What are vertebrates?
Who belong to
five groups of vertebrates: fishes, amphibians, reptiles, birds and mammals. Each of them
forms a systematic unit - a class. However, there is no separate class of the fishes:
vertebrates who live in water belonging to different systematic units form this group. One
can read about them on the pages of general description of particular group.
How many vertebrates are
there in Estonia?
approximately 40,000 species of vertebrates in the world, 484 of them have been found in
Estonia. The distribution of Estonian vertebrates is following: fishes
- 75 species,
amphibians - 11 species, reptiles - 5 species, birds - 328 and mammals
- 65 species.
What are the distinctive
features of vertebrates?
The name - vertebrates - refers to the fact that all of them have a vertebra (backbone). In
addition to backbone they have skull and several other skeletal bones which form an
endoskeleton. All vertebrates are bilaterally symmetrical with two pairs of appendages
limbs, fins, wings, etc. In comparison with invertebrates vertebrates have more developed
organ systems. They have higher nervous system, which is divided into central and
peripheral nervous system. The parts of the central nervous system - the brain and spinal
cord - are in the skull and vertebral column respectively. Circulatory system of
vertebrates is closed - i.e. blood circulates in the blood vessels all the time. The
heart of different species of vertebrates consists of 2 - 4 parts. The body of vertebrates
can be divided into ventral and spinal sides. The body of vertebrates is covered with skin
with different outgrowths: scales, hairs, feathers, etc.
Where do vertebrates
live in all kinds of environments. The fishes live only in water. The amphibians mainly
live on land but they need water for reproduction. The reptiles can be found in very
different environments. Most birds are able to fly. Their nesting places are in forests,
on coasts of various bodies of water, in open fields or in populated areas. The mammals
also live everywhere: in forests, meadows and water, even under land and in human
settlements. Some species of mammals are able to fly.