An ecosystem is a community of plants, animals, and smaller organisms that live, feed, reproduce, and interact in the same area or environment. Every plant and animal could not exist alone on planet Earth. All living organisms need millions of other living organisms to survive. The way these organisms interact with the sun, soil, water, air and each other in a specific space is called an ecosystem. In the following paragraphs, I will talk about the organizations that make up an ecosystem and their organizations. There are two main types of ecosystems: aquatic and terrestrial. An aquatic ecosystem is found in a body of water where animals, plants, and their physical environment interact in the water. The two main parts of aquatic ecosystems are marine ecosystems and freshwater ecosystems. The marine ecosystem covers approximately 71% of the earth's surface and can be divided into different zones and categories. The marine ecosystem area is divided based on water depth and shoreline characteristics. The ocean zone is the open part of the ocean where animals like sharks and whales live. The intertidal zone is the area between high and low tides and includes coral reefs, lagoons and salt marshes. Benthic zone in which many invertebrates live. There are also thousands of plant species that live in the ocean, such as algae, algae, seagrasses, and mangroves. (Mann KH 2006) Aquatic ecosystem is also classified as freshwater ecosystem. These include ponds, lakes, streams, rivers, creeks and wetlands. Ponds and lakes are often called lentic ecosystems. This means they have still or stagnant water, which does not move like rivers or streams. Lakes are often divided into four zones of biotic communities: Littoral zone - Lim...... middle of paper ......ing.• Living things are composed of cells that have a complex and organized structure.• Living things maintain their complex structures and internal environment called homeostasis.• Living things respond to stimuli from their environment.• Living things have the capacity to evolve.• Living things acquire energy from their environment and convert it in different forms.• Living things grow .• Living things reproduce. If something follows one or a few of the rules listed above, it does not necessarily mean it is alive. To be considered living, an object must exhibit all the characteristics of living beings. For example, a virus can be considered a living thing because it has the ability to make someone very sick, but in reality, viruses are not living things. Viruses do not reproduce, have no energy, and do not respond to stimuli. (Audesirk T. 2011)