Phylum Annelida Quiz: Phylum Ctenophora!

Both Annelida (segmented worms) and Mollusca (mollusks) share the characteristic of having trochophore larvae during their first larval stage. The trochophore is a free-swimming, planktonic larva with a ring of cilia that is common to both phyla, indicating a possible evolutionary relationship between them.

The statement is true because Clonorchis sinensis, also known as the human liver fluke, is indeed common in China. This parasitic worm infects the liver and can cause various health problems, including cirrhosis of the liver. If left untreated, it can lead to severe complications and even death.

Ctenophores, also known as comb jellies, have eight comb rows that are made up of long, fused cilia. Cilia are hair-like structures that are found on the surface of many organisms and are involved in various functions such as locomotion and feeding. In the case of ctenophores, the cilia in their comb rows beat in a coordinated manner, creating a beautiful shimmering effect and allowing them to move through the water. The fusion of the cilia in each comb row gives them a stronger and more efficient beating motion, enabling ctenophores to swim and capture their prey effectively.

Flatworms use a specialized organ called protonephridia for osmoregulation. Protonephridia are networks of tubules with flame cells that help regulate the balance of water and salts within the flatworm's body, enabling them to maintain homeostasis in their aquatic or terrestrial environments.

Members in the Phylum Nematoda possess a pair of lateral sensory organs called amphids. Amphids are specialized chemosensory organs that are located on the head of nematodes. They play a crucial role in detecting chemicals in the environment and are involved in various sensory functions such as finding food, mates, and avoiding predators. These sensory organs are important adaptations that enable nematodes to survive and thrive in their habitats.

Free-living platyhelminths, or flatworms, are considered the most primitive bilateral animals and are significant for being the first group to have evolved a true mesoderm. The mesoderm is the middle layer of cells in the developing embryo, giving rise to muscles, the circulatory system, and other internal structures, enabling greater complexity and functionality in the animal's body plan.

Most of the members in Phylum Nematoda are dioecious with amoeboid sperm, and males are smaller than females and have a bent tail for holding females for copulation.

Ocelli are light-sensitive sense organs found in flatworms. These organs help flatworms detect changes in light intensity and direction, allowing them to respond to their environment. Ocelli are simple eyes that can detect the presence or absence of light, but they cannot form images like more complex eyes. Flatworms use their ocelli to navigate and find food sources, as well as to avoid predators. Therefore, ocelli are the correct answer for the light-sensitive sense organs in flatworms.

The cuticle functions in nematodes include acting as a barrier and providing protection, serving as a sensory array to detect changes in the environment, and functioning as a hydrostatic skeleton to aid in locomotion. However, it is not true that the cuticle acts as a hook to burrow into muscle tissue and form cysts for parasitic nematodes.

Cephalopods, which include squids, octopuses, and cuttlefish, are the only class of mollusks that have a closed circulatory system. This system allows for more efficient oxygen and nutrient transport, supporting their active lifestyles and higher metabolic rates. The other classes of mollusks, such as bivalves, gastropods, and chitons, have open circulatory systems.

Ctenophores, also known as comb jellies, do not possess nematocysts (stinging cells) like cnidarians. Instead, they have specialized adhesive cells called colloblasts. Colloblasts are used to capture prey by releasing a sticky substance that helps adhere to and immobilize their prey.

Bivalves do not have a radula. Instead, they are filter feeders that use their gills to capture food particles from the water. The other groups, gastropods, cephalopods, and chitons, typically have a radula, which is a specialized feeding organ used for scraping or cutting food.

Earthworms are hermaphroditic, meaning they have both male and female reproductive organs. However, they are not self-fertilizing, which means they cannot fertilize their own eggs with their own sperm. Instead, earthworms must mate with another earthworm in order to reproduce.

In ctenophores, also known as comb jellies, locomotion is achieved through rows of ciliary plates called costae. These costae beat in a coordinated manner, propelling the ctenophore through the water. This unique method of locomotion distinguishes ctenophores from other marine organisms.

Leeches and oligochaetes (such as earthworms) both possess a clitellum, which is a specialized glandular segment involved in reproduction. This shared characteristic is part of the evidence that leeches evolved from oligochaetes. The clitellum is used in the formation of a cocoon for the protection of fertilized eggs.