Heredity and Evolution
The variations arises by the process of reproduction can be inherited. These variations in the organisms increase the survival chances of the individuals.
The sexually reproducing organisms have two copies of genes for the same trait. The trait that gets expressed is called the dominant trait and the other is called the recessive trait.
Traits in one individual may be inherited separately, giving rise to new combinations of traits in the offspring of sexual reproduction.
The sex determination is different in different species. In human beings, the sex of the child depends on whether the paternal chromosome is ‘X’ (for girls) or ‘Y’ (for
The variations in the species contribute to the genetic drift. Any changes in the non-reproductive tissues caused due to environmental factors are not inheritable.
The speciation occurs when variation is combined with geographical isolation. The classification of organism’s shows evolutionary relationships. The evolution of an organism can be studied not just by the living species but also by studying fossils.
Complex organs may have evolved because of the survival advantage of even the intermediate stages.
During the course of evolution, organs or features may have adapted to new functions for example, feathers are thought to have been initially evolved for warmth and later adapted for flight.
The process of evolution cannot be said to ‘progress’ from ‘lower’ forms to ‘higher’ forms. Rather, evolution seems to have given rise to more complex body designs even while the simpler body designs continue to flourish.
Study of the human evolution indicates that all of us belong to a single species that evolved in Africa and spread across the world.