evolution chapter 03

8/8/2019 Evolution Chapter 03

1/40


2/40


3/40


4/40


5/40


6/40


7/40


8/40


9/40


10/40


11/40


12/40


13/40


14/40


15/40


16/40


17/40


18/40


19/40


20/40


21/40


22/40


23/40


24/40


25/40

A diagrammatic representation of some forms of heterochrony,expressed as logarithmically plotted allometric growth of structures or dimensions y and x. The x-axis may represent body size, the y-axis acharacter such as leg length. The dashed line, with slope 1, is for reference. (A) The blue line shows ontogenetic change in the ancestor from age to age . Growth is positively allometric (slope > 1). (B) Alonger growth period (extension of growth to age + ; purple arrow)results in peramorphosis: an exaggerated structure y in the descendant.

A diagrammatic representation of some forms of heterochrony,expressed as logarithmically plotted allometric growth of structures or dimensions y and x. The x-axis may represent body size, the y-axis acharacter such as leg length. The dashed line, with slope 1, is for reference. (A) The blue line shows ontogenetic change in the ancestor from age to age . Growth is positively allometric (slope > 1). (B) Alonger growth period (extension of growth to age + ; purple arrow)results in peramorphosis: an exaggerated structure y in the descendant.

This diagram at leftdemonstrates thatperamorphosis can

result fromevolutionary changesin either rate of development or theduration of development due to achange in or .

Here x represents body size, y

is the size of some feature thatbegins to develop at at age (onset) and ends at age (offset). Here peramorphosiscan result if the duration of development is extended (a

change from to + ).

This diagram at leftdemonstrates thatperamorphosis can

result fromevolutionary changesin either rate of development or theduration of development due to achange in or .

Here x represents body size, y

is the size of some feature thatbegins to develop at at age (onset) and ends at age (offset). Here peramorphosiscan result if the duration of development is extended (a

change from to + ).

Evolutionary PatternsIn thedescendant,feature ybecomesmoreexaggerated

relative to x.


26/40

Perhaps the most famous example of allometry andperamorphosis is largest of deer, the extinct Irish elk

(Megaceros giganteus ). Its antlers were larger relative to bodymass, than those of any other deer.

Perhaps the most famous example of allometry andperamorphosis is largest of deer, the extinct Irish elk

(Megaceros giganteus ). Its antlers were larger relative to bodymass, than those of any other deer.

The gigantic antlers of the

extinct Irish elk, whichwere larger in relation tobody mass than those of any other deer, are a

peramorphic featureassociated with theanimals extendeddevelopment to a larger

size.

The gigantic antlers of the

extinct Irish elk, whichwere larger in relation tobody mass than those of any other deer, are a

peramorphic featureassociated with theanimals extendeddevelopment to a larger

size.

Evolutionary Patterns


27/40

Paedomorphosis canbe caused bycessation of growth atan earlier age ( - )in a form of paedomorphosiscalled progenesis or by reducing thegrowth of character yin a form of paedomorphosiscalled neoteny.Neoteny is the retention of

juvenile morphological

traits in the sexuallymature adult, whileprogenesis is increasedrate of sexual developmentleading to early maturity inan adult that remains very

small in size.

Paedomorphosis canbe caused bycessation of growth atan earlier age ( - )in a form of paedomorphosiscalled progenesis or by reducing thegrowth of character yin a form of paedomorphosiscalled neoteny.Neoteny is the retention of

juvenile morphological

traits in the sexuallymature adult, whileprogenesis is increasedrate of sexual developmentleading to early maturity inan adult that remains very

small in size.

Evolutionary Patterns.


28/40

Skulls of the progenetic dwarf salamander T horius and a typical

nonprogenetic relative, Pseudoeurycea . The skull of adult T horius hasa number of juvenile features.

Skulls of the progenetic dwarf salamander T horius and a typical

nonprogenetic relative, Pseudoeurycea . The skull of adult T horius hasa number of juvenile features.

The axolotl (shownearlier) is an exampleof neoteny (it reaches

the same size as itsmetamorphosingrelatives) while the tinysalamanders of thegenus T horius areprogenetic, havingfeatures that arecharacteristic of the

juveniles of larger species of salamanders (appearsas if they haveabbreviated

development).

The axolotl (shownearlier) is an exampleof neoteny (it reaches

the same size as itsmetamorphosingrelatives) while the tinysalamanders of thegenus T horius areprogenetic, havingfeatures that arecharacteristic of the

juveniles of larger species of salamanders (appearsas if they haveabbreviated

development).


The space between the paired frontaland parietal bones is a juvenile featurethat is retained in adult T horius .

In most salamanders, the frontal and parietalbones grow together by adulthood.


29/40

Plants of the genus Philodendron , such as thisJamaican climber, are lianas. Many lianas, whichinclude several genera besides Philodendron ,have evolved exposed roots that grow from anaerial stem.

Plants of the genus Philodendron , such as thisJamaican climber, are lianas. Many lianas, whichinclude several genera besides Philodendron ,have evolved exposed roots that grow from anaerial stem.

Heterotopy is the evolutionary

change in the position within theorganism at which a phenotypiccharacter is expressed.

Studies in the distribution of geneproducts have revealed manyheterotypic differences among speciesin gene expression sites.

Heterotypic differences are common amongspecies of plants (for example the stem notleaves of cacti photosynthesize or the growthof roots along the stems of lianas (some for

holdfasts others for the usual root function).

Heterotopy is the evolutionary

change in the position within theorganism at which a phenotypiccharacter is expressed.

Studies in the distribution of geneproducts have revealed manyheterotypic differences among speciesin gene expression sites.

Heterotypic differences are common amongspecies of plants (for example the stem notleaves of cacti photosynthesize or the growthof roots along the stems of lianas (some for

holdfasts others for the usual root function).



30/40

The right hand of two members of the bear family, a brown bear at leftand a panda at right. A small sesamoid bone in bears has beenmodified into a false finger ( thumb ) in the panda which it uses to helpmanipulate bamboo on which it feeds. This is an example of heterotopyin animals.

The right hand of two members of the bear family, a brown bear at leftand a panda at right. A small sesamoid bone in bears has beenmodified into a false finger ( thumb ) in the panda which it uses to helpmanipulate bamboo on which it feeds. This is an example of heterotopyin animals.

V ertebrate bones canprovide an example of heterotopy in animals,

particularly regardingphylogenetically newbones calledsesamoids thatdevelop in tendons or other connectivetissues subject tostress.

Many dinosaurs had ossifiedtendons in their tails and thegiant panda ( A iluropodamelanoleuca ) is famous for itselongated sesamoid (from thewrist) that serves as its thumb.

V ertebrate bones canprovide an example of heterotopy in animals,

particularly regardingphylogenetically newbones calledsesamoids thatdevelop in tendons or other connectivetissues subject tostress.

Many dinosaurs had ossifiedtendons in their tails and thegiant panda ( A iluropodamelanoleuca ) is famous for itselongated sesamoid (from thewrist) that serves as its thumb.



31/40

An example of reduction and loss of structures during evolution. Thenumber of bones in the skull is higher in early fishes (such as theDevonian Eusthenopteron ), from which amniotes were derived, than inearly amniotes (such as the Permian Milleretta ). Among later amniotesare placental mammals such as the dog ( Canis ) in which the skullsports fewer elements still (the reduction in the number in the lower

jaw is especially notable).

An example of reduction and loss of structures during evolution. Thenumber of bones in the skull is higher in early fishes (such as theDevonian Eusthenopteron ), from which amniotes were derived, than inearly amniotes (such as the Permian Milleretta ). Among later amniotesare placental mammals such as the dog ( Canis ) in which the skullsports fewer elements still (the reduction in the number in the lower

jaw is especially notable).

Both paleontological andphylogenetic studies showthat there have been greatincreases in complexity inthe history of life, but it isoften surprising to learnthat morphological

simplification (the reductionor loss of structures) is avery common trend witinclades.

For example, many floweringplants show reduction in thenumber of floral elements whilevertebrates show reductions invarious bones (such as toes or skull bones).

Both paleontological andphylogenetic studies showthat there have been greatincreases in complexity inthe history of life, but it isoften surprising to learnthat morphological

simplification (the reductionor loss of structures) is avery common trend witinclades.

For example, many floweringplants show reduction in thenumber of floral elements whilevertebrates show reductions invarious bones (such as toes or skull bones).



32/40

Frontal view of the heads of male flies in the dispar subgroup of Zygothrica(Drosophilidae). Note the gradation in the shape of the head and eyes among thespecies and within prodispar , dispar , and e x ub eruns . These gradations form aphylogenetic series from narrow to broad, as indicated by the phylogenetic analysiswhich is based on a number of morphological features.

Frontal view of the heads of male flies in the dispar subgroup of Zygothrica(Drosophilidae). Note the gradation in the shape of the head and eyes among thespecies and within prodispar , dispar , and e x ub eruns . These gradations form aphylogenetic series from narrow to broad, as indicated by the phylogenetic analysiswhich is based on a number of morphological features.

The term evolutionary trend can refer to a succession of changes of a character in the same direction, either in a singlelineage or, often, in many lineages independently.

An example is in the fly genus Zygotherica showing a directional trend towards wider heads (also seen in three other fly clades).

The term evolutionary trend can refer to a succession of changes of a character in the same direction, either in a singlelineage or, often, in many lineages independently.

An example is in the fly genus Zygotherica showing a directional trend towards wider heads (also seen in three other fly clades).



33/40

Adaptive radiation of Darwin s finches in the Gal pagos Islands andCocos Island. The bills of these species are adapted to their diversefeeding habits.

Adaptive radiation of Darwin s finches in the Gal pagos Islands andCocos Island. The bills of these species are adapted to their diversefeeding habits.

During evolutionaryradiations (the divergentevolution of numerousrelated lineages within arelatively short time) thelineages are modified for different ways of life (oftentermed an adaptiveradiation).

Here lineage characteristics donot show sustained directionaltrends but rather evolutionaryradiation and may be the mostcommon pattern for long-termevolution.

During evolutionaryradiations (the divergentevolution of numerousrelated lineages within arelatively short time) thelineages are modified for different ways of life (oftentermed an adaptiveradiation).

Here lineage characteristics donot show sustained directionaltrends but rather evolutionaryradiation and may be the mostcommon pattern for long-termevolution.



34/40

Some members of the Hawaiian silversword alliance with different growth forms.(A) This rosette plant lacks a stem except when flowering (as it is here). (B) is astemmed rosette plant and (C) is a small shrub.

Some members of the Hawaiian silversword alliance with different growth forms.(A) This rosette plant lacks a stem except when flowering (as it is here). (B) is astemmed rosette plant and (C) is a small shrub.

Though few species of plants and animals colonized theHawaiian Islands, these silversword plants and their relatives occupy habitats ranging from exposed lava rockto wet forest and show growth forms that include shrubs,vines, trees, and creeping mats; but despite thesedifferences they can form fertile hybrids when crossed.

Though few species of plants and animals colonized theHawaiian Islands, these silversword plants and their relatives occupy habitats ranging from exposed lava rockto wet forest and show growth forms that include shrubs,vines, trees, and creeping mats; but despite thesedifferences they can form fertile hybrids when crossed.



35/40

A sample of the diverse head shapes among the Cichlidae of the African GreatLakes. The morphological differences are associated with differences in dietand feeding mode.

A sample of the diverse head shapes among the Cichlidae of the African GreatLakes. The morphological differences are associated with differences in dietand feeding mode.

These cichlid fishes from the Great Lakes of east Africa have undergone spectacular adaptiveradiations, with the myriad species varying in color,body form, and tooth and jaw structure (reflecting their diverse feeding habits), though each lake supports amonophyletic clade that radiated rapidly.

These cichlid fishes from the Great Lakes of east Africa have undergone spectacular adaptiveradiations, with the myriad species varying in color,body form, and tooth and jaw structure (reflecting their diverse feeding habits), though each lake supports amonophyletic clade that radiated rapidly.



36/40

Genome size variation.The bars indicate therange of size for particular clades. Taxaare arranged from top tobottom in order of supposedly increasing

organismal complexity.Within eucaryotes, thereis little relationshipbetween genome sizeand oraganismalcomplexity. This C-value paradox may bea result of greatvariation amonglineages in the amountof repetitive (noncoding)DNA. (1 pg of DNA isapproximatelyequivalent to 1 billionbase pairs.)

Genome size variation.The bars indicate therange of size for particular clades. Taxaare arranged from top tobottom in order of supposedly increasing

organismal complexity.Within eucaryotes, thereis little relationshipbetween genome sizeand oraganismalcomplexity. This C-value paradox may bea result of greatvariation amonglineages in the amountof repetitive (noncoding)DNA. (1 pg of DNA isapproximatelyequivalent to 1 billionbase pairs.)

The expectation is that physiologically andbehaviorally complex organisms would have

more complex and larger genomes and on abroad scale this holds true.

Lack of correspondence between genome sizeand phenotypic complexity in eukaryotes is the

C-value paradox.

The expectation is that physiologically andbehaviorally complex organisms would have

more complex and larger genomes and on abroad scale this holds true.

Lack of correspondence between genome sizeand phenotypic complexity in eukaryotes is the

C-value paradox.



37/40

Number of genes estimated for some eukaryotes with fullysequenced genomes, arranged on a provisional phylogeny.Multicellular organisms with tissue organization (plants andanimals, represented by blue branches) have more genes thansingle-celled organisms (red branches) or multicellular organisms that lack pronounced tissue organization (some fungiand slime molds; green branches)

Number of genes estimated for some eukaryotes with fullysequenced genomes, arranged on a provisional phylogeny.Multicellular organisms with tissue organization (plants andanimals, represented by blue branches) have more genes thansingle-celled organisms (red branches) or multicellular organisms that lack pronounced tissue organization (some fungiand slime molds; green branches)

When non-coding, repetitive DNA is eliminated from the

comparisons, the phylogenetic transition from unicellular tomulticellular eukaryotes shows a considerable increase in genenumber, but surprisingly little variation among plants andanimals.

But endosymbiotic microrganisms living within eukaryotic hosts have smaller genomes than their free-living relatives

When non-coding, repetitive DNA is eliminated from the

comparisons, the phylogenetic transition from unicellular tomulticellular eukaryotes shows a considerable increase in genenumber, but surprisingly little variation among plants andanimals.

But endosymbiotic microrganisms living within eukaryotic hosts have smaller genomes than their free-living relatives



38/40

Orthology and paralogy in gene families are two forms of homology. When an ancestral gene ( ) undergoes duplication,the resulting two genes ( + ) have a paralogous relationshipto one another (blue arrow). A speciation event after duplicationresults in divergence of the ancestral set of two paralogousgenes. Within the genomes of the two diverged species, the +

still have a paralogous relationship (blue arrows). However,the copies of in species 1 and species 2 are orthologous (redarrows), because the two genes are related to one another viaspeciation, not duplication. Likewise, the copies of in species1 and 2 are orthologous.

Orthology and paralogy in gene families are two forms of homology. When an ancestral gene ( ) undergoes duplication,the resulting two genes ( + ) have a paralogous relationshipto one another (blue arrow). A speciation event after duplicationresults in divergence of the ancestral set of two paralogousgenes. Within the genomes of the two diverged species, the +

still have a paralogous relationship (blue arrows). However,the copies of in species 1 and species 2 are orthologous (redarrows), because the two genes are related to one another viaspeciation, not duplication. Likewise, the copies of in species1 and 2 are orthologous.

Gene duplication is a mutational event by which a new gene ( )arises as a result of a copy of a preexisting gene ( ) , so that asingle gene locus in an ancestor is represented by two loci in thedescendent 9and they undergo further evolutionary sequence change andcan thus be distinguished.

Gene duplication is a mutational event by which a new gene ( )arises as a result of a copy of a preexisting gene ( ) , so that asingle gene locus in an ancestor is represented by two loci in thedescendent 9and they undergo further evolutionary sequence change andcan thus be distinguished.



39/40

The phylogeny of genes in the globin family in the humangenome. Myoglobin consists of a single protein unit, whereasmammalian hemoglobins consist of four subunits, two eachfrom the and subfamilies. Each branch point on the treedenotes a gene duplication event; some of the events aremarked with estimates of when duplication occurred. The originof hemoglobin and myoglobin from a common ancestor geneoccurred in the ancestor of all vertebrates, but the and hemoglobin subfamilies originated by duplication in an ancestor of the jawed vertebrates. The duplication of the hemoglobininto two genes occurred in the ancestor of placental mammals,since the A /G / genes are lacking in monotremes andmarsupials. In some instances, one of the pair of genes formedby duplication became a nonfunctional pseudogene, symbolizedby .

The phylogeny of genes in the globin family in the humangenome. Myoglobin consists of a single protein unit, whereasmammalian hemoglobins consist of four subunits, two eachfrom the and subfamilies. Each branch point on the treedenotes a gene duplication event; some of the events aremarked with estimates of when duplication occurred. The originof hemoglobin and myoglobin from a common ancestor geneoccurred in the ancestor of all vertebrates, but the and hemoglobin subfamilies originated by duplication in an ancestor of the jawed vertebrates. The duplication of the hemoglobininto two genes occurred in the ancestor of placental mammals,since the A /G / genes are lacking in monotremes andmarsupials. In some instances, one of the pair of genes formedby duplication became a nonfunctional pseudogene, symbolizedby .

The phylogenetic relationships among orthologous andparalogous genes can be determined by standard phylogeneticmethods.

The process may repeat over evolutionary time, generating gene

families such as seen here for hemoglobin.

The phylogenetic relationships among orthologous andparalogous genes can be determined by standard phylogeneticmethods.

The process may repeat over evolutionary time, generating gene

families such as seen here for hemoglobin.



40/40

The nonvertebrate chordates (tunicatesand A mphio x us ) have a single cluster of Hox genes, represented by a circle. The

jawless lamprey has four Hox clusters,implying that the single cluster hasundergone two duplications. thegnathostomes (jawed vertebrates0 also

have four clusters that have arisen by twoduplications. It is not certain, however,that the gnathostome clusters arehomologous to those in the lamprey, someof which may have arisen independently.Three of the four clusters of the ancestralgnathostome were duplicated in theancestor of teleost fishes.

The nonvertebrate chordates (tunicatesand A mphio x us ) have a single cluster of Hox genes, represented by a circle. The

jawless lamprey has four Hox clusters,implying that the single cluster hasundergone two duplications. thegnathostomes (jawed vertebrates0 also

have four clusters that have arisen by twoduplications. It is not certain, however,that the gnathostome clusters arehomologous to those in the lamprey, someof which may have arisen independently.Three of the four clusters of the ancestralgnathostome were duplicated in theancestor of teleost fishes.

Many genes are duplicated as parts of large chromosomal blocks(paralogous regions) that often contain hundreds of genes.

Polyploidy (entire genome duplication) occurs commonly in plantsand some animals.

In the example shown here with Hox genes, it is unclear whether the wholegenome or just parts of it, underwent two successive duplications in theancestor of jawed vertebrates, but teleosts do appear to show a polyploid

ancestor.

Many genes are duplicated as parts of large chromosomal blocks(paralogous regions) that often contain hundreds of genes.

Polyploidy (entire genome duplication) occurs commonly in plantsand some animals.

In the example shown here with Hox genes, it is unclear whether the wholegenome or just parts of it, underwent two successive duplications in theancestor of jawed vertebrates, but teleosts do appear to show a polyploid

ancestor.


evolution chapter 03

Documents