9.1 Porifera and Cnidaria

The large opening at the top of the sponge is called the _______.

• Osculum

• Porocyte

• Spicule

• Ostia

Answer explanation

The large opening at the top of a sponge is called the osculum. It allows water to exit the sponge after it has filtered through the body, distinguishing it from other structures like ostia, which are smaller openings.

What are two ways that a sponge could reproduce asexually?

• binary fission

• budding

• regeneration

• gamete production

Answer explanation

Sponge reproduction asexually occurs through budding, where new individuals form from the parent, and regeneration, where sponges can regrow lost parts or even develop into new sponges from fragments.

Tags

NGSS.MS-LS3-2

An anemone would be a cnidarian in a _____ body form (tentacles and mouth facing up).

• Larval

• Polyp

• Medusa

• Free-swimming

Answer explanation

An anemone is a type of cnidarian that exists in the polyp body form, characterized by a cylindrical shape and tentacles. The medusa form is typically free-swimming, while the larval stage is not the adult form.

Animals in the phylum porifera have which type of body symmetry?

• asymmetry

• radial symmetry

• bilateral symmetry

• medial symmetry

Answer explanation

Animals in the phylum Porifera, commonly known as sponges, exhibit asymmetry, meaning they do not have a defined shape or symmetry. This distinguishes them from other animal phyla that display radial or bilateral symmetry.

Animals in the phylum cnidaria have which type of body symmetry?

• asymmetry

• radial symmetry

• bilateral symmetry

• medial symmetry

Answer explanation

Animals in the phylum Cnidaria exhibit radial symmetry, meaning their body parts are arranged around a central axis. This allows them to interact with their environment from all directions, unlike bilateral symmetry which has a distinct left and right.

Which of the following is a correct description of the Cnidarian digestive tract?

• A complete digestive tract consisting of two openings.

• A complete digestive tract consisting of one opening

• An incomplete digestive tract consisting of two openings.

• An incomplete digestive tract consisting of one opening.

Answer explanation

Cnidarians have an incomplete digestive tract with one opening, serving as both mouth and anus. This means food enters and waste exits through the same opening, distinguishing them from organisms with complete digestive systems.

This organelle inside the stinging cells in cnidarians can inject paralyzing toxins into their prey.

• pinacocytes

• lysomatocyts

• choanocytes

• nematocysts

Answer explanation

Nematocysts are specialized organelles in cnidarians that contain toxins and can inject them into prey, paralyzing them. This distinguishes them from other cell types like pinacocytes, lysomatoctyts, and choanocytes.

In cnidarians, their mouths are surrounded by _______________.

• guard cells

• pinacocytes

• tentacles

• spines

Answer explanation

In cnidarians, their mouths are surrounded by tentacles, which are specialized structures used for capturing prey and defense. Other options like guard cells, pinacocytes, and spines do not serve this function.

Water enters the sponge cavity through multiple​ (a)   and exist through the ​ (b)   .

• ostia

• osculum

• porocyte

• pinacocyte

• choanocyte

Answer explanation

Water enters the sponge through small openings called ostia and exits through a larger opening known as the osculum. This flow is essential for the sponge's feeding and waste removal processes.

What is the main difference between sponges and other animals?

• Sponges can move freely

• Sponges do not have any tissues or organs

• Sponges are not made of cells

• Sponges can perform photosynthesis

Answer explanation

The main difference is that sponges lack true tissues and organs, unlike other animals. They are simple organisms that filter water for food and do not have specialized structures for various functions.