Chapter 10 - classification and evolution

What is taxonomy?

Taxonomy is the practice/study of biological classification

What is classification?

Arranging organisms into groups based in their similarities and differences. This makes it easier for scientists to study and identify them.

How many levels are there in the taxonomic hierarchy?

there are 8 levels

What are all of the levels called in a taxonomic hierarchy?

Domain

Kingdom

Phylum

Class

Order

Family

Genus

Species

What is the overall name for a group in the taxonomic system?

A taxon

Are there more or less groups going down the taxonomic hierarchy?

There are more groups but less individuals in each group

What are the three domains?

Bacteria

Archaea

Eukarya

What are the 5 kingdoms?

Plantae (plants)

Animalia (animals)

Protoctista (unicellular eukaryotes)

Fungi (such as yeasts)

Prokaryote (e.g. bacteria)

What is the binomial naming system?

Where all organisms are given two names in Latin that are universally recognised. The first part is the Genus and the second part is the species. The genus is capitalised and the second part is lower case. The binomial name should always be in italics. e.g. Homo sapiens is humans.

Why is the binomial name useful?

It helps to avoid confusion of using common names.

How came up with the binomial naming system?

Carl Linnaeus

What are the features of the five kingdoms?

Give some characteristics of archaea.

• Organisms within this domain are sometimes referred to as the extremophile prokaryotes, as archaea were first discovered living in extreme environments (although not all archaea do)

• Archael cells have no nucleus (and so are prokaryotic)

• They were initially classified as bacteria until several unique properties were discovered that separated them from known bacteria, including:

• Unique lipids being found in the membranes of their cells

• No peptidoglycan in their cell walls

• Ribosomal structure (particularly that of the small subunit) are more similar to the eukaryotic ribosome than that of the bacteria

• Archaea have a similar size range as bacteria (and in many ways metabolism is similar between the two groups)

• DNA transcription is more similar to that of eukaryotes

• Example: Halobacterium salinarum is a species of the archaea domain that can be found in environments with high salt concentrations like the Dead Sea

Give some characteristics of bacteria.

• These are organisms that have prokaryotic cells which contain no nucleus

• They vary in size over a wide range: the smallest are bigger than the largest known-viruses and the largest are smaller than the smallest known single-celled eukaryotes

• Bacterial cells divide by binary fission

• Example: Staphylococcus pneumoniae is a species of bacteria that causes pneumonia

Give some characteristics of ekarya.

• Organisms that have eukaryotic cells with nuclei and membrane-bound organelles are placed in this domain

• They vary massively in size from single-celled organisms that are only several micrometres across, to large multicellular organisms many-metres in size, such as blue whales

• Eukaryotic cells divide by mitosis

• Eukaryotes can reproduce sexually or asexually

• Example: Canis lupus, also known as wolves

What are the key differences between archaea and bacteria?

• The membrane lipids of Archaea consist of branched hydrocarbon chains bonded to glycerol by ether linkages

• The membrane lipids of Bacteria consist of unbranched hydrocarbon chains bonded to glycerol by ester linkages

• The base sequences of ribosomal RNA in Archaea show more similarity to the rRNA of Eukarya than Bacteria

• The primary structure of ribosome proteins in Archaea show more similarity to the ribosome proteins in Eukarya than Bacteria

• Organisms from the Bacteria domain have cells that always possess cell walls with peptidoglycan

• Organisms from the Archaea domain also have cells that always possess cell walls, however these do not contain peptidoglycan

Explain the main features of the 3 domains

Compare the 5 kingdoms

What is phylogeny?

The evolutionary history of organisms

What are the advantages of phylogenic classification

• It produces a continuous tree that doesn't force organisms into specific taxonomic groups where they don't quite fit.

• There is no overlap between the groups produced.

How does phylogeny link to classification.

Classification was based on visible features, which had problems as scientists couldn’t always agree on the importance of different feature. Now it’s mainly based on phylogeny—the evolutionary history and relationships between organisms

What does a phylogenic tree show?

• The relative positions of branching points show distance of shared common ancestors.

• The relative distances between vertical lines shows closeness of species' evolution from common ancestral branches.

• The proximity of species to each other indicates the closeness of their evolutionary relationship.

Why is molecular analysis useful?

• You can compare things like how DNA is stored and the sequence of DNA bases. e.g. the base sequence for human and chimpanzee DNA is about 94% the same.

• You can also compare the sequence of amino acids in proteins from different organisms. e.g. The more similar the amino acid sequence in a certain protein in two different species, the more closely related the species are likely to be.

• This allows scientists to classify organisms according to their phylogeny more accurately than using visible characteristics