ANTRHO105 Exam 3 - Section 3 Ancient Environments, Fossils & First Primates

46 cards audited against the Lecture 15 review. BEFORE studying, read the revised Section 3 guide’s REQUIRED SUPPLEMENTAL, pages 5–12. It teaches the dating, isotope, anatomy, vocabulary, and hypothesis details used here. Assigned source pages: Conservation 34–37; Origins 5–15 and 17–24; Norton Chapter 9. The exact course definition of generalized nocturnal remains unverified and is not tested as a definition.

What is continental drift?

The long-term movement of continents through plate tectonics, changing land connections and geographic barriers.

What was Pangaea?

An earlier supercontinent whose landmasses separated to form today's continental arrangement.

How can continental drift change climate and affect primates?

It changes ocean passages and heat circulation, altering climates and habitats; it also changes dispersal routes and isolation.

What textbook example connects continental drift with cooling?

Separation from Antarctica allowed cold circumpolar circulation and reduced heat transfer from lower latitudes, contributing to cooling.

What broad climate pattern should you recognize?

Long-term cooling with fluctuations: warmer early Eocene and early Miocene conditions, followed by cooler, more variable Pleistocene conditions.

What is an epoch?

A named division of geological time, such as the Paleocene or Eocene.

When were the Paleocene and Eocene, approximately?

Paleocene: 66-56 million years ago. Eocene: 56-34 million years ago; the first true primates appeared in the Eocene.

What were therapsids?

A group within the synapsid lineage that includes mammalian ancestors; they were not dinosaurs.

What is mammal radiation, and when did mammals expand into many open niches?

Evolutionary diversification into many ecological roles, especially after non-avian dinosaurs went extinct; mammals already existed alongside dinosaurs.

What are deep-sea cores used for in reconstructing climate?

They sample layers of marine sediment through time; preserved shells contain oxygen-isotope evidence of past conditions.

What are isotopes?

Forms of the same element with the same number of protons but different numbers of neutrons.

How does extensive ice affect the ocean's oxygen-18/oxygen-16 ratio?

Ice stores relatively more oxygen-16, leaving seawater relatively enriched in oxygen-18; the ratio rises.

What is a fossil, and what is the fossil record?

A fossil is preserved evidence of past life. The fossil record is the accumulated preserved evidence, an incomplete sample of past life.

How does fossilization commonly occur?

Burial protects remains; minerals may fill or replace original material under suitable conditions. Most remains never fossilize.

What parts preserve especially well, and what usually does not?

Hard parts, especially teeth and bones, preserve more readily than soft tissues. Behavior is usually inferred rather than directly preserved.

What is fossil-record preservation bias?

Organisms, body parts and environments differ in preservation and discovery, so the record samples past life unevenly.

Do a species' oldest and youngest known fossils establish its exact origin and extinction?

No. It may have originated before the oldest known fossil and survived after the youngest; the sampled lifespan can be shorter than the actual lifespan.

Why can a fossil-based phylogeny oversimplify evolutionary relationships?

Missing lineages, fragmentary specimens and uneven sampling can hide past diversity and branching relationships.

What does taxa mean?

Taxa is the plural of taxon: named biological groups, such as species, genera or families.

What is stratigraphy?

The study of rock and sediment layers and their order, used to establish relative ages and geological context.

What is the principle of superposition?

In an undisturbed sequence, lower sediment layers are older than layers above them.

How does relative dating differ from numerical dating?

Relative dating orders material as older or younger; numerical dating estimates an age or age range in years.

What are radioactive decay and a half-life?

Radioactive decay is the breakdown of unstable isotopes. A half-life is the time required for half the parent isotope in a sample to decay.

How does carbon-14 dating work?

Living organisms take in carbon. After death, uptake stops and carbon-14 decays at a known rate; the remaining amount is used to estimate age.

Why can't carbon dating date fossils millions of years old?

Carbon-14 has a half-life of about 5,730 years; after roughly 50,000 years too little remains for ordinary radiocarbon dating.

How does potassium-argon dating work?

Potassium-40 decays to argon-40. In suitable volcanic rocks, cooling establishes a clock; isotope measurements estimate the rock's age.

Does potassium-argon dating usually date the fossil itself?

No. It dates associated volcanic rock; dated layers above and below the fossil can constrain the fossil's age.

A fossil lies above a 3-million-year-old volcanic layer and below a 2-million-year-old layer. What age range fits?

Between 2 and 3 million years old, assuming the layers are undisturbed and the fossil was not redeposited.

What combination of features helps identify a fossil as a primate?

Grasping hands and feet, nails on most digits, forward-facing eyes with bony support, a relatively enlarged brain and generalized teeth; use a suite of traits.

What is a postorbital bar?

A bony ring around the eye socket; a bar is not the same as complete bony closure behind the eye.

What does the dental formula 2-1-3-3 describe?

Two incisors, one canine, three premolars and three molars in one quadrant of the mouth, not the entire mouth.

What does the course mean by a maximum dental formula of 2-1-3-3?

Use it as the course's generalized primate formula: groups can have fewer teeth of particular types. It does not mean all primates have that exact formula.

What were plesiadapiforms?

Extinct early primate relatives, prominent in the Paleocene, that provide clues about traits preceding the first true primates.

How does the course contrast plesiadapiform skulls with living strepsirrhines?

Plesiadapiforms in the comparison have longer snouts, smaller brains, enlarged incisors and no postorbital bar; strepsirrhines have a postorbital bar and a more primate-like cranial pattern.

How should you interpret the plesiadapiform hands-and-feet comparison?

The course contrasts claws and less primate-like grasping with strepsirrhine nails and grasping extremities. Traits varied; some plesiadapiforms had grasping specializations, so do not generalize the diagram to every species.

Why was the Eocene environment favorable for early primates?

Warm conditions supported extensive forests, including at higher latitudes, creating arboreal habitats and food opportunities.

What are the five primate-origin hypotheses named on the review?

Angiosperm, visual predation, leaping, generalized nocturnal and terminal branch. The exact course definition of generalized nocturnal remains unverified.

What does the angiosperm hypothesis propose?

Exploiting flowering-plant foods such as fruits and nectar favored primate adaptations, including grasping and visually coordinated use of branches.

What does the visual predation hypothesis propose?

Visually guided capture of small prey favored forward-facing eyes and grasping adaptations.

What does the leaping hypothesis emphasize?

Accurate jumps between supports: distance judgment and secure landings. This is the labeled supplemental explanation for the hypothesis named in the course.

What does the terminal-branch hypothesis emphasize?

Moving and feeding on slender outer branches, favoring grasping and coordination. This is the labeled supplemental explanation for the course term.

How are angiosperm, visual-predation, leaping and terminal-branch ideas different?

They emphasize plant foods, prey capture, jumping, and use of fine outer supports, respectively. Their proposed pressures can overlap.

Which living primates does the course associate with adapids?

Strepsirrhines, especially lemurs. This broad relationship does not establish every adapid as a direct ancestor of a living species.

Which living primates does the course associate with omomyids?

Tarsiers. This is a broad evolutionary association rather than proof that every omomyid was a direct ancestor.

How does the lecture broadly contrast adapids and omomyids?

Adapids are generally presented as larger, diurnal quadrupeds; omomyids as smaller, nocturnal primates, including leapers.

Why is the adapid fossil nicknamed Ida unusual?

It preserves an unusually complete, associated skeleton, unlike the isolated teeth and bone fragments common in the fossil record.