Chapter 3:

3 branches of living things

- Bacteria (Prokaryotic) - Archaea (Prokaryotic) - Eukarya

Multicellular eukaryotic fossils date back as far as

1.6 billion years

The transition to multicellular life began ________ years ago

2.1 billion

The oldest known fossils of our own species are about

200,000 years old

The oldest known fossils that are generally accepted are ________ years old

3.45 billion Potential signs of life date back as far as 3.7 billion years

The oldest chemical traces of life found on rocks are about

3.5 billion years old

How old is the Earth?

4.568 billion years

Plant fossils date back

475 million years

Burgess Shale

A Lagerstatte in Canada that preserved fossils from the Cambrian period - 65,000 specimens - at least 93 species

Define prokaryote. A. A descriptive grouping for microorganisms that lack membrane-bound organelles. B. A grouping useful in the classification of early microorganisms. C. A grouping often used instead of Archaea. D. A single-celled eukaryote. E. A grouping designed to describe early fossils of plants.

A. A descriptive grouping for microorganisms that lack membrane-bound organelles.

Which isotope would be useful for dating a fossil found in relatively recent sediments? A. An isotope with a moderately high probability of decay. B. An isotope with a low probability of decay. C. Rubidium. D. Strontium. E. Any unstable isotope would be useful.

A. An isotope with a moderately high probability of decay.

How can scientists determine that multicellular life arose more than once? A. Animals are more closely related to single-celled eukaryotes than to fungi. B. Fungi can produce multicellular structures. C. Bacteria live as multicellular groups called biofilms. D. Scientists have no idea if multicellular life arose more than once.

A. Animals are more closely related to single-celled eukaryotes than to fungi.

Which group is not considered one of the major lineages of all living organisms? A. Bacteria. B. Microbes. C. Archaea. D. Eukarya.

B. Microbes.

How did the fossils of the Burgess Shale form? A. The animals fell to the bottom of a deep lake and over thousands of years turned to rock. B. The animals dropped into anoxic ocean depths and were covered by fine sediment. C. The animals were rapidly covered by ash falling from a volcano. D. Both a and b.

B. The animals dropped into anoxic ocean depths and were covered by fine sediment.

What allows us to know that synapsids were tetrapods? A. They lived on land. B. They were the dominant land animals. C. They evolved into mammals. D. They had four legs that they used for walking. E. All of the above are true.

D. They had four legs that they used for walking.

Why is a notochord an important adaptation for understanding the evolution of humans? A. The development of a notochord occurred in early fish. B. A notochord is a backbone. C. A notochord is characteristic of chordates. D. A notochord serves to distinguish the Ediacaran fauna from the trilobites. E. The notochord is not an important adaptation for the evolution of humans.

C. A notochord is characteristic of chordates

What evidence did Darwin use to predict the age of the Earth? A. Darwin didn't predict the age of the Earth. B. Darwin couldn't predict the age of the Earth, because he didn't understand radioactive decay. C. Darwin used processes he could observe, such as erosion and sedimentation, to predict that the Earth must be hundreds of million years old. D. It doesn't matter, because Lord Kelvin refuted Darwin's evidence.

C. Darwin used processes he could observe, such as erosion and sedimentation, to predict that the Earth must be hundreds of million years old.

Which outcome would you predict if you could compare the isotopes of fossils of two species of human ancestors and found high ratios of carbon-13/ carbon-12 in one and low ratios in the other? A. The species with high ratios likely lived in grasslands. B. The species with high ratios likely preferred eating shrubby vegetation. C. The species with high ratios likely ate a mixed diet. D. It would depend on what kind of human fossils. E. All of the above. F. None of the above.

C. The species with high ratios likely ate a mixed diet.

What is an isochron? A. The ratio of rubidium (Rb) to strontium (Sr). B. The half-life of an isotope. C. The slope of the line describing the ratio of 87Sr to 86Sr. D. A line on a graph of isotope ratios that indicates mineral samples formed at a similar time.

D. A line on a graph of isotope ratios that indicates mineral samples formed at a similar time.

How did scientists determine that Tyrannosaurus rex could not run very fast? A. They compared skeletal structures of Tyrannosaurus rex to modern animals to determine the size of T. rex's muscles. B. They used living animals to test a model they had developed on the biomechanics of running. C. They used evolutionary theory to determine the most closely related living organisms to Tyrannosaurus rex. D. They developed a biomechanical model of running animals to determine how much force leg muscles of a given size could generate. E. All of the above.

E. All of the above.

What independent lines of evidence have scientists used to determine the history of life on Earth? A. Zircons. B. Behavior of living species. C. Fossilized dung. D. Oxygen isotopes. E. All of the above.

E. All of the above.

Where do modern Stromatolites form?

Extreme environments - Saline lakes - Hot, shallow lagoons

Biomarkers can be preserved for

Hundreds of millions of years

Hominins

Includes humans as well as species more closely related to humans than to chimpanzees. - Humans are the only surviving members within this group

Stromatolites

Layered structures formed by the mineralization of bacteria

Teleosts

Lineage of bony fish compromising most species of aquatic vertebrates - Goldfish - Salmon - Tuna

Synapsids

Lineage of tetrapods emerging 300 mya giving rise to mammals - Pair of openings in skull behind the eyes (Temporal Fenestrae) distinguishing them from other tetrapods

Trilobites

Marine arthropods that diversified during the Cambrian period - Died out during the Devonian period

Chordates

Member of the phylum Chordata, animals that at some point during their development have a notochord; a dorsal, hollow nerve cord; pharyngeal slits or clefts; and a muscular, post-anal tail.

Prokaryotes

Microorganisms lacking a cell nucleus or membrane-bound organelles - Bacteria - Archaea

Biomarkers

Molecular evidence of life in the fossil record - Fragments of DNA - Molecules such as Lipids - Specific isotope ratios

Lagerstatten

Sites with an abundant supply of unusually well-preserved fossils - often including soft tissues - from the same period of time

Radiometric Dating

Technique that allows geologists to estimate the precise ages at which one geological formation ends and another begins

What do geologists use to estimate the age of rocks?

The breakdown of radioactive isotopes

T/F: Many elements have both stable and unstable (radioactive) isotopes

True

T/F: Unstable isotopes have a fixed probability of decay

True

Tetrapods

Vertebrates with 4 limbs, or descended from vertebrates with 4 limbs - Mammals - Birds - Reptiles - Amphibians - Oldest fossils date back 370 million years

The fossil record will never be complete because...

most organisms don't fossilize

Isotopes with high decay probabilities decay ________, and those with low probability decay ________

rapidly, slowly