The habitat of organisms is constantly exposed to various volatile factors. Organisms are able to reflect the parameters of the environment. During the historical development of living organisms, three habitats have been developed. Water is the first of them. In it, life was born and evolved over millions of years. Ground-air - the second environment in which animals and plants emerged and adapted. Gradually transforming the lithosphere, which is the upper layer of land, they created the soil, which became the third habitat.
Each species of individuals living in a particular environment, characterizes its type of energy and metabolism, the preservation of which is important for its normal development. In a state of the environment that threatens the body with a disturbance in the balance of energy and substance metabolism, the body either changes its position in space, or transfers itself to more favorable conditions, or changes the activity of metabolism.
Aquatic habitat
Not all factors play an equal role in the life of aquatic organisms. According to this principle, they can be divided into primary and secondary. The most important of them are the mechanical and dynamic characteristics of bottom soil and water, temperature, light, suspended and dissolved substances in water, and some others.
Aquatic factors
The aquatic habitat, the so-called hydrosphere, occupies up to 71% of the entire planet. The volume of water is almost 1.46 billion cubic meters. km Of these, 95% are the oceans. Fresh water consists of glacial (85%) and groundwater (14%). Lakes, ponds, reservoirs, swamps, rivers and streams occupy a little more than 0.6% of the total amount of fresh water, 0.35% is contained in soil moisture and atmospheric vapors.
The aquatic habitat is inhabited by 150 thousand species of animals (which is 7% of all living creatures of the Earth) and 10 thousand species of plants (8%).
In the region of the equator and tropical zones, the world of animals and plants is the most diverse. As you move north and south from these zones, the qualitative composition of aquatic organisms becomes poorer. Organisms of the oceans are concentrated mainly off the coast. Life is practically absent in open waters, located away from the coast.
Water properties
The physical properties of water determine the vital activity of living organisms in it. Among them, first of all, thermal properties are important. These include high heat capacity, low thermal conductivity, high latent heat of evaporation and melting, and the property of expansion before freezing.
Water is an excellent solvent. In the dissolved state, all consumers absorb inorganic and organic substances. The aquatic habitat facilitates the transport of substances within organisms, and the decomposition products are also excreted in water.
High surface tension of water holds living and non-living objects on the surface and fills the capillaries, due to which terrestrial plants feed.
The transparency of water promotes photosynthesis at great depths.
Ecological groups of aquatic organisms
- Benthos - these are organisms that are attached to the soil, lie on it or live in the thickness of sediments (phytobenthos, bacteriobenthos and zoobenthos).
- Periphyton - animals and plants that are attached or held by the stems and leaves of plants or any surface that rises above the bottom and floats with the flow of water.
- Plankton - free-floating plant or animal organisms.
- Necton - actively swimming organisms with streamlined body shapes that are not connected to the bottom (squids, fish, whales, pinnipeds, etc.).
- Neuston - microorganisms, plants and animals that live at the surface of the water between water and air. These are bacteria, protozoa, algae, larvae.
- Pleiston - hydrobionts, partially located in water, and partially above its surface. These are sailboats, siphonophores, duckweed and arthropods.
The inhabitants of the rivers are called potamobionts.
The aquatic environment is characterized by peculiar living conditions. The distribution of organisms is greatly influenced by temperature, light, water currents, pressure, dissolved gases and salts. Living conditions in sea and continental waters are very different. Sea water is a more favorable environment, close to physiological saline. Continental waters are less favorable for their inhabitants.