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Hilary Term 1 > The timing of angiosperms > Flashcards

The timing of angiosperms Flashcards

1
Q

Describe angiosperm characteristics

A
  • stigmatic pollen germination (pollen tube growth through carpel tissue)
  • stigma/style/ovary (carpel)
  • seeds (ovules) enclosed in carpel
  • carpel(s) becomes the fruit
  • ovules bitegmic
  • bithecate
  • highly reduced gametophytes
  • pollen mostly tectate/columellate
  • phloem and companion cells derived from same mother cell
  • mostly vessels rather than tracheids
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2
Q

Bithecate

A
  • two thecae
  • 2 sporangia in each thecae
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3
Q

Describe the pollen grain of an angiosperm

A
  • nucleated vegetative cell
  • exine
  • pore
  • 2x gametes
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4
Q

Describe pollen apertures

A
  • monosulcate
  • tricolpate
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5
Q

bitegmic

A

two integuments

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6
Q

Describe Dicotyledons

A
  • two cotyledons in embryo
  • primary root persists as a strong taproot, with similar secondary roots
  • herbaceous or woody
  • tricolpate pollen
  • ring of vascular primary bundles with cambium; secondary growth in stem diameter
  • stem differentiated into cortex and stele
  • net-veined broad leaves (seldom sheathing)
  • petiole bearing stipules
  • flowers: 4s or 5s
  • 78%
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7
Q

List some Dicotyledons

A
  • buttercups
  • carnations
  • magnolias
  • water lilies
  • cacti
  • Leguminosaea
  • Asteraceae
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8
Q

List some Monocotyledons

A
  • grasslike flowers
  • petaloid monocots
  • palm trees
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9
Q

List some grasslike flowers

A

grasses, sedges, rushes

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10
Q

List some petaloid monocots

A

orchids, daffodils, tulips, hyacinths, snowdrops

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11
Q

cotyledons

A

seed leaves

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12
Q

tricolpate

A

having three furrows or pores

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13
Q

net-veined leaves

A

pinnate or palmate

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14
Q

petiole

A

stalk

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15
Q

Describe Monocotyledons

A
  • one cotyledon in embryo
  • endosperm likely
  • primary root has short duration (replaced by adventitious roots; fibrous or fleshy bundle system)
  • mostly herbaceous (few arborescent)
  • monocolpate pollen
  • numerous scattered vascular bundles; no definite arrangement in ground parenchyma
  • cambium only exceptionally present
  • no differentiation into cortical and stelar regions in stems
  • leaves parallel-veined; oblong or linear and sheathing at the base
  • petiole seldom developed
  • stipules absent
  • threes or multiples petals
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16
Q

Describe Magnoliids - the basics

A

Dicots with monocot pollen

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17
Q

Summarise angiosperm phylogeny

A
  • extant gymnosperms
  • ANA
  • monocots
  • Ceratophyllaceae
  • Chloranthaceae
  • magnoliids
  • eudicots
18
Q

ANA

A
  • Amborellaceae
  • Nymphaeaceae
  • Austrobaileyales
19
Q

When did angiosperms radiate?

A
  • Cretaceous
  • 0-75%
20
Q

Describe pollen grain indicators

A
  • more widely dispersed
  • occur in greater quantities
  • higher preservation potential in a wider range of sediments
  • directionality
21
Q

Summarise the angiosperm fossil record

A
  • 144Mya: K-T boundary; no evidence
  • 135Mya: Valangian/Hauterivian; monosulcate pollen
  • 125Mya: Barremian; triaperturate pollen
  • 120Mya: Barremian/Aptian; leaves, flowers, carpels
22
Q

Describe the Cretaceous origin of angiosperms

A
  • rapid rise in angiosperms
  • steady increase in species numbers
  • stepwise increase in the number of morphological types
  • fossil record congruent with tree
  • absence of angiosperm pollen in pre-Cretaceous rocks
23
Q

Describe the congruence between fossil record and phylogenetic angiosperm tree

A

monosulcate magnoliid dicots appear first in fossil record, magnoliid flowers also present

24
Q

Describe Axelrod’s Hypothesis

A

Upland Hypothesis

25
Q

Describe the Upland Hypothesis

A
  • long cryptic period of evolution in the Triassic and Jurassic followed by major diversification in the Cretaceous
  • upland habitats lack depositional environments suitable for fossilisation
26
Q

Describe the Cretaceous Origin theory of Angiosperms

A
  • no pre-Cretaceous angiosperm fossils
  • appearance of flowering plants in the Cretaceous fossil record reflects the time of their appearance
27
Q

Describe the main approaches to understand the timing of Angiosperms

A
  • search for pre-Cretaceous fossils
  • find the closest relatives of angiosperms
  • Time Calibrated Phylogenies
28
Q

Archaefructus liaoningensis

A

A Late Jurassic Angiosperm

29
Q

Archaefructaceae

A
  • new basal angiosperm family
  • minimum age: 124.6 mya
  • A. liaonigensis, A. sinensis
30
Q

Describe the Late Triassic Crinopolles pollen group

A
  • reticulate tectum
  • monosulcate pollen with columellae
  • lamellated endexine
  • nexine consists of laminated endexine of uniform thickness as in gymnospermous pollen
  • convergent gymnospermous group or angiosperm stem relatives
  • Newark sequence of Virginia
  • enigmatic, disputed
31
Q

Describe endexine in Early Cretaceous and extant monosulcate angiosperms

A
  • lacking
  • nonlaminated, except under the sulcus
32
Q

Describe the ancestral tectum in angiosperms

A

unknown whether continuous or reticulate.

33
Q

Describe one use of phylogenetic trees

A

estimate stratigraphic incompleteness

34
Q

List the extant Spermatophyte lineages

A
  • Angiosperms = Magnoliophyta (370,000 species)
  • Cycads = Cycadophyta (120 species)
  • Conifers = Coniferophyta (600 species)
  • Gnetales = Gnetophyta (90 species)
  • Ginkgo = Ginkgophyta (1 species)
35
Q

List the extinct Spermatophyte lineages

A
  • Caytoniales
  • Bennettitales
  • Pentoxylon
  • Corystosperms
  • Glossopterids
  • et al
36
Q

Gnetales

A
  • Gnetum: 28 spp.
  • Ephedra: 35spp.
  • Welwitschia: 1 spp.
37
Q

Describe the Ephedra

A
  • functionally dioecious
  • male and female ‘flowers’
  • hermaphrodite unit with non-functional ovules
  • Switch Plant, source of ephedrine
38
Q

Describe the Gnetum

A
  • functionally dioecious
  • female ‘flowers’
  • male ‘flowers’ with non-functioning ovules
39
Q

Describe the Welwitschia

A
  • functionally dioecious
  • male flowers with non-functional ovule
40
Q

Siphonogamy

A

transfer of the male cells to the eggs via pollen tube

41
Q

Describe Gnetales nesting within extant monophyletic gymnosperms

A

8 gene dataset
- 4 plastid
- 3 mitochondrial
- 1 nuclear

42
Q

Angiosperms have a

A

long phylogenetic fuse

Hilary Term 1 (61 decks)

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