Global Climate Patterns & Biomes

Abiotic Factors Influencing Distribution and Abundance

• Abiotic factors are non-living components of the environment that affect organisms, including temperature, precipitation, sunlight, and soil type.

• Latitudinal variation leads to differences in seasonality, temperature, and precipitation. For example, equatorial regions experience less seasonal variation and higher temperatures, while polar regions are colder and have more extreme seasonal changes.

• Geological influences such as mountain ranges can affect precipitation patterns by causing rain shadows, where one side of the mountain receives more rainfall than the other.

• Ocean currents influence coastal temperatures and precipitation. Warm currents can raise temperatures and increase humidity, while cold currents can have the opposite effect.

Predicting Biomes

• Biomes are major ecological communities defined primarily by their dominant vegetation and climate.

• The type of biome present in a region is predicted by average temperature, average precipitation, and the variation in these factors throughout the year.

• Maps showing latitude and climate data can be used to infer the likely biome present in a given location.

Biogeography

Distribution and Abundance of Organisms

• Both present and past abiotic factors (such as climate, geography, and disturbances) and biotic factors (such as competition, predation, and mutualism) control where organisms live and how abundant they are.

Biomes & Biogeographic Regions

• Earth is divided into biogeographic regions based on the distribution of species and evolutionary history.

• Biomes are distributed according to climate patterns and geographic features.

Theory of Island Biogeography

• This theory explains how the number of species on an island is determined by the balance between immigration and extinction rates.

• Larger islands and those closer to the mainland tend to have higher species richness due to higher immigration rates and lower extinction rates.

Interpreting Biogeography Graphs

• Graphs may show relationships between island size, distance from the mainland, and species richness.

• Understanding these graphs helps predict how changes in habitat size or isolation affect biodiversity.

Population Ecology

Population Change

• Population size changes due to births, deaths, immigration (movement into a population), and emigration (movement out of a population).

Fitness Trade-Offs and Resource Allocation

• Organisms face trade-offs in allocating resources to growth, reproduction, and survival, affecting their overall fitness.

Quantifying Population Growth

• r is the per capita rate of increase (birth rate minus death rate per individual).

• rmax is the maximum per capita rate of increase under ideal conditions.

Population Growth Models

• Exponential growth occurs when resources are unlimited and is density independent:

• Logistic growth occurs when resources are limited and is density dependent:

• K is the carrying capacity, or the maximum population size the environment can support.

• Population growth curves can be interpreted to determine which model best fits observed data.

Community Ecology

Species Interactions

• Species interact in ways that affect their fitness:

  • Competition (-/-): Both species are harmed by the interaction.

  • Consumption (+/-): One species benefits, the other is harmed (includes predation, herbivory, parasitism).

  • Mutualism (+/+): Both species benefit.

  • Commensalism (+/0): One species benefits, the other is unaffected.

  • Amensalism (-/0): One species is harmed, the other is unaffected.

Table: Summary of Species Interactions

Niche Concept

• Fundamental niche: The full range of resources a species could use in the absence of competition.

• Realized niche: The actual range of resources a species uses, limited by competition and other interactions.

Competition and Niche Differentiation

• Symmetric competition: Both species are equally affected.

• Asymmetric competition: One species is more negatively affected than the other.

• Competitive exclusion principle: Two species competing for the same limiting resource cannot coexist indefinitely.

• Niche differentiation (resource partitioning) can occur through character displacement, where species evolve differences to minimize competition.

Ecosystem Ecology

Energy Flow and Nutrient Cycling

• Food webs illustrate the flow of energy and nutrients through ecosystems, connecting producers, consumers, and decomposers.

• Photosynthesis transforms solar energy into chemical energy (sugars), which is then available to other organisms.

• Net Primary Productivity (NPP): The amount of biomass produced by plants and other producers, minus the energy they use for respiration.

• Trophic structure: Describes the feeding relationships in an ecosystem:

  • Producers: Organisms that make their own food (e.g., plants, algae).

  • Consumers: Organisms that eat other organisms.

  • Decomposers/Detritivores: Organisms that break down dead material, recycling nutrients.

• Energy flow: Energy moves through the food web and is lost as heat at each trophic level, resulting in a pyramid of productivity.

Biogeochemical Cycles

• Nutrients cycle between biotic (living) and abiotic (non-living) components of ecosystems.

• Reservoirs are places where nutrients are stored (e.g., atmosphere, soil, water, organisms).

• Human impacts can alter nutrient cycling, leading to issues such as eutrophication or climate change.

Table: Examples of Biogeochemical Cycles

Example: In a forest ecosystem, energy enters as sunlight, is captured by trees (producers), transferred to herbivores (primary consumers), then to carnivores (secondary/tertiary consumers), and finally to decomposers. Nutrients like nitrogen and phosphorus cycle between soil, plants, animals, and decomposers.

Additional info: Understanding these ecological principles is essential for interpreting maps, graphs, and scenarios related to climate, biomes, population dynamics, species interactions, and ecosystem processes.