25 Flashcards Preview

nop > 25 > Flashcards

Flashcards in 25 Deck (100):
1

phylogeny

(phylon - tribe, genesis - origin)
the evolutionary history of a species or group of species

2

systematics

an analytical approach to understanding the diversity and relationships of organisms, both present-day and extinct

3

systematists have traditionally studied __ and __ among organisms as a basis for inferring evolutionary relationships. in recent decades, systematists have gained a powerful new tool, __

morphological, biochemical resemblances;

molecular systematics

4

molecular systematics

uses comparisons of DNA, RNA, and other molecules to infer evolutionary relationships between individual genes and even btwn entire genomes

5

fossils can help establish relationships between living organisms b/c

they reveal ancestral characteristics that may have been lost over time in certain lineages

6

in order to infer phylogenies, we must study the __, __, and __ of living organisms, as well as __

morphologies, development, biochemistry, fossils

7

formation of sedimentary rocks

sand and silt eroded from the land are carried by rivers to seas and swamps, where the minerals settle to the bottom along w/ remains of organisms. over millions of years, deposits pile up and compress the older sediments below into layers called strata

8

fossil record

is based on the sequence in which fossils have accumulated in such strata

9

fossils inform phylogeny only if ________, clarifying _______

we can determine their ages,

the order in which various characteristics appeared and disappeared

10

the fossil record is biased

in favor of species that existed for a long time, were abundant and widespread, and had hard shells, skeletons, or other parts that facilitated their fossilization

11

homologies

similarities due to shared ancestry

12

if the morphological divergence btwn related species is great and their genetic divergence is small, then we can infer that

the morphological diversity of the species is controlled by relatively few genetic differences

13

analogy

similarity due to convergent evolution rather than to shared ancestry

14

a potential red herring in constructing a phylogeny is

analogy

15

convergent evolution occurs when

similar environmental pressures and natural selection produce similar (analogous) adaptations in organisms from diff evolutionary lineages

16

homoplasy

similar (analogous) structure or molecular sequence that has evolved independently in 2 species

17

another clue to distinguishing btwn homology and analogy is to consider

the complexity of the characters being compared

18

_____________, the less likely it is that the structures evolved independently.

the more points of resemblance that 2 complex structures have

19

scientists have so far sequenced _____ bases' worth of nucleic acid data from thousands of species

more than 20 billion

20

the fact that molecules have diverged btwn species

doesnt in itself tell us how long ago their common ancestor lived

21

just as w/ morhpological characters, it's necessary to distinguish homology from analogy to determine

the usefulnes sof molecular similarities for evolutionary studies

22

the discipline of systematics dates to ___ when ____

1748; linnaeus published systema naturae "system of nature"

23

systema naturae

linnaeu's taxonomic classification of all plants and animals known at the time

24

taxonomy

an ordered division of organisms into categories based on a set of characteristics used to assess similarities and differences

25

linnaeus' classification was based simply on ____ rather than on ____

resemblances; evolutionary relationships

26

2 useful features of linnaeus' ystem

1. binomial designations for species
2. hierarchical classification

27

binomial

2-part format of the scientific name, instituted by linnaeus

28

genus

1st part of species' binomial name

29

specific epithet

2nd part of species' binomial name; is unique for each species within the genus

30

format of binomial nomenclature

first letter of genus is capitalized, entire bionomial is italicized

31

hierarchical classification from most general to most specific?

kids playing catch on freeways get smashed

domain, kingdom, phylum, class, order, family, genus, species

32

taxon

the named taxonomic unit at any level

33

format of writing taxa?

taxa broader than the genus level aren't italicized, although they're capitalized

34

phylogenetic trees

branching diagrams used by systematists to depict their hypotheses about evolutionary relationships

35

a phylogenetic tree is often constructed from

a series of dichotomies, or 2-way branch points; each branch point represents the divergence of 2 species from a common ancestor

36

vintages

actual ages

37

cladogram

diagram that depicts patterns of shared characteristics

38

a cladogram by itself ______

doesn't imply evolutionary history

39

if ______, then the cladogram forms the basis of a phylogenetic tree

the shared characteristics are due to common ancestry (that is, if theyre homologous)

40

clade

within the phylogenetic tree -- a clade is defined as a group of species that includes an ancestral species and all its descendants

41

cladistics

the analysis of how species may be grouped into clades

42

monophyletic

a valid clade; pertaining to a grouping of species consisting of an ancestral species and all its descendants

43

paraphyletic

consists of an ancestral species and some, but not all, of the descendants

44

a paraphyletic grouping results when

we lack information about some members of a clade

45

after systematists have separated homologous from analogous similarties, they must sort thru the homologies to distinguish btwn __ and __

shared primitive characters and shared derived characters

46

what does "character" refer to

any feature that a particular taxon possesses

47

the characters that are relevant to phylogeny are

the homologous ones

48

shared primitive charaacter

a character that's shared beyond the taxon we're trying to define

49

shared derived character

an evolutionary novelty unique to a particular clade

50

systematists use ____ to differentiate btwn shared derived and shared primitive ccharacters

outgroup comparison

51

outgroup

speices/group that's closely related to the group of species being studied, but clearly not as closely as any study-group members are to each other

52

ingroup

the various species that are being studied

53

outgroup comparison is based on the assumption that

homologies present in both the outgroup and ingroup must be primitive characters that predate the divergence of both groups from a common ancestor

54

the species making up the ingroup display

a mixture of shared primitive and shared derived characters

55

any chronology represented by the branching pattern of a phylogenetic tree is __ rather than __

relative; absolute

56

phylogram

diagram in which the length of a branch reflects the number of changes that have taken place in a particular DNA sequence in that lineage

57

humans and bacteria had a common ancestor that lived ____ years ago, and it was a ____

over 3 billion years ago; single called prokaryote

58

ultrametric tree

same branching pattern as in a phylogram, but all the branches that can be traced from the common ancestor to the present are of equal length

59

ultrametric trees don't contain the info about ___ that can be found in phylograms

diff evolutionary rates

60

ultrametric trees can draw on data from ____ to ____

the fossil record; place certain branch points in the context of geologic time

61

maximum parsimony

principle that states that we should first investigate the simplest explanation that's consistent w/ the facts

62

the most parsimonious tree is the one that

requires the fewest evolutionary events to have occurred in the form of shared derived characters

63

for phylograms based on DNA sequences, the most parimonious tree

requires the fewest base chages

64

maximum nlikelihood

given certain rules about how DNA changes over time, a tree can be found that reflects the most likely sequence of evolutionary events

65

computer programs that search for trees that are parsimonious and likely are

1. "distance" methods minimize the total of all the percentage differences among all the sequences
2. more complex "character-state" methods minimize the total number of base changes or search for the most likely pattern of base changes among all the sequecnes

66

any phylogenetic tree represents

a hypothesis about how the various organisms in the tree are related to one another

67

applying parsimony in molecular systematics is more reliable for

a data set of many long DNA sequences than for a smaller set

68

occassionally misjudging an analogous similarity in morphology as a homologous character is less likely to distort a phylogenetic tree if

each clade in the tree is defined by several derived characters

69

molecular systematics

comparing nucleic acids or other molecules to infer relatedness

70

the ability of molecular trees to encompass both short and long periods of time is based on the fact that

diff genes evolve at diff rates, even in the same evolutionary lineage

71

since the DNA that codes for ribosomal RNA _____, _____

changes relatively slowly, comparisons of DNA sequences in these genes are useful for investigating relationships btwn taxa that diverged hundreds of millions of years ago

72

gene dulication is 1 of the most important types of mutation in evolution b/c

it increases the number of genes in the genome, providing opportnities for further evolutionary changes

73

orthologous genes

refers to homologous genes that are paassed in a straight line from one generation to the next but have ended up in diff genes pools b/c of speciation

74

paralogous genes

result from gene duplication, so they'e found in more than one copy in the same genome

75

orthologous genes can only diverge ____, w/ the result that

after speciation has taken place;

the genes are found in separate gene pools

76

paralogous genes can diverge ___, b/c ____

even while they're in the same gene pool;

they're present in more than one copy in the genome

77

remarkable fact about orthologous genes

they're widespread and can extend over huge evolutionary distances

78

remarkable fact about the number of genes

the number of genes seems not to have increased thru duplication at the same rate as phenotypic complexity m

79

molecular clock

yardstick for measuring the absolute time of evolutionary change based on the observation that some genes and other regions of genomes appear to evolve at constant rates

80

the assumption underlying the molecular clock is that

the number of nucleotide substitutions in orthologous genes is proportional to the time that has elapsed since the species branched from their common ancestor

81

in the case of paralogous genes, the number of substitutions is

proportional to the time since the genes became duplicated

82

we can calibrate the molecular clock of a gene that has a reliable avg rate of evolution by

graphing the number of nucleotide diffferences against the times of a series of evolutionary branch points that are known from the fossil record

83

the graph line representing the evolution rate of the molecular clock can then be used to estimate

the date of evolutionary episodes that can't be discerned from the fossil record

84

the regularity of genetic change that enables us to use some genes as molecular clocks raises the possibility that

many of the changes in these sequecnes result from genetic drift, and the changes are mostly neutral

85

neutral theory

theory that much evolutionary change in genes and proteins has no effect on fitness and therefore isn't influcned by darwinian selection

86

differences in the rate of the molecular clock in diff genes are a function of

how important each gene is

87

if the exact sequence of amino acids a gene specifies is essential to survival, ______

rate of change of genes:

most mutational changes will be harmful and only a few will be neutral

slow

88

if the exact sequence of amino acids is less critical,

rate of change of genes:

fewer of the new mutations will be harmful and more will be neutral.

more quickly

89

in reality, the molecular clock

doesnt run as smoothly as neutral theory predicts

90

many irregularities in molecular clocks are likely to be the result of

natural selection in which some DNA changes are favored over others

91

an abundant fossil record extends back about

550 million years

92

investigators use 2 creteria to identify regions of DNA molecules that can demonstrate the branchin pattern of the tree of life:

1. regions must be able to be sequenced
2. they must've evolved so slowly that homologies btwn even distantly related organisms can still be detected

93

b/c rRNA genes are fundamental to the workings of the cell,

their molecular clock runs so slowly that they can serve as the basis for a universal tree of life

94

tree of life has 3 domains:

bacteria
archaea
eukarya

95

the domain bacteria contains

most of the currently known prokarytes

96

archaea consists of

a diverse group of prokaryotic organisms that inhabit a wide variety of environments

97

eukarya conssts of

all the organisms that have cells containing true nuclei

98

comparisons of complete genomes from the 3 domains show that, esp during the early hsitory of life, there have been

substantial interchanges of genes btwn organisms in the diff domains

99

horizontal gene transfer

in which genes are transferred from one genome to another thru mechanisms such as transposable elements, and perhaps thru fusions of diff organisms

100

the 1st eukaryote may have arisen thru

a fusion btwn an ancestran bacterium and an ancestran archaean