Niche

Niche is what an organism does to make a living.

Fungi feed on dead and decaying organic matter.

Green plants are producers. They change sunlight into food energy. They do require a certain amount of water and nutrients from the soil to do this.

Opossums are opportunistic eaters. They eat plants, they kill and eat small animals, they scavenge from carcasses.

Carnivores are at the top of the food chain. They eat meat.

Herbivores eat plants.

Omnivores eat plants and animals.

We talk about the food chain but it is actually a web. The more connections a food web has, the healthier it is. It is sort of like Ireland during the Potato famine as it is known in the United States or the Hunger as it is known in Ireland. Plenty of food was grown and exported. However, the peasants only ate potatoes.

When the blight affected the potato harvest for several years, many people starved. Others emigrated. Ireland's population was at a historic high of approximately 8 million in 1841. Today the population is slightly over 6 million today.

 http://www.mapspictures.com/ireland/history/ireland_population.php

So when ecologist discuss that an ecosystem does not have enough diversity. This is why it has a problem. If there is one organism that the entire ecosystem revolves around, it's loss will devastate the ecosystem.

The Chestnut blight still affects North American forests. At one time Chestnuts fed people and animals. When the tree virtually disappeared, there are a few that have survived, it left the ecosystem dependent on acorns, pecans, walnuts, hickory nuts to make up for it's loss. Some years they are not enough.

It takes 1000 pounds of vegetable matter to convert to 100 pounds of animal matter. 900 pounds is lost in the energy of day to day living. 100 pounds of herbivore will produce 10 pounds of carnivores. This is why there are much fewer cougars, bobcats, coyotes, wolves compared to herbivores such as deer and rabbits.

I post this picture too many times. But I love how the spiders get busy and build webs in an overgrown field.
You don't notice the webs during the day. The morning dew on them makes them more visible.