Chapter 19

Question 1

Convergent Evolution

Answer 1

The evolution of similar adaptations in distantly related organisms that occupy similar environments.

Question 2

Parallel Evolution

Answer 2

The evolution of similar adaptations in closely related organisms that occupy similar environments.

Question 3

Systematics

Answer 3

The branch of biology that studies the diversity of life and its evolutionary relationships.

Question 4

Phylogeny

Answer 4

The evolutionary history of a group of organisms.

Question 5

Phylogenetic Tree

Answer 5

A branching diagram depicting the evolutionary relationships of groups of organisms.

Question 6

Taxonomy

Answer 6

The science of the classification of organisms into an ordered system that indicates natural relationships.

Question 7

Classification

Answer 7

An arrangement of organisms into hierarchical groups that reflect their relatedness.

Question 8

Describe the goals of systematics.

Answer 8

1. Reconstruct the phylogeny of a group of organisms presented as phylogenetic trees, which are formal hypotheses identifying likely relationships among species.
2. Taxonomy. Most systematists want classifications to mirror phylogenetic history and, thus, the adaptive radiation (evolutionary history) of the group of organisms in question.

Question 9

Why are phylogenetic trees essential for comparison and analysis of evolutionary processes?

Answer 9

Robust phylogenetic hypotheses allow us to distinguish similarities inherited from a common ancestor from those that evolved independently in response to similar environments.

Question 10

Taxonomic Hiearchy

Answer 10

A system of classification based on arranging organisms into ever more inclusive categories.

Question 11

Taxon (plural, taxa)

Answer 11

A taxonomic group of any rank, such as a species, family, or class.

Question 12

Family

Answer 12

A Linnaean taxonomic category that ranks below an order and above a genus.

Question 13

Genus

Answer 13

A Linnaean taxonomic category ranking below a family and above a species.

Question 14

Species

Answer 14

A group of populations in which the individuals are so closely related in structure, biochemistry, and behaviour that they can successfully interbreed.

A Linnaean taxonomic category ranking below genus.

Question 15

Order

Answer 15

A Linnaean taxonomic category of organisms that ranks above a family and below a class.

Question 16

Class

Answer 16

A Linnaean taxonomic category that ranks below a phylum and above an order.

Question 17

Phylum (plural, phyla)

Answer 17

A major Linnaean division of a kingdom, ranking above a class.

Question 18

Kingdom

What are the 5 kingdoms?

Answer 18

A Linnaean taxonomic category that ranks below a domain and above a phylum.

Monera (Prokaryotes), Fungi, Plantae, Animalia, Protista

Question 19

Domain

What are the 3 domains?

Answer 19

The highest taxonomic category; a group of cellular organisms with characteristics that set it apart as a major branch of the evolutionary tree.

Bacteria, Archaea, Eukarya.

Question 20

What categories are used in the Linnaean system of classification?

Answer 20

Domain

Kingdom

Phylum

Class

Order

Family

Genus

Species

Question 21

Homoplasies

Answer 21

Characteristics shared by a set of species, often because they live in similar environments, but not present in their common ancestor; often the product of convergent evolution.

Question 22

What do systematists study?

Answer 22

Traits in which phenotypic variation reflects genetic differences. They try to exclude differences caused by environmental conditions. Useful systematic characters must be genetically independent, reflecting different parts of organisms’ genomes.

Question 23

What is another way to say ‘evolved from’?

Answer 23

‘is homologous to’

Question 24

Mosaic Evolution

Answer 24

Refers to the reality that in all evolutionary lineages, some characteristics evolve slowly, whereas others evolve rapidly.

Question 25

Derived Character

Answer 25

A new version of a trait found in the most recent common ancestor of a group.

Question 26

Ancestral Character

Answer 26

A trait that was present in a distant common ancestor.

Question 27

Are ancestral or derived characters more useful? Why?

Answer 27

Derived characters provide the most useful information about evolutionary relationships because once a derived character becomes established, it is usually present in all of that species’ descendants. Thus, unless they are lost or replaced by newer characters over evolutionary time, derived characters can serve as markers for entire evolutionary lineages.

Question 28

Vertebral Column

Answer 28

The series of vertebrae that surrounds and protects the dorsal nerve cord and forms the supporting axis of the body.

Question 29

Outgroup Comparison

Answer 29

A technique used to identify ancestral and derived characters by comparing the group under study with more distantly related species that are not otherwise included in the analysis.

Question 30

Principle of Monophyly

Answer 30

A guiding principle of systematic biology that defines monophyletic taxa, each of which contains a single ancestral species and all of its descendants.

Question 31

Monophyletic Taxon

Answer 31

A group of organisms that includes a single ancestral species and all of its descendants.

Question 32

Polyphyletic Taxa

Answer 32

A group of organisms that belong to different evolutionary lineages and do not share a recent common ancestor.

Question 33

Paraphyletic Taxon

Answer 33

A group of organisms that includes an ancestral species and some, but not all, of its descendants.

Question 34

Assumption of Parsimony

Answer 34

Assumption that the simplest explanation should be the most accurate.

Question 35

Compare Monophyletic, Polyphyletic, and Paraphyletic Taxons using phylogenetic trees.

Answer 35

Question 36

Traditional Evolutionary Systematics

Answer 36

An approach to systematics that uses phenotypic similarities and differences to infer evolutionary relationships, grouping together species that share both ancestral and derived characters.

Question 37

Contrast the Linnaean system of classification with phylogeny-based systems

Answer 37

Both produce a nested hierarchy where an organism is assigned a series of names that more and more specifically locate it within the hierarchy.

Unlike Linnaean classification, phylogenetic classification only names clades and does not assign ranks to hierarchical levels.

Phylogenetic classification has two main advantages over the Linnaean system:

1. It tells you something important about the organism: its evolutionary history.
2. It does not attempt to “rank” organisms as it can be misleading. For example, cats (Felidae) and the orchids (Orchidaceae) are both family level groups in Linnaean classification.

Question 38

Explain the differences between homoplasies (analogous) and homologous structures

Answer 38

The term homology refers to structures on two or more different species that are similar or the same that came from a common ancestor of the species.

Homoplasy, on the other hand, describes a characteristic that two or more different species have in common that was not inherited from their recent ancestor but evolved independently usually due to natural selection in similar environments or filling the same type of niche as the other species with that trait.

Homology is a product of divergent evolution. The two species were once the same species at the point where they have a most recent common ancestor. Over time, individuals in the population evolved through either some type of selection or isolation from the rest of the population. The species, even though they diverged at that point, still retain some of the characteristics of the common ancestor. These are the homologies.

Convergent evolution is the origin of a homoplasy. These similar traits evolved independently of each other and are not found in the common ancestor of the two species being examined. Instead, each species evolved the trait after diverging and becoming separate species.

Some causes of homoplasies are species living in similar environments, filling the same types of niches, or through natural selection.

The wings of birds and bats are an example of both homology and homoplasy. The bones within the wings are homologous structures. They have the same bone structure with a type of breast bone, large upper arm bone, two forearm bones, and what would be hand bones.

In fact, these structures are also homologous in humans as birds, bats, and humans all share the same common ancestor.

The wings themselves are the homoplasies. Obviously, humans do not have wings. This means wings was not a characteristic of the common ancestor and cannot be homologous. Instead, through natural selection, bats and birds evolved wings to fill a niche and survive in their respective environments. Since the characteristic was derived after they diverged, they are considered homoplasies.

Question 39

Cladistics

Answer 39

An approach to systematics that uses shared derived characters to infer the phylogenetic relationships and evolutionary history of groups of organisms.

Question 40

Clade

Answer 40

A group of organisms that includes all the descendents of a common ancestor and that ancestor. For example, birds, dinosaurs, crocodiles and their extinct relatives form a clade.

Question 41

Cladogram

Answer 41

A branching diagram in which the end points of the branches represent different species of organisms, used to illustrate phylogenetic relationships.

Question 42

Principle of Parsimony

Answer 42

A principle of systematic biology that states that a particular trait is unlikely to evolve independently in separate evolutionary lineages.

Question 43

Tetrapoda

Answer 43

A monophyletic lineage of vertebrates that includes animals with four feet, legs, or leglike appendages.

Question 44

PhyloCode

Answer 44

A formal set of rules governing phylogenetic nomenclature.

Question 45

What is the difference between homologous and analogous characters?

Answer 45

Analogous structures have different evolutionary ancestries but they have the same function. Ex: wings of birds, bats and insects.

Homologous structures are the opposite; they have similar ancestries and common traits but may not have the same function in an organism. Ex: A dolphin’s flipper, a human arm and the leg of a cat.

Analogous structures represent convergent evolution, where natural selection drives species to have the most efficient and practical structures for specific functions.

Question 46

Contrast traditional evolutionary systematics with cladistics.

Answer 46

Traditional evolutionary systematics, groups species that share ancestral and derived characters. Classifications reflect evolutionary branching and morphological divergence.

Cladistics produces phylogenetic hypotheses and classifications that reflect only the branching pattern of evolution ignoring morphological divergence. Cladists group together species that share derived characters.

Question 47

Primary Structure

Answer 47

The sequence of amino acids in a protein.

Question 48

Molecular Clock

Answer 48

A technique for dating the time of divergence of two species or lineages, based on the number of molecular sequence differences between them.

Question 49

Explain how molecular clocks are used to reconstruct evolutionary trees.

Answer 49

Molecular phylogenetics is based on the observation that many molecules have been conserved by evolution. But different adaptive changes and neutral mutations accumulate in separate lineages from the moment they first diverge. Mutations in some types of DNA appear to arise at a relatively constant rate. Therefore, differences in the DNA sequences of two species can serve as a molecular clock, indexing their time of divergence. Large differences imply divergence in the distant past. Small differences suggest a more recent common ancestor.

Mosaic evolution occurs at the molecular level, so different molecules exhibit individual rates of change, and each molecule is an independent clock ticking at its own rate. Researchers study different molecules to track evolutionary divergences over different time scales.

To synchronize molecular clocks, some researchers study DNA sequences that are not parts of protein-encoding genes. Because they don’t affect protein structure, mutations in these sequences are probably not often eliminated by natural selection. Thus, sequence differences between species in non-coding areas probably result from mutation alone and therefore reflect the ticking of the molecular clock more directly. Some researchers also calibrate molecular clocks to the fossil record, so that actual times of divergence can be estimated from molecular data with a fair degree of certainty.

Question 50

How does molecular data contribute to the classifiction of organisms?

Answer 50

Molecular data include nucleotide base sequences of DNA and RNA or the amino acid sequences of the proteins for which they code. Because DNA is inherited, shared changes in molecular sequences (insertions, deletions, or substitutions) provide clues to the evolutionary relationships of organisms.

Question 51

Animalia

Answer 51

The taxonomic kingdom that includes all living and extinct animals.