutrient-rich water rises to the surface
Lake Turnover	Seasonal mixing of water layers in a lake, redistributing nutrients and oxygen

Key Equations

• Net Primary Productivity (NPP):

$\mathrm{NPP} = \mathrm{GPP} - R$

Where $\mathrm{GPP}$ is Gross Primary Productivity and $R$ is energy used for respiration.