Title: BIOLOGY 171
1BIOLOGY 171
CHAPTER 25 Phylogeny and Systematics
2Investigating the Tree of Life
- Phylogeny Evolutionary history of a species
- Systematics Study of the diversity and
relationships of life. - Molecular Systematics Use of DNA, RNA and other
molecular evidence to infer evolutionary
relationships between genes and genomes.
3HOW FOSSILS FORM
- Most fossils are formed in sedimentary rock.
- Most fossils result from preservation of hard
rather than soft parts. - Some fossils result from petrification
4HOW FOSSILS FORM
- TYPES OF FOSSILS
- Thin organic layers sandwiched between layers
of rock. - Molds and prints
- Trace fossils are footprints, burrows, etc.
- Entire organism is preserved.
- Anaerobic environments that prevent decay.
(amber)
5AMBER
FOSSIL TYPES
MOLDS / PRINTS
HARD PARTS
6TRACE
FOSSIL TYPES
PETRIFICATION
ORGANIC LAYER
7 LIMITATIONS OF THE FOSSIL RECORD
- All fossils are accidents of an unusual
sequence of events. - Many types of organisms or body parts are not
easily fossilized. - Only a small fraction of organisms to have
lived produce fossils. - An even smaller fraction of fossils are
discovered.
8Morphological and Molecular Homologies
- Morphological homologies
- Molecular homologies
- Homology vs. Analogy
- Homoplasies
- Evaluating Molecular Homologies
9Evaluating Molecular Homologies
10MOLECULAR BIOLOGY AND SYSTEMATICS
- A. Protein Comparison
- B. DNA Comparison
- DNA-DNA Hybridization
- Restriction Mapping
- DNA Sequencing
- C. Analysis of Fossilized DNA
- D. Molecular Clocks
11CONVERGENT EVOLUTION
12CLASSIFICATION AN OVERVIEW
- EARLY HISTORY
- THEOPHRASTUS
- DE MATERIA MEDICA
- HERBALS - DOCTRINE OF SIGNATURE
- 17TH AND 18TH CENTURY - CLASSIFICATION
- CARLOLUS LINNAEUS
- BINOMIAL NOMENCLATURE
- Systema naturae
- GENUS AND SPECIFIC EPITHET
13TERMINOLOGY OF SYSTEMATICS
- Phylogeny
- Taxonomy
- Classification
- Taxon
- Hierarchy Of Classification
- DOMAIN, KINGDOM, DIVISION, CLASS, ORDER, FAMILY,
GENUS, SPECIES - Phylogenetic Trees
14Taxonomic Hierarchy
15Phylogenetic Systematics
- Cladogram Diagram illustrating patterns of
shared characteristics. If shared
characteristics are homologies then the cladogram
forms the basis of a phylogenetic tree. - Clade Ancestral species and all its
descendants. - Cladistics Pattern of systematics in which
species are grouped into clades.
16CLADOGRAM
17Cladogram
18Cladistics
- A true clade is a group with a single common
ancestor. - Monophyletic single tribe/single common
ancestor. - Paraphyletic A grouping with a single common
ancestor but not all descendents. - Polyphyletic A grouping that lacks a single
common ancestor.
19Cladistics
20Other Cladistic Factors
- Shared Primitive Character A characteristic
that shared beyond the clade under study. - Shared Derived Characteristic Evolutionary
novelty unique to a particular clade. - Ingroup Group of related species under study.
- Outgroup A species or group so species that are
closely related to, but are outside the ingroup.
21Building a Cladogram
22Phylogenetic Trees and Timing
- Phylograms Length of branches reflect the
number of changes that have occurred to a
particular DNA sequence in that lineage. - Ultrametric Trees The pattern is the same as a
phylogram, but all branches traced to a common
ancestor are the same length. Illustrates
survival period for the lineage rather than the
number of DNA changes.
23Phylograms and Ultrametric Trees
Phylograms
Ultrametric Trees
24Criteria for Construction of a Phylogenetic Tree
- Maximum Parsimony Based on the fewest
evolutionary events to have occurred as shared
derived characteristics. - Parsimony Simplest explanation
- Occams Razor
- Maximum Likelihood With certain rules about DNA
changes, over time a tree can be found that
reflects the most likely sequence of evolutionary
events.
25Maximum Parsimony
26Maximum Likelihood
27Genetic Factors for Change
- Phylogenetic Trees as Hypotheses
- Gene Duplication and Gene Families
- Orthologous Genes Homologous genes passed in a
straight line. - Paralogous Genes Duplicated genes found in more
than copy in thesame genome. - Genome Evolution
28Phylogenetic Hypotheses
29Orthologous and Paralogous Genes
30Tree of Life
31Molecular Clocks
- Based on measuring the absolute time of
evolutionary change based on the observation that
some genes or regions of the genome evolve at a
constant rate. - Neutral Theory
- Difficulties with Molecular Clocks
32FOSSIL DATING
- Relative Dating
- Sedimentation Rates
- Absolute Dating
- C-14 or U-238
- C-14 has a half-life of 5,600 years.
- The half-life of U-238 is 4.5 billion years.
- Racemization
33CARBON 14 DATING
34CARBON 14 DATING