Exam 2 (lect 9,11) Flashcards
angiosperm time
200-250 million years ago
sudden appearance of abundant/diverse in Cretaceous period
competitive exclusion hypothesis
why angiosperms exploded so quickly?
exploited more niches and compete with gymnosperms (only adapted to some enviros)
2 hypotheses for gymnosperm to angiosperm
- Anthophyte
2. Gnepine
anthophyte hypothesis
morphological data
gymnosperms NOT monophyletic group but para
Gnetophytes are most closely allied (no archegonia, pollen tube, xylem vessels)
gnepine hypothesis
DNA seq data
angio and gymno are both monophyletic groups
gnetophytes are most closely related to Pines)
no extant close relatives to angiosperms
convergent evol
oldest angiosperm lineage
amborella trichopoda
4 basal groups of angiosperm lineages
- amborella trichopoda
- nymphaeceae (water lilies + relatives)
- austrobaileyales (star anise + relatives)
- Mangoliidae (magnolias + relatives)
star anise
basal angiosperm austrobaileyales spice (chinese cooking) Pho shikimic acid is precursor for tamiflu (antiviral for influenza)
monocots diff from dicots
one cotyledon (seedling after germ) parallel leaf venation (grasses)
dicots diff from monocots
two cotyledons
netlike leaf venation
dicots phyletic group
para b/c basal and then eudicots
monocots phyletic group?
monophyletic
monocot v dicot diversity
mono ~90,000 species
eudictos ~200,000
monocot species ex
bamboos, birds of paradise, onions, grasses, frilium, orchids
inconspicuous flowers
- grasses and other wind pollinated (reduced)
- showy parts can be leaves and not petals (poinsettas w flowers in middle)
- catkins of trees (windpollination, small bunches)
- self fert species (weeds, don’t need to attract pollinator)
anther in life cycle
hold microsporocytes aka microspore mother cells
4 microsporangia in 2 pairs
split at junction when mature, spread pollen
microspore mother cells (2n) divide via meiosis to form tetrads of haploid pollen grains
ovary in angio life cycle
change
holds ovules, fleshy part
microsporangia in gymno v angio
gymno - borne in cones or stobili
angio - borne in flowers (anthers)
angiosperm pollen
3 cells! super reduced male gametophyte
gymno pollen had 5 cells
has tube cell and generative cell
megagametophyte angiosperm
heterosporous
4 megaspores with 3 degenerating
divides 3 times resulting in cell with 8 nuclei
cell walls form 7 cells
one cell has 2 nuclei (polar nuceli, binucleate)
NO archegonia
cell walls of female gametophyte angio
form 7 cells, 3 at the walls
3 antipodals
2 synergids (same end as micropyle, between is the egg cell)
fertiliz angio
after pollination, pollen germ and mature male gametophye grows to female gametophye
pollen tube grows through papilla on stigma on the style
pollen tube
tube nucleus controls growth
coils around ovule to reach micropyle
only living cells on the growing end
synergids
2 cells in the megagametophyte
secrete to direct pollen tube and rupture of pollen tube to release sperm
surround egg cell
on side with micropyle
double fertiliz
- one sperm nucleus fuses with egg (dip zygote)
2. other sperm nuc fuses with the 2 polar nuclei (triploid)
double fertiliz in gnetophyte
common in some but a bit different
ephedra
supports sister theory
anthophyte hypothesis
ovule develop
into seed
zygote to embryo (2n) = new sporophyte
embryonic leaves, cotyledon, primary root
ovary develop
sperm + 2 polar nuclei –> endosperm (3n) = nutrient tissue
fruit! seed coat
darwin abominable mystery
sudden rapid diversification of flowering plants
there is a long unrecorded history of angiosperms prior to creetaceous (not in fossil record)
new caledonia
island off the coast of australia
basal angiosperm (amborella trichopoda)
possible diversification here with no clear fossil record
rapid diversific due to pollinator
gaston de saporta
relationship with insect
explosion of pollinator and flowering at same time
co-radiation/co-diversification
flowers of basal angiosperms
radially symmetric
white or red/maroon
pollinators receive pollen as reward, rarely nectar (bees feed pollen to offspring)
petals/sepal indistinguishable
pollinator of basal angio
insect pollin occured early (ya happening in gymno)
diptera/flies first
beetle pollination
pollinator deceit
trick pollinators to come
heat attract pollinator to lay eggs
mimic insect to ‘mate’
cretaceous flower in fossil record
NJ, 90 mya fossil
similar to water lily (nymphaeaeceae)
beetle pollination involves insect entrapment
water lily pollination
2 openings
- female, beetles with pollen come and get trapped
- cover with male pollen and send off to pollinate other flowers
bat pollination syndrome
night, dull white or green
strong, fermented odors
ample nectar reward (larger animal)
desert SW, tropics
bee pollination syndrome
day, Yellow, blue, purple, UV patterns
light, sweet scent
pollen and nectar reward
coevolution btwn plants and pollinator
possible explanation of rapid angiosperm diversific
darwin’s orchid
gradual increase in nectar spur length due to ongoing coevol with same pollinator. 1:1 interaction
insect with hella long tounge
pollinator shifts
other theory of rapid angiosperm diversific
more often
animals are not a ubiquitous distrib
in part of species range, one pollinator becomes predominant and rapid evol for selection of the pollinator
punctuated change due to pollination shift
columbine genus (aquilegia)
nectar spurs. tested pollinator hypoth
pollination syndromes related to floral traits
nearly non-overlapping distrib of spur lengths among pollination syndromes
bee, humming bird, hawkmoth
hummingbird intermediate
between bee to hawkmoth
eurasia
cannot jump to optimal size for hawkmoth
bird necesary!!
pollinator limitation
shift reproductive strategy
wind pollination
selfing
switch to new pollinator
wind pollination syndrome
lots of flowers, many pollen grains, unisexual flowers (don’t have both parts), open habitats (before leaves on trees)
ragweed, oak, bamboo
self-pollination evol
from outcrossing
do not separate by time (dichogamy)
1. colonizing species ('weedy')
2. marginal habitats (edge of range, fewer plants and pollinators)
3. annual life history (one shot)
arabidopsis thaliana
