Invertebrate or Vertebrate?

Approximately 97% of animals on our planet are invertebrates, or animals with no backbone. When we think of “animals,” we often think of vertebrates (animals with backbones) like lions, tigers, bears and, of course, humans. However, given their large numbers and important functions in our ecosystem, learning how to identify them and their roles is critical to ensuring a sustainable future for our world. In this post, we’ll lay out what makes an animal an invertebrate, how they differ from vertebrates and how they ensure the survival of their vertebrate neighbors.

Invertebrates are animals without spines, while vertebrates have a spine. Invertebrates are sometimes (mistakenly) thought of as primitive because of their lack of developed organs. Their simple internal systems include respiratory systems such as gills or trachea and they often use an open circulatory system to pump their blood. As invertebrates lack an internal skeletal structure, they sometimes have an external skeleton that protects their soft bodies called an “exoskeleton.” In general, invertebrate success often comes from their ability to reproduce extremely quickly, unlike many vertebrates who take years to become fully grown.

Vertebrate animals, on the other hand, have a spine that develops from a notochord they possess as an embryo. They also have defined internal systems like complex respiratory structures, a closed circulatory system and sensory organs that build the nervous system. Vertebrates tend to be larger than invertebrates, thanks to their backbone, which allows their bodies to grow larger and move faster than many invertebrates.

Invertebrate Importance to Vertebrates

Invertebrates can be found in every ecosystem on earth, spanning from rainforests and oceans to deserts and polar regions. Ranging in size from tiny mites to giant squids, the look of invertebrates differs greatly, often depending on their environment. There are roughly 1.25 million invertebrate species that have already been discovered, but, scientists believe that there could be as many as 30 million invertebrate species that have yet to be found.

Comparatively, there are slightly more than 66,000 vertebrate species that have been discovered. That number will continue to grow as more are found, but invertebrates will likely still dominate by a wide margin. Like invertebrates, vertebrates span the ecosystems of all 7 continents. The unique traits of some vertebrates, like mammals, allow them to adapt to the cold by growing thick fur. The quicker motion of vertebrates also helps in cases of migration and running from predators. Invertebrates in similar situations must find other (often slower) ways to adjust to their environments.

Like vertebrates, invertebrates play important roles in our ecosystem, though invertebrates are often overlooked. Pollinators such as bees, butterflies and beetles aid in the reproduction of 80% of the world’s flowers and without them our food system would collapse. The plants pollinated by invertebrates are responsible for textiles like cotton or hemp cloth. Invertebrates are also fantastic soil aerators, which means they keep our soil healthy and full of nutrients for our crops. Vertebrates such as cows, horses, bears and other herbivores (plant eaters) and omnivores (meat and plant eaters) are also dependent on the actions of invertebrate pollinators, given that sources of food come directly from plants those pollinators visit.

Explore Butterfly Pavilion's invertebrate research and conservation efforts.

Not only do invertebrates help us grow delicious food, but like vertebrates, they can also be delicious food. After all, if you choose to be an omnivore (eating meat and plants), you may not only consume hamburgers, BBQ chicken and ham along with your fruits and veggies - you probably eat invertebrates as well. Crabs, lobsters, octopus and shrimp are all popular invertebrate seafood choices. In many Asian and African countries, insects are one of the main sources of protein, with crickets, grasshoppers, maggots and tarantulas on the menu. While you might be saying “yuck!”, know that insects are often a more environmentally-conscious protein choice when compared with animal protein like beef, chicken or park, which are commonly consumed in the United States. Insects require less food, water and land to grow and their populations grow at a faster rate. Some invertebrates, like ants, don’t even need to mate to produce offspring and it often takes only weeks for invertebrates to reach their full size. By contrast, most vertebrates must mate, give birth and go through a years-long growth process to reach maturity.

Invertebrates also ensure biological control, which means they control pests in a natural way. For example, spiders are beneficial in keeping mosquitos, flies and other pesky insect populations down. Without them, insect populations would rise, creating an imbalance in the ecosystem, and undoubtedly frustration for vertebrates.

In sum, invertebrates are critical to our way of life!

Essential, but not Invincible

Many invertebrate species are in danger due to climate change, habitat loss, parasites, pathogens and other challenges. But you have the power to make small changes that can protect the spineless creatures that carry the weight of our world. Buy organic, don’t use harmful pesticides, reduce single-use plastic, plant pollinator-friendly gardens, participate in citizen science projects in your community, and more.

Access free virtual learning programs that can expand your invertebrate knowledge and give you step-by-step instructions on how you can take action for conservation.

Virtual Learning

Our Invertebrate Experts

Examples of Invertebrates & Vertebrates

Test Yourself: Invertebrate or Not?

1. Snake

2. Cuttlefish

3. Stingray

4. Millipede

Sources

CurrentResults.com, Liz Osborn. “Number of Species Identified on Earth.” Number of Species on Earth - Current Results, www.currentresults.com/Environment-Facts/Plants-Animals/number-species.php.

“Invertebrates Pictures & Facts.” Animal Encyclopedia, National Geographic, 2012, www.nationalgeographic.com/animals/invertebrates/.

“Mantis Shrimp Eye Could Improve High-Definition CDs, DVDs.” ScienceDaily, ScienceDaily, 24 June 2011, www.sciencedaily.com/releases/2011/06/110624111944.htm.

“Pollinators.” U.S. Forest Service, U.S. Department of Agriculture, www.fs.fed.us/wildflowers/pollinators/.

Radford, Tim. “Tarantula Venom May Save Lives.” The Guardian, Guardian News and Media, 4 Jan. 2001, www.theguardian.com/science/2001/jan/04/uknews.