A3.2 Classification and Cladistics

Question 1

Reasons for classification system

Answer 1

Information storage and retrieval, identification of an organism or species’ name, predictive value/ (characteristics of a species can be predicted from its group), Researching evolutionary origins (grouping species that share traits that evolved from a common ancestor)

Question 2

Taxa

Answer 2

Groups used to classify organisms (phyla, classes, and orders)

Question 3

Taxonomy

Answer 3

Assigning organism to taxonomic groups

Question 4

King Philip came over for good soup.

Answer 4

Kingdom, Phylum, Class, Order, family, genus, species

Question 5

Disadvantages for Hierarchy of taxa

Answer 5

• can be unclear how populations should be grouped due to the speciation of one species into two.
• There can be disagreement about how species should be grouped into genera or larger groups.
• There can be disagreement about what taxonomic rank a group should have.
• Gradual divergence of species over time makes it hard to objectively determine at what time a species split so taxonomic rankings from domain to genus are inevitably arbitrary.

Question 6

Ideal Classification

Answer 6

Should follow evolutionary relationships, all members of a taxonomic group have evolved from a common ancestor.

Question 7

Criteria for ideal classification

Answer 7

• Every organism that has evolved from the same common ancestor is included the same taxonomic group.
• In each taxonomic group, all species have evolved from the same common ancestor.

Question 8

Importance of Classification criteria

Answer 8

All members if a taxonomic group will have traits inherited from their common ancestor, which allows biologists to create predictions based on classification.

Question 9

Paradigm

Answer 9

Ideal for demonstrating a theory

Question 10

Cladistics

Answer 10

An approach to classification in which groups of species that share a common ancestor are identified but are not given a taxonomic rank.

Question 11

Clade

Answer 11

A group of organisms that have evolved from a common ancestor. (Including ancestral species and all species that evolved from it)

Question 12

Clade can include many living species, or just a few

Answer 12

True

Question 13

What do mutations cause?

Answer 13

Differences in the base sequence and therefore the amino acid sequence of proteins.

Question 14

Over long periods of time between two or more species

Answer 14

Differences in DNA sequences accumulate

Question 15

Molecular clock methods

Answer 15

A method used to estimate the time since two species diverged from a common ancestor based on the differences accumulated in DNA/amino acid sequences over time, assuming that the differences have accumulated at a constant rate.

Question 16

The larger the number of sequence differences…

Answer 16

The longer since two species diverged from a common ancestor

Question 17

Things that effect mutation rate

Answer 17

Generation time, size if the population, intensity of selective pressure.

Question 18

Most recent common ancestor for humans lived…

Answer 18

Estimated to have lived around 150,000 years ago

Question 19

Cladogram

Answer 19

A branching diagram that represents ancestor-descendent relationships, and is constructed by sequencing analysis.

Question 20

Maximum Parsimony

Answer 20

How species could have evolved with the fewest sequence changes.

Question 21

Terminal branches

Answer 21

Ends that represent individual clades, species or groups that are not subdivided on the cladogram.

Question 22

Nodes

Answer 22

Branching points in a cladogram that represent the the point at which a hypothetical ancestral species split to form 2 or more clades.

Question 23

Root

Answer 23

Base of the cladogram and represents the hypothetical common ancestor of the entire clade.

Question 24

Cladograms that are drawn to scale are based on…

Answer 24

Estimates of the time since each species split

Question 25

Phylogeny

Answer 25

evolutionary origins

Question 26

How can we test cladogram accuracy?

Answer 26

Several cladograms can be produced using different genes and checked if they have the same pattern of branching, which ensures the evidence of the evolution is strong.

Question 27

Hypothesis

Answer 27

A provisional explanation for a pattern

Question 28

Cladistics on traditional morphology-based classifications of species

Answer 28

• Confirmed that traditional classification corespond to evolutionary relationships in many cases.
• Indicated that the species in a taxonomic group do not all share a common ancestor in some cases.
• Indicates that species with a common ancestor have been placed in different groups in other cases

Question 29

Three major domains of organisms

Answer 29

Eubacteria, Archaea, and Eukaryotes