Origin and evolution

Question 1

What is the origin of all living things?

Answer 1

LUCA

Question 2

What did the LUCA form?

Answer 2

Bacteria

Archae

Eukaryotes

Question 3

What are the two types of evidence for evolution?

Answer 3

Fossils

DNA and protein sequences

Question 4

Since when have biofilms existed?

Answer 4

Since the origin of bacteria

Strange as bacteria have not evolved greater complexity

Question 5

What is the difference between gram positive and gram negative bacteria?

Answer 5

Gram positive -> one membrane, on outer surface is thick coat of peptidoglycan

Gram negative -> two membranes, between membranes are molecules of peptidoglycan

Question 6

Why is peptidoglycan essential for bacterial life?

Answer 6

Bacteria are stuffed with oncotic molecules

Puts turgor pressure on organism

Peptidoglycan prevents bacteria from bursting

Question 7

How does Penicillin kill bacteria?

Answer 7

Penicillin weakens the peptidoglycan

Bacteria burst

Question 8

How did LUCA form bacteria?

Answer 8

LUCA morphed into peptidoglycan containing cell

Primordial cell = cell with peptidoglycan containing wall

Evolution pushed the wall between two thin membranes or one thick wall

Question 9

Do all bacteria contain peptidoglycan walls?

Answer 9

No

Question 10

What are examples of a bacteria that does not contain a peptidoglycan cell wall?

Answer 10

Tenericutes - live on specialised niches like skin

Thermophiles - modified petidoglycan to overcome extreme conditions

Question 11

What is endosymbiosis?

Answer 11

2 billion years ago non- and photosynthetic bacteria got into proto-eukaryotic cells

Question 12

What did photosynthetic bacteria form?

Answer 12

Photosynthetic organelles in plant cells

Question 13

What did non-photosynthetic bacteria form?

Answer 13

Mitochondria

Key for energy and apoptosis

Mitochondria benefits from being inside cells and cell benefits from having extra energy

Question 14

What is neo-darwinism?

Answer 14

Modern take on Darwin’s theory of survival of the fittest

Neo-darwinism = mutations + genetic recombination

When plants and animals reproduce the offspring contains differences in DNA through genetic recombination

Question 15

How are mutations selected for in Neo-Darwinism?

Answer 15

Mutations in DNA produce variations in proteins

Proteins can become favourable -> kept in gene pool, passed to offspring

Proteins can become unfavourable -> disappear from population

Question 16

Why do bacteria have such low genetic recombination?

Answer 16

They reproduce clonally

Question 17

What is the mechanism in which bacteria can have genetic recombination?

Answer 17

Plasmids

Bacteriophages

Genomic islands

Horizontal gene transfer - responsible for 30% of genes in bacteria

Question 18

How does bacteria transfer DNA in order to allow for genetic recombination?

Answer 18

Naked DNA

Question 19

Mechanisms of horizontal gene transfer

Answer 19

Transformation

Conjugation

Transduction

Question 20

Describe the process of Transformation

Answer 20

Bacteria is taken up from environment via naked DNA and plasmids

Question 21

Describe the process of Conjugation

Answer 21

Some bacteria perform sex

Tube between two cells

DNA transfer from one cytoplasm to another

Question 22

Describe the process of Transduction

Answer 22

Bacteriophages - viruses infect bacteria

Question 23

How many genes are there in a genome of bacteria?

Answer 23

3000

Question 24

How many genes are there in a genome of a human?

Answer 24

19000

Question 25

What is the pan genome?

Answer 25

Number of genes accessible for strain of bacteria

Question 26

Does evolution happen at a constant rate?

Answer 26

Yes

Question 27

Is the rate at which bacteria mutate constant?

Answer 27

No HGT might be constant however

Question 28

What is stress-induced mutagenesis?

Answer 28

Mutations can be enhanced if exposed to external stresses

Question 29

What is an example of stress-induced mutagenesis?

Answer 29

Antibiotics drives antibiotic resistance Bacteria mutate faster to increase resistance to antibiotics

Question 30

How can plasmids be used to increase reisistance to antibiotics?

Answer 30

Bacteria can take up plasmids with antibiotic resistant genes Makes organism into a resistant strain

Question 31

How did bacteria evolve from LUCA?

Answer 31

LUCA -> bacteria Initially bacteria lived in anoxic environment Liquid and air - no oxygen Cyanobacteria started producing oxygen Planet becomes toxic 100s years -> atm contains oxygen Bacteria living under different conditions evolve to these