Dog Vaccination Schedule. Age. Vaccination. 5 weeks. Parvovirus: for puppies at high risk of exposure to parvo, some veterinarians recommend vaccinating at 5 weeks. Check with your veterinarian. 6 & 9 weeks. Combination vaccine * without leptospirosis.*Some puppies may need additional vaccinations against parvovirus after 15 weeks of age. Consult with your local veterinarian. Â§ According to the American Veterinary Medical Association, dogs at low risk of disease exposure may not need to be boostered yearly for most diseases.
In population genetics, directional selection is a mode of natural selection in which an extreme phenotype is favored over other phenotypes, causing the allele frequency to shift over time in the direction of that phenotype.
Popular Answers. Positive selection: also called (Darwinian selection) variants that increase in frequency until they fix in the relevant population. The selective pressure that leads to this fixation is termed positive selection. Negative selection: Also called purifying selection, it means that selection is purging changes that cause deleterious impacts on the fitness of the host. ...