Sponges reproduce asexually in three ways: following fragmentation, via budding, and by creating gemmules. Sponge fragments can be separated by currents or waves. Budding is used by just a few species to reproduce. Most sponge species use sexual reproduction because it provides genetic variability. Sponges get their energy from bacteria living in them. These bacteria affect what kind of organisms can live in close proximity to them.
Sponges are filter-feeders that eat waterborne particles too small for most other animals to consume. They take in oxygen and give off carbon dioxide as a byproduct of this process. Because they cannot move away from harmful substances, sponges must have very efficient immune systems. They are able to quickly destroy any invaders who make it into their cells. In fact, some studies have shown that they have more immune system proteins than humans do.
Sponges come in many different shapes and sizes. Some are flat, while others are round or oval. Many species grow attached to a surface by a thin layer of tissue called mesogloea. Others may float freely in the water column. The majority of sponges are composed of two basic types of cells: an outer covering of fibres (or cortex) and an inner core of fluid (or medulla). However, some species contain additional layers such as a middle cortex/medulla layer structure.
The majority of poriferans that reproduce sexually are hermaphroditic, meaning they produce eggs and sperm at separate periods. Asexually reproducing sponges generate buds or, more often, gemmules, which are packages of many different types of cells enclosed in a protective shell. These buds will eventually develop into new sponges if given the opportunity.
Sponges have evolved various ways to protect their offspring from being eaten by predators and from other sponge species. Some sponges will even guard their territories against intruders. Sponges also have special tissues that absorb water and dissipate its energy as heat, protecting the sponge from drying out during dry seasons or when it is submerged for long periods of time.
Sponges were originally classified as plants because of their thick stems supporting large numbers of thin leaves. However, sponges lack vascular tissue (water-conducting vessels) so they cannot transport nutrients through their bodies like plants can. They get all the oxygen they need from the water in which they live and emit carbon dioxide through their pores. In addition, sponges are not rooted to one spot but instead roam around looking for places where they can grow their hairs to filter out food particles from the water.
It is estimated that there are about 25,000 species of sponge, making them the most diverse group of organisms on earth. Of these, only about 200 have been identified by scientists so far.
Asexual reproduction is often accomplished by fragmentation (during which a portion of the sponge breaks off, settles on a new substrate, and develops into a new individual) or budding (a genetically identical outgrowth grows from the parent and eventually detaches or remains attached to form a colony). Sexual reproduction may also occur within sponges via merismatic division. In this case, two identical spores are produced that will develop into two separate sponges after fertilization occurs.
Sponges are the only animals known to reproduce this way. Although some viruses can infect sponges, they do not reproduce inside the sponge; instead, they kill their host cells. It has been suggested that viruses might use sponges as "laboratories" in which to experiment with new ways of invading living cells.
Sponges have existed for about 500 million years and live mostly in warm oceans. There are more than 700 species of sponge found in all marine environments, from shallow seas to deep waters down to 3000 m. Sponges are filter-feeders and eat bacteria and small pieces of food that fall through the water. They take in water through their porous bodies and then pump out fresh water that is free of debris. This process filters out any organisms in the water that are larger than what can fit through their pores.
Sponges that do not exhibit sexual reproduction in this way are called asexual.
It is widely believed that all sponges are asexual, but this is not true. There are two types of sponge cells: solid fibers and liquid cells. A few species of sponges contain only the first type of cell. These are called acelsius or dry-sponges. The other type of sponge contains both fiber and liquid cells. These are called wet-sponges.
Some wet-sponge species reproduce asexually by dividing into identical copies of themselves. These clones remain genetically identical over many generations if no sexual partners are available. If exposed to a male sponge partner, the female produces eggs and sperm and merges with its partner. This process creates new individuals with different combinations of genes from each parent. Sexual reproduction ensures that genetic diversity is maintained in sponge populations.
Other wet-sponge species cannot merge their bodies with another sponge. Instead, they break off sections of their own body wall and float away to find new homes. These fragmenting sponges can be seed plants or ferns.
Sponges are organized at the cellular level and so lack organs and even well-developed tissues. They do, however, create sperm and eggs and reproduce asexually. Some sponge species are monoecious, whilst others are dioecious. This means that they have males and females, but they cannot mate themselves - the sexes must be separated during reproduction.
In addition to creating sperm and eggs, some sponges also release hormones that control the development of other organisms nearby. This form of geckoism is called "phytophagy" (plant eating) because it provides nutrients for the sponge itself as well as any other organisms it happens to be near at the time. Sponges in this case use the hormones to their own advantage by attracting prey that will eat the contaminated food and release more hormones that control other organisms nearby.
Some scientists believe that all sponges evolved this way from single-cell organisms in order to attract mates or prey. However, this theory has not yet been proven scientifically.
Reproductive Sexuality Sponges, unlike most humans, are hermaphroditic, which means they can produce both eggs and sperm. That's not to suggest they don't fertilize their own eggs. They do this by absorbing sperm from their environment and using this material to fertilize their eggs.
Sponges were first classified as asexual in 1775 when Charles Linnaeus described two species: one found on Sweden and the other on Finland. He noted that they could reproduce only by cloning themselves. This classification was changed when in 1838 Carl Vogel showed that sponges did have reproductive organs like other animals. Since then, more than 10,000 species of sponge have been identified.
Sponges are filter-feeders whose bodies consist of two different types of cells: choanocytes (or foam cells) and meshed fibers. The fibers are connected to each other and provide strength to the sponge. The choanocytes cover the fibers and function as the sponge's immune system by engulfing bacteria and other particles floating in the water.
A sponge's ability to absorb chemicals from its environment makes it useful for cleaning up oil spills. There are several species of sponge that live in marine environments around the world; some even swim with the tide!