Phylogenies & The History of Life

Question 1

What are the estimates for the number of species catalog?

Answer 1

1.5 to 2.3 million species cataloged

5 + or - 3 million in estimated in total

Note: 1 billion to 1 trillion individuals in total.

Question 2

What are the types of characteristics that biologist used to characterize organisms?

Answer 2

Fossil records
Morphology
Physiology
Behavior
Embryological development
DNA and RNA sequences

Question 3

What is Phylogeny? What information do phylogenic relationships provide?

Answer 3

Phylogeny is the evolutionary history and relationship of an organism or group of organisms.

Phylogeny provides information on shared ancestry, and which species is closely related, but does not provide information on how organisms are similar or different.

Question 4

What is a phylogenic tree? How can it be used? What are rooted and unrooted trees?

Answer 4

A phylogenic tree demonstrates the evolutionary pathways and connections among organisms. It is used to construct a tree of life to illustrate when different organisms evolved, and the relationship between those organisms..

Rooted trees are those where there is a single ancestral lineage identified.

Unrooted trees simply show the relationship of the three domains of life (note: no single ancestor as identified)

Question 5

Can you explain the following terms taxon, sister, taxa, nodes, root, polytomy, clade, MRCA?

Answer 5

Taxon is a group of organisms (i.e., species, family, domain, etc.)
Taxa is the plural version of taxon.
Clade is any branch or lineage.
Node is a branch point (note: splitting represents single lineage, evolving into two clades)
Noes are the most recent common ancestor (MRCA) of subsequent clades
Root is at the bottom and shows the ancestral species.
Polytomy is an internal node of a phylogenic tree.

Question 6

Why does rotation at branch points not change the information?

Answer 6

Because each taxon evolution from the branch point was independent of the other.

Question 7

What are some of the limitations of phylogenetic trees?

Answer 7

Unless specified the length of the branch does not indicate amount of time past since the split.
If evolved under different circumstances, selective pressures, the tax may look very different.

Question 8

Why are phylogenetic trees considered to be a hypothesis? Example of a change from the classical view.

Answer 8

Because we cannot go back and confirm the proposed relationships.

Example: it used to be thought that fungi and plants were closely related. It is now understood that fungi are more closely related to animals.

Question 9

Can you explain cladistics using the following terms: cladogram, clade, monophyletic, polyphyletic, monophyly?

Answer 9

• Cladistics is a process to arrange tax by homologous characters into clades (cladogram)
• Monophyletic (monophyly): group of organisms descended from a common evolutionary ancestor
• Polyphyletic: hey group of organisms commonly thought to be the same type, may actually be derived from more than one common evolutionary ancestor, and therefore is not suitable for placing in the same taxon.
• Paraphyletic : groups of organisms descended from a common evolutionary ancestor, but does not include all the descendent groups.

Question 10

Why do phylogenies matter?

Answer 10

Understanding of the evolutionary process
Research unrelated species may help to better understand human health and medical issues
Track evolution of parasites and viruses
Produce more effective drugs
Used technology to produce more productive crops and domesticated animals
Improve conservation efforts for threatened and endangered species

Question 11

What does the field of systematics do?

Answer 11

Systematics is a branch of biology that studies the characteristics of species and how they relate to other species overtime.

The main goal is to identify describe and classify species, then organizes information into a classification system known as taxonomy.

Question 12

How is taxonomy used to classify organisms?

Answer 12

Taxonomy uses a higher article classification system to construct an organize categories of organisms.

Question 13

What is the hierarchical order to classify organisms in different categories?

Answer 13

Each level is considered a taxon (listed from lowest level to highest level)

-Domain
-Kingdom
-Phylum
-Class
-Order
-Family
-Genius
-Species
-Species

Did King Phillip Come Over For Good Soup?

Question 14

How is binomial nomenclature used to name species?

Answer 14

It refers to an organism by a two word scientific name that consists of its genus and species.

The genius is capitalized, whereas the species is lowercase and both are italicized.

Question 15

What is the difference between a species and a sub species?

Answer 15

Sub species are members of the same species that are capable of mating and reproducing viable offspring. However, they are separate due to geographic or behavioral isolation. (Note: other factors could cause separation as well)

Question 16

What is the difference between homologous and analogous characteristics? How do they help us understand evolution?

Answer 16

Homologous characteristics, maybe due to similar evolutionary origin, same ancestral source
or based on genetic and developmental origin.

Analogous characteristics are similar due to functional or ecological constraints and pressures,
and they can be similar due to evolutionary convergence.

Higher levels of complexity, could indicate a shared evolutionary history.

Question 17

What is evolutionary reversal? What is convergent evolution? How can these obscure evolutionary relationships?

Answer 17

• Convergent evolution is when similar environmental pressures are natural selection produce similar adaptations in organisms from different evolutionary lineages (do not share a common ancestor).
• Evolutionary reversal is when ancestral traits are sometimes loss in descendants in one group
• These two situations can obscure true evolutionary relationships and lead to inaccurate cladograms.

Question 18

What is molecular systematics? What are some of its strengths and limitations?

Answer 18

Sophisticated computer algorithms use nucleotide sequences as characteristics in order to discern true evolutionary relationships.

Four different nucleotides may produce sequences that appear homologous when they are not .
Certain mutations will shift sequences making them appear unrelated, when they are .

Question 19

Why does evolution NOT lead to perfection?

Answer 19

Mutations are random
Traits that result due to mutation may be beneficial, harmful or neutral (this depends on the environmental pressure is at the moment)
Evolution is changed in organisms overtime

Question 20

What is a shared ancestral characteristic and how is it used to understand evolution?

Answer 20

I shared ancestral characteristic is found in a common ancestor and all the members of a clan have that characteristic.

This is then used to identify membership to a larger group .

Question 21

What is a shared derived characteristic (synapomorphy and how is this used to understand evolution?

Answer 21

A shared derived characteristic of rose within a larger scale.
It distinguishes those that share it from those that do not And is used to identify branch points (nodes) within the larger clade
provides relatedness information within the larger group.

Question 22

What is the rule of parsimony?

Answer 22

Choose the simplest cladogram with a few steps or events.

This is used to help develop an accurate cladogram.

Question 23

What is the difference between the biological species concept and the phylogenic species concept?

Answer 23

Biological species concept (BSC) define species as groups of in breeding populations that are reproductively isolated

Whereas

Phylogenetic species concept (PSC) define species as a population or set of populations by one or more shared derived characteristics.

Question 24

What is horizontal gene transfer and how can it lead to genetic variation?

Answer 24

Horizontal gene transfer (HGT) is a transfer of genetic material between unrelated species. This adds new traits to organisms that were not previously present.

The following are the three primary modes of HGT in prokaryotes:

Transformation DNA uptake by bacteria
Transduction genes transferred by virus
Conjugation genes transferred between the bacteria via pilus

The following are primary modes of HGT uptake in eukaryotes (much rarer):

Transposon (jumping genes)
Fungi uptake of taxal gene
Carotinoid enzyme transferred