Invertebrates And Vertebrates - Its Differences

In the animal kingdom, animals have been classified into two main categories based on the presence or absence of the backbone or a spinal column. Apart from this, there are more differences between vertebrates and invertebrates. Read on to explore how these classes of organisms differ from each other.

Invertebrate And Vertebrate

Invertebrates

Invertebrates can be simply identified as animals that don’t have a backbone. They are found almost everywhere, from the hottest deserts and the deepest water bodies to the darkest caves and tallest mountains. As stated before, invertebrates are the animals which mainly lack a skeletal system and other developed organs. This means most of them do not possess a rigid body structure and as a result, cannot grow very large. Anatomically, they consist of an open circulatory system where blood flows in an open cavity. Most invertebrates possess a simple respiratory system, with the most common form being gills and trachea.

To compensate for the lack of an internal skeleton, most invertebrates have an external skeleton that protects their soft, inner body. This material is usually made from chitin, a derivative of glucose.

Invertebrates constitute more than 97 per cent of all species in the animal kingdom. The number of invertebrates exceeds more than 2 million species, with more being found almost every other day.

Prominent examples include annelids, arthropods, bivalves, coelenterates, echinoderms, squid, sponges, snails, and octopuses. Some invertebrates possess far superior traits and features to that of vertebrates. For instance, did you know the largest eye in the animal kingdom belongs to the colossal squid – a gigantic invertebrate?

Read More: Invertebrates

Vertebrates

Vertebrates are the most advanced of species in the animal kingdom. Members possess a well defined internal skeleton system, which includes a backbone. In humans, the spinal cord runs along the body between the caudal and cranial regions connecting to the nerve tissues. Vertebrates also have more complex and specialized organ systems when compared to invertebrates. Organ systems like the respiratory systems are quite complex, with many additional functions. Even the sensory organs are more advanced, which helps vertebrates adapt to their respective environment.

On average, the overall count of vertebrates existing on planet earth is around 57,000 to 58,000.

Examples of vertebrate include all chordates such as mammals, birds, fish, reptiles, and amphibians etc. The main characteristics of the vertebrates are that members have bilaterally symmetrical bodies and a brain enclosed by a skull.

Differences Between Invertebrates And Vertebrates

Invertebrates

Vertebrates

Invertebrates do not possess a backbone. Vertebrates possess a backbone and an internal skeleton.
Presence of an exoskeleton Well-developed brain, Internal skeleton, and advanced nervous system.
 Small and slower-moving animals. Large and faster-moving animals.
Have an open circulatory system. Have a closed circulatory system.
Have compound eyes. Do not have compound eyes.
Includes radial or bilateral body symmetry. Includes only bilateral body symmetry.
Have a simple and unorganized nervous system. Have complex and highly specified organs with specified functions.
Composed of only one layer of skin. Composed of two layers of skin, dermis, and epidermis.
Mode of nutrition includes Free-living, Parasitic and Heterotrophic. Mode of nutrition is usually heterotrophic.
95 to 98 percent of animal species are invertebrates. 2 to 3 percent animal species are vertebrates.
Flatworms, arthropods, sponges, insects are few examples Invertebrates. Mammals, fish, reptiles, amphibians, and birds are examples of Vertebrates.

Frequently Asked Questions

1. How are animals classified?

One of the most well-known and primary methods of classifying animals is based on the presence or absence of the backbone. And there are two classifications that fall under it, namely vertebrates and invertebrates.

2. Briefly explain the characteristics of invertebrates.

One of the most primary characteristics is the absence of a spinal cord. This means that the members under this class also lack a hard, bony internal skeleton. But in some members, a hard, exterior structure called the exoskeleton is present, which provides structural strength and protection from predators and environment (eg: crabs, lobsters and ammonites.) Most of the members are motile, but there are exceptions like the sea sponge.

3.  Briefly explain the characteristics of vertebrates.

Vertebrates are more complex organisms when compared to invertebrates. The primary difference between the two is that vertebrates possess a backbone and an internal skeleton. In some vertebrates, the bones are replaced with cartilage, as seen in sharks. Another defining characteristic of vertebrates is that they reproduce sexually.

Learn more about invertebrates, vertebrates and its differences only on BYJU’S Biology.

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