Early humans had been fooled into believing that sponges are plants. But what is the best evidence that the sponge possesses that categorize it as an animal, rather than a plant?
At first glance one may notice that the sponges’ looks more like a plant than an animal. And possibly to some, they may find it hard to believe that sponges are actually animals. Sponges are one of the strangest species that belongs to the animal kingdom as they mainly look more like plant than animal.
To date, there are more than five thousand different kinds of sponges that had been known by humans. They come in many colors and in various shapes and sizes. They resembles like fans, domes, and bowls, trumpets, domes, vases and many everyday shapes we found in our surroundings.
Many species of sponge grows and branch out which is one of the main characteristic of plants and trees. While other species simply flattened their mass of spongy tissues and spreads out on the surface of rocks, shells or wood where they are attached.
There sizes vary from an inch long to the big three foot height or width.
One of the animal’s unique characteristic is that they lost the ability to move about. And even they are considered as a living animal, they do not react when they are touch. They also lack many of the common characteristics of animals such that they do not have a distinctive head or a mouth. They do not have eyes, ears, feelers as well as other sense organs. They also do not possess major organs such as heart, stomach, muscles and even a nervous system.
If cut in two, all we can see is a slimy mass with holes or channels that runs through it. Simply, one wonders how come this creature is categorized as animal. These characteristic of the sponges had fooled early scientists of thinking that these creatures belong to the plant kingdom rather than in the animal kingdom.
But what was the evidence that makes the sponges an animal? By simply observing the way the animal feeds. Sponges captures it food to eat. And unlike plants, they do not have the ability to make their own food. But rather captures tiny microorganisms and plants from the water that it lives. They do this by the use of a tube-like wall that makes up the sponges body which acts like a sieve or a filter. These walls collect and strains tiny organisms out of the water. They do this by forcing the water in and out the sponge by the beating action of their tiny, whip-like treads called the flagella. The flagella are composed of cells which capture the food and are collected at its bottom by a sticky substance that catches the food.
Some of the food that was collected in the flagella is digested there while the excess is passed on to the rest of the sponge body cells.
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