Major Evolutionary Transitions

Question 1

Describe a major evolutionary transition

Answer 1

• a change in the way information is passed from generation
• coined by Maynard-Smith and Szathamry

Question 2

What can a major evolutionary transition lead to?

Answer 2

a transition in individuality: a new kind of individual from a group of previously independent individuals

Question 3

Major evolutionary transitions comprise a

Answer 3

disruption to the gradualism of evolution.

Question 4

Describe some major evolutionary transitions

Answer 4

• independent genetic replicators to chromosomes
• prokaryotic to eukaryotic cells
• sexual reproduction from asexual clones
• multicellularity from protists
• eusociality
• language

Question 5

Describe the production of the heterotrophic protoeukaryote

Answer 5

• invagination of the plasmamembrane to create the endomembrane system of the endoplasmic reticula, nuclear envelopes and nucleus
• endosymbiogenetic acquisition of a free-living facultatively anaerobic alphaproteobacterium by an anaerobic archaeon host

Question 6

Describe the protoeukaryote

Answer 6

cells working together to achieve a common goal

Question 7

Describe the formation of the ancestral autotrophic eukaryote was formed

Answer 7

• secondary acquisition of a photosynthetic cyanobacterium
• conversion of this into a photosynthetic plastid

Question 8

Describe the major evolutionary transition of sexual reproduction from asexual clones

Answer 8

• allows the separation of the germline from the somatic cells
• allows for crossing over and recombination
• sterilises some cells
• requires a mated pair

Question 9

Describe the major evolutionary transition of multicellularity from protists

Answer 9

• capable by plants, fungi and animals
• ancestors undergo clonal group formation
• e.g. animals, fungi, red algae, gren plants, volvocine algae, brown algae, ciliates. cyanobacteria, actinobacteria and methanobacteria

Question 10

Describe subsocial multicellularity

Answer 10

• stay with their parent
• clonal relatedness
• e.g. Homo sapiens

Question 11

Describe semisocial multicellularity

Answer 11

• cells formed are potentially non-clonal
• relatedness <1
• facultatively multicellular
• slime moulds
• Portuguese man o’war

Question 12

Describe semisocial slime moulds

Answer 12

• spore forming (reproduction and dispersal)
• stalk (sterile, evolutionary dead-end)
• not multicellular organisms
• not obligate: can exist as unicellular amoeba

Question 13

Describe semisocial Portuguese man o’war

Answer 13

• cell colony and differentiated to a degree
• not clonal
• tentacles have a different genetic lineage

Question 14

Describe complex multicellularity

Answer 14

• obligate
• requires subsocial development, alongside a single celled stage.

Question 15

Describe the 5 non-clonal “multicellular” lineages

Answer 15

facultative multicellular organisms.

Question 16

Describe the 12 clonal multicellular lineages

Answer 16

• 3 facultative
• 9 obligate

Question 17

Describe eusociality in Blattodea

Answer 17

• Hymenopteran social cockroaches
• formation of nests, containing a ventilation shaft, chimney, fungus combs, nursery galleries and the royal cell
• individuality has transformed from solitary to colony living

Question 18

Describe the process of a major evolutionary transition

Answer 18

• solitary individuals coming together to form a cooperative group
• cost
• occurs at all levels of group complexity
• groups sometimes manage to achieve a new higher level of individual

Question 19

Describe sociality in Suricatta suricatta

Answer 19

• colonial living
• co-operative lifestyle creates high promiscuity; low intragroup relatedness of siblings
• as promiscuity increases from 1-20, sibling relatedness falls from 0.5 to 0.26
• decreases the r parameter of Hamilton’s rule
• less benefit (less selection towards) acting co-operatively
• eusociality is not achieved

Question 20

How is promiscuity measured?

Answer 20

number of mates

Question 21

Describe a driving factor towards the achievement of a major evolutionary transition

Answer 21

Number of mates

Question 22

How did the Hymenopterans achieve eusociality?

Answer 22

intragroup selection (that is governed by Hamilton’s rule) has been eliminated

Question 23

Describe the elimination of intragroup selection

Answer 23

can occur by either the alignment of genetic interest through sufficient relatedness, or through the repression of competition

Question 24

How is competition repressed?

Answer 24

• selection against mutants: genetic clonality eliminates selection
• intertwining fates of cells: e.g. parliament of genes repressing transposons

Question 25

co-operative group formation mechanism is

Answer 25

a crucial and profound factor in selection elimination, and major evolutionary transition.

Question 26

Describe subsocial colonies

Answer 26

• nests form from queens
• daughter offspring of 0.5 relatedness are the first helpers
• siblings stay in the group
• sibling relatedness is the same as offspring relatedness
• depend on promiscuity

Question 27

Describe honeybee (Apis mellifera) colonies

Answer 27

• queen has multiple mates
• secondary order of workers are sterile
• ancestors were monogamous: polygamy evolved later (sterile ancestors could not reinnovate fecundity)

Question 28

Describe semisocial colonies

Answer 28

• siblings of relatedness <0.5, or unrelated individuals of negligible relatedness come together to forma nest
• relatedness of nephews and nieces is less than the relatedness of offspring

Question 29

Describe the major evolutionary transition to eusociality with respect to subsocial and semisocial colony development

Answer 29

• only ever occurred in lineages with a strictly monogamous ancestor
  polygamous ancestor have remained solitary.

Question 30

Sphecid, Polistine and vespine wasps, and the Halictine and Corbiculate bees,