Mention the important general characters of Urochordata.

Urochordata, also known as tunicates or sea squirts, are marine invertebrates belonging to the phylum Chordata. While they may appear quite different from other chordates, such as fish or mammals, they still possess some key characteristics that align them with the chordate group. Here are some important general characters of Urochordata:

Chordate Features: Urochordates possess the fundamental characteristics of chordates, albeit in a modified form. They exhibit a notochord during their larval stage, which is a flexible rod-like structure providing support. Additionally, they have a dorsal nerve cord and pharyngeal slits or gill slits.

Body Structure: Urochordates typically have a sac-like body covered by a tough, outer tunic or cuticle, which gives them their common name "tunicates." The tunic is composed of a carbohydrate called cellulose. The body can be solitary or colonial, and they attach themselves to surfaces such as rocks, shells, or other substrates.

Filter-Feeding: Urochordates are primarily filter feeders. Water enters the body through an incurrent siphon and passes through a mucous net or sieve-like structure called the pharyngeal basket. The pharyngeal basket contains numerous gill slits, which trap food particles and allow water to exit through an excurrent siphon.

Simple Digestive System: Urochordates have a relatively simple digestive system. Food particles are captured by the pharyngeal basket and transported to the stomach, where digestion occurs. Undigested waste is expelled through an anus located near the excurrent siphon.

Circulatory System: Urochordates possess an open circulatory system. They have a simple heart that pumps hemolymph (a fluid equivalent to blood) through vessels to various body parts. However, their circulatory system is less complex compared to higher vertebrates.

Reproduction: Urochordates can reproduce both sexually and asexually. Most species are hermaphroditic, meaning individuals have both male and female reproductive organs. Fertilization occurs internally, and the development of embryos varies among different species.

Larval Stage: Urochordates have a distinct larval stage called a tadpole larva. The larva possesses the characteristic features of chordates, such as a notochord, a dorsal nerve cord, and pharyngeal slits. The tadpole larva is typically free-swimming before undergoing metamorphosis into the adult form.

These are some of the important general characters of Urochordata. It's worth noting that there is considerable diversity within this group, with approximately 3,000 described species, each with its unique adaptations and characteristics.