Fossil Practical II - The Sponges

Some sponges do not have spicules. This statement is true because not all sponges have spicules, which are tiny needle-like structures made of calcium carbonate or silica. While spicules provide structural support for many sponges, some species have evolved to lack these skeletal elements. These sponges rely on other methods, such as collagen fibers or spongin, to maintain their shape and structure. Therefore, it is accurate to say that some sponges do not have spicules.

Sponges have a sessile benthic life habit, meaning they are permanently attached to a substrate and live on the bottom of aquatic environments. They are immobile and do not move around like demersal or vagrant benthic organisms. Sponges are also epifaunal, meaning they live on the surface of the substrate rather than burrowing into it.

During the Ediacaran Period, which occurred approximately 635 to 541 million years ago, most organisms did not possess hard parts such as shells or skeletons. This is supported by the fossil record, which shows a lack of preserved hard structures during this time. Instead, the faunal assemblages of the Ediacaran Period consisted mainly of soft-bodied organisms, including various types of worms, jellyfish-like creatures, and other early forms of complex life. Therefore, the statement that most faunal assemblages in the Ediacaran Period possessed no hard parts is true.

The inside of the sponge is called the spongocoel and is lined with a special type of cells called choanocytes. Choanocytes have a collar of microvilli surrounding a flagellum, which helps in creating water currents and capturing food particles. The spongocoel is a central cavity within the sponge where water flows through, allowing the choanocytes to filter and extract nutrients from the water.

The Ediacaran period is known for the appearance of the first multi-celled organisms in the fossil record. This period, which occurred between 635 and 541 million years ago, marks an important milestone in the evolution of life on Earth. During this time, diverse and complex organisms such as jellyfish-like creatures and segmented worms emerged, paving the way for the development of more complex life forms in later periods. The presence of these fossils in the Ediacaran period provides evidence for the beginnings of multi-cellularity in the history of life.

The statement is true because choanocytes are specialized cells in sponges that have collars lined with flagella. These collars create a water current that brings in food particles. When food particles get caught on the collars, amoebocytes, which are mobile cells, move around the sponge and disperse the food particles to other cells for digestion and absorption. This process helps the sponge obtain nutrients and is an essential part of their feeding mechanism.

You've got it backwards. The porocytes are the "pores" of the sponge, from which the flagella draws things IN from, whereas the osculum in the top, from where things exit the sponge.

Glass sponges, which have 6-ray silica spicules and form glass skeletons of SiO2, belong to the class Hexactinellida.

The given statement is false. The geologic range of sponges is not limited to the Cambrian period but extends beyond it to the present day. Sponges are one of the oldest known animal groups and have existed for millions of years. They can be found in a wide range of environments, from freshwater to marine habitats, and are still present in the present era. Therefore, the correct answer is False.

Demospongiae is the correct answer because this class of sponge is known to have a body composed of the protein "Spongin", which is similar in composition to hair and fingernails. Calcarea, sclerospongiae, and hexactinellida are not known for having a body composed of Spongin.

Sponges are categorized as Porifera. Porifera is a phylum of animals that includes sponges. This phylum is characterized by their multicellular bodies with pores and channels that allow water to flow through them. Sponges are filter feeders and they lack true tissues and organs. Therefore, the correct answer is porifera.

Sclerospongiae is the correct answer because these sponges are known for creating stony skeletons made of calcium carbonate (CaCO3), silica spicules, and spongin. This class of sponges is unique in their ability to form hard structures, which distinguishes them from other classes such as Calcarea, Demospongiae, and Hexactinellida.

The gel-like layer that serves as a biological "glue" between the outer and inner cells of a sponge is called mesoglea.

The correct answer is Metazoans. Metazoans are multi-celled organisms that have loose associations with single-celled Protists forming simple colonies for survival. This distinguishes them from Protozoans, which are single-celled organisms. Eukaryotic refers to organisms that have cells with a distinct nucleus, while Prokaryotic refers to organisms that lack a nucleus.

Sorry! Spicules are the supporters of the sponge. They make great friends.