Classification Systems Flashcards
Classification (Taxonomy)
Hierarchical arrangement of organisms into orderly groups based on their similarities
Taxon
A category in which related organisms are placed
Clade
A group of organisms that are monophyletic, the group comprises of all of the descendants of a particular ancestor organism
Hierarchy of Taxa
Domain -Kingdom - Phylum - Class - Order - Family - Genus - Species
Linnean System
Modern system of naming, two-words genus and species
Biological Species Concept
A species is a group of similar organisms whose members can interbreed with each other in their natural environments to produce viable and fertile offspring
Viable Offspring
Living
Fertile
Can produce their own offspring
Limitations of Biological Species Concept
Asexual production, apomixis, fossils, ring species
Apomixis
Asexual seed formation
Ring Species
A connected series of populations, each of which interbreeds with closely sited related populations, but for which there are at least two ‘end’ populations which are too distantly related to interbreed
Methods of Reproduction
A form of mathematical classification based on the number of offspring a species produces and the level of parental involvement required to care for them
r reproduction
Unstable and unpredictable environments (exponential population growth)
K Reproduction
Stable environments (logistic population growth), have carrying capacity
Carrying Capacity
The size of the population that can be supported indefinitely on the available resources and services of that ecosystem
Molecular Sequences (Phylogeny), Cladistics
A classification process to group all organisms based on common ancestors uses evolutionary lines of descent rather than structural similarities, the more similar the molecular sequence, the more closely related species are
Molecular Clock
The way in which scientists use base pairs to determine the time between common ancestors of species
Limitations of Cladistics
Genes and proteins may mutate at different rates, the rate of change for a particular gene may differ between different groups of organisms, over long periods of time early changes may be reversed by later changes, confounding the result
Assumptions of Cladistics
Common ancestor, bifurcation, physical change over time
Common Ancestor Assumption
Because all life evolved from a single ancestor, any group of organisms will share a common ancestor at some point in the past, biodiversity has been produced by the reproduction of existing organisms
Bifurcation Assumption
New kinds of organisms may arise when existing populations divide into exactly two groups, does not consider interbreeding or that new features can emerge independently
Physical Change over Time Assumption
The offspring of an ancestral species diverge dichotomously in a process called cladogenesis, it suggests that all speciation event are singular splits, the new generation of a particular organism will be the same as their parent generation (pleiomorphic)or different in only one way (apomorphic)
