Ecology Chapter: Primary Production

Chapter 18: Primary + Secondary Production

• Ecosystem ecologists study the complex interactions of energy, water, and nutrient flows in ecosystems, and how these processes sustain life. This field of study is crucial for understanding the ecological balance and the health of different ecosystems.
• Primary production is the process through which new organic matter is created per unit area in an ecosystem over a specified time period. This is a fundamental aspect of the energy flow in ecosystems, as it establishes the basis for food chains and supports all life forms that rely on this organic matter for energy.
  • Gross primary production (GPP) refers to the total amount of primary production accomplished by all producers in an ecosystem, including plants, algae, and some bacteria. This metric provides insight into the overall productivity of an ecosystem.
  • Net primary production (NPP) is derived from gross primary production by subtracting the energy used for respiration by the producers. This calculation represents the biomass that is available for consumption by herbivores and higher trophic levels, making it an essential component for evaluating the energy available to consumers within the ecosystem.
• Secondary production denotes the generation of biomass by consumers within an ecosystem, such as animals and microorganisms that feed on the primary producers. This process is vital for recycling nutrients within the ecosystem and supports higher trophic levels.
• Trophic levels categorize the various positions in a food web based on the number of energy transfers from primary producers to consumers. Understanding these levels helps define the structure of ecosystems and the relationships among different organisms.
  • Primary producers occupy the first trophic level, where they convert sunlight into organic material through photosynthesis, serving as the foundation for all other trophic levels.
  • Primary consumers, which include both herbivores and detritivores, occupy the second trophic level. They obtain energy by consuming primary producers or decomposing organic material, respectively.
  • Secondary consumers are positioned at the third trophic level and consist of carnivores that prey on primary consumers. This group further illustrates the flow of energy through the ecosystem.
  • Tertiary consumers make up the fourth trophic level, feeding on secondary consumers and highlighting the continuation of energy transfer through the food web.
• Terrestrial primary production is often influenced by several limiting factors, including temperature, moisture, and nutrient availability. These factors can significantly impact the productivity levels of different ecosystems.
  • The highest rates of primary production are typically observed in warm and moist conditions, which facilitate optimal plant growth and energy capture.
  • Actual evapotranspiration, which refers to the amount of water that is evaporated and transpired, has a strong correlation with terrestrial primary production. This relationship emphasizes the importance of water availability in supporting ecosystem productivity.
• Soil fertility plays a crucial role in influencing terrestrial primary production by determining the availability of essential nutrients for plant growth.
  • Adding nutrients, particularly in nutrient-poor environments such as dry meadows, can lead to significant increases in primary production. This highlights the value of managing soil health and nutrient addition in agricultural and natural ecosystems.
• Aquatic primary production is often constrained by the availability of nutrients, mainly phosphorus, which is a critical element for phytoplankton growth in freshwater ecosystems.
  • A strong relationship exists between phosphorus levels and phytoplankton biomass, as adequate phosphorus concentrations are essential for supporting the primary producers that form the base of aquatic food webs.

Chapter 20: Succession + Stability

• Succession refers to the gradual changes in plant, animal, and microbial communities in a given area after a disturbance or the implementation of a new habitat. Understanding this process is critical for restoration ecology and conservation efforts.
  • Primary succession occurs on newly exposed geological substrates, such as volcanic rock or glacial landscapes, where soil has not yet formed. This process begins with pioneer species that are capable of colonizing harsh environments.
  • Secondary succession takes place in areas where soil and organic matter remain, such as following a forest fire or other disturbances. This type of succession typically occurs more rapidly due to the existing soil nutrients.
  • Pioneer communities consist of the initial organisms, such as lichens and mosses, that colonize disturbed areas. They play a crucial role in modifying the environment, making it more suitable for later successional species.
  • Climax communities are the stable, mature communities that develop at the end of a succession process. These communities are relatively stable and persist until they are disrupted by a significant disturbance, which could initiate the process of succession once more.
• Ecologist Frederic Clements proposed that succession is a predictable series of events that follows a consistent pattern of species interactions, leading to the development of a climax community.
• Conversely, Henry Gleason viewed succession as a more chaotic process, driven primarily by the independent responses of species to their particular environmental conditions, suggesting that variances in local species might lead to differing successional outcomes.
• Primary succession studies conducted in locations such as Glacier Bay demonstrated a clear progression in plant diversity over time, though the findings also suggested that the predictability Clements proposed was not entirely supported by empirical data, indicating a more complex reality.
• In temperate forests, studies of secondary succession revealed that species richness often increases as succession progresses. This phenomenon suggests that disturbances might promote biodiversity by creating opportunities for various species to establish themselves.
• Succession is also observable in rocky intertidal communities, where ecological succession occurs among intertidal boulder communities, illustrating the adaptability of communities in response to environmental changes.
• Mechanisms of succession can be explained by three primary models—facilitation, tolerance, and inhibition. These models describe how species interactions can either promote or hinder the establishment and growth of subsequent species during the successional process.

Chapter 22: Geographic Ecology

• Geographic ecology delves into understanding the spatial distribution of plant and animal life, and how geographical features influence these patterns across different landscapes.
• Island biogeography is a specific subfield that examines the factors affecting species richness on islands, including size and distance from the mainland. These factors are critical in determining how many species can thrive in those isolated environments.
  • Research in this area explores the relationships between the area of the island and species richness, as larger islands typically support more species due to greater habitat diversity, alongside the distance from the mainland, which affects immigration and extinction rates.
• Latitudinal gradients in species richness show a notable trend: species richness generally increases from the polar regions toward the equator. This pattern can be attributed to a range of factors, including historical climate stability, environmental heterogeneity, higher productivity, and more favorable living conditions found in tropical regions.
• The dynamics of historical and regional influences are also critical in shaping species richness and diversity. This includes the impact of evolutionary processes, past climatic conditions, and human activities that may have altered natural habitats.

Chapter 23: Global Ecology

• The atmosphere at the Earth's surface primarily consists of clean, dry air made up of nitrogen, oxygen, and argon, alongside lower quantities of carbon dioxide and various trace gases that are essential for life.
• The greenhouse effect is a natural phenomenon that warms the Earth's surface. This warming occurs through the absorption and re-emission of infrared radiation by atmospheric gases, thus maintaining temperatures suitable for life.
• The El Niño Southern Oscillation (ENSO) constitutes a global climate pattern characterized by periodic warming (El Niño) and cooling (La Niña) of ocean surface temperatures in the Pacific Ocean. These fluctuations have widespread effects on global weather patterns, influencing climate across various regions.
• Human activity has significantly altered atmospheric composition over recent decades, leading to increased concentrations of greenhouse gases. This anthropogenic impact has been pivotal in shaping current climate patterns and accelerating global warming, thereby influencing ecological and atmospheric processes on a global scale.

This quiz covers key concepts related to primary production in ecosystems, including definitions, calculations, and the roles of various trophic levels. It also examines factors affecting primary and secondary production and discusses nutrient dynamics in marine environments. Test your knowledge on phytoplankton biomass and nutrient limitations!