Answer to Question #219927 in Zoology for Dagmawi Minilik

Question

Instruction

✓Clear readable writing is recommended

✓The total number pages must be 6 or 7

✓submitted date 26-07-2021

#Q. Select three of the different phyla of invertbrates you learned and discuss in detail based on the following criteria.

√ Reproduction

√ symmetry

√ Respiration and Circulation

√ Nervous system

√ Digestion and excretion

Answer 1

protozoans – single-celled organisms such as amoebas and paramecia.

annelids – earthworms, leeches.

 

arthropods – insects, spiders, crustaceans such as shrimp, crabs, lobsters.

 

Arthropoda is the largest phylum with about nine lakh species. They may be aquatic, terrestrial or even parasitic. They have jointed appendages and a chitinous exoskeleton. This phylum includes several large classes and contains the class Insecta which itself represents a major portion of the animal species in the world. They possess the ability to survive in every habitat.

Arthropods reproduce by sexual reproduction, which involves the generation and fusion of gametes. Most arthropods are either male or female, and they undergo internal fertilization. Once the egg has been fertilized, the female usually lays the egg, and it continues developing outside of the mother's body.

Arthropods are bilaterally symmetrical, meaning their left and right halves are mirror-images of each other -- humans, dogs, cats, fish and many other types of animals display bilateral symmetry.

Arthropods have what is referred to as an open circulatory system, where blood fills the body cavity of the animal, since they have skeletons, the leftover space is instead filled with blood which covers the other organs, keeping them bathed in blood. This cavity is referred to as a haemocoel, or blood cavity.

The arthropod nervous system consists of a dorsal brain and a ventral, ganglionated longitudinal nerve cord (primitively paired) from which lateral nerves extend in each segment. The system is similar to that of annelid worms, from which arthropods may have evolved.

Arthropods ingest food through their mouth, which then passes through the pharynx and down the esophagus, similar to many other animals. It eventually reaches the midgut or stomach, where it begins to break down and digest. Waste products pass through the anus of the animal, like many other living organisms.