Question

Do diploid animals always have homologous chromosomes in each cell

Answer 1

No, having only homologous chromosomes in each cell is not a condition of diploid animals. The prime example of this is the sex chromosome in humans which is denoted as XX in mfemales and XY in males. As such, in females, all 23 pairs of chromosomes are homologous in each cell, whereas in males there are 22 pairs of homologous chromosomes along with 1 pair of sex chromosomes.

Although, it cannot be denied that majority of the diploid animals have homologous chromosomes in each cell with one chromosome of the homologous pair inherited from father and one from mother, it is not a prequisite for a cell to be considered diploid. Any cell that has chromosome number as 2n, with 'n' being the haploid number of chromosomes is considered diploid in nature.