Difference Between Vertebrates and Invertebrates

Main Difference – Vertebrates vs Invertebrates

Vertebrates and invertebrates are the two subdivisions into which all animals on earth can be categorized. Animals are multicellular, heterotrophic organisms, classified under the kingdom of Animalia. The main difference between vertebrates and invertebrates is that vertebrates consist of a backbone whereas invertebrates do not consist of a backbone. Therefore, vertebrates always show bilateral symmetry but, invertebrates show both bilateral and radial symmetry. Vertebrates include fish, amphibians, reptiles, birds, and mammals. Invertebrates include sponges, jellyfish, worms, mollusks, arthropods, and starfish. Vertebrates have a higher organization in their body structures when compared to invertebrates.

Key Areas Covered

1. What are Vertebrates
       – Definition, Characteristics, Examples
2. What are Invertebrates
      – Definition, Characteristics, Examples
3. What are the Similarities Between Vertebrates and Invertebrates
      – Outline of Common Features
4. What is the Difference Between Vertebrates and Invertebrates
      – Comparison of Key Differences

Key Terms: Animals, Brain, Invertebrates, Heart, Nervous System, Notochord, Pharyngeal Clefts, True Tail, Vertebral Column, Vertebrates

What are Vertebrates

Vertebrates are animals that have a backbone. They are classified under the phylum Chordata of the kingdom Animalia. Vertebrates are the most-organized animals on earth. This category includes fish, amphibians, reptiles, birds, and mammals. The most significant characteristic of vertebrates is the presence of a spinal cord, notochord, and the vertebrae. The notochord is a hollow nerve cord that occurs in the mid-dorsal line of the body during the embryonic period. In adults, it is replaced by the spinal column. The well-developed brain is located in the cranium.

Figure 1: Backbone of Humans

Vertebrates also have a pharyngeal gill slit pairs. The esophagus and the mouth cavity are connected to each other by the gill slits. Some fish have a cartilaginous endoskeleton. All other vertebrates have a bony endoskeleton. The heart of the vertebrates is muscular and can be composed of two, three or four chambers. Vertebrates possess kidneys for the excretion. They also have paired fins or limbs. 

What are Invertebrates

Invertebrates are the animals that do not have a backbone. Invertebrates are the most abundant animals on earth, and they live in most habitats. Invertebrates include sponges, jellyfish, worms, molluscs, arthropods, and starfish. Invertebrates do not also develop a notochord. The blood temperature of invertebrates is equal to the temperature of the outside environment. Therefore, invertebrates are called cold-blooded animals. Due to the lack of a strong endoskeleton, invertebrates are small and slow.

Figure 2: Vertebrates and Invertebrates

Most invertebrates consist of a segmented body, containing a head, thorax, and abdomen. The respiration occurs through the skin in most invertebrates, and some of them develop gills. Some invertebrates develop a chitinous exoskeleton. Most invertebrates are hermaphrodites. The classification of vertebrates and invertebrates is shown in figure 2. 

Similarities Between Vertebrates and Invertebrates

• Vertebrates and invertebrates belong to the kingdom Animalia.
• Both vertebrates and invertebrates show bilateral symmetry.
• Gills are present in some vertebrates and invertebrates.
• Both vertebrates and invertebrates have a nervous system.
• Both vertebrates and invertebrates have a heart.

Difference Between Vertebrates and Invertebrates

Definition

Vertebrates: Vertebrates are animals that have a bony or cartilages vertebral column.

Invertebrates: Invertebrates are the animals that do not have a backbone or a vertebral column.

Backbone

Vertebrates: Vertebrates possess a backbone.

Invertebrates: Invertebrates possess a backbone.

Notochord

Vertebrates: Vertebrates possess a stiff-supporting rod called notochord in the mid-dorsal line beneath the nerve cord during the embryonic period.

Invertebrates: Invertebrates do not possess a notochord.

Size

Vertebrates: Vertebrates are large animals.

Invertebrates: Invertebrates are small and slowly-moving animals.

Species

Vertebrates: Vertebrates include only 2% of the animal species.

Invertebrates: Invertebrates include 98% of the animal species.

Pharynx

Vertebrates: The pharynx of vertebrates have pharyngeal clefts to increase the efficiency of breathing.

Invertebrates: Invertebrates do not have pharyngeal clefts.

Central Nervous System

Vertebrates: The central nervous system of vertebrates is a hollow tube, which is located in the mid-dorsal line.

Invertebrates: The central nervous system of invertebrates is a solid tube, which is located in the mid-ventral line.

Living Endoskeleton

Vertebrates: Vertebrates consist of a living endoskeleton, which is composed of a skull and vertebral column. The endoskeleton grows in size with the growth of the animal.

Invertebrates: Some of the invertebrates consist of a non-living exoskeleton.

Heart

Vertebrates: The heart is located in the abdomen of the vertebrates. 

Invertebrates: The heart of the invertebrates is located dorsally.

Circulatory System

Vertebrates: Vertebrates have a closed circulatory system.

Invertebrates: Most invertebrates have an open circulatory system.

Blood Temperature

Vertebrates: The blood temperature of vertebrates does not depend on the temperature of the outside environment.

Invertebrates: The blood temperature of invertebrates is the same as the temperature of the environment.

Hepatic Portal System

Vertebrates: Vertebrates have a hepatic portal system, which carries blood from the alimentary system to the liver.

Invertebrates: Invertebrates have a hepatic portal system.

Red Blood Cells

Vertebrates: Vertebrates have red blood cells, which contain hemoglobin.

Invertebrates: Invertebrates do not have red blood cells. Their respiratory pigments occur in the blood plasma.

Appendages/Limbs

Vertebrates: Vertebrates do not have more than two pairs of limbs.

Invertebrates: Invertebrates can have more than two pairs of appendages.

Skin

Vertebrates: The skin of the vertebrates consist of two layers: the outer epidermis and the dermis.

Invertebrates: The skin of the invertebrates consist of a single layer.

Eyes

Vertebrates: The eyes of the vertebrates occur as an outgrowth from the brain.

Invertebrates: The eyes of the invertebrates occur as an outgrowth of the skin.

Compound Eyes

Vertebrates: Vertebrates do not have compound eyes.

Invertebrates: Most invertebrates have compound eyes.

Unisexual/Hermaphroditic

Vertebrates: All vertebrates are unisexual animals.

Invertebrates: Most invertebrates including sponges, worms, snail, and slugs are hermaphroditic animals.

Examples

Vertebrates: Vertebrates include fish, amphibians, reptiles, birds, and mammals.

Invertebrates: Invertebrates include sponges, jellyfish, worms, molluscs, arthropods, and starfish.

Conclusion

Vertebrates and invertebrates are the two major classifications of animals. Vertebrates have a backbone while invertebrates do not have a backbone. Vertebrates include the animals of the phylum Chordata. Invertebrates include the lower animals than chordates. The main difference between vertebrates and invertebrates is the presence or absence of a backbone.

Reference:

1.“Vertebrates.” Vertebrates | Definition, Vertebrate Characteristics | [email protected], Available here. Accessed 1 Sept. 2017.
2. “Invertebrates.” Invertebrates | List, Characteristics of Invertebrates | [email protected], Available here. Accessed 1 Sept. 2017.

Image Courtesy:

1. “Backbone (PSF)” By Pearson Scott Foresman – Archives of Pearson Scott Foresman, donated to the Wikimedia Foundation (Public Domain) via Commons Wikimedia
2. “Vertebrates and invertebrates” by Siyavula Education (CC BY 2.0) via Flickr