The subarachanoid space lies between the arachnoid and pia mater. It is filled with cerebrospinal fluid. All blood vessels entering the brain, as well as cranial nerves pass through this space. The term arachnoid refers to the spider web like appearance of the blood vessels within the space.
Why do biologists organize living things into groups? What do the levels of classification indicate about the relationship between organisms? What characteristics are used to classify organisms into domains and kingdoms? What is the scientific study of how living things are classified called? Taxonomy
How Scientist Classify Today How do scientists know to which groups an organism belongs? They look at many traits. They compare the traits of one organism with those of another. Scientists also compare organism living today with those that lived long ago. Letâs look at how scientists classify living things. Classifying based on how organism are related Living things that are closely related are in many of the same classification groups. For example, if two plants are closely related, they will be in almost all of the same groups. If they are not closely related, they will not be in very many of the same groups.