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* As a reproductive unit. The species is the taxonomic unit that describes all organisms capable of reproducing by producing fertile offspring.
* As a unit of evolution. Due to reproduction, each species is also the unit of evolution. Given that each species is the result of interbreeding between members over the length of their history, member organisms are more closely related to each other than to any other organisms. So they have in common certain structural and functional characteristics and share the species’ gene pool.
*As an ecological unit. Being evolutionary units, all species are also ecological units. Each one is defined by its ecological niche: its place in nature (it lives in a certain environment, it uses certain materials, it eats certain types of food, with certain habits, it reproduces following certain habits, etc.)
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MATTER AND ENERGY IN ECOSYSTEMS
To understand the relationships within an ecosystem, it is useful to visualise the food or trophic structure. To do this, all the organisms of the biocenosis must be grouped according to how they obtain nutrients.
Trophic networks are representations of all the trophic chains in an ecosystem and how they interconnect with each other.
Producers
Primary consumers
Secondry consumers
Ternary consumers
The environmental factors are all the components of an ecosystem, whose presence or variation influences the organism that from the biocenosis. The environmental factors can be abiotic and biotic.
Biotic. These factors refer to any organism or the behavior of any organism which affects the life of the other organisms within the system. We can distinguish intraspecific and interspecific relationships:
Abiotic. These factors are the physical and chemical elements of an ecosystem. The most important abiotic factors are:
- Intraspecific relationships are relationships between members of the same species. The most important are competition, where animals compete for resources such as food, mates, territory, etc., and associations, including related individuals (family) or not related (gregarious).
- Temperature; most living things cannot live at temperature below 0ºC or above 50ºC).
- Light; essential for autotrophic organisms.
- Interspecific relationships are relationships between members of different species. They are classified according to the effects that individuals of interacting species have on each other, using symbols:
- Water; without water life cannot exist.
– (negative effects), + (positive effect) and 0 (no effects).
Some of the most common are Competition (-,-); Predation (+,-); Parasitism (+,-); Commensalism (+,0) and Mutualism
Skeleton tasmanian tiger
Background photo by t.shigesa