It reduces genetic diversity and increases the proportion of deleterious recessive alleles
Explanation:
Inbreeding occurs when two genetically-related organisms mate and produce offspring. The breeding of genetically close individuals results in a loss of genetic variation in the population, as there is less "mixing" of different alleles to produce heterozygous (possess 2 different alleles) individuals.
This means that there is an increased chance that any deleterious alleles will become expressed (as there is less variation and more likely that homozygous individuals exist). These can be deleterious and potentially disease-causing. This reduces the fitness of the population.
The thorns are the most obvious feature of a rose that was created by its adaption to the environment. The thorns are modified leaves which grow out of the stem. The rose adapted to predators who would feed heavily on its foliage or stem by growing thorns