The Vast Majority Of Animal Species Alive Today Belong To Which Major Group?

Introduction to Invertebrates

Invertebrates are animals without backbones. Fig. three.2 shows some examples of invertebrate animals. Ask most people to give you an example of an animal, and they will answer with familiar examples like birds, dogs, cats, monkeys, whales, fishes, and frogs. These are all animals we telephone call vertebrates. They have dorsal nerve cords that are encased in hard protective backbones or vertebrae (singular: vertebra). Most of the animals featured on television and in zoos are vertebrates. Perhaps we think of vertebrates first when talking virtually animals because to humans, these organisms are familiar and comfortable. However, the vast majority of animal life on our planet is fabricated upwards of animals without backbones: the invertebrates. Of the approximately 35 phyla in the kingdom Animalia, merely i phylum—the phylum Chordata—contains animals that accept backbones.

Fig. 3.2. (A) Red encrusting sponge (Monanchora arbuscula; phylum Porifera)

Fig. iii.2. (C) Deep-water shrimp (Heterocarpus ensifer; phylum Arthropoda) Fig. 3.2. (D) Marine king ragworm (Alitta virens; phylum Annelida)

Scientists continue to debate the total number of living species on Globe. Scientists accept formally described approximately i.6 million species. New species continue to exist discovered, peculiarly amidst groups that accept modest body sizes or live in remote areas such equally the deep sea, polar ice, or cloud forests. Estimates of the total number of species range from two million to 20 one thousand thousand. The International Marriage for the Conservation of Nature (IUCN) offers a low-cease gauge of approximately 1.37 1000000 surviving species of animals. Among these 1.37 one thousand thousand animal species, simply about 66,800 species are vertebrates. The remaining 1.iii one thousand thousand species are invertebrates.

Fig. 3.3. Percent contribution of species from the major groups within the kingdom Animalia. Source: International Matrimony for the Conservation of Nature (IUCN) 2015

In terms of species diverseness, the invertebrates far outpace the vertebrates. Only 5 pct of all known living animal species are vertebrates or animals with backbones (Fig. 3.3). The vast bulk of animal species (95 percent) are invertebrates. Among all animal species, one particular group easily claims the highest number of species: the insects. Insects—a grouping within the phylum Arthropoda—have evolved into several millions of species, specially beetle insects (order Coleoptera). Approximately 3 out of every iv beast species is an insect, and one in three animal species is a beetle!

Scientists recall that 1.37 one thousand thousand animal species offers a low-terminate guess of the full number of creature species on Globe. What might happen to our pie graph (Fig. 3.3) as more species are discovered and described? In full general, information technology is reasonable to think that nearly of the large mammals and other vertebrates have been found and described, with only a very small proportion (such as deep bounding main fishes) remaining as yet unknown. Many invertebrates are small and dwell in hard-to-reach places. For example, the group of worms called nematodes currently consists of about 200,000 described species. However, scientists believe that in that location may exist as many as 1,000,000 species in beingness. There are probably thousands upon thousands of invertebrates as yet undescribed. The percentage of animals without backbones is likely only to increase as new species are discovered.

Major Invertebrate Phyla

Biologists currently recognize 35 dissimilar phyla within the kingdom Animalia. Many of these phyla are relatively obscure and rare. For instance, the phylum Cycliophora contains only one genus of microscopic animals found exclusively on the mouthparts of lobsters.

This unit of measurement volition discuss the defining characteristics of the post-obit nine major animal phyla: