Hobbies And Interests
The Big Picture
Planet Earth is composed of biomes; these are the large, distinct regions like tundra, coniferous forest or temperate grasslands. The ocean has several biomes, depending on depth and temperature. Within the biome are ecosystems, which break down further, in ecological terms, into population, community and individual. An ecosystem can be as small as your garden pond, or as large as the Gobi Desert. So the ecosystem can seem somewhat vague but fits into a hierarchy as understood by the scientific community.
Flows
Energy flows. Virtually all energy in an ecosystem starts with the sun and photosynthesis. Grass grows with sunlight, a mouse eats the grass and seed and an owl eats the mouse. The second law of thermodynamics applies here and energy is given off as heat by the mouse and the owl. In ecosystem talk the grass is a primary producer, the mouse is a primary consumer and the owl is a secondary consumer, with the whole process being called a food chain.
Cycles
Within the food chain the nutrients are cycling. The grass takes nutrients from the soil and carbon dioxide from the air, which then pass into the mouse. Mouse droppings and urine are rich in nitrogen, and when the mouse is eaten, the owl takes in nutrients. Owls cough up pellets formed of the indigestible parts, like fur and bones. These pellets are eaten by beetles and the larvae of a relative of the clothes moth. Nutrients cycle from one organism to another, and when plants and animals die the nutrients return to the soil, with some bacterial and fungal help.
Balance
To maintain the ecosystem there must be enough grass, enough mice and enough owls. If the grass dies, the mice will leave, or not reproduce in sufficient numbers and the owls will fly elsewhere or not reproduce. The next year, there may be a good crop of grass and the mice will have a successful year and there will be too many mice because there aren't enough owls. The mice will eat all the grass and some will starve. If all the grass seeds are eaten there will be no grass the next year.
Connections
As well as events in one region affecting another region, there can be connections between one organism and another that affect another unrelated organism. Many plants depend on a specific insect to pollinate them and the flower needs to ready for pollination at the same time the insect is available. A disconnect could occur if the insect is early to hatch because it is triggered by warmth, while the flower is not yet mature because the plant hasn't been exposed to enough sunlight.
Complexity
The example of grass, mice and owls is a simplification of every ecosystem. The reality is more complex and many ecosystems have migratory species. Something affecting a species in its winter range can therefore have an effect on its summer range, which could be thousands of miles away. For example, if pesticides used in South America affect bats that migrate to North America, there may be a lack of mosquito eaters there and a higher incidence of mosquito borne diseases.