How many Species are there on the Planet Earth

Scientists estimate that there are about 8.7 million Species of Plants and Animals on the Planet Earth

Biodiversity is the term used to describe the tremendous diversity of life on Earth. Biodiversity refers to all living things including plants, bacteria, animals, and humans.

Scientists estimate that there are about 8.7 million species of plants and animals. However, only about 1.2 million species have been identified and described so far, most of them insects. That means millions of other organisms remain complete mysteries. These differences are what scientists use to distinguish one species from another. Organisms that have evolved differently and can no longer breed together are called distinct species. All organisms that can reproduce with each other are classified as one species.

As for how many animals there are in the world, someone can only give estimates based on various calculations. However, it is understandable that this number is not 100% accurate.
The most accurate estimate of the total number of species on Earth includes 6.5 million land-dwelling species and 2.2 million deep-sea species.
There are millions of different species of animals, and the number of species keeps changing as scientists learn new facts. Animals are divided into two major categories Invertebrates and Vertebrates.

Vertebrates are creatures with backbones, whereas invertebrates lack them. On the other hand, most invertebrates belong to the phylum Arthropods, while vertebrates belong to the phylum known as Chordates. Vertebrates are further divided into six categories.
1. Mammals
Interestingly, humans belong to the group of vertebrates known as mammals. Mammary glands produce milk for females to nourish their offspring, and the neocortex, fur or hair, and the three middle ear bones are characteristic of the group of vertebrates known as mammals that form the class Mammalia. They are a diverse collection of 5,000 to 5,500 species that have evolved to survive in a variety of environments.
Mammals differ from other vertebrates in several ways. Most mammalian species are found on land, but some live in freshwater and marine environments. Current studies document long-term global rates of 25 species recognized each year.
2. Reptiles
Reptiles are air-breathing animals with characteristic skin composed of scales, bony plates, or both. The method of laying eggs is different from that of other cold-blooded animals. Except for snakes, all have backbones and most are four-legged. Reptile skin is mostly scaly, so they often lose the outer layer of skin. Unlike birds and mammals, reptiles do not maintain a constant body temperature.
3. Amphibians
Amphibians are cold-blooded, water-dependent animals that live on both land and water. Other animals can only exist on land or in water, but amphibians have a special ability to survive in both environments. These creatures are born with gills. Some lose them as they mature, while others retain them for life.
4. Fish
Fish refers to a broad group of aquatic organisms. Fish species are about the same size as all other vertebrate species combined. It is expected that there are many more species of fish than any other vertebrate. Fish come in different sizes and shapes and different environments depending on the number of species identified as fish.
Fish are aquatic, lacking digitized limbs such as fingers and toes, but do have gills. There are about 34,800 species of fish in the world, more than all other vertebrate species combined.
6. Birds
Birds are considered vertebrates because they have wings and feathers. The easiest way to distinguish birds from other animals is by looking at their wings. All birds have wings and fins that allow them to swim, threaten, and perform mating dances.
Birds have lighter skeletal systems than most other vertebrates, packed with air sacs, cavities, and crevices to keep them light and enhance their ability to fly.

Invertebrates

Animals that have cells but no skeleton are called invertebrates. Invertebrates make up more than 95% of all animal species worldwide. They can survive in many different environments depending on how they live and how they reproduce.
Invertebrates live in every environment on earth, from oceans and rainforests to deserts and polar regions.
So far, it has identified 1.5 million species of invertebrates. However, scientists estimate that up to 30 million species of invertebrates are still discovered.