Lab 4

Question 1

Enclosed Orbits

Answer 1

All modern primates have some kind of bony enclosure of the eye.

Question 2

Post-Orbital Bar

Answer 2

a loop of bone that encloses the eye.

Question 3

Post-Orbital Wall

Answer 3

so that the eye is fully protected by bone.

Question 4

Orbital Convergence

Answer 4

when the eye sockets of an animal face forward (allows for stereoscopic vision)

Question 5

Fused Mandible

Answer 5

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.

Question 6

Unfused Mandible

Answer 6

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.

Question 7

Tooth Comb

Answer 7

Some primates have elongated lower anterior dentition (incisors and canines) that forms a tooth comb, which is used for feeding and grooming.

Question 8

Number of Premolars

Answer 8

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.

Question 9

Bilophodant Molars

Answer 9

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.

Question 10

Auditory Structures

Answer 10

On the base of the skull primates have some external bony structures that are involved in hearing.

Question 11

Petrosal Auditory Bulla

Answer 11

a bony formation that protects the middle ear

Question 12

Auditory Meatus

Answer 12

Ear Hold

Question 13

Tympanic Tube

Answer 13

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.

Question 14

Tail

Answer 14

Most primate groups have tails, but some do not.

Question 15

Body Posture

Answer 15

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)

Question 16

Pronograde

Answer 16

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.

Question 17

Orthograde

Answer 17

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.

Question 18

Cladogram

Answer 18

A cladogram — a kind of phylogenetic tree — is a branching diagram that depicts the evolutionary relationships within a lineage.

Question 19

Node

Answer 19

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.

Question 20

Last Common Ancestor (LCA)

Answer 20

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).

Question 21

Tip

Answer 21

The ends of the branches are called tips and represent groups of related animals (such as Primates or Whales).

Question 22

Clade

Answer 22

A clade is a branch on the tree of life: a group of organisms consisting of an ancestor and all its descendants.

Question 23

Root

Answer 23

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.

Question 24

Outgroup

Answer 24

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

Question 25

Sister Taxa

Answer 25

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.

Question 26

Ancestral Traits

Answer 26

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.

Question 27

Derived Traits

Answer 27

in contrast occur when only a subset of group members possess that trait.

Question 28

Shared Derived

Answer 28

If the derived trait is restricted multiple members of the group, it is called a shared derived trait.

Question 29

Unique Derived

Answer 29

If the derived trait is restricted to only one member of the group, it is called a unique derived trait.

Question 30

Cladistics

Answer 30

a method of reconstructing evolutionary relationships using shared, derived traits

Question 31

Lumpers

Answer 31

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.

Question 32

Splitters

Answer 32

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.