Sensory peripheral nervous system and the motor peripheral nervous system
Answer:
Changes in the environment affect the food sources available for birds. For example, if a flood was to occur, there would be an abundance of fish to birds to eat. So birds with bigger beaks will be able to eat fish, to live and reproduce offspring with bigger beaks. While birds with smaller beaks will not be able to catch fish to eat, therefore decreasing the population of birds with smaller beaks.
There is only one pair of sister chromatids in mitosis, in meiosis I, there are two pairs of sister chromatids that combine to form homologous chromosomes.
