CHAPTER 3 Ecosystem Ecology

Chapter 3.1

All ecosystems must include a few basic components in order to maintain a diverse range of organisms. It is necessary for an ecosystem to be able to interact with neighboring systems. Organisms and chemical exchange must be able to cross over ecosystem boundaries in order to not only preserve the biome's ecology but also the Earth's global environment overall. The components of an ecosystem are dependent on factors such as temperature, precipitation, location, and water sources. Ecosystems may be distinguished from each other from the biotic and abiotic components they contain. While all ecosystems are distinguishable from each other, some are more than others. For example, it is easy to identify the boundaries from a lake to a desert. Many processes in ecosystems can occur outside of it's ecosystem's boundaries. An alligator can leave a lake to hunt for food on land.

Chapter 3.2

Ecosystems have trophic levels that describe the movement of energy. Trophic levels are the successive levels of organisms consuming one another that includes 4 levels; producers, primary consumers, secondary consumers, and tertiary consumers. Although not all organisms neatly fit into anyone level it gives a general overview of movement of energy through consumption.

Energy flow begins with sunlight that is absorbed by producers through photosynthesis. Producers are eaten by primary consumers. Next is secondary consumers who eat primary consumers. Lastly is tertiary consumers who eat secondary consumers.

A food chain is the sequence of consumption from producers through tertiary consumers.

A food web is a complex model of how energy and matter move between tropic levels.

An autotroph or producer, is an organism that produces complex organic compounds from simple substances present in its surroundings, generally using energy from light or inorganic chemical reactions. Autotrophs typically use photosynthesis which changes solar energy into oxygen and glucose.

Other organisms such as herbivores eat producers to fuel cellular respiration which is a process by which the chemical energy of "food" molecules is released and partially captured in the form of ATP. Carbohydrates, fats, and proteins can all be used as fuels in cellular respiration, but glucose is most commonly used as an example. Carbon dioxide is a byproduct of cellular respiration. Anaerobic respiration is the process of producing cellular energy without oxygen. Whereas aerobic uses oxygen.

Consumers or heterotrophs are organisms that derive its nutritional requirements from complex organic substances. Types of consumers include carnivores, omnivores, and herbivores. Carnivores eat other consumers. Omnivores eat both consumers and producers. Herbivores eat producers. Producers are organisms that use energy from the Sun to produce usable forms of energy.

Each trophic level eventually produces dead individuals and waste products. Three groups of organisms feed on this dead organic matter: scavengers, detritivores, and decomposers. Scavengers are organisms that eat dead animals. Detritivores, such as dung beetles, specialize in breaking down dead or waste tissues into smaller particles that can be processed by decomposers.

Environmental scientists measure the ecosystem's productivity using the gross primary productivity (GPP) and net primary productivity (NPP). GPP is the total amount of solar energy that producers in an ecosystem capture via photosynthesis over a given amount of time. NPP is the energy captured by producers in an ecosystem minus the energy producers respire.

net primary productivity = gross primary productivity - respiration by producers

Measurement of NPP allows us to compare productivity of different ecosystems. Producers grow best in environments with ample sunlight, water and nutrients, and warm weather.

Ecological efficiency is the proportion of consumed energy that can be passed from one trophic level to another. Ecological efficiency ranges from 5 to 20 percent averaging around 10 percent.

Chapter 3.3

The movement of matter within and between ecosystem is biogeochemical cycle. In ecosystems, we measure the movement of matter by defining the pools, which contain the matter, and the flows, which move the matter. Each cycle, hydrological, carbon, nitrogen, and phosphorus, all contain pools and flows.

In the hydrologic cycle, as water forms into each state of matter (liquid gas and solid), it is in a pool. The transferring of water to each process in the cycle is defined as the pool. In this cycle, bodies of water are warmed by the sun which cause the water to evaporate. The evaporated water forms clouds, then condense and form precipitation. Water then is absorbed in the ground either directly from precipitation or from surface runoff. This ground water eventually forms back into a body of water where the cycle begins again. Humans have the ability to alter this cycle by building aqueducts which can cut off the movement of water between bodies, causing them to dry up and evaporate faster.

In the carbon cycle, several processes occur. There is exchange between the carbon in the ocean and the atmosphere. Plants then take in carbon from the atmosphere. The plant is either consumed, transferring the carbon to the organism that consumed it, or dies, decomposes, and releases carbon back into the atmosphere. The atmosphere also obtains carbon from combustion, or the burning of fossil fuels which releases carbon. Humans have the ability to alter this cycle from excessive burning of fossil fuels.

In the nitrogen cycle, during nitrogen fixation, nitrogen is converted from an atmospheric gas to forms that can be utilized by producers (as ammonia NH4+). After it is converted, nitrification occurs. During this step ammonia is converted to nitrite (NO2-) then to nitrate (NO3-). Then assimilation occurs, where producers absorb the elements into their tissues. Consumers obtain nitrogen by eating the producer. Then mineralization occurs when fungi and bacteria break down organic matter found in waste. It is then converted it into inorganic compounds such as ammonium during ammonification. Humans may affect this cycle by using fertilizers containing nitrogen, increasing the amount of nitrogen in ground water.

The phosphorus cycle begins with the mining, weathering of phosphate rocks, or the use of phosphate fertilizing, which releases phosphorus into the soil and water. It then can be used by producers which are they consumed by consumers, and moves throughout the food web. It can precipitate out of solutions and form sediments, forming phosphate rocks. When humans use fertilizer containing phosphorus, it increases the amount of phosphorus in the ground, then in ground water, then in bodies of water, which can lead to algal bloom. This absorbs all light and kills organisms under the waters surface.

Chapter 3.4
  • A disturbance in an ecosystem is an event caused by physical, chemical or biological agents resulting in changes in population or community composition. When these disturbances occur through a result of human activity, they are defined as anthropogenic. They can also occur naturally.
  • A watershed is all the land in a given landscape that drains into a particular stream, river, lake, or wetland. Biogeochemical and hydrological cycles can be monitored through studying watersheds.
  • Resistance is a measure of how much a disturbance can effect flows of energy and matter in an ecosystem. Reliance is the rate at which an ecosystems returns to its original state after a disturbance.
  • Restoration ecology is the study and implementation of restoring damaged ecosystem. Currently, they are working on two high profile ecosystem restoration projects. These include the Florida everglades and the Chesapeake bay. Their goal is to restore water flows and nutrient inputs.
  • The intermediate disturbance hypothesis states that ecosystem experiencing intermediate levels of disturbance are more diverse than those with high or low disturbance levels. For example, in a species of snails imposes an intermediate level of disturbance to algae, the algae species is more diverse. If it imposed a high or low level of disturbance, the algae would be less diverse.
Chapter 3.5

Instrumental values are tools used to accomplish a goal, while intrinsic values are independent to any benefit of humans. For example, in relation to cars, gasoline is an instrumental value. We use gasoline as a tool to benefit off of. Gasoline does not directly transport us to a desired location, but we still require it to. An intrinsic value used by humans can include consuming food. We eat food and directly benefit from it by absorbing the energy.

  • Provisions, which may include lumber, food, rubber, and furs, are used directly by humans.
  • Regulating services include the regulations of environmental conditions which allow humans to live.
  • Support systems include pollination of food crops which humans consume.
  • Resilience allows species to be diverse. This allows them to better survive changes and disturbances. This can include plants surviving and regulating nitrogen in the atmosphere, which is required for human life.
  • Cultural services provide cultural or aesthetic benefits which people enjoy admiring.

Friedland, Andrew, and Rick Relyea. "Chapter 3" Environmental Science for AP. 2nd ed. W.H. Freeman, 2015. 67-99. Print.


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