Invertebrate

Invertebrate is the group of animals that neither possess a vertebral column nor do they develop a vertebral column in their lifetime. It is derived from the notochord. The Invertebrates animals are different from Vertebrate animals as the Vertebrate animals possess bony or cartilaginous vertebral columns. Among all the living beings, more than 90 percent of living beings are Invertebrates. Invertebrates animals include a diverse group including sea stars, earthworms, jellyfish, sea urchins, sponges, lobsters, crabs, insects, spiders, snails, clams, and squids. Invertebrate has their importance. Invertebrate animals are important as parasites or agents that transmit parasitic infections. These Invertebrates are also important as agricultural pests. Invertebrate zoology is the study of all the Invertebrates animals names, that is, it is the study of animals without a backbone( the structure which is found in fish, amphibians, reptiles, mammals, and birds). The division of Invertebrates into two groups was done by Carl Linnaeus.

Define Invertebrates:- 

Invertebrates are not Vertebrates since they lack a Spinal Cord or Backbone. Animals without a Spine are known as Invertebrates. Invertebrates make up roughly 97 percent of all living things. Porifera, Cnidaria, Platyhelminthes, Nematoda, Rotifera, Mollusca, Annelida, Arthropoda, and Echinodermata are the nine phyla that make up the Invertebrate kingdom. Invertebrates are the most diverse and abundant animal group on the planet. Invertebrates account for more than 140,000 species in the United States, a number that is increasing as additional species are discovered. Approximately 200 Invertebrates in the United States are on the endangered species list.

A cold-blooded animal with no backbone is known as an Invertebrate. Invertebrates, such as insects, spiders, and worms, can live on land or in water. Crustaceans (like crabs and lobsters), mollusks (like squids and clams), and coral are examples of Marine Invertebrates.

Types of Invertebrates:

Arthropods make up 85 percent of Invertebrates or 923,000 species. Mollusks have around 100,000 different species. The following are some of the most frequent Invertebrates:

1. Protozoans- These are single-celled like an amoeba 

2. Annelids-  These include earthworms and leeches

3. Echinoderms- These include sea urchin, sea cucumber

4. Molluscs- They include snails, Octopus

5. Arthropods- Insects, spiders come under this category.

Where are they mostly found?

Invertebrates come in a wide variety of shapes and sizes. They can be found in freshwater, saltwater, on land, and in other animals as parasites. Invertebrates can be carnivorous (eat meat), herbivorous (consume plants), or omnivorous (eat both) (meat and plant eaters). Some Invertebrate species can produce their own food by growing bacteria and cells inside their bodies. Invertebrates can stay in one place or fly, swim, float, crawl, or burrow.

Characteristics of Invertebrates-

Invertebrates lack a backbone and have soft bodies due to the lack of an internal skeleton (endoskeleton) to provide support. Instead, many have external (exoskeleton) components that give support and protection. Invertebrates are also cold-blooded, which means they can't control their body temperature, which fluctuates depending on the surroundings.

Morphology of Invertebrates-

Most multicellular organisms have symmetrical body designs, whether they are radial, bilateral, or spherical. However, a small percentage of the population lacks symmetry. All gastropod species are examples of asymmetric Invertebrates. Snails and sea snails with helical shells are good examples of this. Slugs appear to be symmetrical from the outside, however, their pneumostome (breathing hole) is on the right side. Other gastropods develop outward asymmetry as they mature, such as Glaucus atlanticus, which has asymmetrical cerata. The genesis of gastropod asymmetry is a point of contention among scientists.

Nervous System of Invertebrates- 

Invertebrates have neurons that are different from mammalian ones. Invertebrates' cells fire in reaction to stimuli that are similar to those experienced by mammals, such as tissue injuries, high temperatures, or pH changes. The medical leech, Hirudo medicinalis, was the first Invertebrate in which a neuron cell was discovered.

Respiratory System of Invertebrates-

The open respiratory system of terrestrial arthropods, which consists of spiracles, tracheae, and tracheoles to carry metabolic gases to and from tissues, is one type of Invertebrate respiratory system. Although the number of spiracles varies widely among insect orders, each segment of the body can only have one pair of spiracles, each of which links to an atrium and has a rather big tracheal tube behind it. The tracheae are cuticular exoskeleton invaginations that branch (anastomose) throughout the body, with diameters ranging from a few micrometers to 0.8 mm. Tracheoles are the tiniest tubes that enter cells and act as diffusion sites for water, oxygen, and carbon dioxide.

Reproduction in Invertebrates- 

Most Invertebrates, like Vertebrates, reproduce in part by sexual reproduction. They make specialized reproductive cells that go through meiosis to make smaller, motile spermatozoa or larger, non-motile eggs. These join together to produce zygotes, which evolve into new people. Others can reproduce asexually, or in certain cases, both sexually and asexually.

Did You Know?

1. In the 21st century, the two most commonly used model organisms for study purposes are Invertebrates. The fruit fly Drosophila melanogaster and the nematode Caenorhabditis elegans are very commonly used as model organisms. They were among the first life forms that were genetically sequenced. Due to the reduced state of their genomes, this sequencing of genes was facilitated.

2. Starfish are also Invertebrates. They are called sea stars because of their arms which look like rays coming out of their bodies. Starfish live deep in the ocean and on the shore. There are over 1600 species of starfish. Starfish move with tube feet with the help of hydraulic pressure.

Conclusion

Invertebrates form a key element in the food chains. They serve as food for human beings. Invertebrates can support birds, fish, and many other species of Vertebrates. Invertebrates are often given less focus as compared to Vertebrates. They are often considered mere pests. With heavy use of pesticides in the 21st century all over the world, there has been a large decrease in the population of Invertebrates like bees, wasps, and other terrestrial insects. It was in the 20th century when Invertebrate zoology became popular in the fields of natural sciences, with prominent discoveries in different fields of medicines and genetics. Invertebrates are often used by scientists in aquatic biomonitoring to evaluate the different effects of water pollution and climate change.