Question

List three important distinguishing features of arthropods, reptiles and mammals.

Answer 1

Animals can be classified into six broad categories: complex, nervous-system-equipped multicellular species and the ability to follow or capture their food. There are the six major animal types, ranging from the easiest (spineless invertebrates) to the most difficult (mammals that can adapt to a wide range of habitats).

Complete Answer:

Arthropods	Mammals	Reptiles
Without backbones, there are also a lot of animals. These are classified as invertebrates and are part of the arthropoda phylum.	It belongs to the mammal group if an animal consumes milk while it is a baby and has fur/hair on its body.	Reptiles are a genus of scaly-skinned creatures.
Arachnids (spiders) and insects are two of the most commonly known classes in this phylum.	Animals such as rodents (mice, squirrels), carnivora (cats, dogs, bears), primates (humans, monkeys) and many more are among the placental mammals. Non-placental mammals, such as kangaroos and opossums, belong to a group called marsupials, and via a placenta they do not feed their young developing ones.	More than 8,700 species account for the largest classes of living reptiles: turtles (order Testudines), tuatara (order Rhynchocephalia [Sphenodontidae]), lizards and snakes (order Squamata), and crocodiles (order Crocodylia, or Crocodilia).
It has a hard, body-protecting exoskeleton. Chitin makes up the exoskeleton.	The epidermis of the mammals' outer layer is composed of hair.	The epidermis of the reptiles' outer layer is made up of scales.
Definitely, insects are cold blooded.	Lifestyles eventually diverged, and hairy mammals that had endothermic (warm-blooded) physiology and mammary glands to feed their young came from the synapsid side.	The majority of modern reptiles have ectothermic physiology (cold-blooded). No reptile has produced specialised skin glands for feeding its young, living or extinct, so far.
The heart is divided into valve-separated parts.	Mammals have a heart of 4 chambers.	Reptiles have a heart of 3 chambers.
They breathe through the surface of the body, the trachea and the gills.	Mammals give birth to young people.	Reptiles are mainly egg-laying animals, except for some of the species that give birth to young people as well.

Note: There are some parallels between mammals and reptiles—they both have spinal cords, for example The main similarity between mammals and arthropods is the presence of lungs for breathing out of water. Tetrapods and arthropods have grown separately from each other.
Example for Mammals: Humans
Example for Reptiles: Crocodile
Example for Arthropod: Insects