The food chain comprises all living things and is a true reflection of their interdependence and the complex balance of life. If one animal's source of food disappears, such as from over-fishing or hunting, many other animals in the food chain are impacted and may die.
Breaking one link on the chain means all of the organisms above that link are in threat of extinction (like the domino effect). Since the food chain provides energy that all living things must have in order to survive, it is imperative that we protect it.
 Why should I be aware of this?
A significant portion of the Pacific Ocean, twice the size of Texas, is full of plastic. Some of these minuscule pieces of plastic are so small that they are barely visible to the eye. As they swirl in the seas and oceans, they resemble fish food and are eaten by the small fish. The plastic thus enters the food chain.
Evidences of plastic's entry into the food chain were seen when dead bodies of a large number of seabirds that had been washed ashore were found to contain plastic: things like bottle caps, cigarette lighters, tampon applicators, and colored scraps. Apparently these resemble baitfish to the seabird. Scientists say these toxins cause obesity, infertility and other problems amongst humans.
 How does this affect me?
In recent times, directly or indirectly man has caused the maximum damage to the food chain. He has hunted animals, razed forest for farming and development, and wreaked havoc everywhere. This adverse impact on the food chain might affect our health, the environment and our planet.
When we spray pesticides, we not only put the food chain in danger, but also affect out health by introducing chemicals in our food.
 All about food chain
The food chain consists of four main parts:
- Sun -- The sun is the source of energy for all activities on the earth.
- Producers -- This includes all plants, which harness the energy of the sun and make their own food.
- Consumers - These include all organisms that cannot manufacture their own food and eat food manufactured by something else. While herbivores are primary consumers and the second largest biomass in an ecosystem, carnivores or animals that eat the herbivores make up the third largest biomass, and are also known as secondary consumers. Consumers include
- herbivores --animals that eat plants.
- carnivores -- animals that eat other animals.
- parasites --animals that live off of other organisms by harming it.
- scavengers -- animals that eat dead animal carcasses.
- Decomposers: These mainly comprise bacteria and fungi that convert dead matter into gases such as carbon and nitrogen to be released back into the air, soil, or water. Without decomposers, the earth would be covered in trash. Decomposers also recycle the nutrients so that it can be used again by producers.
Both the sea and the land have a complex food chain.
 On Sea
All sea creatures rely on other sea creatures for food. At the bottom of the food chain here are the sea plants and plankton. These are eaten by many types of fish and animals such as the snail, shrimp, jellyfish, and sea star. These small animals and fish in turn become food for larger fish, such as the tuna and mackerel, which are then eaten by larger fish and animals, such as the shark and dolphin. Sharks are much needed to maintain the balance of the marine ecosystem. However, they are killed for food and other things.
 On Land
On the land plants or bugs are eaten by smaller animals who in turn are eaten by larger animals. At the top of the food chain on land are humans who eat many of the plants and animals on earth. A break in the food chain can impact everyone, humans also. To understand the food chain in the wild, take the example of the zebra and the grass. The zebra eats the grass. Larger predators like the lion eat the zebra.
 Food chain and the environment
 Air Pollution
Human activity cause air pollution and lead to global warming. Apart from increasing the sea levels, rise in earth’s temperatures can cause other alterations in the ecology, including modifying the quantity and pattern of rainfall -- which can have its own ramification on the food chain.
Lower agricultural outputs, glacier melting, lesser summer stream flows, genus extinctions and rise in the ranges of disease vectors are likely to be the other consequences. Global warming has already made species like golden toad, harlequin frog of Costa Rica extinct and a number of species are threatened with extinction.
The rise of carbon dioxide emissions and the resultant climate warming from the burning of fossil fuels are making oceans warmer and more acidic which in tuen are damaging coral reefs, the world's most diverse marine ecosystem.
 Plastic pollution
The plastic pollution is not just a cause of alarm because it is not biodegradable but it is also making its way into the food chain. Its obvious victims include dead seabirds that have been found on shores, their stomachs full of small plastic items such as bottled water caps, cigarette lighters, tampon applicators, and colored scraps that, to a foraging bird, resemble baitfish. These small plastic waste items are not just affecting sea birds but the entire marine foodchain from whales down to zooplankton. There is a growing and disturbing proof that we are ingesting plastic toxins constantly, and that even slight doses of these substances can severely disrupt gene activity.
By hunting animals nearly to extinction, everything above the animal in the food chain is put in danger. A 'chain reaction' in the food chain can be perilous!
As overfishing depletes prized species like tuna, cod and swordfish, commercial fishermen are moving farther down oceanic food webs in search of a catch, it has been observed. If this quest is pursued to its logical end, scientists warn, it will lead to a wholesale collapse of marine ecosystems.
A team of Canadian and American scientists say that the overfishing of large sharks has led to an explosion of small predators that are devastating populations of shellfish.
The steep drop in shark numbers along the U.S. Atlantic coast since 1970 has caused an increase in 12 of 13 species - rays, skates, and smaller sharks eaten mainly by large sharks.
The abundance of one of these species, the cownose ray, has increased 20 times and its prey - scallops, clams, oysters, and other shellfish - have been reduced. The loss of scallops has reduced water quality because scallops and other shellfish filter sea water. And the cownose ray is now feeding voraciously on other shellfish, like oysters and clams.
 90 degrees
An iceberg more than four times the size of Greater London is damaging marine wildlife off the coast of Antarctica by blocking sunlight to a huge expanse of ocean, It has created a build-up of sea ice that has killed the tiny marine phytoplankton - a key element in the Antarctic food chain.
Phytoplankton turns sunlight into food for smaller marine life, notably the shrimp-like krill which is an important source of food for fish, which are in turn eaten by seals and penguins. Sea ice stops sunlight getting to the shallower depths of the sea where phytoplankton grow. The result is that the C-19 iceberg has created the equivalent of a desert.
- One sea animal dissected by Dutch researchers contained 1,603 pieces of plastics.
- One symptom of this practice of fishing down the food chain is that second-level creatures normally preyed upon by the fish at the top of the chain are increasingly appearing on restaurant menus.
- An iceberg more than four times the size of Greater London is damaging marine wildlife off the coast of Antarctica by blocking sunlight to a huge expanse of ocean. This build-up of sea ice has killed the tiny marine phytoplankton - a key element in the Antarctic food chain.
- Human activity is currently responsible for emitting 30 million tons of CO2 each year, 12 million tons of which accumulate in the atmosphere.
- The Food Chain
- Our oceans are turning into plastic...are we? -- Best Life Magazine
- The Balance of Nature -- Food Chain
- Study Finds When Sharks Disappear, So Do Shellfish
- BIODIVERSITY: As Sharks Vanish, Chaotic New Order Emerges
- Huge iceberg destroying Antarctic food chain
- Man Moves Down the Marine Food Chain, Creating Havoc, The New York Times