Which generalization is best supported by the information on this map? No trade occurred between East Africa and the Persian Gulf region.
The monsoon winds influenced trade between East Africa and India.
Trading states developed primarily in the interior of East Africa.
Trade encouraged the spread of Islam from East Africa to Arabia.

The Living Things in an Ecosystem

Organisms within an ecosystem are comprised of several species of living things -- from the microscopic to the very large. A pond ecosystem’s living things, for example, range in size from the algae and zooplankton in a drop of pond water to the larger fish, amphibians, lilies and cattails that make their homes in the pond. Meanwhile, a community is defined by all the different populations of varied species co-existing and thriving within that same habitat. The resilience of the community hinges on a cycle -- or chain of events and processes -- that creates food and energy for all the organisms within the ecosystem. The ecosystem’s cycle encompasses the producers, consumers and decomposers who cycle energy through the food web so that there is constant productivity, decomposition and nutrient cycling.

The Nonliving Things in an Ecosystem

The nonliving things in an ecosystem create and define the ecosystem's environment and include sunlight, temperature, precipitation, weather, landscape, soil chemistry, water chemistry and even base nutrient supply. These abiotic components are vital to the ecosystem’s health because they are keystones in its energy flow and nutrient cycle. Energy from sunlight is transformed into chemical energy through photosynthesis by plants, which are the base producers in most ecosystems. Essential nutrients and elements -- such as carbon, nitrogen, oxygen -- that are necessary for the biochemical processes of life are obtained from the surrounding atmosphere, soil, water and physical environment. Energy and elements are endlessly cycled within the ecosystem because of the interaction between its biotic (living) and abiotic (nonliving) elements.

The Relationship Between Living And Nonliving Things

Biotic and abiotic elements of an ecosystem are closely tied to one another. Nonliving factors determine what living things can be supported in an ecosystem. Similarly, the living things in a habitat affect the nonliving things there. For example, plants can affect soil chemistry or certain algae influence water chemistry. An ideal ecosystem is balanced among its parts, both biotic and abiotic, so that energy flow and nutrient cycling are stable enough for all organisms to reproduce and thrive. Any disruption -- like the removal or addition of an abiotic or biotic factor -- to the ecosystem can impact numerous aspects of its organization. For example, introducing an invasive species or a toxic pollutant throws the ecosystem's structural organization off kilter, often with domino-like effects.

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