4C4The diversity of species

within an ecosystem may influence the stability of the

ecosystem

a. Natural and artificial ecosystems with fewer component parts and with little diversity among the parts are often less resilient to changes in the environment.

A typical example of an artificial ecosystem is a farmland or agro-ecosystem. ◦This is a natural system altered by man through

farming

Artificial Ecosystem

It differs from a natural ecosystem for four reasons:

• it is simpler, because the farmer gives priority to one type of plant only, fighting against all those animal and vegetal species that might damage it;

• the energy is supplied by man, through machinery, fertilizers, plant chemicals, selected seeds, farming practices

• the biomass (harvest) is removed when ripe. This makes the ecosystem an open system, i.e. one that depends on external sources to reintroduce fertilizing substances, fit for feeding a new process of birth and development of organic matter (the plants).

A natural ecosystem fertilizes itself, instead, since the biomass remains in its original place

• the use of polluting substances, such as chemical fertilizers, parasite killers and other non-biodegradable chemicals

These build up in the ecosystem or disperse in the subsoil, sometimes seriously polluting underground water-bearing layers, seas and rivers.

b. Keystone species, producers, and essential abiotic and biotic factors contribute to maintaining the diversity of an ecosystem.

The effects of keystone species on the ecosystem are disproportionate relative to their abundance in the ecosystem

When they are removed from the ecosystem, the ecosystem often collapses.

. Define a keystone species

Keystone species are the species which are critical in maintaining the relationship of an ecosystem.

Keystone species are those species whose importance to an ecosystem’s structure, composition, and function is disproportionately large relative to their

abundance. These species can be of any life form, but

they have in common an effect on their environment that is always greater than what can be expected based on their biomass

Types of Keystone Species

Well-studied examples include sea stars, beavers, bears, corals, elephants, and hummingbirds.

A keystone species is often, but not always, a predator.

A few predators can control the distribution and population of large numbers of prey species.

Define which organism is the keystone species

Ecosystem – Mackenzie Mountains in Western Canada

Tundra and Boreal forestBoreal forests are Coniferous forests,

the largest ecosystem on Earth

A single mountain lion near the Mackenzie Mountains in Canada can roam an area of hundreds of kilometers.

The deer, rabbits, and bird species in the ecosystem are at least partly controlled by the presence of the mountain lion.

Their feeding behavior, or where they choose to make their nests and burrows, are largely a reaction to the mountain lion's activity.

Scavenger species, such as vultures, are also controlled by the activity of the mountain lion.

3. Describe what would happen to the ecosystem if the keystone species was removed

A keystone species' disappearance would start a domino effect

If the keystone species disappears, the ecosystem would fall apart.

Other species in the habitat would also disappear and become extinct.

The keystone species' disappearance could affect other species that rely on it for survival.

For example, the population of deer or rabbits would explode (____?____ growth) without the presence of a predator.

The ecosystem cannot support an unlimited number of animals, and the deer soon compete with each other for food and water resources.

Their population usually declines without a predator such as a mountain lion.

Without the keystone species, new plants or animals could also come into the habitat and push out the native species.

Some species of hummingbirds are keystone species in the Sonoran Desert of North America.

Hummingbirds pollinate many varieties of native cactus and other plants.

In areas of the Sonoran Desert with few hummingbirds, invasive species such as buffelgrass have taken over the ecosystem.

http://www.youtube.com/watch?v=_IWw8Ruz8Uo

Bozemanhttp://

www.youtube.com/watch?v=0-PE3ve3w2w