All living organisms are made up of one or more cells, which are the basic building blocks of life. Even unicellular organisms are intricate! Atoms join together to form molecules, which then join together to form cell organelles and structures. Similar cells form tissues in multicellular organisms. A living organism is made up of cells. The cells divide, and the organisms’ bodies grow as the number of cells increases. A living thing that experiences growth is a tree. The growing process is not visible in the road, pen, or water because they are not living things.
Protochordata
Protochordata organisms are lower chordate organisms. Despite not belonging to a specific taxonomic group, these organisms constitute a significant portion of Chordata. Protochordata have a notochord (a structure that provides support to an organism’s body) for a period of time or all of their lives. These organisms, also known as Acraniata, lack a proper skull and cranium.
“Protochordata” refers to primitive chordates. It includes a diverse range of organisms and is also the major division of the phylum chordata. Because they lack a true skull, these organisms are also known as acraniata. This phylum’s organisms have a notochord at some point in their life cycle.
Characteristics
- Protochordate is all aquatic, mostly marine creatures.
- Symmetry: The bodies of protochordata organisms are bilaterally symmetrical, which means that they can be divided into two equal halves when a plane is passed longitudinally.
- Organisms are triploblastic, which means they have ectoderm on the outside, endoderm on the inside, and mesoderm in the middle. Coelomates are organisms. Coelomate refers to the presence of true coelom surrounded by mesoderm.
- Organ-system level of organisms: Organisms in this phylum have organ-system level of organisms.
- The body of organisms at one point in time consists of a long, rod-like structure that provides support known as the notochord.
Classification
Protochordate is divided into three subphyla based on the type of notochord they have. They are as follows: Hemichordata, Urochordata, and Cephalochordata.
Hemichordata
- Hemichordata are all marine organisms. Some live in solitary confinement, while others may be colonial.
- Their bodies are unsegmented, cylindrical, and stout, giving them a worm-like appearance. They are bilaterally symmetrical and triploblastic. The body wall is composed of a single layer of epidermis and smooth longitudinal fibres.
- Hemichordata may have tentacles or arms after the collar, but locomotory appendages are absent. Their circulatory systems are comprised of a dorsal heart and longitudinal dorsal and ventral vessels.
- Hemichordata’s blood is colourless and devoid of corpuscles. They have an entire digestive tract. To feed on microorganisms and other debris, all hemichordata use a ciliary mechanism or filtering.
- The body of hemichordata has a broad surface that allows for easy breathing. Otherwise, breathing is accomplished through a pair or multiple pairs of gill slits.
- The excretory system includes the glomerulus, or proboscis gland. Hemichordata’s nervous system is made up of an epidermal plexus or nerve cells as well as nerve fibres.
- Hemichordate sexes can be united or separated, and gonads can exist in multiple pairs or just one. Asexual reproduction is widespread. Internal or external fertilisation are two other reproductive characteristics.
- Hemichordates include Cephalodiscus, Balanoglossus, and Rhabdopeura.
Cephalochordata
- Cephalochordata are also filter feeders and marine organisms. Cephalochordata’s tails remain throughout their lives.
- Their body wall is made up of myotomes, which gives them a fish-like appearance. Cephalochordata does not develop a brain and instead rely on the nerve cord throughout their lives.
- Their notochord remains intact throughout their lives, reaching up to the head or cephalic region. Excretion occurs in Cephalochordata via paired protonephridia with solenocytes (a type of flagellated cell).
- They have a lot of gill stilts, which they keep even when they’re adults. These lead to the atrium. Cephalochordata have been observed burrowing and swimming freely. Amphioxus, for example.
Urochordata
- This subphylum’s organisms are mostly found in marine environments. Organisms are sessile and filter-feeders. This subphylum’s organisms are also known as tunicates because their bodies are surrounded by a leathery sheath known as tunicin.
- The notochord appears in the tail of these organisms during the larval stage but is absent in the adult.
- Retrogressive metamorphosis refers to a phenomenon in which larvae are much more developed than adults. The larva has a neural tube, whereas adults have a dorsal ganglion.
- The respiratory system of these organisms is made up of gills. These organisms’ circulatory systems are open, which means that the tissues are washed directly in blood.
- These organisms’ circulatory systems are open, which means that the tissues are washed directly in blood. These organisms have no excretory organs. Budding is the mode of reproduction in these organisms.
For example, Herdmania and Selpa.
Difference between Protochordate and Vertebrates
Protochordates are an animal group that is distinct from vertebrates. They are a more primitive group of animals with some characteristics that vertebrates do not have. Protochordates, for example, lack a backbone as well as vertebrae. They typically have a simpler body plan than vertebrates and fewer different types of tissue.
- Protochordates are creatures that, at some point in their lives, have a notochord. They do not have a vertebral column (i.e. an evolved notochord). Cephalochordates have a notochord throughout their lives. As a result, the existence of protochordate is confirmed.
- Vertebrates have a well-developed notochord, which is also known as the Vertebral Column. However, the more accurate response is that during the embryonic stage (as an embryo in the mother’s womb), vertebrates have a notochord in their bodies, which develops into the vertebral column.
FAQs on Protochordates
Question 1: What’s the Hemichordata’s body composition?
Answer:
- Unsegmented, thick body with a vase- or worm-like shape.
- There are three separate regions: the proboscics, collar, and trunk.
- They have organ-system level organisation, are bilaterally symmetric, and triloblastic.
Question 2: How does Hemichordata reproduce?
Answer:
- Sexes are either separated or united. The gonads can be found in multiple pairs or just one.
- Fertilization can be either external or internal. Asexual reproduction is possible.
- Tornaria larvae may develop into free-swimming organisms.
Question 3: What is the meaning of Urochordata?
Answer:
The Urochordata are a chordate family that includes tunicates and lancelets. Tunicates are filter-feeders that live in seawater. Lancelets are small fish-like creatures that can be found in both salt and fresh water. Urochordates are the most basic chordates, with no backbone.
Question 4: What Sets Protochordates Apart From Vertebrates?
Answer:
Protochordates are an animal group that is distinct from vertebrates. They are a more primitive group of animals with some characteristics that vertebrates do not have. Protochordates, for example, lack a backbone as well as vertebrae. They typically have a simpler body plan than vertebrates and fewer different types of tissue.
Question 5: What are the properties of a protochordate?
Answer:
- They are most frequently found in seawater.
- Their bodies are triploblastic, coelomates, and symmetric on both sides.
- For stability, their bodies develop a long, rod-like structure called the notochord at a specific point in their lives.
- They are classified according to organ system.