C1. Classification of Organisms Flashcards
Phylogeny
What is it?
What does it show us?
What does the first branch point show?
What does each following branch point represent?
What do close branches represent?
Phylogeny is the study of the evolutionary history of groups of organisms. Phylogeny tells us who’s related to whom and how closely related they are.
All organisms have evolved from shared common ancestors (relatives). This can be shown on a phylogenetic tree like the one in Figure 1.
This tree shows the relationship between members of the Hominidae family (great apes and humans). The first branch point represents a common ancestor of all the family members. This ancestor is now extinct. Orangutans were the first group to diverge (evolve to become a different species) from this common ancestor.
Each of the following branch points represents another common ancestor from which a different group diverged. Gorillas diverged next, then humans, closely followed by bonobos and chimpanzees.
Closely related species diverged away from each other most recently. E.g. humans and chimpanzees are closely related, as they diverged very recently. You can see this because their branches are close together.
Taxonomy
What is it?
What are the specific groups called?
What does hierachy mean?
What are the three domains?
What kingdom are all animals in?
What is a species?
Taxonomy is the science of classification. It involves naming organisms and organising them into groups. This makes it easier to identify and study them. Scientists now take into account phylogeny when classifying organisms, and group organisms according to their evolutionary relationships.
There are eight levels of groups used to classify organisms. These groups are called taxa. Each group is called a taxon.
The groups are arranged in a hierarchy, with the largest groups at the top and the smallest groups at the bottom. Organisms can only belong to one group at each level in the hierarchy - there’s no overlap.
Organisms are first sorted into three large groups (or taxa) called domains- the Eukarya, Bacteria and Archaea. Related organisms in a domain are then sorted into slightly smaller groups called kingdoms, e.g. all animals are in the animal kingdom. More closely related organisms from that kingdom are then grouped into a phylum, then grouped into a class, and so on down the eight levels of the hierarchy.
As you move down the hierarchy, there are more groups at each level but fewer organisms in each group. The organisms in each group also become more closely related. The hierarchy ends with species the groups that contain only one type of organism (e.g. humans). A species is a group of similar organisms able to reproduce to give fertile offspring.
The binomial system
The nomenclature (naming system) used for classification is called the binomial system - all organisms are given one internationally accepted scientific name in Latin that has two parts.
The first part of the name is the ______name and has a _________ ______. The second part is the species name and begins with a __________ _______. Names are always written in ______(or they’re _____________if they’re handwritten).
The binomial system
The nomenclature (naming system) used for classification is called the binomial system - all organisms are given one internationally accepted scientific name in Latin that has two parts.
The first part of the name is the genus name and has a capital letter. The second part is the species name and begins with a lowercase letter. Names are always written in italics (or they’re underlined if they’re handwritten).
