Chapter 23: Phylogeny and Fossils

Question 1

define phylogeny

Answer 1

history of decent with branching (portrayed by phylogenic trees)
-depicts the process of speciation

Question 2

define node

Answer 2

point of branching off on a phylogenic tree

Question 3

define phylogenics

Answer 3

the study of evolutionary and genetic relationships among organisms

• aim is to discover the pattern of evolutionary relatedness of the species
• phylogenies are hypotheses! not given truth

Question 4

define taxonomy

Answer 4

the classification of organisms

-aim is to classify organisms into closely related groups (kingdom, phylum, class, order, family, genus, species)

Question 5

in what scenario are two species/groups of species considered to be the most closely related?

Answer 5

when two species/groups of species share a common ancestor not shared by any other species or group (sister groups)

Question 6

define “taxon”

Answer 6

another word for “group”

taxa= plural

Question 7

define monophyletic

Answer 7

all members share a single common ancestor not shared by with any other species or group of species
(to separate the group from the tree, you would only need to make one cut)
-preferred because we can trace evolution for one common ancestor through all of its descendants

Question 8

define paraphyletic

Answer 8

includes a common ancestor and some, but not all, of its descendants
(to separate group from the tree you would need to make more than one cut)

Question 9

define polyphyletic

Answer 9

groupings that exclude the last common ancestor of all the members

Question 10

define genus

Answer 10

closely related species

Question 11

define family

Answer 11

closely related genera (plural for genus)

Question 12

define order

Answer 12

closely related families

Question 13

define class

Answer 13

closely related orders

Question 14

define phylum

Answer 14

closely related classes

Question 15

define kingdom

Answer 15

closely related phyla (plural for phylum)

Question 16

what are the three domains of life?

Answer 16

Eukarya (eukaryotes)
Bacteria
Archaea

Question 17

define characters

Answer 17

• the anatomical, physiological, or molecular features that make up organisms
• to be useful, they must vary (but not within species) and must have a genetic basis

Question 18

define polytomy

Answer 18

a node with more than two immediate descending

branches (unresolved sister groups)

Question 19

define- homologous characters

Answer 19

characters that are similar because of descent from a common ancestor

Question 20

define - analogous characters

Answer 20

characters that are similar due to independent adaptation by different species
-result of convergent evolution

Question 21

define synapomorphies

Answer 21

a shared derived character or trait state that distinguishes a clade from other organisms

Question 22

define cladistics

Answer 22

phylogenic reconstruction on the basis of synapomorphies

Question 23

define parsimony

Answer 23

choosing the simpler of two or more hypotheses to account for a given set of observations (finding the simplest tree, easiest to follow with the least changes)

Question 24

what ways do fossils inform our phylogenies?

Answer 24

1. Allow us to calibrate phylogenies in terms of time
2. Provide a record of extinct species
3. Place evolutionary events in context with the Earth’s
   history

Question 25

define fossils

Answer 25

remains of once living organisms, preserved through time in sedimentary rocks

Question 26

define trace fossils

Answer 26

tracks and trails of organisms, but not the fossilized organism itself

Question 27

define molecular fossils

Answer 27

sterols, bacteria, lipids, and some pigment molecules that accumulate in sedimentary rocks which document organisms

Question 28

Burgess Shale

Answer 28

sedimentary rock formation that accumulated on a deep seafloor in what is now British Colombia
-waters on the basin floor contained almost no oxygen, so mud entombed organisms and protected them from decay

Question 29

Messel Shale

Answer 29

• in a lake in what is now Germany (more recent that Burgess Shale)
• releases of toxic gases from deep in the lake suffocated animals and their carcasses settled in oxygen-lacking muds and were preserved

Question 30

define geological timescale

Answer 30

the series of time divisions that mark earth’s long history

-calibration of the timescale became possible with the discovery of radioactive decay

Question 31

define radioactive decay

Answer 31

the breakdown of an unstable nucleus

Question 32

when did life originate on Earth?

Answer 32

more than 3.5 billion years ago

Question 33

how old is the Earth?

Answer 33

4.5 billion years

Question 34

how long ago did animals appear on the earth?

Answer 34

only 600 million years ago, fairly recently

Question 35

what is the best known mass extinction?

Answer 35

mass extinction at the end of the cretaceous period

• eliminate dinosaurs (except birds) and made way for the age of mammals
• probably caused by a large meteorite

Question 36

what was the most devastating mass extinction?

Answer 36

occurred at the end of the Permean period

Question 37

define Protists

Answer 37

all eukarya except land plants, fungi, and animals