Speciation and Phylogeny Flashcards
Macroevolution
Evolution of taxa through geological time or the derivation of daughter species from preexisting species. All macroevolution is the evolution of a new species.
Speciation
Macroevolutionary phenomenon in which existing species give rise to new species through microevolutionary processes. Biodiversity arrises from additive processes of speciation.
Typological classification
Classification by appearance and behaviour.
Biological Species
Group of populations all of whose members actually or potentially interbreed and produce fertile offspring-actual or potential gene flow.
Non Biological Species
Defines species in terms of genetic resources and evolutionary fate.
Morphological Species
Based upon physical similarity, appeals to fossils and asexual species.
Phylogenetic Species
Phylogenies=family trees-shows evolutionary relationships among organisms. Species are the smallest unit in phylogeny, arise from unique circumstances.
Reproductive Isolation
Species generally closely adapted to environment. Adaptations disrupted when species interbreed-reproductive isolation prevents this from happening.
Isolating Mechanisms
Prezygotic- Egg and sperm never encounter each other or fertilization doesn’t take place
Postzygotic-Fertilization takes place, but offspring cannot reproduce easily (mules) (reduced hybrid fertility-hybrid breakdown)
Temporal Partitioning
Organisms not active/reproducing at the same time
Habitat Partitioning
Organisms do not live in same habitat, so they never meet.
Behavioural Isolation
Courtship ritual or appropriate signal required before mating takes place.
Mechanical Isolation
Male and female sex organs must fit together.
Gametic Isolation
Species have specific recognition molecules on the surfaces of their gametes.
Allopatric Speciation
Based primarily on spatial separation of founding population from rest of species (blocks geneflow). Followed by establishment of reproductive isolation.
Sympatric Speciation
No large scale geographical distance to reduce gene flow, differences among individuals cause them to choose different habitats, resulting in speciation.
Polyploid Speciation
Number of chromosomes in an individual doubles, restricting it from mating with others in its species. 80% of plant species.
Hybrid Zones
Areas where individuals of two closely related species can meet and possibly interbreed, producing hybrids. Can result in the two species losing their separate identities.
Adaptive Radiations
Rapid diversification from an ancestral species into a multitude of different forms-star shaped phylogenies. Happens due to changes in environment.
Punctuated Equilibrium Model
Speciation is extremely quick, species stable outside speciation events. Still slow.
Gradualism
Gradual speciation, species change slowly through time, may take millions of years.
How much time is there usually between speciation events?
On average 6.5 million years.
Homologous Structures
Organ inherited from unique common ancestor, modified in various adaptive ways-displays basic common structure.
Convergent Evolution
Produces organisms that look very similar but are not closely related-due to similar selection processes acting on ancestors.
Analogous Structures
Structures which resemble one another but are not derived from a common ancestor.
Systematics
Classification of living species based upon evolutionary relationships.
Linnean Classification
Originally set up without evolutionary assumptions, but corresponds well with phylogeny-avoids problems with common names.
Binomial Designation
Every species given unique name-genus and species, with scientific description.
Genus
Group of similar species, all which share a common ancestor and some homologies which they share with the common ancestor but not any other species. Second lowest level in systematic hierarchy, no emergent properties.
Systematic Hierarchy characteristics
Higher levels-more inclusive. Each succeeding level indicates unique common ancestor of all included groups further back in time.
Cladistics
Way of erecting phylogenetic tree for groups of taxa whih will result in a classification mapping out the phylogenetic tree as a testable hypotheses.
Clade
Evolutionary groups consisting of ancestral species and all of its descendents. Defined by shared derived characteristics
What does it mean that shared derived characteristics are uninformed?
All vertebrates have a spinal column, so its presence is of no use in classification among the vertebrates.
Doing cladistics requires…
Character matrix and outgroup- known to be distantly related to all members of the group being classified, polarizes character states.
Parsimony
The phylogeny requiring the fewest evolutionary changes is best. Have to assume the smallest number of evolutionary steps is actually what happened.
Molecular systematics
DNA and molecular similarity should vary directly with evolutionary distance. Can also be used to construct phylogenies, but may disagree with morphological phylogenies.
How useful is molecular data?
Mitochondrial DNA- used for high resolution, relatively recent evolution
rRNA- useful for evolution through deep time-kingdoms and domains.
