Animal Kingdom Vertebrates

i) Phylum Chordata:

Animals named as chordae are the classification steps covering both primitive chordates and vertebrate animals. All chordates have four common features. These;

1. They have a simple skeletal structure (notochord) located between the digestive system and the nerve cord.

2. They have gill slits in their sinks.

3. At least one period of their lives, they keep the hollow nerve cord above the notochord, in the back. From this structure in the embryo, the brain and spinal cord are formed in vertebrates.

4. There is a tail at the back of the body.

Primitive Chordates: Primitive chordates are like a transition form from invertebrates to vertebrates. Generally, closed circulatory system is seen. They live in the sea. There is a small spine in the back. They have a simple internal skeleton and digestive systems. They make gas exchanges from the body surface. The most well-known examples are amphioxus, herdmania, cephadoliscus and balanoglossus.

Amphioxus

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Vertebrates:

General characteristics of vertebrate animals are as follows;

• Their bodies are covered with multilayered epithelium.
• They have an internal skeleton structure consisting of cartilage and bone tissue.
• The spine consists of segmental vertebrae from the beginning to the tail.
• The circulatory system is closed.
• They make lung or gill breathing.
• They have developed brains protected within the skull.
• They feed holozoically, meaning they get their nutrients solid, like herbivores or carnivores.
• In the embryonic periods, gill slits are found.
• The notochord formed in the embryonic period is replaced by the spine.
• They reproduce sexually.
• The excretory organ is the kidneys.
• There is a nerve strip on the back.

We can examine vertebrates in five groups, fish, amphibians, reptiles, birds and mammals.

1. Class Pisces (Fish):

• They live in seas and fresh waters. They breath through their gills.
• They have internal skeletons made of bone and cartilage. They usually have fins and scales.
• Their hearts are two-eyed. They have clean blood in their bodies and dirty blood in the heart at all times.
• They are separate sexual and ovulate, external fertilization.
• Discharge materials are ammonia and urea. They are cold-blooded creatures.
• With the air pouches, they descend to the bottom and come out, swim with their fins.
• Fishes are examined in three groups: jawless fishes (Class Agnatha), cartilaginous fishes (Class Chondrichthyes) and bony fishes (Class Osteichtyes). 

a) Jawless Fishes (Class Agnatha):

• It has no jaws and teeth. They carry notochord in the adult period.
• They have soft bodies without scales.
• They do not have double fins.
• Some feed as parasites.
• Petromizon and myxini are examples of jawless fish.

Petromizon

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b) Cartilaginous Fishes (Class Chondrichtyes): 

• They have an internal skeleton made of bone-free cartilage.
• They usually live in the seas.
• They have jaws and double fins.
• Many of them are predatory and some of them are fed with plankton.
• There are no swimming pouch, so they constantly float, so as not to sink.
• Internal fertilization is observed. Others lay their eggs in water after wrapping them in a protective shell. Others give birth to their offspring.
• Sharks, stingrays and scythe are examples.

Shark

c) Bony Fishes (Class Osteichtyes):

• They have an internal skeleton consisting of bone. There are species living in both fresh waters and seas.
• Their skin is covered with scales, these scales, which are hard, protect the body.
• They have swimming pouches, they breathe with their gills. Some species have simple-built lungs that exchange gas.
• Their hearts are made up of two chambers.
• They are cold-blooded creatures.
• Most types of external fertilization occur. In some species, internal fertilization and childbirth takes place.
• There are examples such as sea bass, tuna anchovy.

Sea bass

2. Class Amphibia (Amphibians): 

• They are animals that spend a part of their lives in water and part of them on land.
• Many of them undergo metamorphosis during their development.
• They have gill breathing in their larva and lung and skin breathing in their adults.
• Their skin is always moist, they have glands that secrete mucus.
• They are cold-blooded creatures.
• Their hearts are three-chambered. Blood in the heart is dirty and clean blood is mixed. It has a closed circulatory system.
• There is external fertilization.
• Discharge products are ammonia and urea.
• They hibernate. They eat carnivorous.
• Frogs, salamander are examples of this group.

Salamander

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3. Class Reptilia (Reptiles):

• Reptiles are land creatures whose bodies are covered with keratin scales. These scales protect the skin from drying and abrasion.
• They make lung breathing.
• Hearts of reptiles other than crocodiles have three chambers. The heart of crocodiles has four chambers. There are closed circulation systems.
• They are cold-blooded creatures.
• Reptiles reproduce by internal fertilization and external development. Their eggs are shelled.
• Turtle, snake, lizard, crocodiles and extinct dinosaurs are examples of this group

Crocodile

4. Class Aves (Birds): 

• They live in all ecosystems around the world.
• Their bodies are covered with feathers that provide flying and insulation.
• Its front limbs have become wings.
• There is no tooth in their jaws.
• Birds are both carnivorous and herbivorous creatures.
• They make lung breathing. Lung bladders reduce body weight, making it easier to fly.
• They are warm-blooded animals. Their hearts are four-chambered and dirty and clean blood do not mix in their hearts.
• Their bones have air gaps to store more air and fly more comfortably.
• Urinary waste is uric acid.
• Internal fertilization and external development are observed. They take care of the hatched egg and grow it up to a certain age.
• Ostrich, penguin, chicken, flamingo, owl, sparrow are some examples.

Owl

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5. Class Mammalia (Mammals): 

• It is the most evolved group of vertebrates, including humans. There are species living in seas and on land.
• Their bodies are covered with hair. In some species, the skin is bare.
• Mammals breathe lungs and have vesicles (called alveoli) in their lungs.
• Most species can make their own sounds.
• Their hearts are four-chambered. Dirty and clean blood circulates separately. They are warm-blooded creatures.
• Females have milk glands.
• There is internal fertilization. After birth, the offspring are fed with milk secreted from the mammary glands of the mother.
• Nervous systems are very developed.
• There are different teeth on their jaws. Hunter species have more incisors, while herbivorous species have more grinding teeth.

Mammals are divided into three groups: beaked mammals, marsupial mammals and placenta mammals.

Monotremes are the only mammals that lay eggs. They incubate. After their offspring hatch, they feed on the mammary glands without nipples. Digestive and excretion wastes are thrown through a single opening, this structure is called cloak. Echidna and platypus are examples of this group.

Echidna

Platypus

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As marsupial mammals do not carry placenta, offspring are born before they complete their development. They pass to the mother's pouch and feed on the milky glands here and complete their development. Koalas, kangaroos, and possums are examples of this group.

Koalas

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Placental mammals are the most common mammalian group. They reproduce by internal fertilization and internal development. The development of the embryo is completed in the womb. The organ called placenta is formed between the developing baby in the womb and the mother. This structure provides the feeding of the puppy until birth. Therefore, the gestation period lasts longer than marsupial mammals. Hedgehog, lemur, elephant, rabbit, cat, dog, human, dolphin, bat and whale are some examples.

Cat

Whale

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The Original Author: Mrs. Şerife (Erden) SARICA