Vertebrates Defintion

Vertebrates Defintion

Vertebrate are the animals belonging to the sub-phylum Vertebrata. They belong to the Phylum Chordata. The characteristics of phylum chordata is the presence of notochord, a dorsal hollow nerve cord and paired pharyngeal gill slits. The members of subphylum Vertebrata possess notochord during the embryonic period. The notochord is replaced by a cartilaginous or bony vertebral column in the adult. All vertebrate are chordates but all chordates are not vertebrates. Special characteristics of vertebrates other than the vertebral column are, they have a muscular heart which is two, three or four chambered. For excretion they have kidneys and appendages that are paired which may be fins or limbs.

Vertebrate Characteristics

General characteristics of the sub-phylum Vertebrata are as follows: 

• Vertebrates have a well developed brain.
• Brain is set inside a bony box, known as cranium.
• Notochord is present in all chordates during sometime of development, it is formed on the dorsal side of the primitive gut in the early embryo stage.
• Most vertebrates possess guts with a non-terminal anus. 
• The mouth cavity and the oesophagus is connected by the pharyngeal gill slits to a muscular tube pharynx, which opens to the exterior.
• They possess a dorsal hollow nerve tube at some stage of their life. 
• Possess a dorsal cartilaginous nerve rod known as the notochord. 
• At some stage of their life possess gill slits in the pharyngeal region.
• Have partially open circulatory system.
• Possess two pairs of appendages.
• The endoskeleton is made of cartilage or bone.
• The first vertebrates were jawless fishes with single caudal fin.
• The advancement of vertebrates with a hinged jaw which opened new food options and jawed fishes became the dominant creatures in the sea.
• All vertebrates have a heart and closed circulatory system.
• Reproduction is normally sexual.
• Feed on variety of organic materials.
• Unisexual animals, have one pair of gonads.

Vertebrates

Vertebrates are the most organized organisms on Earth. They belong to the sub-phylum Vertebrata. They are not the most numerous group of animals, they are the most advanced group of animals.The characteristics that makes vertebrates special are the presence of the spinal cords, vertebrae and notochords.

            

Most vertebrates have a very well developed nervous system. The vertebrates also have muscles and skeletons which help them move around efficiently and perform a complex moves.

 Vertebrates include the majority of the Phylum Chordate, having about 64,000 species described. Vertebrates make about 4% of all described species.

Vertebrates have a long history on earth - more than 500 million years, from the Cambrian era until date. First Vertebrates have said to be appeared around the Cambrian period of the Paleozoic era about 525 million years ago, they are said to be adapted to feeding algae in shallow waters and moving around from place to place. 

Common examples of invertebrates

Examples of Invertebrates

Invetebrates include all animals that do not belong the phylum chordata. Common examples include clams, snails, spiders, cockroach, worms, star fish, octopus.

Porifera -

 Sponges, Sycon (scypha), Spongilla (fresh water sponge) and Euspongia (bath sponge).

Cnidaria -

  Aurelia, Adamis, Hydra, Sea anemones, Physalia (Portugese man-of-war), Pennatula (sea-pen), Gorgonia (sea-fan), Meandrina (brain coral).

Ctenophora -

 Pleurobranchia and Ctenophora.

Platyhelminthes - 

Taenia (tapeworm), Fasciola (liver fluke).

Aschelminthes -

  Ascaris (round worm), Wuchereria (filaria worm), Ancylostoma (hookworm).

Annelida -

  Nereis, Pheretima (earthworm) and Hirudinaria (blood sucking leech).

Arthropoda -

  Apis (honey bee), Bombyx (silkworm), Laccifer (lac insect); Mosquitoes - Anopheles, Culex and Aedes; Locusta (locust) ; Limulus (king crab).

Mollusca - 

Chaetopleura (Chiton), Loligo (squid), Pila (apple snail), Pinctada (pearl oyster), Sepia (cuttlefish), Loligo (squid), Octopus (devil fish), Aplysia (sea hare), Dentalium (tusk shell).

Echinodermata -

  Asterias (star fish), Echinus (sea urchin), Antedon (Sea lily), Cucumaria (sea cucumber), Ophiura (brittle star).

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Phylum Mollusca

• It is the second largest phylum.
• Habitat - Molluscs are terrestrial or aquatic; they may be marine or fresh water.
• Level of organization - They have an organ-system level of organization.
• Body symmetry - Bilaterally symmetrical.
• Body wall - triploblastic. Coelomate animals.
• Body is covered by a calcareous shell.
• Body is unsegmented, they have a distinct head, muscular foot and visceral hump.
• The radula - Mouth of the molluscs contain tongue-like organ called radula, which has many rows of teeth, which is used to scrape food.
• Mantle - It is a fold of skin that surrounds the body organs.
• It is a soft and spongy layer of skin that forms a mantle over the visceral hump.
• The space between the hump and the mantle is called the mantle cavity.
• Feather like gills are present in this cavity.
• These gills have respiratory and excretory in functions. Anterior head region has sensory tentacles.
• Example: Pila, Octopus, Pearl oyster, Loligo, Sea-hare, Chiton
• 

Phylum Echinodermata

• All the members are marine, live mainly on the ocean floor.
• These animals have an endoskeleton of calcareous ossicles, and hence the name echinodermata (spiny bodied).
• Level of organization - Organ-system level of organization.
• Body symmetry - The adults are radially symmetrical, but the larvae are bilaterally symmetrical.
• Body wall - Triploblastic. Coelomate animals.
• Digestive system is complete.
• The mouth is present on the ventral side and anus on the dorsal side.
• The most distinctive feature is the water vascular system.
• This helps in locomotion, capture and transport of food and respiration.
• Excretory system is absent.
• Sexes are separate.
• Reproduction is by sexual means.
• Fertilization is usually external.
• Development is indirect with free-swimming larva.
• Example: Star fish, Sea urchin, Brittle star.
• 

Phylum Arthropoda

• It is the largest phylum of the Animalia.
• It includes insects, spiders, crayfish, etc.
• Level of organization - They have organ-system level of organization.
• Body symmetry - They are bilaterally symmetrical.
• Body wall - triploblastic, segmented. Coelomate animals.
• The body of arthropods is covered by chitinous exoskeleton.
• Body is divided into head, thorax and abdomen.
• Jointed appendages - arthros - jointes, poda - appendages, hence the name is derived from this characteristic.
• All the arthropods have jointed appendages which give arthropods a wide range of controlled motions.
• Respiration is through organs like gills, book gills, book lungs or tracheal system.
• Circulatory system - It is of open type.Sensory organs are present, antennae, eyes (compound and simple), statocysts or balance organs are present.
• Excretion - It takes place through malphigian tubules.
• Mostly they are dioceious. Fertilization is usually internal.
• They are oviparous animals.
• Development may be direct or indirect.
• Examples: Honey bee, Silkworm, Lac insect, Mosquitoes, Locust, Crab
• 

Phylum Annelida (Segmented worms)

• Habitat - They may be aquatic either marine or fresh water; or terrestrial; free-living and sometimes parasitic.
• Level of organization - They exhibit organ-system level of body organization and bilateral symmetry.
• Body wall - They are triploblastic.
• Coelom - They are coelomate animals.
• Body is metamerically segmented. The body surface is distinctly marked out into segments of metameres and hence, the phylum name Annelida.
• Locomotion - They possess longitudinal and circular muscles which help in locomotion.
• Aquatic annelids posses lateral appendages, parapodia which help in swimming.
• Circulatory system is closed.
• Osmoregulation and excretion is by Nephridia.
• Neural system - It consists of paired ganglia connected by lateral nerves to a double ventral nerve cord.
• Nereis is dioecious, but earthworm and leeches are monoecious.
• Reproduction is sexual.
• Examples: Nereis, Pheretima (earthworm), and Hirudinaria (blood sucking leech)
• 

Phylum Aschelminthes (Nematoda)

• The body of worms of aschelminthes in cross-section is circular, hence the name round worms.
• Habitat - They may be free-living, aquatic and terrestrial or parasitic in plants and animals.
• Level of organization - Round worms have organ-system level of organization.
• Body symmetry - They are bilaterally symmetrical.
• Body wall - They are triploblastic animals.
• Coelomic cavity - They are pseudocoelomate animals.
• Digestive system - This is the first phylum to have a complete digestive system, with a well developed muscular pharynx.
• Excretory system - An excretory tube removes body wastes from the body cavity through the excretory pore.
• They are dioecious - the sexes are separate i.e., males and females are distinct. Often females are longer than the males.
• Fertilization is internal.
• Development may be direct - the young ones resemble the adult, or indirect.
• Examples: Ascaris (round worm), Wuchereria (filaria worm), Ancylostoma (hookworm).
• 

Phylum Platyhelminthes

• They are commonly called as flatworms, they have dorso-ventrally flattened body.
• Habit - They are mostly endoparasites found in animals and human beings.
• Habitat - Fresh-water and salt water; terrestrial.
• Body symmetry - Flatworms are bilaterally symmetrical.
• Body wall - They are triploblastic animals.
• Coelomic cavity - They are acoelomate animals
• Level of organization - Organ level of organization.
• Digestive system - In flatworms digestive system is incomplete, that is the digestive cavity has a single opening.
• Parasitic flatworms possess hooks and suckers to hold on to the body of the host. Some forms absorb nutrition directly from the host, through their body surface.
• Osmoregulation and excretion is carried out by specialized cells cells flame cells.
• Sexes are not separate.
• Fertilization is internal and development is indirect, having many larval stages.
• Some members like Planaria possess high regeneration capacity.
• Examples: Taenia (tapeworm), Fasciola (liver fluke).

Phylum Ctenophora :

• Ctenophores are commonly known as sea walnuts or comb jellies.
• Habitat -
•  They are exclusively marine animals.
• Body symmetry -
•  They are radially symmetrical.
• Body wall -
•  They are diploblastic organisms.
• Level of organization -
•  Ctenophores exhibit tissue level of organization.
• Digestion 
• is both extracellular and intercellular.
• Locomotion -
•  The body bears eight external rows of ciliated comb plates, these help in locomotion.
• Bioluminescence
• is a property of living organism to emit light is well-marked in ctenophores.
• Reproduction 
• - Sexes are not separate, reproduction is by sexual means only.
• Fertilization
• is external with indirect development.
• Example: Pleurobrachia

Phylum Cnidaria (Coelentrata) 

• Habitat -
•  They are aquatic mostly marine animals, they are sessile or free-swimming. 
• Level of organization -
•  They exhibit tissue level of organization.
• Body wall - 
• They are diploblastic animals, body wall is made of 2 layers, outer ectoderm and inner endoderm.
• Body symmetry - 
• They are radially symmetrical.
• Digestive system - 
• They have a central gastro-vascular cavity with a single opening hypostome, which serves as both the mouth and the anus.
• Digestion-
•  is extracellular and intracellular.
• Specialized cells known as the cnidoblasts or cnidocytes which contain the stinging capsules or nematocytes are present on the tentacles and the body. Cnidoblasts are used for anchorage, defense and for the capture of prey.
• Some cindarians like corals have skeleton composed of calcium carbonate. 
• Cnidarians exhibit two basic body forms called polyp and medusa. The polyp is a sessile form ann cylindrical in shape like the Hydra, Adamsia etc. The medusae form is umbrella shaped and free-swimming forms like Aurelia or jelly-fish. 
• Metagenesis -
•  Cnidarians which exhibit both polyp and medusae form are exhibit alteration of generation, this is known as metagenesis. Poplyps produce medusae asexually and medusae form the polyps sexually. 
• Locomotion - 
• The body contains nerve network that allows movement of tentacles and body.
• Examples:
•  Aurelia (medusa), Adamsia (polyp)

life cycle of animals

Now we will discus the life cycle of animals(chicken).

Life cycles with three stages

Some animals, such as chicken, cockroaches and frogs, have three stages in their life cycles.

The three stages are the egg, the young, the adult. The young of some of these animals look different from the adults.

THE LIFE CYCLE OF A CHICKEN

Egg:-

During the egg stage, the chicken develops inside the egg. The eggshell protects the developing chick. The egg yolk provide the developing chick with food.
                         

Young:-

The chicken hatches after about three weeks.

The chick looks like its parent.

The chick grows to become a chicken.

                           

Adult:-

A hen( adult female chicken) usually lays one egg each day.

 

Fact about chicken is that newborn chicks have a hard lump on their beaks, called an egg tooth. The chick uses its tooth to break the shell of its egg. The egg tooth usually falls off within a day after the chicken hatches.

Life Cycle

Life cycle of Animals:-

What is life cycle?

A life cycle is made up of all the stages of an animal’s life. These stages include the animal entering the world, and undergoing changes, growth, as well as reproduction.

Different animals go through different stages of development in their life cycles. Some animals, such as reptiles, birds, amphibians and some insects and fish, go through a three-stages life cycle. 

                                           

Other animals, such as some insects, go through a four-stage life cycle.

The life cycle of plants start from seed or spores, and not eggs.

The life cycle of plants are different from the life cycles of animals.