Quiz 18: Processes of Evolution
Autosomal recessive disorder: It is one of the different ways a trait or disorder can pass down through generations. Since, it is autosomal disorder the affected genes are autosomes. As it is a recessive disorder both the copies of genes should be of abnormal type. Then only the disease will be expressed. People who carry only one defective gene are called carriers. They have the ability to transmit the same abnormal gene to their children, but they themselves are not affected. However, the individuals of a population can show variations in the details of the shared traits. These variations can be dramatic among the sexual reproducers. Thus, among a cluster of families, there can be reoccurrence of the blue offspring as these contain a recessive trait which is lack of enzymes that maintains the hemoglobin in its normal molecular form. Blueoffsprings contains the defective genes which make the skin of affected individuals to dark blue color and hence blue form of hemoglobin accumulates in blood and shows blue color.
According to Charles Darwin and Alfred Wallace individuals don't evolve but populations do. Population is a group of individuals which belongs to same species in a specified area. Individuals in a population share certain features called as morphological traits. Individuals in a population interbreed and are reproductively isolated from other species. Hence, they evolve among themselves.
Sexual selection can explains the version of a gender related trait which gives the individuals an advantage in reproductive success. Sexual dimorphism is one outcome of sexual selection. This sexual dimorphisms shows males are larger and flashier than females. By this model of natural selection, winners are the ones that are better at attracting mates and successfully reproducing compared to the others of the population. So, the population of tropical birds studied by Martha explains that the males have brightly colored tail feathers and the females don't have because, this is to attract the opposite sex, mate and develop the desired species among them and these differences are due to sexual dimorphism of a sexual selection.