Amoebozoa

Tiny life forms move like jelly.

They use long arms to move. These arms also grab food. The food goes inside the cell. Some have hard shells. Others are soft and naked.

They live in ponds and soil. Some are very small. Some can grow very large. They have lived on Earth for a long time. These little things are truly amazing.

Amoebozoa is a big group of tiny living things. We call them amoeboid protists. Most are just one single cell. Some are even larger. Slime molds are part of this group. They can grow into many cells. They can cover several square meters.

Many members have blunt arms. These arms are called pseudopods. They use these arms to move. They also use them to grab food. The cell flows into the arm to eat. This way of eating is called phagocytosis.

Some members are naked. Others have hard shells. These shells are called tests. Some build tests from tiny bits of dirt.

These life forms are very old. Scientists found fossils in old rocks. Some are 750 million years old. These fossils look like shells we see today. Amoebozoa live in many places. You can find them in salt water. You can find them in fresh water. They also live in soil and moss.

Amoebozoa is a huge group of living things called amoeboid protists. There are about 2,400 different species that scientists have described. Most of these are single cells, but some can grow much larger. For example, slime molds can become multicellular. They can even grow to cover several square meters of ground.

These creatures are found in many different places. You can find them in salt water and fresh water. They also live in soil, moss, and leaf litter. Some live as parasites that live inside other organisms.

Moving and eating are very important for these cells. Many amoebozoans use blunt, fingerlike arms called pseudopods. They move by flowing their inner liquid, called endoplasm, into these arms. The outer layer, called ectoplasm, runs backwards along the outside. To eat, they use a way of life called phagocytosis. The cell uses its pseudopods to surround food particles. Then, it seals the food into little bubbles called vacuoles to digest it.

Some amoebozoans are naked and have no covering. Others have shells, which scientists call tests. Some members, like those in the order Arcellinida, make these rigid shells. Some make shells from organic materials. Others, like the genus Difflugia, build shells from collected particles. These particles are held together with a kind of cement. Some cells even have tiny scales on their bodies.

These living things have been around for a very long time. Scientists have found fossils called vase-shaped microfossils in old rocks. These fossils show that amoebozoans existed during the Neoproterozoic Era. Some of these fossils are 750 million years old. They include species like Melanocyrillium hexodiadema and Palaeoarcella athanata. These ancient fossils look very much like modern shell-bearing amoebozoans. This tells us they have stayed similar for millions of years.

Scientists use many tools to study how they are related. They use molecular genetic analysis to look at their DNA. This helps them see that Amoebozoa is a special group. They are a sister group to Opisthokonta. This is a large group that includes both animals and fungi. Some scientists even call the combination of these groups Amorphea. This helps us understand how all life is connected.

Amoebozoa is a major taxonomic group of amoeboid protists. It contains about 2,400 described species. These organisms are incredibly diverse in their forms and lifestyles. Some are tiny single cells. Others are large, multicellular slime molds. They live in many environments. You can find them in salt water and fresh water. They also inhabit soil, moss, and leaf litter. Some species live as parasites or symbionts. Others can cause disease in humans and other living things.

The way these cells move and eat is quite unique. Most amoebozoans use blunt, fingerlike projections called pseudopods. The cell body is divided into two distinct layers. The inner mass is a granular endoplasm. The outer layer is a clear ectoplasm. During movement, the endoplasm flows forward. Meanwhile, the ectoplasm runs backward along the outside. This flow allows the cell to crawl. Some cells use a monopodial form. In this state, the entire cell functions as one large pseudopod.

Nutrition in Amoebozoa occurs mainly through phagocytosis. This is a process where the cell surrounds food. The pseudopods reach out and wrap around a particle. This seals the food into internal bubbles called vacuoles. Inside these vacuoles, the food is digested and absorbed. Some species have a posterior bulb called a uroid. This structure may accumulate waste. The waste is then periodically detached from the cell. When food is scarce, many species form cysts. These hardy structures can be carried by the air. In slime molds, these are called spores. They often form on structures called fruiting bodies or sporangia.

Members of Amoebozoa vary greatly in their physical structures. Most species are "naked," meaning they lack a hard covering. Some have a loose coat of minute scales. However, the order Arcellinida is different. These organisms form rigid shells called tests. Each test has a single opening called an aperture. This opening allows the pseudopods to emerge. Some tests are made from organic materials. Others, like the genus Difflugia, are built from collected particles. These particles are held together with a cement.

Size is another area of great variation. Many species are very small. Some are only 10 to 20 micrometers in diameter. Other species are among the largest protozoa. The species Amoeba proteus is a famous example. It can reach 800 micrometers in length. Because of its convenient size, it is a common model organism in laboratories. Even larger are the multinucleate amoebae like Chaos and Pelomyxa. These can reach several millimeters in length. Some multicellular slime molds are even more massive. The "dog vomit" slime mold, Fuligo septica, can cover several square meters.

Scientists use molecular genetic analysis to study these organisms. This helps them understand the evolutionary history of Amoebozoa. It is considered a monophyletic clade. This means all members share a common ancestor. Modern studies show Amoebozoa is a sister group to Opisthokonta. Opisthokonta is a large group containing animals and fungi. Together, these two groups are sometimes called Amorphea. This relationship is a key part of the eukaryotic tree of life.

The history of these organisms goes back millions of years. Fossil evidence supports this long existence. Scientists have found vase-shaped microfossils in very old rocks. These fossils date back to the Neoproterozoic Era. Some specimens are 750 million years old. These include species like Melanocyrillium hexodiadema and Palaeoarcella athanata. These fossils share features with modern shell-bearing amoebozoans. For example, P. athanata looks similar to the modern genus Arcella. This suggests that the basic body plans of Amoebozoa have remained stable for a very long time.