Chapter 28

Front 1

Intact Fossils

Back 1

If decomposition does not occur, organic remains can be preserved.

Fossils of this type are the actual former living object still intact in original organic form.

Where they are found:

-Caves

Front 2

Compression Fossils

Back 2

Forms when sediments accumulate on top the material weighing down and compressing it into a thin film of organic material.

Where they are found:

-river beds/stream

Front 3

Cast Fossils

Back 3

In a mold, the former organism is completely dissolved and all that is left is a life-like negative cavity creating a mold. A cast is taking it one step further whereby, after the mold is formed, the cavity is slowly filled with minerals and an exact copy in stone is formed of the former organism.

Front 4

Permineralized Fossils

Back 4

Minerals are deposited in the cells of the organism which crystallize the cell walls and create a very life-like fossil that can even retain internal structures as they were when alive.

This happens only when the decomposition process is very slow.

Front 5

Paleontologists

Back 5

Scientist who studies fossils. Fossils are ranked on the sedimentary level they were found and compared relative to the surrounding layers.

Front 6

Habitat bias

Back 6

Organisms that live in areas where sediments are actively being deposited -including beaches, mudflats, and swamps - are much more likely to form fossils than organism that live in other habitats (i.e. near active volcanic mountains).

-location is the factor that determines if an extinct species is discovered.

Front 7

Taxonomic and tissue bias

Back 7

Slow decay is key in fossilization, so organisms with hard structures like bone or shells are likely to leave fossil evidence.

Front 8

Temporal bias

Back 8

Recent fossils are much more common than ancient fossils.

Sedimentary layer form in sequence (one over the other). As this continues, layer that are deepest experience more heat and pressure which can destroy any remains contained.

Front 9

Abundance bias

Back 9

Organism that are abundant, widespread, and/or present on Earth for long periods of time leave evidence much more often than do species that are rare, local, or ephemeral (short-lived).

Front 10

Radiometric dating

Back 10

a technique used to date materials such as rocks or carbon, usually based on a comparison between the observed abundance of a naturally occurring radioactive isotope and its decay products, using known decay rates.

Front 11

Radiometric curve

Back 11

Radioactive decay occurs at a constant exponential or geometric rate.
The rate of decay is proportional to the number of parent atoms present.

Front 12

Precambrian

Back 12

Spans the interval from earth's formation to the appearance of most animal groups about 542 mya.

Divided into Hadean, Archaean, and Proterozoic eons.

1. Hadean

-moon forms, earth formation ends, liquid water forms.

2. Archaean

-first oceans, life forms appear, photosynthetic microbes begin to add to the oxygen levels.

3. Proterozoic

-rocks begin to show evidence of O2, first Eukaryotes form, oxygen levels equal to present day.

Front 13

Phanerozoic Eon

Back 13

Spans the interval between 542 mya to the present.

Divided into Paleozoic, Mesozoic, and Cenozoic eras (these can be further subdivided into periods, and further still into epochs)

1. Paleozoic

-initial diversification of animals, plants, and fungi; land animals first appear, mass extinction occurs which obliterates 90% of life.

2. Mesozoic

-Dinosaurs were the most dominant animal, Gymnosperm were most dominant plant.

3. Cenozoic

-Mammals were the most dominant animal, Angiosperm were the most common plant (why? ability to attract pollinators).

Front 14

Eras

Back 14

a major division of geological time; an era is usually divided into two or more periods.

-marked by a distinctive character, event.

Front 15

Phylogenetic Tree

Back 15

A graphical summary that shows the ancestor-descendant relationships among populations, species, or higher taxa.

-identifies who is related to whom.

Front 16

Fossil Records

Back 16

The total collection of fossils that have been found throughout the world. Since the fossils or rocks around them can be age dated, a time frame can also be established.

Front 17

Phylogeny

Back 17

The evolutionary history of a group of organisms. This can be graphically represented with a phylogenetic tree.

Front 18

Branch

Back 18

Represents a population through time.

Front 19

Node (fork)

Back 19

A point within the tree where a branch splits into two or more branches.

Front 20

Outgroup

Back 20

A taxon that diverged prior to the taxa that are the focus of the study (branch C in image).

Front 21

Root

Back 21

The most ancestral branch in the tree.

Front 22

Polytomy

Back 22

A node that depicts an ancestral branch dividing into three or more descendant branches (see pg. 506, Table 28.1 in text).

Front 23

Tip (terminal node)

Back 23

Endpoint of a branch (called leaves in this image). It represents a living or extinct group of genes, species, families, phyla, or other taxa.

Front 24

Character

Back 24

Any genetic, morphological, physiological, or behavioral characteristic to be studied.

Front 25

Ancestral trait

Back 25

A characteristic that existed in an ancestor.

Front 26

Derived trait

Back 26

A characteristic that is modified from the ancestral trait, found in a descendant.

-comes about through mutation, selection, and genetic drift.