Answer:
Phenotypic variation is the variation which appears in the phenotype or morphology of the organism. Natural selection is the mechanism of evolution in which the adapated organism to the environment is selected or highly favoured during the course of evolution.
A phenotype is the results of the genetic change which to be established in a population has to be passed on to the generation.
Since variation in phenotypic traits allows the organism to leave indifferent circumstances therefore phenotypic variation proves essential condition to natural selection.
Ciliates move (c) using cilia. It is a group of protozoans. Cilia is an organelle of ciliates. It is a hair-like organelle that helps the ciliate move. It is also used in many ways like food gathering. It could even be used to sweep down food to their central channel.
Answer: The circulatory system and the respiratory system.
Explanation:
Gas exchange between tissues and the blood is an essential function of the circulatory system. In humans, other mammals, and birds, blood absorbs oxygen and releases carbon dioxide in the lungs. Thus the circulatory and respiratory system, whose function is to obtain oxygen and discharge carbon dioxide, work in tandem.
