Sponges Study Guide


Sponges have been here for a very long time. They have fossil records from approximately 600 million years ago to the Precambrian period of the earth’s history. There are approximately 8,550 different sponge species. They have been scientifically classified into phylum porifera, which comprises four classes, namely Demospongia, Hexactinellida, Calcarea, and Homoscheloromorpha.

Are Sponges Living beings?

Sponges are living animals, and they live in water. Sponges are stuck to the bottom of oceans, seas, and rivers. Out of 8,550 sponge species, only 150 are found in freshwater. The rest of them live in saltwater.

Is a Sponge an invertebrate?

Sponges like corals are immobile marine invertebrate animals. However, most sponges are very different organisms with dissimilar anatomy, feeding process, and reproductive processes.

The major differences are:

  • Corals are complex multicellular organisms. Sponges are simple creatures without having any issues.
  • Corals can only survive in saltwater. On the other hand, most sponges are present in oceans. Many species of sponges are also found in freshwater and estuaries.

Types of Sponges

Two basic types of sponges are:

  • Encrusting
  • Free-standing

Encrusting sponges normally cover the rock’s surface in the same way how a moss covers a rock on land.

Free-standing sponges have more volume inside compared to their exterior surface area. They grow into very big sizes with strange shapes.

Sponge as an Ocean animal

  • Sponges are important creatures of coral reef ecosystems.

  • A huge population of sponges can greatly affect water quality on the reef because sponges filter water, collect bacteria, and manage carbon, nitrogen, and phosphorus.

  • Some sponge species are assumed to make carbon biologically in nutrient-exhausted coral reefs.

  • They excrete a form of poop that other organisms feed on, increasing productivity all over the ecosystem.

  • In this way, sponges defend the reef from variations in nutrient density, light, and temperature, which benefits other reef organisms in their survival.

  • The skeleton of a sponge adapts well to its specific habitat, which allows it to live on rocky surfaces or soft sedimentary surfaces like mud and sand.

  • Some sponges also attach themselves to floating debris.

  • Water filters through a sponge’s porous exterior.

  • Tiny hairlike structures inside a flagella sponge generate currents to filter bacteria from the sponge’s cells and trap food inside them.

  • This makes the sponge gain some motion, receive food and oxygen, and dissipate waste.

Sea Sponges

a. How do sponges obtain oxygen?

Sponges obtain oxygen from water. Water contains oxygen which enters into sponge cells through a process known as diffusion. So, oxygen enters into the sponge’s body from the water.

b. How do sponges eat?

Sponges eat food by passing water through their bodies. This process is called filter-feeding.

c. Are sponges carnivores?

Most of the sponges are filter feeders, and they eat tiny particles of phytoplankton and bacteria. Sponges from the genus Chadorhizidae are carnivores.

d. What does it mean that sponges are sessile?

Sponges live attached to the seabed. Since they are attached, they are termed sessile.

e. Is a sea sponge a plant or an animal?

Sea sponges are one of the simplest multicellular organisms. Due to their appearance, they are often mistaken for plants. They might not have the body parts that most animals have, like the central nervous system and digestive system, but they are animals.

f. Do sea sponges move?

Sea sponges do not move. People often confuse sponges as plants due to the characteristics of Porifera. Like plants, they do not move. They are sessile. They are stuck in one place at the bottom of oceans, seas, and rivers.

g.What eats sea sponges?

Sea sponges are eaten by two organisms, namely hawksbill, sea turtles, and nudibranchs.


  • Sponges are simple aquatic animals having dense and porous body structures. They have body structures that are greatly adaptive to their habitats.
  • Sponges do not move. Sponges are found stuck in the floors of oceans, seas, and rivers. The majority of sponge species are found in saltwater. Only a few species are found in freshwater.
  • Sponges are important creatures of the coral reef ecosystem. Sponges help in the survival of other creatures.
  • Sponges are invertebrates.
  • Encrusting and Freestanding are two basic types of sponges.
  • Water regulates into sponge’s body through their pores with the help of the beating of flagella.
  • They take in oxygen from the water through a process called diffusion.


1. What are simple invertebrates?

Invertebrates are animals that do not have a spinal column or a backbone. Sponges are the simplest form of invertebrates.

2. Which animals are known as Poriferans animals?

Sponges belong to the phylum Porifera. They are known as Poriferans animals.

3. Are humans evolved from sponges?

According to a study published in the journal Science, humans and sponges had a common ancestor more than 700 million years ago. This implies that the functional mechanism of humans has been preserved in sea sponges all this time.

4. What is the oldest phylum of animals?

Sponges are the oldest phylum of all animals.

5. Which is the first phylum?

Sponges were the first phylum.

6. What came before sponges?

Comb jellies were the first creatures on earth. They came before sponges.

7. Who created the phylum Chordata?

William Bateson created the phylum Chordata.

8. What class is a sponge?

Sponge species are scientifically classified into the phylum Porifera.

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  1. Sponges https://flexbooks.ck12.org/cbook/ck-12-biology-flexbook-2.0/section/11.4/primary/lesson/sponges-bio/ Accessed 3 Dec 2021
  2. Sponge https://www.britannica.com/animal/sponge-animal Accessed 3 Dec 2021
  3. What is a sponge?https://oceanservice.noaa.gov/facts/sponge.html Accessed 3 Dec 2021

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