Evolution Lecture 8

Question 1

Three domains of life?

Answer 1

Bacteria, Archaea, Eukarya.
Bacteria, Archaea & most eukaryote groups are microbial life-forms. Each domain has its own biologically unique characteristics.

Question 2

Prokaryotic Cells

Answer 2

Bacteria and Archaea. They are singular celled. Have less DNA. To small to see with the naked eye.

Question 3

Taxis

Answer 3

What 50% of all prokaryotes are capable of doing. A directed movement toward or away a stimulus (eg. nutrients.)

Question 4

First direct evidence of life came from what?

Answer 4

Fossilized stromatolites.

Question 5

Stromatolites

Answer 5

Layered rocks that form when certain prokaryotes bind thin films of sediment together.

Question 6

How do some Bactria move?

Answer 6

Flagella

Question 7

Importance of Prokaryotes

Answer 7

On Earth for ~3.5 billion years. First cellular life on earth.

Responsible for most of biological activity in
many ecosystems (e.g. Ocean; Soil). Very important for the earth.

More prokaryotes than human cells in body.

Cause many major diseases & infections. They interact with us.

Biotechnology. Used to make pharmaceuticals.

Question 8

Bacteria

Answer 8

Includes almost all well-known prokaryotes
– e.g. all known disease-causing species. Often the shape is circular or short rods.

Question 9

How do bacteria reproduce?

Answer 9

Binary fission. One cell pinching to become two cells.

Question 10

Bacterial cell envelope?

Answer 10

Usually two bounding membranes: Plasma membrane and outer membrane. Peptidoglycan wall between the membranes (complex polymer of sugars and amino acids). It has its own biochemistry.

Question 11

Gram-postive Bacteria

Answer 11

Have simpler walls with a relatively large amount of peptidoglycan. No outer membrane. Many soil bacteria, also many causes of diseases. Have the ability to make these really resistant cell stages (because of thick peptidoglycan wall).

Question 12

Gram-negative Bacteria

Answer 12

Has less peptidoglycan and are structurally more complex, with an outer membrane that contains lipopolysaccharides.

Question 13

What are Gram-negative Bacteria and Gram-postive Bacteria used for?

Answer 13

Used in medicine for treatment implications.

Question 14

A few types of bacteria?

Answer 14

– Spirochetes
– Gram-positive bacteria
– Cyanobacteria (photoautotrophs)
– Proteobacteria

Question 15

Spirochetes

Answer 15

Has a distinct shape (long and think spiral structures). They swim rapidly like a corkscrew. They typically cause diseases.

Question 16

Cyanobacteria (photoautotrophs)

Answer 16

Photosynthesis in ocean is formed by this important photoautotrophs. Perform oxygen photosynthesis.

Question 17

Proteobacteria

Answer 17

Very diverse, ie. E coli.

Question 18

Archaea

Answer 18

Some (many) are extremophiles (live under extreme conditions) e.g. Some are extreme thermophiles
(some grow at 110°C). Many are methanogens (live in low oxygen environments) - produce methane as a waste product of energy metabolism. Not as well known.

Question 19

Archaea cell envelope?

Answer 19

No ‘outer membrane’; no peptidoglycan. Cell membrane lipids are chemically different from those of Bacteria and eukaryotes. They have branched hydrocarbons. This is because the biochemical process that makes them is a different process.

Question 20

What are most similar?

Answer 20

Archaea and Eukaryotes. The architecture of RNA polymerase in them are very similar.

Question 21

Polytomy

Answer 21

The point where the relationship amount species is unknown.

Question 22

Bacterial origins of mitochondria and plastids (chloroplasts)?

Answer 22

Endosymbiosis is where bacterial cell became incorporated into a eukaryotic cell.

Question 23

The origin of eukaryotic cells?

Answer 23

Endomembrane system, including nuclear envelope
evolves conventionally (not by symbiosis). Endosymbiotic alphaproteobacterium becomes mitochondrion. Endosymbiotic alphaproteobacterium
becomes mitochondrion. It’s likely that a bacterium swallowed by a more complex Archaea- related call eventually evolved into a mitochondrion- a major step in eukaryote evolution. It lost many features of the cell, independent cell organelles.

Question 24

Ancestors of modern eukaryotes were what?

Answer 24

Very prokaryotic like, with very few internal cell organelles.

Question 25

Some prokaryote-cell-like features of mitochondria and plastids?

Answer 25

Divide by binary fission. Have (prokaryotic-like) ribosomes in cytoplasm. Have their own genomes (DNA)! Encode some RNAs, and proteins that
are translated on the organelle ribosomes.

Question 26

Eukaryote Diversity?

Answer 26

Animals, Plants and Fungi are only small parts. All lineages except those in red circles are groups of ‘Protists’ (note that this makes protists a paraphyletic group).

Question 27

Protists

Answer 27

Most of eukaryote diversity. Abundant in most ecosystems. Important photosynthesisers (‘algae’). The major predators of prokaryotes. Parasitic protists cause some major diseases (e.g. malaria).

Question 28

Origins of animals and fungi?

Answer 28

Phylogenies of molecular sequences show that animals and fungi are quite closely related but independently evolved from single- celled protistan ancestors).

Question 29

Plants evolved from what?

Answer 29

Photosynthetic ‘green algal’ protists.

Question 30

Do we still identity new kingdoms?

Answer 30

Scientists are still identifying many new ‘kingdom-level groups’ of microbes.