The piano is one of the most popular instruments in the world. It is a chordophone which...

Native American settlement (Crow Nation)

The Crow are Native Americans who inhabited the Yellowstone River valley.

Underground waters

Groundwater and aquifers are types of underground waters.


Ports must provide necessary infrastructure and services for industry and marine transport.

Types of surface epithelium

Surface epithelia cover the external and internal surfaces of the body

Male reproductive system

The reproductive system consists of organs which work together for the purpose of...

Common carp

Freshwater fish used as food in many parts of the world.

Types of synovial joints

Synovial joints can be categorised by the direction of movement they allow.

Patellar reflex

The reflex triggered by the stretching of the thigh extensor muscle is the patellar reflex.

Endocrine system

Glands of the endocrine system secrete hormones into the blood.


The zygote is the initial cell formed when two gamete cells are joined by means of sexual...

Paramecium caudatum

Common ciliated eucaryotic unicellular organisms widespread in freshwaters.

Grass snake

A type of snake with a characteristic spot on its neck.

Freshwater pearl mussel

A species of mollusc widespread in freshwaters.

Common earthworm

The anatomy of annelids is demonstrated through the example of the common earthworm.


Jellyfish are free-swimming marine animals, a species of Cnidaria, the most ancient group...

European mole

Moles are small subterranean mammals with modified, spade-like forelegs.

Cockchafer (Maybug)

The cockchafer (or maybug) is a widespread bug in Europe. Its larvae, known as chafer...

Red deer

Red deer are even-toed ungulates, ruminants. Their males have spectacular antlers.

Large white butterfly

The large white butterfly is a common species of butterflies, through which we...

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