Midterm

Question 1

4 extinct Devonian lineages

Answer 1

cooksonia, horneophyton, rhynia, agalophyton

Question 2

order of relevant lineages and mya

bonus: remember the ones before and after?

Answer 2

COSD
cambrian 540
ordovician 490
silurian 440
devonian 410

before: proto-cambrian
after: carboniferous

Question 3

radiation lag-time hypothesis

Answer 3

WGD offers an opportunity for radiation, but it is not sufficient alone. there must also be an ecological opportunity or selective pressure.
related: 2 groups of organisms with the same WGD could evolve very different in different environments

Question 4

sequential replacement hypothesis

Answer 4

as a new lineage becomes more dominant, another loses dominance

OR
rise and diversification of a lineage coincides with the decline of another previously dominant group

Question 5

gene balance hypothesis

Answer 5

genes interact with each other so if a gene is duplicated but its interactors remain single copy, it could disrupt the balance of genes and their functions, leading to a loss in fitness since the organism can no longer carry out the more complex functions

Question 6

methods of gene duplication

Answer 6

WGD
transposans: transposable elements
retroduplication: reverse transcription
tandem duplication/aka unequal crossing over

Question 7

outcomes of gene duplication (5)

Answer 7

NEW: neofunctionalization (old copy retains original function)
REMAIN/SHARED: subfunctionalization / duplication-degeneration-complementation (DDC)
LOSS/NEGATIVE: pseudogenization & loss
REMAIN/POSITIVE: gene dosage effect: increased expression of that gene was beneficial, like if happened to be energy making gene that was duplicated
LOSS/NEGATIVE: gene balance (genes often interact, so if one is duplicated while its interactors remain single copy, it could reduce fitness of the genome)

Question 8

turnover-pulse hypothesis

Question 9

microphyll vs megaphyll origin

Answer 9

microphylls originated ONCE
while megaphylls originated MULTIPLE times

Question 10

enation theory

Answer 10

DE NOVO theory for origin of microphylls
gradual growing/elaboration of leafless axis, followed by de novo vascularization of the enation

Question 11

what are enations?

Answer 11

scaly, leaflike structures that lack vascular tissue, found in Rhynia

Question 12

Chert

Answer 12

silica based rock, preserves plant fungi fossils very well

Question 13

why was branching innovation important?

Answer 13

allowed for dev of leaves (leaves are modified branches)
allowed for dev of polysporangiaphytes
specialization of rep. forms like flowers
indeterminate growth, growth after releasing spores

Question 14

2 basic hypotheses for microphyll evo

Answer 14

telome theory (co-option)
enation theory (de novo)

Question 15

telome theory

Answer 15

co-option theory about evo of microphylls
2 parts: reduction , then sterilization
reduction: existing lateral branch systems were reduced until microphylls were left
sterilization: successive sterilization of sporangia

Question 16

2hypotheses for evo of megaphylls

Answer 16

overtopping: in dichotomously branching plants, one would become dominant while the other would stop growth upwards and stay lateral, begin webbing
planation: dichotomous branches turn at 90 degree angle, webbing

Question 17

webbing

Answer 17

growth of tissue between lateral branch veins - necessary for dev of megaphylls