Chapter 16 - Taxonomy and Evolution

Question 1

When did cells first appear?

Answer 1

3.8 billion years ago

Question 2

Early Earth was like what?

Answer 2

Extremely hot, (anoxic), with reduced organic, inorganic chemicals in abundance.

Question 3

RNA World

Answer 3

a hypothetical stage of evolution, where self-replicating RNA molecules proliferated before the evolution of DNA and proteins.

Question 4

Initial Cell Electron Transfer System

Answer 4

Likely primitive, through just one carrier but still allowed for development of a proton motive force to conserve energy.

Question 5

What happened as Chemolithoautotrophs proliferated?

Answer 5

Organic material would accumulate in the environment, providing conditions needed for development of chemoorganotrophic organisms

Question 6

What did new chemoorganotrophic organisms do?

Answer 6

They lead to oxidized organic compounds, with their more negative redox potential and increased number of electrons - likely leading to lengthened electron transport chains - resulting in faster growth and speeding up diversity.

Question 7

How long ago did cells with phototrophic pigments evolve?

Answer 7

3.5 billion

Question 8

What did phototrophs initially utilize

Answer 8

anoxygenic phototrophy, utilizing sulfur products as an electron donor when performing CO2 fixation.

Question 9

Stromatolites

Answer 9

Layered rocks that form when minerals are incorporated into thick mats of microbes, growing on water surfaces. Ancient stromatolites contain fossilized microbial mats made up of cyanobacteria-ike cells

Question 10

How long ago did cyanobacterial ancestors evolve?

Answer 10

2.5-3.3 billion years ago

Question 11

What did cyanobacterial ancestors evolve?

Answer 11

They developed oxygenic photosynthesis by acquiring two photosystems and the pigment chlorophyll a.

Question 12

What did cyanobacterial ancestor evolution lead to?

Answer 12

Being able to utilize water as an electron donor, causing oxygen to accumulate in Earth’s atmosphere.

Question 13

Great Oxidation Event

Answer 13

Cyanobacterial ancestors evolution to cause oxygen to fill atmosphere - changed types o metabolism possible, allowed for the use of oxygen as final electron acceptor.

Question 14

Ozone shield

Answer 14

a layer around earth made of ozone (O3) and serves to block out much of the UV radiation from sun. Allowed for organisms to start inhabiting the surface of the planet, as opposed to ocean or soil.

Question 15

How did Ozone shield develop?

Answer 15

As O2 was released into atmosphere, it was converted to O3 when exposed to UV light.

Question 16

Endosymbiosis

Answer 16

Offers explanation for development of eukaryotic cells - the idea that a cell ingested another cell, a free-living bacterium, but did not digest it.

Question 17

What did endosymbiont have?

Answer 17

capabilities that proto-euakaryotic cells lacked - such as ability for phototrophy (chloroplasts) or oxidative phosphorylation (mitochondria).

Question 18

What happened after a period of time of endosymbiosis

Answer 18

The two cells became mutually dependent upon one another, with the endosymbiont becoming and organelle.

Question 19

Endosymbiont

Answer 19

what’s engulfed

Question 20

chloroplast came from what

Answer 20

cyanobacterial ancestor

Question 21

mitochondria came from what

Answer 21

gram negative bacillus ancestor

Question 22

Evidence of endosymbiosis

Answer 22

Mitochondria and Chloroplasts both have a single, circular chromosome, undergo binary fission separate from eukaryotic cell, have 70s sized ribosomes, lipid bilayer with a 2:1 ratio of protein to lipid, have rRNA sequence that place them phylogenetically with bacteria.

Question 23

Phylogeny

Answer 23

Reference to the development of an organism evolutionarily

Question 24

What do molecular techniques that assess organisms genomes utilize?

Answer 24

ribosomal RNA (rRNA) nucleotide sequences - which provides most accurate information about the relatedness of microbes

Question 25

What is Nucleic acid hybridization? (DNA-DNA hybridization)

Answer 25

commonly used tool for molecular phylogeny. Compares similarities between genomes.

Question 26

How does Nucleic acid hybridization (DNA-DNA hybridization) work?

Answer 26

Genomes of two organisms are melted to separate complementary strands, and then allowed to cool down. Strands that have complementary base sequences will re-anneal.

Question 27

Nucleic acid sequencing

Answer 27

use rRNAs from small ribosomal subunits, allowing direct comparison of sequences.

Question 28

Why ribosomal sequences?

Answer 28

Idea because the genes encoding do not change very much over time, nor strongly influenced by horizontal gene transfer.

Question 29

Molecular chronometer

Answer 29

aka way to track genetic changes over a long period of time, even between closely related organisms.

Question 30

Last universal common ancestor (LUCA)

Answer 30

Root of phylogenetic tree, last common ancestor for organisms being compared

Question 31

Node

Answer 31

branchpoint - organisms diverged

Question 32

length of branch

Answer 32

amoutn of molecular changes over time

Question 33

external nodes

Answer 33

specific taxa or organisms (although they can represent specific genes)

Question 34

clade

Answer 34

group of organisms that have a particular ancestor in common

Question 35

taxonomy

Answer 35

organization of organisms based on relatedness

Question 36

phenetic classification

Answer 36

Classification that relies on phenotypes (physical appearance) of organisms

Question 37

phylogenetic classification

Answer 37

Classification that relies on evolutionary relationships of organisms

Question 38

genotypic classification

Answer 38

Classification that compares genes or genomes between organisms

Question 39

polyphasic approach

Answer 39

most popular - combines all three types of classification

Question 40

microbe species

Answer 40

No current species definition. The most commonly used is one that relies on both genetic and phenotypic information with a threshold of 70% DNA-DNA hybridization and 97% 16s DNA sequence identity needing to be present for two organisms to be deemed as same species.