(Bio 105) Chapter 12 Diversity of Life

•Remember that any phylogenetic tree is a part of ..., and similar to a real tree, it does not grow in only one direction after a new branch develops.

the greater whole

•For example, in the most inclusive grouping, scientists divide organisms into three domains: ...

Bacteria, Archaea, and Eukarya

•Scientists refer to an organism by its genus and species names together, commonly called a scientific name, or ... ØThis two-name system is called ... ØThe scientific name of the wolf is therefore Canis lupus.

Latin name, binomial nomenclature

•.... (which literally means "arrangement law") is the science of naming and grouping species to construct an internationally shared classification system. -The taxonomic classification system (also called the .... after its inventor, Carl Linnaeus, a Swedish naturalist) uses a hierarchical model.

Taxonomy, Linnaean system

•When a characteristic that is similar occurs by ...(convergent evolution), and not because of a close evolutionary relationship, it is called an ... structure.

adaptive convergence, analogous

•It is easy to assume that more closely related organisms look more ..., and while this is often the case, it is not always true.

alike

•However, chimpanzees and humans show considerable ..., including the degree to which the jaw protrudes in the adult and the relative lengths of our arms and legs.

anatomical differences

•It is important to note that sister taxa share an ...., which does not mean that one taxon evolved from the other.

ancestor

•Clades must include the .... and all of the ... from a branch point.

ancestral species, descendants

•Before Darwin's theory of evolution was developed, naturalists sometimes classified organisms using ..., but since the theory of evolution was proposed in the 19th century, biologists work to make the classification system reflect ... ØThis means that all of the members of a taxon should have a ... and be more closely related to each other than to members of other taxa.

arbitrary similarities, evolutionary relationships, common ancestor

•The point where a split occurs in a tree, called a ..., represents where a single lineage evolved into distinct new ones. -Many phylogenetic trees have a single branch point at the base representing a common ancestor of all the branches in the tree.

branch point

•The ... and the ... in phylogenetic tree structure also imply evolutionary change.

branch point, branches

•By comparing ingroup members to each other and to the outgroup members, we can determine which characteristics are evolutionary modifications determining the .... of the ingroup's phylogeny. -If a characteristic is found in all of the members of a group, it is a .... because there has been no change in the trait during the descent of each of the members of the clade.

branch points, shared ancestral character

•But there are other decisions to be made, for example, what if a species presence in a clade is supported by all of the shared derived characters for that clade except one? -One conclusion is that the trait evolved in the ancestor, but then .... in that one species. -Also a character state that appears in two clades must be assumed to have .... in those clades.

changed back, evolved independently

•Recent genetic analysis and other advancements have found that some earlier taxonomic classifications do not reflect actual evolutionary relationships, and therefore, ... must be made as new discoveries take place.

changes and updates

•Sometimes the significant ... are identified on a branch or branch point. -Also the branch point that gives rise to organisms with legs is indicated at the common ancestor of mammals, reptiles, amphibians, and jawed fishes.

character changes

•These inconsistencies are common in trees drawn from ... and complicate the decision-making process about which tree most closely represents the real relationships among the taxa.

character data

•Presently, the most accepted method for constructing phylogenetic trees is a method called .... -This method sorts organisms into ..., groups of organisms that are most closely related to each other and the ancestor from which they descended. -Consequently, all of these organisms also have amniotic eggs and make a single clade, also called a ... group.

cladistics, clades, monophyletic

•Constructing a phylogenetic tree, or ..., from the character data is a monumental task that is usually left up to a computer. -The computer draws a tree such that all of the clades share the same list of ...

cladogram, derived characters

•As the information about DNA sequences grows, scientists will become ... to mapping the evolutionary history of all life on Earth.

closer

•However, unrelated organisms may be distantly related yet appear very much alike, usually because .... to similar environmental conditions evolved in both. -An example is the streamlined body shapes, the shapes of fins and appendages, and the shape of the tails in fishes and whales, which are mammals. -These structures bear ... because they are adaptations to moving and maneuvering in the same environment—water.

common adaptations, superficial similarity

•All life on Earth evolved from a ...

common ancestor

•The small branch that plants and animals (including humans) occupy in this diagram shows how recently these groups had their origin ... with other groups.

compared

•Scientists collect information that allows them to make evolutionary ... between organisms.

connections

•Scientists find these terms useful when distinguishing between clades during the building of phylogenetic trees, but it is important to remember that their meaning depends on .....

context

•A branch point with more than two groups illustrates a situation for which scientists have not ... relationships. -An example is illustrated by the three branches leading to the gorilla subspecies; their exact relationships are not yet understood.

definitively determined

Cladistics rests on three assumptions. •The first is that living things are related by ... from a common ancestor, which is a general assumption of evolution.

descent

•The third assumption is that traits change enough over time to be considered to be in a ....

different state

•It is also assumed that one can identify the actual ... of change for a state. -In other words, we assume that an amniotic egg is a later character state than non-amniotic eggs. -This is called the .... -We know this by reference to a group outside the clade: for example, insects have non-amniotic eggs; therefore, this is the older or ancestral character state.

direction, polarity of the character change

•Similar to detective work, scientists must use ... to uncover the facts.

evidence

•A phylogenetic tree is rooted and shows how different organisms, in this case the species and subspecies of living apes, ...

evolved from a common ancestor

•Recently, newer technologies have uncovered surprising discoveries with unexpected relationships, such as the fact that people seem to be more closely related to ... than ... are to plants.

fungi

A .... system has levels and each group at one of the levels includes groups at the next lowest level, so that at the lowest level each member belongs to a series of .... -An ... is the nested series of directories on the main disk drive of a computer.

hierarchical, nested groups, analogy

•Sometimes two segments of DNA in distantly related organisms randomly share a ... in the same locations, causing these organisms to appear closely related when they are not. -For example, the fruit fly shares ... of its DNA with humans -In this situation, computer-based statistical algorithms have been developed to help identify the actual relationships, and ultimately, the coupled use of both ... and ... is more effective in determining phylogeny.

high % of bases, 60% morphologic and molecular info

•Features that overlap both morphologically and genetically are referred to as ...; the similarities stem from common evolutionary paths.

homologous structures

•Similar traits can be either homologous or analogous. -... traits share an evolutionary path that led to the development of that trait, and .... traits do not. -Scientists must determine which type of similarity a feature exhibits to decipher the phylogeny of the organisms being studied.

homologous, analogous

•Scientists consider phylogenetic trees to be a ... of the evolutionary past because one cannot go back through time to confirm the proposed relationships. -Unlike with a taxonomic classification, a phylogenetic tree can be read like a map of evolutionary history. -... characteristics are used to construct phylogenetic trees.

hypothesis, Shared

•Different genes change evolutionarily at different rates and this affects the level at which they are useful at ... relationships. -.... evolving sequences are useful for determining the relationships among closely related species. -More ... evolving sequences are useful for determining the relationships between distantly related species. -To determine the relationships between very different species such as Eukarya and Archaea, the genes used must be very ...., slowly evolving genes that are present in both groups, such as the genes for ribosomal RNA.

identifying, rapidly, slowly, ancient

•Comparing phylogenetic trees using different sequences and finding them similar helps to build confidence in the ...

inferred relationships

•Cladistics compares ingroups and outgroups. -An ... (lizard, rabbit and human in our example) is the group of taxa being analyzed. -An .... (lancelet, lamprey and fish in our example) is a species or group of species that diverged before the lineage containing the group(s) of interest.

ingroup, outgroup

•Within each domain is a second level called a ....

kingdom

•Another aspect of phylogenetic trees is that, unless otherwise indicated, the branches do not show ...., they show only the order in time of evolutionary events. -What the tree does show is the ... in which things took place.

length of time, order

•Some organisms may be very closely related, even though a minor genetic change caused a ... morphological difference to make them look quite different. -For example, chimpanzees and humans, the skulls of which are shown in Figure 12.7 are very similar genetically, sharing 99 percent1 of their genes.

major

•If two closely related lineages evolved under significantly different surroundings or after the evolution of a ..., they may look quite different from each other, even more so than other groups that are not as closely related.

major new adaptation

•To aid in the tremendous task of choosing the best tree, scientists often use a concept called ..., which means that events occurred in the simplest, most obvious way. -This means that the "best" tree is the one with the fewest number of character ...., the fewest number of ...., and the fewest number of .... throughout the tree.

maximum parsimony, reversals, independent character changes, character changes

•New analysis of ... not only confirms many earlier classifications, but also uncovers previously made errors. -... can include differences in the amino-acid sequence of a protein, differences in the individual nucleotide sequence of a gene, or differences in the arrangements of genes. -Phylogenies based on ... assume that the more similar the sequences are in two organisms, the more closely related they are

molecular characters

•With the advancement of DNA technology, the area of ..., which describes the use of information on the molecular level including DNA sequencing, has blossomed.

molecular systematic

•Also, groups that are not closely related, but evolve under similar conditions, may appear ... to each other than to a close relative.

more similar

•In the case of phylogeny, evolutionary investigations focus on two types of evidence: -... (form and function) and ....

morphologic, genetic

•The hierarchical classification of groups ... within more inclusive groups is reflected in diagrams.

nested

•So, for the organisms in Figure 12.5, just because a vertebral column evolved does not mean that invertebrate evolution ceased, it only means that a ...

new branch formed

•Scientists use a tool called a ... to show the evolutionary pathways and relationships between organisms. -A ... is a diagram used to reflect evolutionary relationships among organisms or groups of organisms.

phylogenetic tree

•Biologists map how organisms are related by constructing ... -In other words, a "..." can be constructed to illustrate when different organisms evolved and to show the relationships among different organisms.

phylogenetic trees, tree of life

•Each domain contains several kingdoms. Within kingdoms, the subsequent categories of increasing specificity are: ...

phylum, class, order, family, genus, species

•Organisms that share similar ... and ... tend to be more closely related than those that do not.

physics features, genetic sequences

•One dramatic and recent example was the breaking apart of ..., which until the 1970s were all classified as bacteria. -Their division into Archaea and Bacteria came about after the recognition that their large genetic differences warranted their separation into two of three fundamental branches of life.

prokaryotic species

•A sometimes confusing aspect of "ancestral" and "derived" characters is that these terms are .... -The same trait could be either ancestral or derived depending on the .... being used and the .... being compared.

relative, diagram, organisms

•These tools and concepts are only a few of the strategies scientists use to tackle the task of .... of life on Earth.

revealing evolutionary history

•Scientists call such trees ..., which means there is a single ancestral taxon at the base of a phylogenetic tree to which all organisms represented in the diagram descend from. -When two lineages stem from the same branch point, they are called ..., for example the two species of orangutans.

rooted, sister taxa

•In contrast, consider the amniotic egg characteristic of Figure 12.9. -Only some of the organisms have this trait, and to those that do, it is called a .... because this trait changed at some point during descent. -This character does tell us about the relationships among the .... of the clade; it tells us that lizards, rabbits, and humans group more closely together than any of these organisms do with fish, lampreys, and lancelets.

shared derived character, members

•Computer programs search through all of the possible trees to find the small number of trees with the ... pathways. -Starting with all of the .... in a group of organisms, scientists can determine the order of evolutionary events of which those traits occurred that is the most obvious and simple.

simplest evolutionary, homologous traits

•In the evolution of life on Earth, the three domains of life—Archaea, Bacteria, and Eukarya—branch from a ...

single point

•The important factor is that all of the organisms in the clade or monophyletic group stem from a ... on the tree. -This can be remembered because monophyletic breaks down into "mono," meaning ...., and "phyletic," meaning ....

single point, one, evolutionary relationship

•Clades can vary in ... depending on which branch point is being referenced.

size

•The branch point, or ..., represents a common ancestor that existed in the past, but that no longer exists. -Humans did not evolve from chimpanzees (nor did chimpanzees evolve from humans) although they are our closest living relatives. -Both humans and chimpanzees evolved from a common ancestor that lived, scientists believe, ...years ago and looked different from both modern chimpanzees and modern humans.

split, six million

•The second is that speciation occurs by .... of one species into two, never more than two at a time, and essentially at .... -This is somewhat controversial, but is acceptable to most biologists as a simplification.

splits, one point in time

•Recent study of the DNA of domestic dogs and wolves suggest that the domestic dog is a ... of the wolf, not its own species, thus it is given an extra name to indicate its ... status, Canis lupus familiaris.

subspecies

•Each ... name is capitalized except for species, and the ... and ... names are italicized.

taxon, genus, species

•Although these traits appear interesting because they .... the clade, in cladistics they are considered .... when we are trying to determine the relationships of the members of the clade because every member is the same.

unify, not helpful

•This phylogenetic tree is rooted by an organism that lacked a ... column. At each branch point, organisms with different characters are placed in different groups.

vertebral

By following pathways of similarities and differences—both ... and ...—scientists seek to ... of evolution from single-celled organisms to the tremendous diversity of creatures that have crawled, germinated, floated, swam, flown, and walked on this planet.

visible, genetic, map the history

Taxonomic levels move toward specificity. -Notice how within the domain we find the dog grouped with the widest diversity of organisms. -These include plants and other organisms not pictured, such as fungi and protists. -At each sublevel, the organisms become more similar because they are more closely related.

widest diversity, similar

•In another example, insects use ... to fly like bats and birds. -We call them both wings because they perform the same function and have a superficially similar form, but the ... of the two wings is completely different. -The difference in the development, or ...., of the wings in each case is a signal that insects and bats or birds do not share a common ancestor that had a wing.

wings, embryonic origin, embryogenesis

•Organisms also have a common name that people typically use, such as domestic dog, or ....

wolf