Biotic Relationships

Biotic ecological factors also influence biocenose viability; these factors are considered as either intraspecific and interspecific relations.

Intraspecific relations are those which are established between individuals of the same species, forming a population. They are relations of co-operation or competition, with division of the territory, and sometimes organization in hierarchical societies.

Interspecific relations—interactions between different species—are numerous, and usually described according to their beneficial, detrimental or neutral effect (for example, mutualism (relation ++) or competition (relation --). The most significant relation is the relation of predation (to eat or to be eaten), which leads to the essential concepts in ecology of food chains (for example, the grass is consumed by the herbivore, itself consumed by a carnivore, itself consumed by a carnivore of larger size). A high predator to prey ratio can have a negative influence on both the predator and prey biocenoses in that low availability of food and high death rate prior to sexual maturity can decrease (or prevent the increase of) populations of each, respectively. Selective hunting of species by humans which leads to population decline is one example of a high predator to prey ratio in action. Other interspecific relations include parasitism, infectious disease and competition for limiting resources, which can occur when two species share the same ecological niche.

The existing interactions between the various living beings go along with a permanent mixing of mineral and organic substances, absorbed by organisms for their growth, their maintenance and their reproduction, to be finally rejected as waste. These permanent recyclings of the elements (in particular carbon, oxygen and nitrogen) as well as the water are called biogeochemical cycles. They guarantee a durable stability of the biosphere (at least when unchecked human influence and extreme weather or geological phenomena are left aside). This self-regulation, supported by negative feedback controls, ensures the perenniality of the ecosystems. It is shown by the very stable concentrations of most elements of each compartment. This is referred to as homeostasis. The ecosystem also tends to evolve to a state of ideal balance, reached after a succession of events, the climax (for example a pond can become a peat bog).

Other Abiotic Factors

Abiotic stress is caused in living organisms by nonliving environmental factors, such as drought , extreme temperatures , soil conditions, and high winds. Plants are especially dependent on environmental factors, and continued abiotic stress can have harmful effects on them or force natural selection Geological Change

Many years ago the Earth was still very unstable, rapid and extreme geological change would have wiped out adapted organisms and promoted change in the more adaptive organisms.

The most primitive fish are invertebrates, of which some still exist today. These would most likely be the first fish to occupy Earth, having diversified from the primitive crustaceans that occupied the sea beforehand. These primitive and relatively unspecialised organisms would have adapted over a long period of time (millions of years) to take into account the factors above.

Also, as competition increased and available habitats decreased, fish would have had to be more aggressive or more co-operative in their nature to survive in the long term. This has led to species like the shark, which is of phenomenal size and represents danger.

Other species have taken a different approach, adopting chemical defences as a means of survival. Others have adapted to occupy very low altitudes, thus avoiding some of the more competitive habitats closer to the water surface.

All in all, fish, alongside the later developing mammals, would successfully dominate the seas. In the future, mammals would occupy the sea from land, but fish done the opposite; they evolved from sea on to land just like the arthropods intended.