Oganesson is the heaviest element in the periodic table today, its atomic mass is more than 294 atomic mass units, which is almost 25 times heavier than a

The class Mammals has about 4,000 species. Representatives of the class reached the most progressive development in the process of evolution and are distributed almost everywhere, with the

The meaning of birds During the feeding period, many birds regulate the number of insects and small rodents, restrain the increase in the number of insect pests of

The ecological groups of birds were formed in connection with adaptation to life in similar conditions (birds of different orders developed similar features of structure and behavior). Birds

There are currently over 9000 bird species. They differ in their origin, lifestyle and features of the external and internal structure. All birds are divided into three groups:

Signs of Similarity between Modern Birds and Reptiles Unlike amphibians, birds and reptiles have dry skin. The feathers of birds, like the scales of reptiles, are composed of

Birds are dioecious animals with pronounced sexual dimorphism (females differ from males). Birds breed by laying eggs. Males develop paired testes. Females have one left ovary (eggs develop

Respiratory system The respiratory system is formed by the airways and lungs with air sacs. Air passes through the nostrils into the respiratory tract: the nasal cavity, larynx,

Digestive system The digestive system of birds, like other vertebrates, is represented by the digestive tract and glands. Digestive tract: Mouth – pharynx – esophagus – goiter (in

The skeleton and muscles are part of the musculoskeletal system. The skeleton provides support for the body and organs of movement, protects the most important organs. Due to