Table of Contents
An Introduction to the Solar System
The solar system is made up of the sun and everything that orbits around it. This includes planets, moons, asteroids, and comets. The solar system is located in the Milky Way galaxy.
Characteristics of Protochordata
- Protochordata are an ancient group of animals that evolved from a common ancestor over 550 million years ago. They are the simplest chordates, and include the lancelets and tunicates.
- Protochordates are marine animals that live in the ocean depths. They are filter feeders that use a sucking apparatus to extract food from the water.
- They are bilaterally symmetrical and have a simple body plan with a head, a tail, and a dorsal nerve cord. They have a notochord, which is a primitive spinal cord, and a dorsal hollow nerve cord.
- They are a primitive group of animals and share many features with more complex chordates. For example, they have a nerve cord, a notochord, and a simple body plan.
Classifications of Protochordata
There are three main classifications of Protochordata: Tunicates, Lancelets, and Hagfish.
- Tunicates are the most primitive and are characterized by their sac-like body shape. They lack a backbone and a true brain, and are filter-feeders that extract food from the water around them.
- Lancelets are more advanced than tunicates, and are characterized by their eel-like body shape. They have a backbone and a true brain, and are active predators that consume other small marine organisms.
- Hagfish are the most advanced of the Protochordata and are characterized by their serpent-like body shape. They have a backbone and a true brain, and are scavengers that consume dead marine organisms.
Hemichordata
- Hemichordata is a phylum of marine animals that includes the acorn worms and the pterobranchs. These animals are all filter feeders, and they use a variety of methods to capture food particles from the water.
- Hemichordates have a proboscis, which is a long, tubular structure that they use to suck food particles into their mouths. They also have a ciliated feeding organ called a collar that they use to collect food from the water.
Urochordata
- The Urochordata are a group of chordates that includes tunicates and lancelets. Tunicates are filter-feeders that live in marine environments.
- Lancelets are small, fish-like creatures that live in both salt and fresh water. Urochordates are the simplest of the chordates, and they lack a backbone.
Cephalochordata
- Cephalochordata is a phylum of chordates that includes the lancelets. These small, fish-like animals are marine and live in both salt and fresh water. They are filter feeders and use a long, thin filament called a “lancelet” to capture food particles from the water.
- Cephalochordates are the simplest chordates, and lack a true brain, backbone, and cranium.
What Makes Protochordate Different From Vertebrates?
- Protochordates are a group of animals that are different from vertebrates. They are a more ancient group of animals and have some features that vertebrates do not have.
- Protochordates do not have a backbone, for example, and they also lack vertebrae. They typically have a simpler body plan than vertebrates, and they do not have as many different types of tissue.
