Looking after pets provides several benefits in terms of children's social interactions, and factual and conceptual knowledge about these animals. In this study we investigated effects of rearing experiences on children's factual knowledge and alternative conceptions about animals. Data obtained from 1,541 children and 7,705 drawings showed very strong bias towards rearing vertebrates and a general ignorance of invertebrates. Experiences with rearing animals significantly contributed to children's knowledge about animal's internal organs. Children who reported keeping two or more animals acquired better scores in our study than children keeping only one or no animals. Moreover, the misclassification of invertebrates was not influenced by children's experiences of keeping animals. Although girls showed better knowledge about the anatomy of animals and actually kept more animals than did boys, they also more frequently misclassified invertebrates by drawing bones inside the bodies of the animals, hence allocating them to the vertebrates. We propose that science activities with animals should be more focused on rearing invertebrates and improving children's attitudes and knowledge about them. (Contains 7 figures and 4 tables.)