Module 4 Flashcards
(20 cards)
Alternative ways to form a evolutionary tree? Pros and cons?
An evolutionary tree represents the evolutionary history and diversification of organisms, also named as a phylogenic tree. It can be interpreted as discrete and striving upwards towards a goal. New species appear suddenly (gradual process), direct lines towards extant species, is only hypothetical and does not represent time. (Shows only patterns of descent, not phenotypic similarity, shows only patterns of descent not when particular species evolved or how much change occurred in each linage, not assume that a taxon on a tree has evolved from the taxon next to it, they both evolved from a common ancestor).
Cladogram: A cladogram is a diagram used to represent a hypothetical relationship between groups of animals, called a phylogeny. It does not show how ancestors are related to descendants, nor does it show how much they have changed but can be used to imply evolutionary relationships by the number of synapomorphies.
Phylogram: A phylogram is a phylogenetic tree that has branch lengths proportional to the amount of character change. It provides insight in the evolutionary history and does not rank organisms.
Cladistics? Data? Pros and cons?
The data can be based on morphology, paleontology, biochemistry, or genetics.
Problems in cladistics:
Difficult to compare the importance of different
characters
Difficult to decide what makes up independent characters
Analogous traits may be mistaken for homologous traits
Different are useful for different analysis
HGT can have provided a new set of genes, not a common ancestor
Phylogenetic that are based on different sets of characters may look different, but usually show a high degree of consistently, example. morphology and DNA
Cladistics is a more detailed classification system than basic biological taxonomy that considers only physical similarities between species. Cladistics goes beyond this to incorporate quantitative measurements and puts emphasis on evolution and genealogy when comparing organisms.
Systematics?
The study of the diversification of living forms, both past and present, and the relationships among living things through time.
Phylogeny?
The study of evolutionary relationships between a group of organisms from a common ancestor – root.
Clade?
A monophyletic group – ancestral species and all descendants.
Homology?
A trait or genotypic or phenotypic similarities shared from a common ancestor.
Analogy?
A trait shared but not from a common ancestor, but has evolved independently in these two linages, usually due to convergent evolution, as they became adopted to similar lifestyles.
Convergent evolution?
A potential source of confusion in cladistics, as it implies homology. This happens when similar environmental pressures and natural selection produce similar – analogous adaptations in organisms from different evolutionary linages
Homoplasy?
A shared character between two or more animals that did not arise from a common ancestor. The opposite of a homology and will occur when two distinct groups of animals evolve, convergent evolution, or convergence. Homoplasy is also known as an analogous trait
Monophylly?
Represent a clade in a tree with ancestral species - root and all descendants.
Paraphyly?
Represent the most recent common ancestral species but not all descendants
Polyphyly?
Represent distantly related species without the inclusion of a common ancestor.
Maximum parsimony?
Law of least resistance. The final grouping of all species in a tree should include the fewest changes as possible – the fewest evolutionary events as measured by the origin of shared derived morphological traits, or fewest base changes in DNA.
Shared ancestral character?
A shared trait with their ancestor. For example, backbone, a character that originated in an ancestor of the taxon. Primitive – a synapomorphy found in both in and outgroup. Taxa – related groups.
Shared derived character?
A trait shared by a group but not found in all ancestors. For example, hair might be an evolutionary unique novelty to a clade. Or – recent synapomorphy missing in the outgroup but found in some taxa in the ingroup.
Synapomorphy?
A trait shared by a group of descendants from a common ancestor, can be referred to homology.
Outgroup?
A taxonomic group that with high probability separated from the ingroup. Before further split into subgroups and before the shared ancestor of the ingroup was alive.
Cladogram?
A cladogram is a diagram used to represent a hypothetical relationship between groups of animals, called a phylogeny. It does not show how ancestors are related to descendants, nor does it show how much they have changed but can be used to imply evolutionary relationships by the number of synapomorphies.
Phylogram?
A phylogram is a phylogenetic tree that has branch lengths proportional to the amount of character change.
Ultrametric tree?
A rooted tree that indicates how much time has passed since branching points. Since it is based on the molecular clock theory (rate of DNA changes is equal in all organisms), the root distance to the leaves are equidistant.
