Lecture 15 Classification

Question 1

What is the timeline of life evolution?

Answer 1

Life evolved between 4.5-3.5 billion years ago.

Question 2

How did eukaryotes emerge?

Answer 2

Eukaryotes emerged from bacteria.

Question 2

When did aerobic metabolism evolve?

Answer 2

Aerobic metabolism evolved after anaerobic metabolism, following the “Great Oxidation Event” once O2 was present.

Question 3

What is the significance of the Great Oxidation Event?

Answer 3

The Great Oxidation Event created conditions for aerobic metabolism, leading to the development of multicellularity and diversity.

Question 4

What is the endosymbiotic theory?

Answer 4

The endosymbiotic theory proposes that eukaryotic organelles such as mitochondria and chloroplasts originated from bacteria through a process involving phagocytosis by protist-like protoeukaryotes.

Question 5

What events led to the development of symbiosis?

Answer 5

The development of symbiosis involved phagocytosis by a protist-like protoeukaryote, followed by the establishment of symbiotic relationships and selection with genome reduction by the microbe.

Question 6

Define a species in prokaryotic classification.

Answer 6

a collection of strains that share many stable properties and differ significantly from other groups of strains.

Question 7

Compare phenetic and phylogenetic classifications.

Answer 7

Phenetic classification groups organisms based on phenotypic similarity, while phylogenetic classification is based on direct comparison of genetic material and gene products.

Question 8

Provide examples of prokaryotic morphologies.

Answer 8

Examples include cocci (spherical), bacilli (rod-shaped), spirilla (spiral-shaped), and vibrio (comma-shaped).

Question 9

How is the phylogenetic tree of life defined?

Answer 9

The phylogenetic tree of life is defined by comparing genetic sequences, often using SSU rRNA gene sequencing.

Question 10

Explain FAME and its role in classification.

Answer 10

FAME involves lipid analysis for classification.

Question 11

Describe MALDI-TOF and its advantages.

Answer 11

MALDI-TOF is a protein analysis method with advantages like quick identification and little training requirement.

Question 12

What are the limitations of MALDI-TOF?

Answer 12

high instrument cost, reliance on a database, inability to identify non-cultivatable microbes, and dependency on the presence of similar organisms in the database.

Question 13

Describe the procedure for 16S rRNA gene sequencing.

Answer 13

The procedure involves PCR amplification, gel electrophoresis, and sequencing of the 16S rRNA gene.

Question 14

What is the resolution of 16S rDNA at different taxonomic levels?

Answer 14

16S rDNA has good resolution at the genus and family levels but lacks resolution at the species and strain levels.

Question 15

How do gene loss, convergent evolution, and horizontal gene transfer contribute to diversity?

Answer 15

Gene loss, convergent evolution, and horizontal gene transfer contribute to diversity by introducing variations and unique traits among organisms.

Question 16

What factors may cause discrepancies between phylogenetic and phenetic classifications?

Answer 16

Discrepancies may arise due to gene loss, convergent evolution, and horizontal gene transfer, impacting the accuracy of phenetic classifications.

Question 17

Why is 16S rDNA important in phylogeny?

Answer 17

16S rDNA is important in phylogeny because it is a conserved gene present in all bacteria and archaea, allowing for broad taxonomic classifications.

Question 18

What are the limitations of 16S rDNA at the species/strain level?

Answer 18

16S rDNA lacks resolution at the species and strain levels, making it more suitable for broader taxonomic classifications.

Question 19

What challenges exist in classifying microbes below the subspecies level?

Answer 19

Classifying microbes below the subspecies level is challenging due to high variability, genetic exchange, and the presence of horizontal gene transfer.

Question 20

How do gene loss, convergent evolution, and horizontal gene transfer impact phylogeny and phenetics?

Answer 20

can lead to discrepancies between phylogenetic and phenetic classifications by introducing variations that may not align with evolutionary relationships.