Question

Science-(Biology)
please help​

Answer 1

$\huge\mathfrak\red{Answer}$

_____________________❤❤

The science of classifying organisms is called taxonomy. Every species discovered so far are classified into five kingdoms – one among them is Kingdom Animalia or the animal kingdom. The members of kingdom Animalia are further classified into different Phyla, Class, Order, Family, and Genus based on certain identifiable characteristic features.

One of the most fundamental forms of classification of animals is the presence or absence of the notochord. Hence, two major groups exist, namely: Chordates and Non-chordates.

Non-chordates and the Chordates

The notochord is a flexible rod made out of a material similar to cartilage. If an animal has a notochord during any stage of its life, it is classified as a chordate. Contrary to popular belief, chordates do not exclusively include vertebrates.

There are invertebrates that possess a notochord during some point in their lives and hence, are classified as chordates. Thus all vertebrates are chordates but not all chordates are vertebrates.

Non-chordates

Non-chordates are animals without a notochord – the rod-like elastic structure that supports the body. This phylum consists of a small group of worm-like, marine species with an organ-system level of organization.

Members of phylum Porifera, Coelenterata, Ctenophora, Platyhelminthes, Aschelminthes, Annelida, Arthropoda, Mollusca, Echinodermata and Hemichordata fall under Non-chordates.

The general characteristic features of Non-Chordates are:

They are cylindrical, triploblastic, coelomate, or pseudocoelomate animals.

Respiration in these animals takes place through gills, trachea or body surface.

Most of the times, sexes cannot be distinguished among the members.

Modes of reproduction involve sexual and asexual

Fertilization is external, though internal fertilization also occurs in some species.

The body of non-chordates generally includes an open type of circulatory system.

Examples of this phylum include Balanoglossus and Saccoglossus.

Chordates

Chordates are animals characterized by the presence of notochord at some stage during their development. Members possess a hollow nerve cord and pharyngeal gill slits. The other general characteristic features of Chordates are as follows:

They are bilaterally symmetrical, triploblastic, and coelomate with the organ-system level of organization.

They hold a post-anal tail

The body includes a closed circulatory system.

In some members of Phylum Chordata, the notochord is present only in the larval tail, and in some, it is present throughout their life from head to tail region.

Chordates have many sub-divisions and Protochordates are one of the earliest to evolve.

Examples of this phylum include Ascidia, Salpa, Doliolum, Amphioxus or Lancelet.

Phylum Chordata is divided into three subphyla: Urochordata, Cephalochordata, and Vertebrata.

Subphylum – Urochordata

It is also referred to as Tunicata which are marine animals. The body of these animals is surrounded by a leathery covering (similar to a tunic, hence the name). Larvae are free-swimming, the notochord is present only in the tail of larvae and after settling on the seabed, they get transformed into sessile adults. They are generally hermaphrodites.

Examples include – Ascidians, Doliolum, Oikopleura, etc.

Subphylum – Cephalochordata

It mainly consists of small, fish-like marine animals in which the notochord is extended along the entire body. The animals also include pharynx, which is large with numerous gill- slits. Members of this subphylum have separate sexes.

Example include – Amphioxus or lancelet.

Subphylum – Vertebrata

In this subphylum, the vertebral column is mainly replaced by and includes a well-developed head. The brain is protected in a cranium and the endoskeleton may be cartilaginous or bony. They may be jawless or with jaws

____________________❤❤

$\huge\mathfrak\red{Ansh my life}$❤❤