Lineages → These are the taxonomic groups of interest placed in the extremes of the lines called branches ⇒ Elephant species X, Y, Z
Nodes → These are the ramification points, which are also known as divergence points. They represent the location of the most recent common ancestor ⇒ The red spot in the graph shows the location o the most recent ancestor between species X and Y
Root → This is the older common ancestor that all lineages share. The first one in the tree ⇒ The blue spot in the graph show the oldest common ancestor shared by the three species
Two or more lineages are more related to each other if they share a recent common ancestor -In this example, X and Y are more related to each other-. This means that they all diverge from the same node.
Two or more lineages are less related to each other if they lack a recent common ancestor. This is, the node from which these lineages diverge is placed far away in the tree.
primary immunodeficiency diseases are present at birth and usually stem from genetic errors, whereas secondary immunodeficiency diseases are acquired after birth and are due to agents such as infections, irradiation, or steroids
Answer: absolute certainty is often difficult to achieve. Scientific uncertainty generally means that there is a range of possible values within which the true value of the measurement lies.