unicellular animals - a category of organisms, which is outside the system.This means that they can not be entirely attributed to any particular kingdom.Unicellular organisms characterized by a lack of highly tissue.All animals belonging to this group are not together any common features.The only thing that unites them - a simple structure.
Single-celled animals usually so tiny that they can be seen only under a microscope.Their habitat - wet.This soil and water as well as human body, animal.All of them anyway by different devices are adapted to different conditions.In the first place - is a form of the body.She may not have clear boundaries, constantly changing, and may, on the contrary, be streamlined, spindle-like or elongated.And different types of symmetry: radial, translational, rotational, double-sided.Some single-celled animals have a shell on the outside, the other, those that live in deep water - unusual growths.
cells from which the body is composed of these organisms may contain from one to several nuclei.The shell is a membrane, or only, or more dense, capable of longer stretch pellicle.
Moves celled organism with the help of various ciliary prolegs, flagella.They also respond to the impact of external factors such as changes in temperature, lighting, availability of chemicals.
Food celled animals receive in different ways.So, during phagocytosis outgrowths cytoplasm capture solid particles of food.Pinocytosys place in several stages: first, the entire cell surface captures the liquid and then absorbs the substances contained in it, recycles them using digestive enzymes, which are filled vacuoles.Inside, some of the simplest (chlorella) have chloroplasts that are using photosynthesis from inorganic substances can produce organic.
also the entire surface of the body is involved in gas exchange simple: go through it outward decay products and excess water.
multiply single-celled animals and sexually and asexually.It depends on the conditions in which they exist.Asexual reproduction occurs so.First, several divided core pieces, and then the same number of divided parts and cytoplasm.Thus, one of the simplest organism can have several (at least two).
In sexual reproduction involving male and female individuals.Their structure and size may vary, and may be the same.As a result of the merger of a zygote, which then reproduces asexually already own.It happens that individuals come into contact, exchange of nuclei particles.In this case, the zygote is not formed.
When the conditions are not conducive to normal life simple, their body becomes round, covered with a dense shell.Since forming cysts.Once conditions improve, the body is released from the thick film and begins to lead the same lifestyle as before.
accepted that single-celled animals first appeared in the course of evolution on Earth.The most ancient are archaea and bacteria.They are similar in many ways (eg, lack of core, the presence of a ring chromosome), for this reason, before they are assigned to one group.But modern science has proved that archaea have their own features in the structure and has evolved a little bit the other way.Although they also difficult to classify, as before.The fact that in the laboratory archaea never grown, and have been found during the analysis of samples taken from the places where they live.
unicellular organisms - this link, without which it is impossible to complete biocoenosis.After all, they eat many animals, which themselves serve as food for even a number of inhabitants of our planet.
