Dominant alleles are always expressed when they are present. Recessive alleles are masked by dominant alleles.
Therefore, two copies of a recessive allele are required to show the recessive trait. Either one or two copies of a dominant allele produces the dominant trait.
Therefore, for dominant brown eyes, BB or Bb gives brown eyes, bb gives blue eyes.
For recessive long tails, tt gives short tails, TT and Tt gibe long tails
The deer and tick have a parasitism relationship as only the tick benefits from the relationship and the deer is being harmed. If Both were benefiting it would differ.
