A3.2 Classification and Cladistics

State 4 reasons why classification is needed

1. To retrieve and store info

2. Identification

3. Predicting traits

4. Finding evolutionary origins

Why is classification useful for predictive values?

As traits are shared within a species

Why is classification useful for finding evolutionary origins?

If a group of organism share traits, links could be made to their origin

Name the taxa in order

Kingdom, Phylum, Class, Order, Family, Genus, Species

What is the name of the process of assigning organisms to taxa?

Taxonomy

What are the drawbacks to the taxa heirachy?

• can be unclear how populations should be grouped into

• disagreements on how to group species into larger groups

• disagreements on the rank of taxa

Why do biologists have doubt about the heirachy of taxa?

Because taxonomy is arbitrary

What do biologists agree is the ideal means of classification follows?

Evolutionary relationships

Following the classification dependant on evolutionary relationships, what do all taxanomic groups share?

A common ancestor

What are the two criteria which need to be met to judge whether classification follows evolutionary relationships

• Every organism that has evolved from a common ancestor is included in the taxanomic group

• Every taxanomic group has evolved from a common ancestor

What do taxanomic groups share if they are descended from a common ancestor?

Similar characteristics

Why is it useful for Biologists when taxanomic groups have evolved from the same common ancestor?

Because they can predict characteristics within a group

What is the alternative to classifying according to taxa?

To classify using clades

Define clade

A group of organisms that have evolved from a common ancestor

What is the most objective way of classifying organisms into clades?

By comparing the base sequences of genes or amino acid sequences in proteins

If it using base sequences of genes or amino acid sequence is unavailable, what is another way of classifying organisms into clades?

Using morpholigical traits

Do all species only belong to one clade?

No

Explain how species can be part of different clades?

Smaller clades are nested in larger clades

What causes a change in DNA base sequences or amino acid sequences?

Mutations

What can we use to find when a set of species shared a common ancestor?

By finding the difference in number of mutations

What do we assume when using mutations to calculate when species have diverged from a common ancestor?

That mutations occur at a common rate

What is the process of dating divergences of species from common ancestors using mutations called?

The molecular clock

What is a cladogram?

A branching diagram that represents ancestor-descendant relationships

What about cladograms is useful when dating species?

It shows the sequence of divergence

What is a terminal branch?

The ends that represent an individual clade (species or group of species that are not subdivided)

What is a node?

The point at which a hypothetical ancestral species split to form two or more clades

What is a root?

The starting point of a cladogram that represents the hypothetical common ancestor of the entire clade

Give an example of a species that was re-classified after the use of base sequencing

The figwort family

What happened to classification after the use of base sequencing?

Many species were "re-classified”

Before 1977, what were the two recognised domains?

Prokaryote and eukaryote

After 1977, what was the prokaryote domain split into?

Archaea and eubacteria

Currently, what are the three domains?

Archaea, eubacteria, and eukaryotes

What are the components of te binomial naming system?

Genus + species

What is introgression?

The process by which hybrids form over many generations with an unequal distribution from each species

What is backcrossing?

When a hybrid species reproduces with a species of one of their parents

What is a clade also known as?

A monophyletic group

What is a sister group?

A group of closest relatives on a cladogram

What is an outgroup?

A group that is less closely related to others in a cladogram

What is a derived trait?

characteristics that have evolved recently

What is another name for a derived trait?

Apomorphic

What is a primative trait?

characteristics that evolved early

What is another name for a primative trait?

A plesiomorphic trait

What is phylogeny?

Study of the evolutionary past of species

What is phylogenetics?

Methods used to anylise relationships and study phylogeny

What are archaea?

Single celled organisms often found in extreme conditions

What are archaea found in extreme conditions called?

Extremophiles

What are the three types of extremophiles?

• Halophiles: salt loving

• Thermophiles: heat loving

• Methanophiles: methane loving

Where are halophiles found?

In the dead sea or salt mines

Where are thermophiles found?

In hot springs or hydrothermal vents

Where are methanophiles found?

In landfills, marhses, paddy fields,…