Introduction to Ecology and Behavioural Ecology: Key Concepts and Biomes

Introduction to Ecology

What is Ecology?

Ecology is the scientific study of how organisms interact with each other and with their environment. The primary goals of ecology are to understand the distribution and abundance of organisms and to identify the impacts humans have on the environment. Ecology is closely linked with evolution, as evolutionary processes shape ecological interactions and vice versa.

• Distribution: Where organisms are found geographically.

• Abundance: How many individuals of a species exist in a given area.

• Human Impact: Human activities can alter ecological systems, sometimes with far-reaching consequences.

Example: Rachel Carson's book Silent Spring (1962) highlighted the ecological consequences of DDT pesticide use, which led to declines in bird populations due to bioaccumulation and thin-shelled eggs in raptors.

Levels of Ecological Study

Ecology can be studied at multiple biological scales, each with distinct questions and approaches:

• Biosphere: Global processes and patterns, such as climate and ocean currents, that affect species distributions.

• Ecosystem: Movement of energy and matter between abiotic (non-living) and biotic (living) components.

• Community: Interactions among populations of different species in the same area.

• Population: Dynamics of a single species, including density, distribution, and composition.

• Individual: Morphological, physiological, and behavioral adaptations to the environment.

Determinants of Distribution and Abundance

Biogeography

Biogeography is the study of how organisms are distributed geographically. The distribution and abundance of organisms are influenced by both abiotic (non-living) and biotic (living) factors.

• Abiotic factors: Climate (temperature, moisture), soil, light, nutrients, etc.

• Biotic factors: Interactions with other species, such as competition, predation, mutualism, and parasitism.

Example: The presence or absence of competitors, mutualists, predators, or parasites can limit a species' range.

Niche Models

Niche models illustrate the range of environmental conditions a species can tolerate. Some species have broad tolerances (generalists), while others are more specialized (specialists).

Climate and Its Effects on Ecology

Latitudinal Gradients

Solar radiation per unit area declines with increasing latitude, making the tropics warmer and the poles colder. This is a fundamental driver of global climate patterns.

Global Air Circulation and Rainfall

Hadley cells are large-scale atmospheric circulation patterns that cause the tropics to be moist and regions around 30° latitude to be dry. Warm, moist air rises at the equator, cools, and drops rain, while dry air descends at higher latitudes.

Seasonality

Seasons are caused by the Earth's 23.5° tilt on its axis, which affects the angle and duration of sunlight received at different latitudes throughout the year.

Regional Effects

• Mountains: Create rain shadows, where moist air rises and cools on one side, causing precipitation, while dry air descends on the other side, creating arid conditions.

• Oceans: Moderate coastal climates due to water's high specific heat capacity. Ocean currents (gyres) transport warm and cold water, influencing regional climates.

Terrestrial Biomes

Biomes are major groupings of ecological communities defined by dominant vegetation and governed by average temperature and precipitation.

Biome	Temperature	Moisture	Key Features
Tropical Wet Forests	Warm	High	High species diversity, high biomass
Subtropical Deserts	Extreme	Low	Low diversity, slow growth, drought adaptations
Temperate Grasslands	Moderate	Low-Moderate	Fertile soil, fire regimes, dense growth
Temperate Forests	Moderate	Moderate	Deciduous trees, seasonal photosynthesis
Temperate Coniferous Forests	Mild winters	High	Conifer canopy, understory plants
Boreal Forests (Taiga)	Low	Low	Cold-tolerant conifers, low diversity
Arctic Tundra	Very low	Very low	Low biomass, permafrost, low diversity

Aquatic Biomes

About 70% of Earth's surface is covered by water. Four main physical factors affect the distribution and abundance of aquatic organisms:

1. Salinity: Proportion of solutes in water; affects osmosis and water balance.

2. Water flow: Physical movement of water; influences dispersal and habitat structure.

3. Nutrient availability: Distribution of nutrients and oxygen, often affected by seasonal turnover in lakes.

4. Water depth: Determines light penetration and thus photosynthetic productivity.

Example: Lake turnover redistributes nutrients and oxygen, supporting aquatic life.

Introduction to Behavioural Ecology

Behaviour and Behavioural Ecology

Behaviour is an action in response to a stimulus. Behavioural ecology studies behavioural adaptations that evolved in response to selection pressures, with implications for fitness (reproductive success).

• Proximate causation (HOW?): Explains how actions occur (genetic, neurological, hormonal, etc.).

• Ultimate causation (WHY?): Explains why actions occur (evolutionary history, natural selection).

Common Questions in Behavioural Ecology

1. What should I eat?

2. Where should I live?

3. Whom should I mate with?

4. How should I communicate?

5. When should I cooperate?

Foraging Behaviour Example

In Drosophila (fruit flies), genetic variation in foraging behaviour is controlled by the for gene. "Rovers" move after feeding, while "sitters" stay in one location. The fitness advantage of each strategy depends on population density.

• Optimal foraging theory: Animals maximize benefits and minimize costs when foraging, balancing energy gain and predation risk.

Habitat Selection and Navigation

Animals select habitats based on quality, population density, and resource availability. Navigation strategies include:

• Piloting: Using familiar landmarks.

• Compass orientation: Using the sun, stars, or Earth's magnetic field.

• True navigation: Ability to locate a specific place on Earth.

Migration is an adaptation to track seasonal resources, despite costs in time, energy, and increased predation risk.

Additional info: This guide covers foundational concepts in ecology and behavioural ecology, including the scales of ecological study, determinants of species distribution, climate effects, terrestrial and aquatic biomes, and the basics of behavioural ecology. It is suitable for exam preparation in introductory college biology courses.