Evolution - Napa Valley College · Evolution Characteristics derived from a common ancestor are...
Transcript of Evolution - Napa Valley College · Evolution Characteristics derived from a common ancestor are...
Evolution
The process by which the genetic structure of populations changes over time.
Divergent evolution
Goldfields and Ahinahina (silversword) a highly evolved member of the composite family.
Evolution
Euphorbia and Astrophytum are only distantly related, but have independently converged on a very similar body form.
In convergent evolution, unrelated species become similar in appearance as they adapt to the same kind of environment.
Evolution
Characteristics derived from a common ancestor are termed homologous. Analogous or homoplasy includes convergent evolution. Similar evolutionary pathways under similar environmental conditions = Similarity of structure in unrelated or distantly-related organisms
A. Equisetum (Division Sphenophyta). B. Casuarina (Division Anthophyta). One is a flowering tree and the other is a non-flowering plant with an apical spore-bearing cone (strobilus).
Coevolution: describe cases where two (or more) species reciprocally affect each other’s evolution.
• Predator/prey and parasite/host • Competitive species • Mutualistic species
Exclusive “matches” between plants and insects
Evolution
Species = “Kind” A group of organisms capable of interbreeding and producing fertile offspring of both genders.
Species concept: genetic isolation
Morphological species A population or group of populations that differs morphologically from other populations
Heteromorphyc generations Sterile hybrids and asexual reproduction Equisetum x ferressii
Some problems with the species concept
Iris
Platanus x hybrida A fertile hybrid from 2 species isolated for at least 50 million years
Some problems with the species concept
Developmental plasticity. However, through artificial selection Brasica oleracea has proven to be highly flexible and has been bred for its leaves, inflorescence, stalks, leaf buds and roots.
Artificial selection
Broccoli, kohlrabi, cabbage, collard greens, cauliflower, brussel sprouts and kale
Some problems with the species concept
Taxonomy uses a hierarchical classification system Linnaean (binomial) system of classification: genus and specific epithet = species name. Pinus flexilis –Limber pine P. lambertiana – Sugar pine P. morrisonicola – Taiwan white pine P. monticola –Western white pine - A named taxonomic unit at any level is called a taxon.
Diversity and its order
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Diversity and its order Members of different taxon may be grouped into subgroups
Subkingdoms Subphylums or Subdivisions Subclass Suborder Subfamily Subgenus Subspecies Varieties*
Binomila name + var. Pinus elliottii var. elliottii Pinus elliottii var. densa
The International Code of Botanical Nomenclature (ICBN)
• Only one correct name that is accepted worldwide • The value of a scientific name is that it is an identifier • Not necessarily of descriptive value • Not necessarily accurate
Diversity and its order
The ICBN • Plants • Blue-green algae • Fungi • Photosynthetic Protista and taxonomically related non-photosynthetic groups.
Different rules and codes for • Fossils
• Cultivated plants (International Code of Nomenclature for Cultivated Plants)
Diversity and its order
Diversity and its order
A botanical name is fixed to a taxon by a “type” Names in Latin (or Greek) Authority Navicula tripunctata (O.F. Müller) Bory 1822 Nomen conservandum, to avoid disadvantageous nomenclatural changes
• Family • Genus • Species
Phacelia nashiana = P. campanularia
Navicula tripunctata (O.F. Müller) Bory 1822
Modern phylogenetic systematics are based on cladistic analysis. A phylogenetic diagram (tree) is also called a cladogram. A clade is a group of organisms which consist of
1) all the descendants of an ancestral organism 2) the ancestor itself.
A B C D E F G H I
Systematics and cladistics
Monophyletic pertains to a taxon that is derived from a single ancestral species. à only legitimate cladogram type! Polyphyletic pertains to a taxon whose members were derived from two or more ancestors not common to all members. Paraphyletic pertains to a taxon that excludes some members that share a common ancestor with members included in the taxon.
Systematics and cladistics
Systematics and cladistics
Possession of unique features that reflect a common evolutionary origin vs. widespread features present in the common ancestor and lost over the time in some of the members of the group.
Principle of parsimony
Adoption of the simplest assumption in the formulation of a theory or in the interpretation of data, especially in accordance with the rule of Ockham's razor. Homology is preferred over analogy or homoplasy
A universal evolutionary tree. Ribosomal RNA
Nucleic acids: • Data for understanding evolutionary relationships
• Genes with different rates of change in different lineages
• Non-coding sequence used as neutral markers that reflect past evolutionary events
Serial endosymbiotic theory
Systematics uses diverse approaches:
Morphology Anatomy Palynology Microscopy Biochemistry Molecular Biology Genetics Physiology Ecology Evolution Bioinformatics
Systematics and cladistics Molecular data alone may not provide the most accurate account of phylogenetic relationships
Attendance
What are the four kingdoms of eukaryotes? What is the binomial system of nomenclature? Explain the difference between taxonomy and systematics