What are Lower Invertebrates?
Lower invertebrates are a classification of animals that includes all invertebrates except for the vertebrates. This group includes everything from the simple, one-celled animals like the amoeba to the more complex animals like the crayfish. Lower invertebrates typically have a simple body plan with few or no limbs, and they lack a backbone.
Classification of Lower Invertebrates
- There are many different types of lower invertebrates, including arthropods, mollusks, and annelids. Arthropods are the largest and most diverse group of lower invertebrates, and include insects, spiders, and crustaceans. Mollusks are a diverse group of animals that includes clams, oysters, and snails. Annelids are a group of worms that includes earthworms and leeches.
- Each of these groups of animals has unique characteristics that help to distinguish them from one another. Arthropods are characterized by their jointed legs and hard exoskeletons. Mollusks are characterized by their soft bodies and shells. Annelids are characterized by their segmented bodies and bristles.
- Despite their differences, these groups of animals share some common characteristics. They all are invertebrates, meaning they do not have a backbone. They also all have a circulatory system, which helps to distribute nutrients and oxygen throughout their bodies.
- Lower invertebrates play an important role in the food chain. Arthropods, in particular, are a major source of food for many other animals. They are also important pollinators and help to recycle nutrients back into the environment.
Porifera are a phylum of animals that include sponges. They are mostly marine animals, but there are a few freshwater species. They are simple animals without a true body cavity, and their cells are not organized into tissues. They feed by filtering food particles out of the water that flows through their bodies.
The phylum Platyhelminthes contains a diverse and large group of flatworms. These animals are characterized by their flattened body shape and their lack of a backbone. Platyhelminthes includes a variety of parasitic and free-living organisms.
The parasitic flatworms are often very damaging to their hosts. Some species can cause serious diseases in humans, animals, and plants. The free-living flatworms are much more benign, and many are important members of the food web. Some species are even used in biomedical research.
Despite their diverse appearances, all members of the phylum Platyhelminthes share certain characteristics. They all have a flattened body shape and they all lack a backbone. Additionally, they all have a simple body plan with a single layer of cells. This layer is called the epidermis.
The phylum Platyhelminthes is a very large and diverse group of animals. It includes a wide range of parasitic and free-living organisms. The parasitic flatworms can be very damaging to their hosts, while the free-living flatworms are much more benign. All members of the phylum Platyhelminthes share certain characteristics, including a flattened body shape and a lack of a backbone.
Phylum Cnidaria / Coelenterata
The phylum Cnidaria, also known as the Coelenterata, includes creatures such as jellyfish, corals, and sea anemones. These animals are characterized by their possession of stinging cells, called cnidocytes, which are used to paralyze prey or defend against predators. Cnidarians typically have a sac-like body shape and a single opening, the mouth, through which they eat and excrete waste. Most cnidarians are aquatic, but a few species can live on land.
The phylum ctenophora is a group of invertebrates that includes marine animals such as sea jellies and comb jellies. These animals are characterized by their cilia, which are used for movement. They also have a unique feeding system that involves the use of comb-like plates to capture prey.
The phylum Ctenophora includes the comb jellies. These animals are named for the combs of cilia that line their bodies and beat to create currents that move the animals through the water. There are about 100 species of ctenophores.
Comb jellies are predators that eat small prey such as copepods. They use their combs of cilia to create currents that draw the prey near. Then the animals use their tentacles to grab the prey and eat it.
Comb jellies are not very common in the ocean, but they can be found in both the Atlantic and Pacific oceans. They usually live in the lower parts of the water column, where the water is warmer and more stable.
Comb jellies are not very well understood, and scientists are still learning about their biology and ecology. They are important in the ocean food web, and their loss could have serious consequences for the marine ecosystem.
Phylum Aschelminthes/ Nematoda
The phylum Aschelminthes, also known as nematoda, is a group of animals that includes roundworms and hookworms. These animals are characterized by their simple body plan and lack of a backbone. Nematodes are typically small, and many are parasitic. They range in size from a few millimeters to several meters in length.
The phylum Aschelminthes/ Nematoda contains roundworms. These worms are often parasites, living in the body of another animal. Some roundworms are free-living, but most are parasites. Roundworms are very thin and can grow up to one meter long. They have a simple body with a head and a tail. They have a nerve cord down the middle of their body and a simple brain. Their mouth is at the front of their head and they have no eyes or ears. Roundworms eat plant or animal material. Some roundworms can cause diseases in humans and other animals.