Block 2 - Phylogeny/ taxonomy and Speciation Flashcards
What is phylogeny?
The evolutionary history of a species or a group of related species
Tree of life
Binomial nomenclature
Gives the name of the species
Two part names - genus and a specific epithet
Written: Genus π¦π±πͺπ΅π©π¦π΅
List the taxomonic groups from broad to narrow
Domain
Kingdom
Phylum
Class
Order
Family
Genus
Species
What is a basal taxon?
Diverges early in the history of a group and originates near the common ancestor of the group
What is a monophyletic group?
Also known as a clade - siginifying that it consits of the ancestor species and all of itβs descendands
What is a paraphyletic group?
Consists of the ancestral species and some but not all of the descendants
What is a polyphyletic group?
Includes distantly related species but does not include their most recent commin ancestor
What is the maximum parsimony of a phylogeneyic tree?
Assumes that the tree that requires the fewest evolutionary events (appearances of shared derived characters) is the most likely
What is the maximum liklihood of a phylogenetic tree?
Based on probability rules about how DNA changes over time and assumes a tree can be found that reflects the most likely sequence of evolutionary events
What is the meaning of orthologous?
Found in a single copy in the genome and are homologous between species
Can be traced to a common ancestor
What are paralogous genes?
Resulting from gene duplication - thus found in more than one copy in the genome.
Can diverge witin the species that carries them and often evolve new functions
What is the role of horizontal gene transfer?
Disparities between gene trees can be explained by HGT. The movement of genes from one genome to another - results in substantial interchanges of genes between organisms in different domains
What is reproductive isolation?
The existance of biological factors (barriers) that impede two species from producing viable offspring
What is the offspring from two different species called?
A hybrid
How do prezygotic barriers act? 3 ways
Blocking fertilisation from occuring by:
Stopping speices from attempting to mate
Preventing the successful completion of mating
Hindering fertilisation if mating is successful
How to postzygotic barriers work? 3 ways
Prevent the hyrid zygote from developing into a viable, fertile adult by:
Reduced hybrid viability
Reduced hybrid fertility
Hyrbid breakdown
List 5 examples of prezygotic barriers
- Habitiat isolation:
. Rarely encounter each other as they occupy different habitats - Temporal isolation:
. Species breed at different times of the day, different seasons or different years - Behavioural isolation:
. Courtship rituals and other behaviours unique to a species are effective barrier to mating - Mechanical islolation
. Morphological differences can prevent successful completion of mating - Gametic isolation
. Sperm of one species may not be able to fertilise the eggs of another species
List 3 examples of postzygotic barriers
- Reduced hybrid viability
. Genes of the different parent species may interact and impair the hybridβs development or survival in itβs environment - Reduced hybrid fertility
. Hybrids may be sterile - Hybrid breakdown
. Some first generation hybrids are fertile but when they mate with each other or with either parent species, offspring of the next generation are feeble or sterile
What is allopatric speciation?
Gene flow is interupted or reduced when a population is divided into geographically isolated subpopulations.
Separated popilations may eveolve independenly through mutation, natural selection and genetic drift
What is sympatric speciation?
Speciation occurs in populations that live in the same geographic area.
Gene flow can be interupted by polyploidy, sexual selection and habitat differentiation
What is polyploidy?
The presence of extra sex hormones due to accidents during cell division. More common in plants than in animals.
Can create a new biological species in sympatry within a single generation.
Many important crops are results of polyploidy (eg oats, cotton, potatoes, tobacco and wheat)
