Lab 4 Flashcards
Enclosed Orbits
All modern primates have some kind of bony enclosure of the eye.
Post-Orbital Bar
a loop of bone that encloses the eye.
Post-Orbital Wall
so that the eye is fully protected by bone.
Orbital Convergence
when the eye sockets of an animal face forward (allows for stereoscopic vision)
Fused Mandible
Having a fused mandible, where the left and right sides of the mandible form one bone with no visible suture, is the derived condition in primates.
Unfused Mandible
The ancestral condition is to have an unfused mandible with the right and left halves of the mandible meeting at a visible suture along the midline.
Tooth Comb
Some primates have elongated lower anterior dentition (incisors and canines) that forms a tooth comb, which is used for feeding and grooming.
Number of Premolars
The number of premolars a primate has can be diagnostic. The ancestral mammalian condition is to have 4 premolars, but some groups have more derived conditions, like the primates. The ancestral condition in primates is to have 3 premolars, but some primates have lost a premolar and only have 2, as in humans.
Bilophodant Molars
Some primates have a very particular molar cusp configuration called bilophodont. Bilophodont molars have two cusps on each side of the tooth connected by ridges, called lophs, that run perpendicular to the tooth row. This is thought to be an adaptation for chewing fibrous vegetation.
Auditory Structures
On the base of the skull primates have some external bony structures that are involved in hearing.
Petrosal Auditory Bulla
a bony formation that protects the middle ear
Auditory Meatus
Ear Hold
Tympanic Tube
The more derived condition is to have a bony tube (tympanic tube) on the underside of the skull between the auditory meatus and the bulla.
Tail
Most primate groups have tails, but some do not.
Body Posture
Primate body posture can be divided into two main types. We can determine which type of posture a primate has by examining the shape of their thorax, the placement of their scapulae, and the number of lumbar vertebrae they have (Pronograde and Orthograde)
Pronograde
Primates that are pronograde hold their vertebral column horizontally and are always quadrupedal. Their thorax is narrow and long. Their scapulae are placed along the lateral sides of their thorax, along the sagittal plane. Pronograde primates tend to have more lumbar vertebrae (more than five) that allow them to have a more flexible lower back.
Orthograde
Primates that are orthograde hold their vertebral column slightly more vertically and can practice quadrupedalism or bipedalism. Their thorax is broad and short. Their scapulae is placed more towards the back or dorsal side of their thorax, oriented more in the coronal plane. Orthograde primates have fewer lumbar vertebrae, giving them a shorter, stiffer lower back.
Cladogram
A cladogram — a kind of phylogenetic tree — is a branching diagram that depicts the evolutionary relationships within a lineage.
Node
The points where branches split off from the main trunk, or from other branches, are called nodes. The nodes in this cladogram are labeled A, B, C, D and E.
Last Common Ancestor (LCA)
Each node represents the point at which a population of interbreeding individuals diverged into two (or more) species. That population represents the last common ancestor (LCA) of all subsequently diverging groups. For example, on the above cladogram node D would be the LCA between the whales and the lineage that leads to the Euarchonta (tree shrews and primates).
Tip
The ends of the branches are called tips and represent groups of related animals (such as Primates or Whales).
Clade
A clade is a branch on the tree of life: a group of organisms consisting of an ancestor and all its descendants.
Root
The root is usually at the bottom, but cladograms can also be shown in other orientations, such as sideways, usually with the root at the left and the tips at the right. In many cladograms, including this one, the root hangs off to the left, indicating the connection of this clade to the larger tree of life.
Outgroup
The taxon that branches off farthest down the tree is the outgroup. If the other taxa share a trait with the outgroup, that trait is considered ancestral for the other groups on the cladogram
Sister Taxa
On this cladogram, tree shrews and primates are sister taxa, meaning they are more closely related to each other than they are to any other taxa.
Ancestral Traits
are common to all members of a group. In other words, they evolved in the ancestor of that group and are often present in the descendants.
Derived Traits
in contrast occur when only a subset of group members possess that trait.
Shared Derived
If the derived trait is restricted multiple members of the group, it is called a shared derived trait.
Unique Derived
If the derived trait is restricted to only one member of the group, it is called a unique derived trait.
Cladistics
a method of reconstructing evolutionary relationships using shared, derived traits
Lumpers
Some people, called lumpers, prefer broader classifications that keep track of major differences among organisms and are willing to accept more variability (i.e. more diverse shapes and forms and/or scale of the observed variation) in a genus.
Splitters
Other people, called splitters, prefer fine-grained classifications that keep track of smaller differences and allow only a minimal degree of difference between individuals of a species and/or genus.
