Human Evolutionary Biology – Quiz 2 Study Guide

Lecture 6: Fossils and Fossilization

What is a fossil?

This is any evidence of past animal or plant life preserved in the earth’s crust.

Define the two major categories of fossils with examples.
1. 1. Body fossils: These comprise the remains of an animal. Common examples are bones and teeth.
  2. Trace fossils: These provide evidence of the activities of extinct organisms. Examples include footprints, coprolites, impressions, and nests or burrows.
Describe the process of fossilization.

Fossilization is the preservation of organisms’ body parts or environmental traces. It usually occurs by mineralization, where, under specific conditions, minerals in groundwater crystallize around and within organisms’ body parts. The first step in body fossil formation is rapid burial. Next, mineralization follows. Water containing minerals permeates the buried body tissues, and minerals in the water replace the biochemical structure of the tissue. Following the mineralization process, the original structure of the body tissue persists, although the original material does remain intact.

What type of rocks are fossils primarily found in?

Sedimentary rocks

What is the difference between a mold and a cast?

A mold is an impression of an organism’s body part (or entire body) left by the organism in its environment. Conversely, a cast is a mold filled with material that undergoes mineralization and preservation.

What is taphonomy?

The scientific study of what happens to organisms after they die.

Understand the difference between primary and secondary context.
- Primary context: The setting in which an organism’s remains were originally deposited.
- Secondary context: Settings where fossils are found in locations other than where the organismal remains were originally deposited.

Lecture 7: Geology and Dating

What is relative dating?

Relative dating is a method of fossil dating that only determines whether a fossil lived before or after another fossil or during a certain event in the past. It does not give a precise numeric date.

What is absolute dating?

Absolute dating is a fossil dating technique that directly estimates the age of organic remains and geological formations.

What is Stratigraphy?

The study of the sequential layering of sedimentary deposits.

Explain the three core principles of stratigraphy (superposition, original horizontality, original lateral continuity)

The Principle of Superposition: In an undisturbed sequence, each layer (stratum) is more recent than the one beneath.
The Principle of Original Horizontality: Strata are arranged horizontally or in an alignment close to horizontal orientation when they are deposited.
The Principle of Original Lateral Continuity: All parts of a stratum were once a single layer, though a later activity may disrupt the layer.

How is original horizontality disrupted?

A key process in the disruption of original horizontality is plate tectonics. The earth’s crust comprises huge plates that move and collide against each other, thus disrupting their original orientation. The earth’s crust movement may also cause earthquakes, leading to islands, volcanoes, rift valleys, ridges, and mountain formations.

What is an unconformity? What is an intrusion?

An unconformity is a gap in the stratigraphic record due to non-deposition or erosion, while an intrusion is the substitution of a part of the original stratigraphic profile with more recent or younger material.

What is Biostratigraphy?

A relative dating technique that builds on basic stratigraphic analysis based on faunal correlation.

What is Paleomagnetism?

A relative dating technique that involves studying the earth’s magnetic field.

Why are the Rift valleys of East Africa useful to paleoanthropologists?

The Rift Valleys of East Africa are useful to paleoanthropologists because they expose the deeply buried sediments, where fossils can be discovered.

Be able to list the ages of layers (from oldest to youngest) in a stratigraphic diagram like the one shown below:

Ages of layers (from oldest to youngest)

Lecture 8: Skeletal Biology

Major organic and inorganic components of bones and teeth and what they provide.

Organic Components
- Collagen: It provides elasticity, flexibility, and strength to bones.
- Amelogenins: A non-collagenous protein important for the growth of enamel crystals.
Inorganic Component
- Hydroxyapatite‡ (a type of calcium phosphate): It provides stiffness

Two main forms of bone tissue: compact and trabecular

Compact: It is cortical, densely packed, and functions to provide mechanical strength.
Trabecular: It is spongy or cancellous and provides structural support without adding excessive weight. The trabecular bone also maintains calcium and phosphate levels in the body and facilitates red blood cell production.

Bone development pathways: endochondral intramembranous (which is the one most bones follow?)

Endochondral bone development involves the formation of a cartilage model, which is then replaced by bone, while intramembranous bone development does not require a cartilage precursor. Instead, bone directly develops within connective tissue. Notably, most bones follow the endochondral bone development pathway.

Three main forms of tooth tissue: enamel, dentin, and cementum (Which one is the hardest substance in the body?)

Enamel: It covers the tooth crown. It is the hardest substance in the body. Enamel is 96% inorganic, primarily hydroxyapatite. It has no living cells, nerves, or blood cells. Though brittle, the high mineral content makes the enamel very hard.
Dentin: Dentin surrounds the internal pulp chamber and is covered by enamel. It constitutes 70% inorganic hypoxyapatite, 20% organic components (mostly collagen), and 10% water. It is porous and less brittle since it is less mineralized. Additionally, dentin is a living tissue that can grow and regenerate.
Cementum: This is a bone-like tissue covering the roots of the teeth. The cementum covers the porous dentin surface and serves as an attachment for ligaments that provide anchorage to the tooth in the jaw. Slightly softer than dentin, cementum constitutes 45% inorganic hydroxyapatite, 33% organic component (primarily collagen), and 22% water. Cementum formation is a continuous process that ensures tooth stability.

Lab 3: Human Skeletal Biology

Appendicular axial skeleton
- The appendicular skeleton includes the clavicle, scapula, humerus, pelvic girdle, radius, ulna, carpals, metacarpals, phalanges, femur, patella, tibia, fibula, tarsals, metatarsals, and phalanges.
- The axial skeleton includes the skull, sternum, ribs, spine (vertebrae), and coccyx.
Major bones of the body based on the lab presentation in the Module folder and activity.

Major bones of the body include the skull, vertebra, clavicle, sternum, scapula, humerus, ribs, pelvis, sacrum, ulna, radius, carpals, metacarpals, phalanges, femur, patella, tibia, fibula, tarsals, metatarsals, and phalanges.

Lecture 9: Comparative Skeletal Biology

Different types of primate locomotion and some skeletal features associated with them (especially intermembral index): arboreal quadrupedalism, terrestrial quadrupedalism, vertical clinging and leaping, suspensory, knuckle-walking

Arboreal quadrupedalism: Movement through relatively continuous networks of branches. This approach is good for small to medium-sized animals. Skeletal features associated with this mode include long tails, mobile shoulders and elbow joints, and short forelimbs and hindlimbs of similar length. Arboreal quadruped animals also have moderately long hand and foot phalanges with moderate curvature.
Terrestrial quadrupedalism: Locomotion mode that also constitutes skillful climbing, but the movement is mostly on the ground. Terrestrial quadrupeds have reduced tails, restricted shoulder and elbow joints, and long fore and hind limbs of similar length. Their metapodials are robust with short, straight hand and foot phalanges.
Vertical clinging and leaping: Clinging to vertical supports and leaping from support to support using hindlimbs. Vertical clingers and leapers have large hands, short, slender forelimbs, a long lumbar region, long, powerful hindlimbs, and large feet.
Suspensory: Locomotion mode that primarily involved brachiation and climbing. Brachiation is a hand-on-hand swinging movement, while climbing is a suspensory movement that typically involves other limbs besides the hands. Skeletal features associated with this mode include mobile wrists, long forelimbs, short hindlimbs, and mobile hips and shoulders.
Knuckle-walking: This involves walking on knuckles when on the ground. Some skeletal features of knuckle-walkers include long forelimbs, short hindlimbs, and long curved phalanges on the hand.

How to calculate an intermemberal index and forms of locomotion associated with different indices (VCL <90, quadrupedal ~100, suspensory/knuckle-walking >105)

Intermembral Index =

Intermemberal Index	Associated Forms of Locomotion
<90	Vertical Clinging and Leaping
~100	Quadrupedalism
>105	Suspensory and Knuckle-Walking

The most common mode of locomotion among primates

Arboreal quadrupedalism

Types of teeth and their functions: incisors, canines, premolars, molars

Incisors: Used for grasping, nipping, stripping, scraping, and ingesting food in small chunks.
Canines: Used for stabbing, biting, and holding prey (for wild animals). In humans, canines are incisiform and mostly function like additional incisors.
Premolars: They have molar-like functions and are used to break food into smaller chunks.
Molars: Used to further break food into much smaller chunks by shearing, slicing, crushing, and grinding.
- Thought experiment: How do the different types of teeth function when you eat a sandwich?

First, the incisors are used to grasp, scrap, and ingest the sandwich by breaking it into small pieces. Next, the canines function as additional incisors to break the sandwich into smaller pieces. Premolars then break the sandwich pieces into small chunks, which are then refined into much smaller chunks by the molars through crushing and grinding.

Heterodont homodont

Heterodont means having different types of teeth, while homodont means having a similar type of teeth throughout the mouth.

Dental features associated with fruit-eating vs. leaf-eating
- Dental features associated with fruit-eating: Broad incisors and low rounded/blunt molar cusps that fit into opposing basins.
- Dental features associated with leaf-eating: Small incisors and high sharp molar crests.

Lecture 10: Classification, Systematics, and Vertebrate Evolution

What is taxonomy?

The science of classifying, naming, and describing organisms.

Carolus Linnaeus’ three major contributions to classification: (1) based on natural features, (2) binomial nomenclature, (3) consistent hierarchical classification

(1) Based on natural features: Carolus Linnaeus’ classification involved using only organisms’ physiological and anatomical characteristics.

(2) Binomial nomenclature: Linnaeus introduced a less cumbersome and more consistent naming method, separating the description from the name.

(3) Consistent hierarchical classification: Linnaeus’ classification involved listing each species only in one group and grouping all life hierarchically.

What is Binomial nomenclature?

Naming of organisms using their genus and species name.

Homology Analogy. Examples for both with primates.
- Homology: The existence of similar skeletal structures in different animals due to shared ancestral heritage. For instance, monkeys and fish have vertebrae.
- Analogy: The existence of similar skeletal structures in different animals as a result of a similar function. For instance, monkeys have four bony limbs, while fish have four rayed fins. Thus, one or both configurations must be derived.
Ancestral Derived features.

Ancestral features are characteristics similar to those of the common ancestor, while derived features differ from the characteristics of the common ancestor.

What is a Clade?

A clade is a natural group that includes a common ancestor and all its descendants.

What are vertebrates?

Vertebrates are a group of animals with a stiff structure running throughout their body, with a spinal cord above and a digestive tract below.

When did most dinosaurs go extinct?

At the end of the Mesozoic at 66 Ma

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Question

Review your notes and the lecture slides emphasizing the points mentioned below. Be sure you are able to define any words in bold. Handwritten or online flashcards (e.g., Quizlet) may be helpful for review.

Human Evolutionary Biology – Quiz 2 Study Guide

Lecture 6: Fossils and Fossilization

What is a fossil?
Define the two major categories of fossils with
Describe the process of
What type of rocks are fossils primarily found in?
What is the difference between a mold and a cast?
What is taphonomy?
Understand the difference between primary and secondary context

Lecture 7: Geology and Dating

What is relative dating?
What is absolute dating?
What is Stratigraphy?

·Explain the three core principles of stratigraphy (superposition, original horizontality, original lateral continuity)

How is original horizontality disrupted?
What is an unconformity? What is an intrusion?
What is Biostratigraphy?
What is Paleomagnetism?
Why are the Rift valleys of East Africa useful to paleoanthropologists?

Be able to list the ages of layers (from oldest to youngest) in a stratigraphic diagram like the one shown below:

Lecture 8: Skeletal Biology

Major organic and inorganic components of bones and teeth and what they
Two main forms of bone tissue: compact and trabecular
Bone development pathways: endochondral intramembranous (which is the one most bones follow?)
Three main forms of tooth tissue: enamel, dentin, and cementum (Which one is the hardest substance in the body?)

Lab 3: Human Skeletal Biology

Appendicular axial skeleton
Major bones of the body based on the lab presentation in the Module folder and activity.

Lecture 9: Comparative Skeletal Biology

Different types of primate locomotion and some skeletal features associated with them(especially intermembral index): arboreal quadrupedalism, terrestrial quadrupedalism, vertical clinging and leaping, suspensory, knuckle-walking
How to calculate an intermembrane index and forms of locomotion associated with different indices (VCL <90, quadrupedal ~100, suspensory/knuckle-walking

>105)

Most common mode of locomotion among primates
Types of teeth and their functions: incisors, canines, premolars, molars

o Thought experiment: How do the different types of teeth function when you eat asandwich?

· Heterodont vs. homodont

Dental features associated with fruit eating vs. leaf eating

Lecture 10: Classification, Systematics, and Vertebrate Evolution

What is taxonomy?
Carolus Linnaeus’ three major contributions to classification: (1) based on natural features, (2) binomial nomenclature, (3) consistent hierarchical classification
What is Binomial nomenclature?
Homology Analogy. Examples for both with primates.
Ancestral Derived features.
What is a Clade?
What are vertebrates?
When did most dinosaurs go extinct?

Human Evolutionary Biology – Quiz 2 Study Guide