Airports provide infrastructure and services necessary for aviation.
Ports must provide necessary infrastructure and services for industry and marine transport.
Organs that detect signals of the environment or of the body and transmit them to the brain as nerve impulses.
The axolotl, also known as Mexican salamander, is an amphibian species that keeps its gills even in adulthood.
Cossacks, members of independent semi-military communities, played an important role in the history of Ukraine.
A presentation of the major administrative units of China.
The adrenal glands are responsible for maintaining homeostasis and producing a rapid response in stressful situations.
This animation demonstrates the anatomy of amphibians through the example of a common species of frogs.
This scene explains the structure and functions of the bones.
Widespread heterotrophic unicellular organisms with constantly changing shapes
Jellyfish are free-swimming marine animals, a species of Cnidaria, the most ancient group of Eumetazoans.
The most ancient group of animals, they live underwater, lack real tissues and body symmetry.
There are two basic cell types: prokaryotic and eukaryotic cells.
This animation demonstrates how horse chestnut trees change throughout the seasons
Practise the English alphabet, build words from letters.
Practise the German alphabet and form words from the letters.
Practise the Russian alphabet, build words from letters.
Two meshing gears transmit torque during their rotational motion.
Types of bridges include beam-, arch-, suspension-, cantilever and truss bridges.
System that satisfies consumers’ demands of water supply, wastewater disposal, electricity, heat and gas supply and telecommunication.