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Epilobium hirsutum seed head dispersing seeds. In spermatophyte plants, seed dispersal is the movement, spread or transport of seeds away from the parent plant. [1] Plants have limited mobility and rely upon a variety of dispersal vectors to transport their seeds, including both abiotic vectors, such as the wind, and living vectors such as birds.
A pyramid of energy or pyramid of productivity shows the production or turnover (the rate at which energy or mass is transferred from one trophic level to the next) of biomass at each trophic level. Instead of showing a single snapshot in time, productivity pyramids show the flow of energy through the food chain. Typical units are grams per ...
In order to more efficiently show the quantity of organisms at each trophic level, these food chains are then organized into trophic pyramids. [1] The arrows in the food chain show that the energy flow is unidirectional, with the head of an arrow indicating the direction of energy flow; energy is lost as heat at each step along the way. [2] [3]
Ants disperse seeds in fairly predictable ways, either by disposing of them in underground middens or by ejecting them from the nest. [2] These patterns of ant dispersal are predictable enough to permit plants to manipulate animal behaviour and influence seed fate, [ 13 ] effectively directing the dispersal of seeds to desirable sites.
Like many wetlands, some ecosystems do not organize as a strict pyramid because aquatic plants are less productive than long-lived terrestrial plants such as trees. Ecological trophic pyramids are typically one of three kinds: 1) pyramid of numbers, 2) pyramid of biomass, or 3) pyramid of energy. [6] Food webs have trophic levels and positions.
[2] [3] Species at the bottom of the food chain, such as algae and other autotrophs, consume non-biological resources, such as minerals and nutrients of various kinds, and they derive their energy from light or chemical sources. Species higher up in the food chain survive by consuming other species and can be classified by what they eat and how ...
The efficiency with which energy or biomass is transferred from one trophic level to the next is called the ecological efficiency. Consumers at each level convert on average only about 10% of the chemical energy in their food to their own organic tissue (the ten-per cent law). For this reason, food chains rarely extend for more than 5 or 6 levels.
The mean chain length of an entire web is the arithmetic average of the lengths of all chains in the food web. [13] The food chain is an energy source diagram. The food chain begins with a producer, which is eaten by a primary consumer. The primary consumer may be eaten by a secondary consumer, which in turn may be consumed by a tertiary consumer.