CLASSIFICATION AND EVOLUTION
(a) The biological classification of species.
● To include the taxonomic hierarchy of kingdom, phylum, class, order, family,
genus and species AND domain.
Taxonomists classify all the species of life on earth on a number of hierarchical
levels; the reasons for this include the following:
● For convenience.
● To make the study of living things more manageable; if several members in a
group have a specific characteristic, it is likely another species in the group
will have the same characteristics, so they can be predicted.
● To make it easier to identify living organisms; by using a clearly defined
system of classification, the species an organism belongs to can be identified.
● To help us see the relationships between species; as species in the same
group probably share the same characteristics, they are likely to have evolved
from a common ancestor set, so evolutionary links can be established.
One of the systems used to classify organisms is taxonomic hierarchy, where similar
or related groups at one hierarchical level are combined into more inclusive groups at
the next higher level. The current system of classification uses eight taxonomic
levels:
● Domain: the domain is the highest taxonomic rank. There are three domains:
Archaea, Eubacteria and Eukaryotae.
● Kingdom: the kingdom is traditionally subdivided into five groups, Plantae,
Animalia, Fungi, and Protoctists are all eukaryotes and single-celled
organisms, with no true nucleus, are grouped into Prokaryotae.
● Phylum: the phylum is a major subdivision of the kingdom. A phylum contains
all the groups of organisms that have the same body plan, e.g. possession of a
backbone (chordata).
● Class: the class is a group of organisms that all possess the same general
traits, e,g, the same number of legs. Eg. Mammalia
● Order: the order is a subdivision of the class using additional information
about the organisms, e.g. the class mammal is divided into meat-eating
animals (order Carnivora) and vegetation-eating animals (order Herbivora).
● Family: the family is a group of closely related genera, e.g. within the order
Carnivora we might recognise the ‘dog’ family or the ‘cat’ family.
● Genus: the genus is a group of closely-related species, such as Homo for our
interspecific relationships.
● Species: the species is the most most basic unit of classification. All members
of a species show some variations, but all are essentially the same.
Taxonomic rank ‘Humans’
(a) The biological classification of species.
● To include the taxonomic hierarchy of kingdom, phylum, class, order, family,
genus and species AND domain.
Taxonomists classify all the species of life on earth on a number of hierarchical
levels; the reasons for this include the following:
● For convenience.
● To make the study of living things more manageable; if several members in a
group have a specific characteristic, it is likely another species in the group
will have the same characteristics, so they can be predicted.
● To make it easier to identify living organisms; by using a clearly defined
system of classification, the species an organism belongs to can be identified.
● To help us see the relationships between species; as species in the same
group probably share the same characteristics, they are likely to have evolved
from a common ancestor set, so evolutionary links can be established.
One of the systems used to classify organisms is taxonomic hierarchy, where similar
or related groups at one hierarchical level are combined into more inclusive groups at
the next higher level. The current system of classification uses eight taxonomic
levels:
● Domain: the domain is the highest taxonomic rank. There are three domains:
Archaea, Eubacteria and Eukaryotae.
● Kingdom: the kingdom is traditionally subdivided into five groups, Plantae,
Animalia, Fungi, and Protoctists are all eukaryotes and single-celled
organisms, with no true nucleus, are grouped into Prokaryotae.
● Phylum: the phylum is a major subdivision of the kingdom. A phylum contains
all the groups of organisms that have the same body plan, e.g. possession of a
backbone (chordata).
● Class: the class is a group of organisms that all possess the same general
traits, e,g, the same number of legs. Eg. Mammalia
● Order: the order is a subdivision of the class using additional information
about the organisms, e.g. the class mammal is divided into meat-eating
animals (order Carnivora) and vegetation-eating animals (order Herbivora).
● Family: the family is a group of closely related genera, e.g. within the order
Carnivora we might recognise the ‘dog’ family or the ‘cat’ family.
● Genus: the genus is a group of closely-related species, such as Homo for our
interspecific relationships.
● Species: the species is the most most basic unit of classification. All members
of a species show some variations, but all are essentially the same.
Taxonomic rank ‘Humans’
