CONNECTIONS, CYCLES, FLOWS AND FEEDBACK LOOPS Environmental Systems

Systems Describe Interactions A system is a network of interdependent components and processes, with materials and energy flowing from one component of the system to another. Ecosystem  Represents complex collection of animals, plants, and their environment through which materials and energy move.

Systems Describe Interactions We can use general terms to describe the components of a system.  Variables store resources such as energy, matter and water and flows from one variable to another. Plants and animals represent variables. (sun, plants, bunny, coyote, death)

Systems are Described in Terms of their Characteristics Open systems are systems that receive input (energy, water, etc.) from their surroundings and produce outputs that leave the system. Throughput is a term we can use to describe the energy and matter that flow into, through, and out of a system. (think about income!)

A wetland is an open system!  Nutrients and water are received from upstream. Plants and algae transform the nutrients into vegetation, which then becomes part of the fish. Then a heron catches the fish, eats it, then flies off to another water source.

Positive feedbacks refer to factors that result from a process and, in turn, increase that same process. (ex. Over abundance of nutrients in a wetland, increases plant growth and can lead to a biological collapse) Negative feedback refer to factors that result from a process and, in turn, decrease that same process (ex. Too many fish in a pond)

Negative feedback loops tend to maintain stability in a system. We often think of systems exhibiting homeostasis, or a tendency to remain more or less stable and unchanging.

Life Depends on the Sun Remember our example of the coyote eating the rabbit as an ecological system?  The daisies get their energy from the sun, making food during photosynthesis  The rabbit eats the daisies and receives energy from the plant.  When the coyote eats the rabbit, small amounts of energy are transferred from the rabbit to the coyote.

The daisies are called producers. It makes its own food. This means they are autotrophic. Both the rabbit and the coyote are consumers, they get their energy from eating other organisms. They are heterotrophs. Note: Almost all producers get their energy directly from the sun while consumers get their energy indirectly from the sun.

Who Eats What? Consumers that eat only producers are called herbivores. Consumers that eat only other consumers are called carnivores. Consumers that eat both producers and other consumers are called omnivores. Consumers that get their energy from breaking down dead organisms are called decomposers.

Energy Transfer We already learned that every time one animal eats another a transfer of energy occurs. We can trace the path of energy by studying food chains, food webs and trophic levels.

Food Chains and Webs A food chain is a sequence in which energy is transferred from one organism to the next, in a chain. Entire ecosystems are more complex than that, as many organisms are eaten by and eat many other organisms. A food web shows all the feeding relationships in an ecosystem.

Trophic Levels Each step in the transfer of energy through an ecosystem is called a trophic level. Every time energy is transferred, less of it is available to organisms at the next trophic level. Organisms use energy to carry out functions of living (about 90%), that means only 10% is passed on to the next trophic level.

Questions from “Environmental Science” Page 61, Questions Page 72, Questions 1 a, b, d, 3, 4, 6, 7, 8, 16

Elements of Life Matter is recycled and doesn’t disappear  matter is neither created nor destroyed but rather is recycled over and over again. It can be tranformed or recombined, but it doesn’t disappear; everything goes somewhere (think of the what we through away!) Just four elements— oxygen, carbon, hydrogen, and nitrogen (symbolized as O, C, H, and N)— make up more than 96 percent of the mass of most living organisms.

Organisms use some elements in abundance, others in trace amounts, and others not at all. Carbon is a particularly important element because chains and rings of carbon atoms form the skeletons of organic compounds.