Chapter 25
Download
1 / 35

Chapter 25 - PowerPoint PPT Presentation


  • 112 Views
  • Uploaded on

Chapter 25. Phylogeny and Systematics. Overview: Investigating the Tree of Life. Phylogeny is the evolutionary history of a species or group of related species. Systematics is an analytical approach to understanding the diversity and relationships of organisms, both present-day and extinct

loader
I am the owner, or an agent authorized to act on behalf of the owner, of the copyrighted work described.
capcha
Download Presentation

PowerPoint Slideshow about ' Chapter 25' - vian


An Image/Link below is provided (as is) to download presentation

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.


- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -
Presentation Transcript
Chapter 25

Chapter 25

Phylogeny and Systematics


Overview investigating the tree of life
Overview: Investigating the Tree of Life

  • Phylogeny is the evolutionary history of a species or group of related species

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

  • Uses morphological

  • Biochemical

  • and molecular comparisons to infer evolutionary relationships


Sorting homology from analogy
Sorting Homology from Analogy

  • Homology is similarity due to shared ancestry

  • Analogy is similarity due to convergent evolution

  • Convergent evolution occurs when similar environmental pressures and natural selection produce similar (analogous) adaptations in organisms from different evolutionary lineages


These organisms have analogous structures from

Living in similar environments, but do not share a

Recent common ancestor


Evaluating molecular homologies
Evaluating Molecular Homologies

  • Not as simple as you would think

  • Systematists use computer software to find and realign similar sequence in DNA between two species


Concept 25 2 phylogenetic systematics connects classification with evolutionary history
Concept 25.2: Phylogenetic systematics connects classification with evolutionary history

  • Taxonomy is the ordered division of organisms into categories based on characteristics used to assess similarities and differences

  • In 1748, Carolus Linnaeus published a system of taxonomy based on resemblances.

    • two-part names for species

      • (binomial nomenclature)

    • hierarchical classification


Binomial nomenclature
Binomial Nomenclature classification with evolutionary history

  • Genus species

  • G. species


Le 25 8

LE 25-8 classification with evolutionary history

Panthera

pardus

Species

Panthera

Genus

Felidae

Family

Carnivora

Order

Mammalia

Class

Chordata

Phylum

Animalia

Kingdom

Eukarya

Domain


Le 25 9

LE 25-9 classification with evolutionary history

Panthera

pardus

(leopard)

Mephitis

mephitis

(striped skunk)

Lutra lutra

(European

otter)

Canis

familiaris

(domestic dog)

Canis

lupus

(wolf)

Species

Genus

Panthera

Mephitis

Lutra

Canis

Family

Felidae

Mustelidae

Canidae

Each branch point represents the divergence of two species

Systematists depict evolutionary relationships in branching phylogenetic trees

Carnivora

Order


Le 25 un497

LE 25-UN497 classification with evolutionary history

Leopard

Domestic cat

Common ancestor

“Deeper” branch points represent progressively greater amounts of divergence

Wolf

Leopard

Domestic cat

Common ancestor


Concept 25.3: Phylogenetic systematics informs the construction of phylogenetic trees based on shared characteristics

  • A cladogram depicts patterns of shared characteristics among taxa

  • A clade is a group of species that includes an ancestral species and all its descendants

  • Cladistics studies resemblances among clades


Cladistics
Cladistics construction of phylogenetic trees based on shared characteristics

  • Clades can be nested in larger clades, but not all groupings or organisms qualify as clades


Le 25 10a

LE 25-10a construction of phylogenetic trees based on shared characteristics

Grouping 1

A valid clade is monophyletic, signifying that it consists of the ancestor species and all its descendants

Monophyletic


Le 25 10b

LE 25-10b construction of phylogenetic trees based on shared characteristics

Grouping 2

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

Paraphyletic


Le 25 10c

LE 25-10c construction of phylogenetic trees based on shared characteristics

Grouping 3

A polyphyletic grouping consists of various species that lack a common ancestor

Polyphyletic


Shared primitive and shared derived characteristics
Shared Primitive and Shared Derived Characteristics construction of phylogenetic trees based on shared characteristics

  • In cladistic analysis, clades are defined by their evolutionary novelties

  • A shared primitive character is a character that is shared beyond the taxon we are trying to define

  • A shared derived character is an evolutionary novelty unique to a particular clade


Outgroups
Outgroups construction of phylogenetic trees based on shared characteristics

  • An outgroup is a species or group of species that is closely related to the ingroup, the various species being studied

  • Systematists compare each ingroup species with the outgroup to differentiate between shared derived and shared primitive characteristics



Le 25 11

LE 25-11 outgroup and ingroup must be primitive characters that predate the divergence of both groups from a common ancestor

TAXA

Lancelet

(outgroup)

Salamander

Lamprey

Leopard

Turtle

Tuna

Hair

Amniotic (shelled) egg

CHARACTERS

Four walking legs

Hinged jaws

Vertebral column

(backbone)

Character table

Leopard

Turtle

Hair

Salamander

Amniotic egg

Tuna

Four walking legs

Lamprey

Hinged jaws

Lancelet (outgroup)

Vertebral column

Cladogram


Phylogenetic trees and timing
Phylogenetic Trees and Timing outgroup and ingroup must be primitive characters that predate the divergence of both groups from a common ancestor

  • Phylogenetic trees depict RELATIVE TIMING –

    • Four walking legs appeared after vertebral columns but before hair


Le 25 12

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

Fish

Lancelet

Amphibian

Rat

Bird

Human

Mouse

LE 25-12

In a phylogram, the length of a branch in a cladogram reflects the number of genetic changes that have taken place in a particular DNA or RNA sequence in that lineage


Maximum parsimony and maximum likelihood
Maximum Parsimony and Maximum Likelihood outgroup and ingroup must be primitive characters that predate the divergence of both groups from a common ancestor

  • Systematists can never be sure of finding the best tree in a large data set

  • They narrow possibilities by applying the principles of maximum parsimony and maximum likelihood

  • The simplest explanation is the best explanation and therefore most likely


Le 25 14

LE 25-14 outgroup and ingroup must be primitive characters that predate the divergence of both groups from a common ancestor

Human

Mushroom

Tulip

Human

0

30%

40%

Mushroom

0

40%

Tulip

0

Percentage differences between sequences

Tree 2 – Mushrooms must have slowed DNA mutation rates and plants sped up

25%

15%

15%

20%

15%

10%

5%

5%

Tree 1: More likely

Tree 2: Less likely

Comparison of possible trees


Phylogenetic trees as hypotheses
Phylogenetic Trees as Hypotheses outgroup and ingroup must be primitive characters that predate the divergence of both groups from a common ancestor

  • The best hypotheses for phylogenetic trees fit the most data: morphological, molecular, and fossil

  • Sometimes the best hypothesis is not the most parsimonious


Le 25 16

LE 25-16 outgroup and ingroup must be primitive characters that predate the divergence of both groups from a common ancestor

Lizard

Bird

Mammal

You cannot just use one characteristic as a basis for phylogeny

Four-chambered

heart

Mammal-bird clade

Lizard

Bird

Mammal

Four-chambered

heart

Four-chambered

heart

Lizard-bird clade


Concept 25 4 much of an organism s evolutionary history is documented in its genome
Concept 25.4: Much of an organism’s evolutionary history is documented in its genome

  • Comparing nucleic acids or other molecules to infer relatedness is a valuable tool for tracing organisms’ evolutionary history

  • Really useful for organisms that have diverged a long time – like humans and monerans

  • “Seven Daughters of Eve” uses mDNA


Gene duplications and gene families
Gene Duplications and Gene Families is documented in its genome

  • Gene duplication increases the number of genes in the genome, providing more opportunities for evolutionary changes

  • Orthologous genes are genes found in a single copy in the genome

    • They can diverge only after speciation occurs

  • Paralogous genes result from gene duplication, so are found in more than one copy in the genome

    • They can diverge within the clade that carries them, often adding new functions


Le 25 17a

LE 25-17a is documented in its genome

Ancestral gene

Speciation

Orthologous genes

Genes are found in separate gene pools

- Human & mice b hemoglobin genes


Le 25 17b

LE 25-17b is documented in its genome

Ancestral gene

Gene duplication

Paralogous genes


Genome evolution
Genome Evolution is documented in its genome

  • The widespread consistency in total gene number in organisms indicates genes in complex organisms are very versatile and that each gene can perform many functions

  • Humans have five times as many genes as yeast – so our genes must be more versatile


Molecular clocks
Molecular Clocks is documented in its genome

  • The molecular clock is a yardstick for measuring absolute time of evolutionary change based on the observation that some genes and other regions of genomes seem to evolve at constant rates


Neutral theory
Neutral Theory is documented in its genome

  • Neutral theory states that much evolutionary change in genes and proteins has no effect on fitness and therefore is not influenced by Darwinian selection

  • It states that the rate of molecular change in these genes and proteins should be regular like a clock


Difficulties with molecular clocks
Difficulties with Molecular Clocks is documented in its genome

  • The molecular clock does not run as smoothly as neutral theory predicts

  • Irregularities result from natural selection in which some DNA changes are favored over others

  • Estimates of evolutionary divergences older than the fossil record have a high degree of uncertainty


Applying a molecular clock the origin of hiv
Applying a Molecular Clock: The Origin of HIV is documented in its genome

  • Phylogenetic analysis shows that HIV is descended from viruses that infect chimpanzees and other primates

  • Comparison of HIV samples throughout the epidemic shows that the virus evolved in a very clocklike way


The universal tree of life
The Universal Tree of Life is documented in its genome

  • The tree of life is divided into three great clades called domains: Bacteria, Archaea, and Eukarya

  • The early history of these domains is not yet clear


ad