There are so many wonderful microscopic organisms in the world. If it occurred to anyone to compile a list of the seven wonders of the microworld, then volvox algae would certainly be included in this list.
Green algae
Volvox is green algae. They exist in the form of a colony. Why are volvox classified as unicellular organisms? The answer is quite simple: each individual small alga is a cell that has two flagella and hairs.
Single cells are connected to each other by thin filaments of the cytoplasm, which allow the entire colony to swim in concert. Apart from hairs and flagella, individual representatives also have a small red spot, the so-called peephole.
Differentiation of cells gives uniqueness to representatives of algae. Each colony has a beginning and an end, in other words, the North and South poles. In the first region, a more pronounced accumulation of developed eyes is observed. This helps the algae swim towards the light. Thus, a colony of unicellular organisms outwardly may well pass for a multicellular organism.
Volvox: structure
When answering the question why volvox is referred to as unicellular organisms, it is worth mentioning that a single cell can reach 2 millimeters in diameter (up to 2 cm in larger colonies), so they can be easily seen with the naked eye. Individual algae are connected by thin strands of cytoplasm.
The structure of volvox algae is quite simple. The central cavity is filled with mucus. All cells have two flagella, which are attached at the front end. Each cell in the cell performs its function of nutrition, respiration and excretion. The shape can be spherical, elliptical or oval. The outer layer is also covered with mucus. Each cell has one eye in the form of a spot at the front end.
Breeding
The reproduction methods of volvox algae are quite interesting and even exciting. They can reproduce both asexually and sexually. A close examination reveals that most colonies have within them specific spheres called gonads.
This is a sign of asexual reproduction. Gonads are grown from cells around the equator of a colony. These cells enlarge and undergo a series of divisions until they form small spheres. In this case, the flagella appear inside the new circle. To extract them, the cell must turn itself inside out.
Volvox can reproduce their own kind also sexually. Like asexual reproduction, special cells accumulate around the equator. Male and female create colonies of various germ cells.
Sperm cells are formed by division. Female reproductive cells do not divide, but simply increase in size. Most species have both male and female colonies. And some are hermaphrodites.
Volvox and sunlight
Observation of groups of colonies under a light microscope is truly a spectacular sight. If enough space is left under the cover for sliding, the small green spheres will slowly begin to float towards the backlight.
Finding a volvox is very easy. All they need is pretty clean and warm water, rich in nutrients. The right time to watch is summer. Scooping some green samples, you can see how in a jar of water from the "flowering pond" algae will reach for the light.
Habitat
Why are volvox classified as unicellular organisms? Let's figure it out. Volvox has a unicellular structure, it cannot exist alone, therefore it often forms spherical colonies with a capacity of up to 50,000 individuals. This is not just a cell, it is a whole microscopic organism. It has its own vital processes. That is why volvox is classified as unicellular organisms.
A favorable habitat for such algae are fresh water bodies. These microorganisms are found in ponds, ditches and even in shallow puddles. Volvox algae are among the oldest on the planet. According to scientists, such a colonial way of life they led another 200 million years ago.
Volvox is the most developed organism of its kind. It forms spherical, ellipsoidal or ovoid colonies. Algae cells contain chlorophyll; therefore, they themselves feed by photosynthesis. Each individual cell works for the benefit of its colony, and together they act as one organism.