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Biodiversity plays a major role in the productivity and functioning of ecosystems, affects their ability to provide ecosystem services. [2] For example, biodiversity is a source of food, medication, and materials used in industry. Recreation and tourism are also examples of human economic activities that rely on these benefits.
Food chain in a Swedish lake. Osprey feed on northern pike, which in turn feed on perch which eat bleak which eat crustaceans.. A food chain is a linear network of links in a food web, often starting with an autotroph (such as grass or algae), also called a producer, and typically ending at an apex predator (such as grizzly bears or killer whales), detritivore (such as earthworms and woodlice ...
An exception occurs in deep-sea hydrothermal ecosystems, where there is no sunlight. Here primary producers manufacture food through a process called chemosynthesis. [5] Consumers (heterotrophs) are species that cannot manufacture their own food and need to consume other organisms. Animals that eat primary producers (like plants) are called ...
Other researchers believe that the relationship between species diversity and productivity is unimodal within an ecosystem. [27] A 1999 study on grassland ecosystems in Europe, for example, found that increasing species diversity initially increased productivity but gradually leveled off at intermediate levels of diversity. [28]
Two species of comparable biomass may have very different life spans. Thus, a direct comparison of their total biomasses is misleading, but their productivity is directly comparable. The relative energy chain within an ecosystem can be compared using pyramids of energy; also different ecosystems can be compared. There are no inverted pyramids.
Keystone species are species that have large effects, disproportionate to their numbers, within ecosystem food webs. [157] An ecosystem may experience a dramatic shift if a keystone species is removed, even though that species was a small part of the ecosystem by measures of biomass or productivity . [ 158 ]
Gross primary production (GPP) is the amount of chemical energy, typically expressed as carbon biomass, that primary producers create in a given length of time.Some fraction of this fixed energy is used by primary producers for cellular respiration and maintenance of existing tissues (i.e., "growth respiration" and "maintenance respiration").
Out of a total of 28,400 terawatt-hours (96.8 × 10 ^ 15 BTU) of energy used in the US in 1999, 10.5% was used in food production, [3] with the percentage accounting for food from both producer and primary consumer trophic levels. In comparing the cultivation of animals versus plants, there is a clear difference in magnitude of energy efficiency.