Name any two temporary embryonic structures in invertebrates that provide evidence for evolution.

Hint: In the early stages of life, certain structures were present in the organism. Then after evolution there occurs changes in certain features. In the early embryonic stage still, certain structures are observed.

Complete step by step answer:
The two temporary embryonic structures in invertebrates that provide evidence for evolution are notochord the rod-like structure which is present in the larvae of certain vertebrates and pharyngeal gill slits present in the embryonic structures in vertebrates. These structures will be considered as evidence of evolution are:
1) A notochord is a primitive beginning to the backbone. It appears in embryos as a small flexible rod made from the cells of mesoderm, which is one of the three layers of cells of embryos.
They are cartilaginous skeletal rods supporting the body in all embryonic and some adult chordate animals that include humans. Since it is composed of stiffer tissue, it allows for skeletal support of the organism. As our backbone fully forms, the discs in our back where the pieces of notochord are found as a sort of gelatinous material.
2) The pharyngeal gill slits are present in the embryonic structures in vertebrates. These are filter- feeding organs found in Invertebrate chordates and hemichordates that are living in aquatic environments. These are repeated openings that appear along the pharynx caudal to the mouth and are controlled by similar developmental mechanisms. In some species of hemichordates, the number of gill slits is more than 200- gill slits.

Note:
- The notochord that is oriented from head to tail and is found between the digestive tube and the nerve cord.
- Notochords, and backbones, are what separates us from the more primitive living creatures that we encounter.
- In certain chordates, the notochord remains there for life such as the lamprey and the sturgeon.
- The pharyngeal gill slits are the repeated segments that open along the pharynx caudal to the mouth and are controlled by similar developmental mechanisms.
- These are repeated openings that appear along the pharynx caudal to the mouth.