The biospheres is the global sum of all ecosystems. It can also be called the zone of life on Earth. From the broadest biophysiological point of view, the biosphere is the global ecological system integrating all living beings and their relationships, including their interaction with the elements of the lithosphere, hydrosphere, and atmosphere.
Limiting factors are environmental influences that constrain the productivity of organisms, populations, or communities and thereby prevent them from achieving their full biological potential which could be realized under optimal conditions. Limiting factors can be single elements or a group of related factors.
Nutrients are cycled back into the ecosystem, but energy only moves in one direction through the community from producers to herbivores to carnivores.
Trophic level describes the position of the organism in relation to the order of nutrient and energy transfers in an ecosystem. Organisms that eat the same type of food belong to the same trophic level.
Food chains show a single pathway taken by nutrients and energy through the trophic levels.
In reality, ecosystems have more complex food webs , showing the different cross-linked food chains.
Interactions in Ecosystems Activity Using the food web on the right, predict what might happen if a disease killed all the krill in the ecosystem. Which species would be affected, and how? Try drawing a new food web. 2 CHAPTER
One especially amazing example of commensalism occurs between the Pearlfish and a particular species of sea cucumber. The Pearlfish spends the day inside the alimentary tract (‘intestines’) of the sea cucumber, and at night emerges from its anus to feed on small crustaceans! In this manner it gets a safe place to live; and while not appearing to gain any benefit from the relationship, the cucumber is not harmed.
In a parasitic relationship, the host species is always exploited to some degree, although often in such a way that its health is impaired only slowly. This allows the parasite to exploit its host over a longer period. Many parasites only spend a portion of their lives in the relationship, either to reproduce, or during an initial growth stage.
Parasites can be divided into two basic categories, Ectoparasites and Endoparasites , the former referring to external parasites, and the latter internal parasites.
the Boxer crab, carries a pair of small anemones in it s claws . When approached by a predator it waves these around presenting the stinging tentacles so as to deter the marauder. The anemones benefit from the small particles of food dropped by the crab during feeding.
Mimicry is a form of symbiosis where a species may mimic the colours, patterns, or even behaviour of another species for one of two reasons. Either to be able to get closer to unsuspecting prey or in the case of a harmless species; to gain protection by imitating a predator or poisonous species.
One of the most interesting mimic species is the Mimic octopus. It takes on the form of a variety of different animals by bunching up or elongating its arms to mimic anything from a stingray to a Lionfish or even a sea-snake. It could be that this species employs mimicry both as a means of defence and predation
A particular type of mutualistic interrelationship that many divers will have encountered is ‘Cleaning symbiosis ’, The fish being cleaned are often termed ‘client fish’ and the sites they go to to be cleaned are known as ‘Cleaning stations’ ... in tropical waters these areas of the reef are quite clearly defined by the numbers of stationary fish and their attendant cleaner organisms.