Pages 490-493; 505-516

Question 1

Species

Answer 1

defined as an evolutionary independent population or group of populations.

Question 2

Biological species concept

Answer 2

the main criterion for identifying species is reproductive isolation (causes no gene flow).

Question 3

Prezygotic isolation (biological species concept)

Answer 3

prevents individuals of different species from mating.

• Temporal – populations are isolated because they breed at different times.
• Habitat – populations are isolated because they breed in different habitats.
• Behavioral – populations do not interbreed because their courtship displays differ.
• Gametic barrier – matings fail because eggs and sperm are incompatible.
• Mechanical – matings fail because male and female reproductive structures are incompatible.

Question 4

Postzygotic isolation (biological species concept)

Answer 4

the offspring of matings between members of different species do not survive or reproduce.

• Hybrid viability – hybrid offspring do not develop normally and die as embryos.
• Hybrid sterility – hybrid offspring mature but are sterile as adults.

Question 5

Disadvantages of biological species concept

Answer 5

the criterion of reproductive isolation cannot be evaluated in fossils or in species that reproduce asexually. The concept is also difficult to apply when closely related populations do not happen to overlap with each other geographically.

Question 6

The morphospecies concept

Answer 6

researchers identify evolutionarily independent lineages by differences in size, shape, or other morphological features. Distinguishing features are most likely to arise if populations are independent and isolated from gene flow.

Question 7

The morphospecies concept is widely applicable.

Answer 7

It is useful when biologists have no data on the extend of gene flow, and it is equally applicable to sexual, asexual, or fossil species.

Question 8

Disadvantages of morphospecies concept are:

Answer 8

• May lead to the naming of two or more species when there is only one polymorphic species with differing phenotypes.
• It cannot identify cryptic species, which differ in traits other than morphology.
• The morphological features used to distinguish species are subjective.

Question 9

The phylogenetic species concept

Answer 9

identifies species based on the evolutionary history of populations.

Question 10

Monophyletic group (phylogenetic species concept)

Answer 10

also called a clade or lineage; consists of an ancestral population, all of its descendants, and only those descendants.

Question 11

Synapomorphy

Answer 11

identifies monophyletic groups; a trait that is found in two or more taxa that is present in their most recent common ancestor, but is missing in more distant ancestors. Can be identified at the genetic, developmental, or structural level.

Question 12

Under the phylogenetic species concept, species are defined

Answer 12

as the smallest monophyletic groups on the tree of life.

Question 13

Phylogentic species

Answer 13

re made up of populations that share one or more synapomorphies.

Question 14

Advantages of the phylogenetic species concept:

Answer 14

• Can be applied to any population (fossil, asexual, or sexual).
• It is logical because different species have different synapomorphies only if they are isolated from gene flow and have evolved independently.

Question 15

Disadvantage of the phylogenetic species concept

Answer 15

carefully estimate phylogenies are available only for a tiny (though growing) subset of populations on the tree of life.

Question 16

subspecies

Answer 16

populations that live in discrete geographic areas and have distinguishing features, but are not considered distinct enough to be called separate species.

Question 17

phylogeny

Answer 17

evolutionary history of a group of organisms.

Question 18

phylogenetic tree

Answer 18

graphical summary of this history, showing the ancestor-descendant relationships among populations, species, or higher taxa, and clarifying who is related to whom.

Question 19

tree of life

Answer 19

most universal or all phylogenetic trees, depicting the evolutionary relationships among all living organism on Earth.

Question 20

branch

Answer 20

represents a population through time. length means nothing usually.

Question 21

node (forks)

Answer 21

represent hypothetical common ancestors; a point within the tree where a branch splits into two or more branches.

Question 22

outgroup

Answer 22

a taxon that diverged prior to the taxa that are the focus of the study; helps to root the tree. Species that is closely related to the group being studied, but not part of it. Used to establish the polarity of each trait (whether a trait is ancestral or derived).

Question 23

root

Answer 23

the most ancestral branch in the tree.

Question 24

polytomy

Answer 24

a node that depicts an ancestral branch dividing into three or more (rather than two) descendant branches; usually indicates that insufficient data were available to resolve which taxa are more closely related.

Question 25

tips

Answer 25

where the taxa themselves are located, they are never within the tree. None of the taxa are presumed to be ancestors of others, even if some of the taxa are extinct.

Question 26

sister taxa

Answer 26

Tips connected by a single node on a tree

Question 27

character

Answer 27

is any genetic, morphological, physiological, or behavioral characteristic to be studied.

Question 28

ancestral trait

Answer 28

a characteristic that existed in an ancestor.

Question 29

derived trait

Answer 29

one that is a modified form of the ancestral trait, found in the descendant. Originate via mutation, selection, and genetic drift.

Question 30

Multiple outgroups are often used to estimate

Answer 30

ancestral character states.

Question 31

Cladistic approach

Answer 31

Hennig; based on the principle that relationships among species can be reconstructed by identifying shared derived characters – synapomorphies. Powerful method of estimating phylogenies because it is based on homology.

Question 32

homology

Answer 32

occurs when traits are similar due to shared ancestry.

Question 33

homoplasy

Answer 33

similarity in organisms due to reasons other than common ancestry.

Question 34

Polyphyletic group

Answer 34

an unnatural group that does not include the most recent common ancestor.

Question 35

Paraphyletic group

Answer 35

a group that includes an ancestral population and some of its descendants, but not all.

Question 36

parsimony

Answer 36

the most likely explanation or pattern is the one that implies the least amount of change. To implement parsimony analysis, biologists use computer programs that compare the branching patterns that are theoretically possible in a phylogenetic tree and count the number of changes in DNA sequences required to produce each pattern.

Question 37

Since independent evolution of traits should be rare compared with similarity due to shared descent, the tree that implies

Answer 37

the fewest overall evolutionary changes is hypothesized to be the one that most accurately reflects what really happened during evolution.

Question 38

cladograms

Answer 38

trees created using cladistics analysis; focus on branching patterns. The branch lengths themselves are arbitrary, although some analyses produce trees whose branch lengths represent genetic distance or time since divergence.

Question 39

convergent evolution

Answer 39

common cause of homoplasy; occurs when natural selection favors similar solutions to the problems posed by a similar way of making a living in different species.

Question 40

gene families

Answer 40

particular gene is found in gene clusters and similar genes are often found in the same order on the chromosome.

Question 41

SINEs (short interspersed nuclear elements)

Answer 41

parasitic DNA sequences; occasionally insert themselves into the genomes of mammals.

Question 42

If decomposition does not occur,

Answer 42

the organic remains can be preserved intact.

Question 43

If sediments accumulate on top of the material and become cemented into rocks

Answer 43

such as mudstone or shale, the sediments’ weight can compress the organic material into a thin, carbonaceous film.

Question 44

If the remains decompose after they are buried

Answer 44

the hole that remains can fill with dissolved minerals and create an accurate cast of the remains.

Question 45

If the remains rot extremely slowly,

Answer 45

dissolved minerals can gradually infiltrate the interior of the cells and harden into stone, forming a premineralized fossil, such as petrified wood.

Question 46

habitat bias

Answer 46

organisms that live in areas where sediments are actively being deposited – including beaches, mudflats, and swamps – are much more likely to form fossils than are organisms that live in other habitats.

Question 47

taxonomic and tissue bias

Answer 47

slow decay is almost always essential to fossilization, so organisms with hard parts such as bones or shells are most likely to leave fossil evidence.

Question 48

temporal bias

Answer 48

recent fossils are much more common than ancient fossils. Older fossils are more vulnerable to crushing, heating, melting, and distortion by various chemical and physical processes. They are also more likely to be subducted further into the Earth’s interior by the sliding and collision of tectonic plates.

Question 49

abundance bias

Answer 49

organisms that are abundant, widespread, and/or present on Earth for longs periods of time leave evidence much more often than do species that are rare, local, or ephemeral.