The fertilized egg is called a zygote , and develops into a multicellular embryo which eventually becomes a new diploid organism. While this general scheme holds for many animals, there are numerous exceptions. Some insects , notably social insects such as bees, may produce haploid offspring, and animals such as Hydra may reproduce by asexual budding. There is also a great deal of variation among organisms that do follow the general scheme. We suggest that you go deeper into our exhibits on animals to learn more about the many ways that animals go and have gone about their lives, or you can look at the alternation of generations page to find out more on how animals differ from other organisms.
Animals are heterotrophic.
One feature common to all animals is their ecological role as consumers , that is, they cannot manufacture their own food, and so must eat other organisms, or from other organisms, to obtain nourishment. This includes both carnivores such as wolves, which eat other animals, and herbivores such as cows, which eat plants. These organisms range from ticks to tapeworms, and may be relatively harmless or may cause disease. These organisms are vital to the food web because they recycle nutrients which would otherwise become unavailable. Earthworms and vultures are both examples of detrivores.