BIO.B.3 Adaptations and Evolution
Topic Summary for Classification:
To study Earth’s great diversity of organisms, biologists must give each organism a name. Biologists also must organize living things into groups in a logical way. Therefore, biologists need a classification system. The science of naming and grouping organisms is called systematics.
Classical Classification
In the 1730s, Carolus Linnaeus developed a naming system, called binomial nomenclature.
In binomial nomenclature, each species is assigned a two-part scientific name:
The first part of the name refers to the genus, or a group of similar species.
The second part of the name is unique to each species.
Linnaeus’s system of classification has seven different levels. From smallest to largest, the levels are species, genus, family, order, class, phylum, and kingdom. Each of the ranking levels is called a taxon.
Just as a genus is a group of similar species, a family is a group of similar genera.
An order is a group of similar families.
A class is a group of similar orders.
A phylum is a group of similar classes.
A kingdom is a group of similar phyla.
Evolutionary Classification
The study of evolutionary relationships among organisms is called phylogeny. Classification based on evolutionary relationships is called phylogenetic systematics, or evolutionary classification.
Evolutionary classification places organisms into higher taxa whose members are more closely related to one another than they are to members of any other group. The larger the taxon, the further back in time all of its members shared a common ancestor.
In this system, organisms are placed into groups called clades. A clade is a group of species that includes a single common ancestor and all descendants of that ancestor. A clade must be a monophyletic group. A monophyletic group must include all species that are descended from a common ancestor, and cannot include any species that are not descended from that common ancestor.
A cladogram is a diagram that shows how species and higher taxa are related to each other. A cladogram shows how evolutionary lines, or lineages, branched off from common ancestors.
In a cladogram, the place where the ancestral lineage splits is called a fork, or a node. Nodes represent the point where new lineages last shared a common ancestor.
The bottom of the diagram, or the root, represents the ancestor shared by all of the organisms on the cladogram.
Cladistic analysis relies on specific shared traits, or characters. A derived character is a trait that arose in the most recent common ancestor of a particular lineage and was passed to all of its descendants.
All organisms have DNA. Because DNA is so similar across all forms of life, this molecule can be compared in different species. In general, the more derived genetic characters two species share, the more recently the species shared a common ancestor and the more closely related they are.
Topic Summary for Classification:
To study Earth’s great diversity of organisms, biologists must give each organism a name. Biologists also must organize living things into groups in a logical way. Therefore, biologists need a classification system. The science of naming and grouping organisms is called systematics.
Classical Classification
In the 1730s, Carolus Linnaeus developed a naming system, called binomial nomenclature.
In binomial nomenclature, each species is assigned a two-part scientific name:
The first part of the name refers to the genus, or a group of similar species.
The second part of the name is unique to each species.
Linnaeus’s system of classification has seven different levels. From smallest to largest, the levels are species, genus, family, order, class, phylum, and kingdom. Each of the ranking levels is called a taxon.
Just as a genus is a group of similar species, a family is a group of similar genera.
An order is a group of similar families.
A class is a group of similar orders.
A phylum is a group of similar classes.
A kingdom is a group of similar phyla.
Evolutionary Classification
The study of evolutionary relationships among organisms is called phylogeny. Classification based on evolutionary relationships is called phylogenetic systematics, or evolutionary classification.
Evolutionary classification places organisms into higher taxa whose members are more closely related to one another than they are to members of any other group. The larger the taxon, the further back in time all of its members shared a common ancestor.
In this system, organisms are placed into groups called clades. A clade is a group of species that includes a single common ancestor and all descendants of that ancestor. A clade must be a monophyletic group. A monophyletic group must include all species that are descended from a common ancestor, and cannot include any species that are not descended from that common ancestor.
A cladogram is a diagram that shows how species and higher taxa are related to each other. A cladogram shows how evolutionary lines, or lineages, branched off from common ancestors.
In a cladogram, the place where the ancestral lineage splits is called a fork, or a node. Nodes represent the point where new lineages last shared a common ancestor.
The bottom of the diagram, or the root, represents the ancestor shared by all of the organisms on the cladogram.
Cladistic analysis relies on specific shared traits, or characters. A derived character is a trait that arose in the most recent common ancestor of a particular lineage and was passed to all of its descendants.
All organisms have DNA. Because DNA is so similar across all forms of life, this molecule can be compared in different species. In general, the more derived genetic characters two species share, the more recently the species shared a common ancestor and the more closely related they are.