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biology > Lecture 21 - Plant Diversity (Part 1) > Flashcards

Lecture 21 - Plant Diversity (Part 1) Flashcards

1
Q

Describe the greening of Earth

A
  • Cyanobacteria emerged ~1.2 billion years ago
  • Other fungi, algae, “plants” joined ~700 million years ago
  • Earliest evidence of trees in Megouasag (Micmac for “red cliffs”)
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2
Q

Describe the earliest evidence of trees in Megouasag (Micmac for “red cliffs”)

A
  • Archaeopteris is a historical tree
  • Fossil beds are ~380 million years old
  • Development of lignin
  • Had fern-like leaves
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3
Q

Describe how plants are part of Archaeplastida

A

• Unicellular, multicellular and/or colonial members
• 2 main clades
1. Green algae
2. Red algae
• Use of photosynthetic pigments allows for the adaptation to different
environments and also identifies members

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4
Q

What are the 2 main clades part of Archaeplastida?

A
  1. Green algae (paraphyletic)

2. Red algae (monophyletic) -> have a holdfast, stipe, blade

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5
Q

Many plant traits appear in algae, some of which were acquired independently. What are the traits?

A
  • Multicellularity
  • Photosynthetic pigments (i.e. chlorophylls)
  • Cell walls composed of cellulose
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6
Q

What is the 4 points of evidence that Charophytes (Supergroup Archaeplastida, Green algae) are closest relatives to terrestrial plants?

A
  1. Rings of cellulose-synthesising proteins
    • Many algae produce cellulose in cell walls, but charophytes and land
    plants have distinctive circular rings of proteins in the plasma membrane
  2. Flagellated sperm
    • In plant species that have flagellated sperm, they most resemble the
    sperm in charophytes compared to other algae
  3. Formation of phragmoplast
    • Microtubules and associated proteins present in charophytes and land
    plants after cytokinesis, guiding the assembly of cell plate formation

• Molecular analyses of nuclear, mitochondrial and chloroplast DNA also support this

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7
Q

Why is moving to land beneficial for plants?

A
  • Sporopollenin is a polymer that prevents desiccation

* More unfiltered sunlight, carbon dioxide, nutrients in soil -> life is good!

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8
Q

Sporopollenin

A

is a polymer that prevents desiccation

• Common in charophytic algae living at the edge of shallow ponds

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9
Q

Why does moving to land for plants have challenges?

A
  • Water is scare, harder to disperse sperm

* Have to grow against gravity

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10
Q

What are the wide range of adaptions to allow for survival on land for plants?

A
  • Accessory pigments to help with UV protection, antioxidant effects
  • Cuticle
  • Stomata (pores)
  • Formed SYMBIOTIC relationships with fungi (roots did not immediately happen)
  • Developed MERISTEMS to allow for vertical growth
  • Alternation of generations life cycle
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11
Q

Analysis of fossilized spores shows…

A

plants colonized land ~450 million years ago

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12
Q

Plants can be broadly classified based on the presence of what?

A

vascular tissues

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13
Q

Which are Non-vascular plants?

A
  • Liverworts
  • Mosses
  • Hornworts
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14
Q

What falls under Vascular plants?

A
  • Seedless vascular plants

* Seed plants

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15
Q

Which are Seedless Vascular Plants?

A
  • Lycophyta (club mosses, spike mosses, quillworts)

* Monilophytes (ferns, horsetails, whisk ferns)

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16
Q

Which are Seed Plants?

A
  • Gymnosperms (ginkgos, cycads, gnetophytes, conifers)

* Angiosperms (flowering plants)

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17
Q

Describe the Haplo-Diplontic Life Cycle or the Alternation of Generations of Plants

A

1) Gametophyte produces haploid gametes (1n) via mitosis
2) Two gametes (1n) come together via fertilisation to produce a diploid zygote (2n)
3) The zygote (2n) develops into the multicellular sporophyte
4) The sporophyte (2n) produces unicellular haploid spores (1n) by meiosis
5) The spores (1n) develop into multicellular haploid gametophytes (1n)

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18
Q

Bryophytes have a dominant haploid or diploid stage?

A

haploid stage!

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19
Q

Describe phylogenetic analyses that suggest bryophytes diverged early in plant
lineage evolution

A

• Earliest spores of plants (450-470 million years ago) more similar to
liverwort spores
• ~430 million years ago spores similar to mosses and hornworts showed up
in the fossil record

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20
Q

Describe the Bryophyte gametophytes (gamete producing bodies)

A 
• Haploid (1n), dominant stage
• Protonema 
• Gametophore
• Rhizoids
• Gametangia
    - Archegonia 
    - Antheridia
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21
Q

Protonema

A

threadlike filaments that develop into “buds” which grow via a meristem to produce the gametophores
- part of the bryophyte gametophytes (gamete producing bodies)

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22
Q

Gametophore

A

“gamete bearer”, produces gametes via mitosis

- part of the bryophyte gametophytes (gamete producing bodies)

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23
Q

Rhizoids

A

“root-like” filaments that anchor the gametophyte

- part of the bryophyte gametophytes (gamete producing bodies)

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24
Q

Gametangia

A

produces the gametes

- part of the bryophyte gametophytes (gamete producing bodies)

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25
Q

Archegonia

A

female, produces the egg

  • part of gametangia
  • part of the bryophyte gametophytes (gamete producing bodies)
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26
Q

Antheridia

A

male, produces sperm

  • part of gametangia
  • part of the bryophyte gametophytes (gamete producing bodies)
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27
Q

Gametophytes

A

gamete producing bodies

- part of bryophyte

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28
Q

Describe Bryophyte sporophytes (spore producing bodies)

A
  • Diploid (2n), reduced stage
  • Seta
  • Foot
  • Capsule
  • Peristome
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29
Q

Sporophytes

A

spore producing bodies

- part of Bryophytes

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30
Q

Seta

A

stalk supporting the sporangium

- part of Bryophyte sporophytes

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31
Q

Foot

A

absorbs nutrients from the gametophyte, supports the seta

- part of Bryophyte sporophytes

32
Q

Capsule

A

sporangium, produces spores via meiosis

- part of Bryophyte sporophytes

33
Q

Peristome

A

“teeth” on the capsule to regulate spore dispersal

- part of Bryophyte sporophytes

34
Q

Bryophytes have a dominant…

A

gametophyte stage

35
Q

Describe the Haplo-Diplontic Life Cycle or the Alternation of Generations of Bryophytes

A

1) Spores (1n) develop into threadlike protonema
2) Protonema (n) produces “buds” the develop into gametophytes (n)

Gametangia
• Antheridia -> male, sperm
• Archegonia -> female, egg

3) Sperm must swim through water to reach the egg
• Gametes produced via mitosis

4) Zygote develops into a sporophyte embryo (2n)
5) Sporophyte grows a seta that emerges from the archegonium
6) Attached by the foot, the sporophyte (2n) remains nutritionally dependent on the female gametophyte (n)
7) Meiosis occurs in the 2n capsule, producing spores

36
Q

Bryophytes are…

A

ecologically important

37
Q

Describe Bryophytes

A
  • Common in moist forests and wetlands, moist bare soil
  • Many ASSOCIATE with NITROGEN-FIXING BACTERIA
  • Can survive HARSH environments (cold, dry)
  • Some Sphagnum moss species COMPRISE PEAT

• Many bryophyte species also have a MEDICINAL or CULTURAL importance in many Indigenous nations
- Bandages for wounds, baby diapers!

38
Q

What is the 5 pieces of evidence that Byrophytes are ecologically important?

A
  1. Help retain MOISTURE!
  2. Help retain NITROGEN within the environment!
  3. Can TOLERATE complete water loss and can re-establish when moisture returns -> poikilohydric!
  4. Some Sphagnum moss species comprise PEAT!
  5. Many bryophyte species also have a MEDICINAL or CULTURAL importance in many Indigenous nations
    • Bandages for wounds, baby diapers!
39
Q

Describe how some Sphagnum moss species comprise peat

A

• Preserves organisms from decaying due to the low temps, pH, and oxygen
levels of peatlands

  • Important fuel source (Finland and Ireland uses a lot of it!)
  • Horticultural nutrient to help retain moisture in soils
  • Carbon sink -> 30% of the world’s carbon is stored in peatlands comprising 3% of Earth’s surface
40
Q

Describe what the seedless vascular plants were the first to

A
  • First to grow tall due to the rigid structure of vascular tissues
    • Arose ~425 million years ago
41
Q

Compared to nonvascular plants, vascular plants (these new plants) now had what?

A

• Branched sporophytes now dominant stage
• Not nutritionally dependent on the gametophyte
• Still lack true roots
• Vascular tissues
- Xylem
- Phloem

42
Q

Over time, sporophytes and gametophytes evolved to be of similar size, eventually leading to…

A

a larger sporophyte and reduced gametophyte that we see in larger, present
day plants

43
Q

Xylem

A

water transport, structural support

44
Q

Phloem

A

nutrient transport

45
Q

What is the Fern Life Cycle or Alternation of Generations (Haplo-diplontic)?

A

1) Sporangia release spores (n).
- Spores develop into a bisexual
photosynthetic gametophyte

2) Each gametophyte (n) produces
antheridia and archegonia via
mitosis. 
- Sperm usually fertilises
the egg of another gametophyte

3) Sperm uses flagella to swim
to the egg, attracted via positive
chemotaxis to the archegonium

4) Zygote (2n) develops into a new sporophyte (2n), which grows out of the archegonium of the parent gametophyte

5) Sporophytes (2n) produce sori,
clusters of sporangia (2n) which will
produce spores via meiosis

46
Q

What are the adaptations that Seedless Vascular Plants evolved?

A
  1. Transport of nutrients in vascular tissues
  2. Evolution of roots
  3. Evolution of leaves
  4. Shoot system
  5. Root system
47
Q

Describe the transport of nutrients in vascular tissues

A
  • Xylem -> water conducting tissues
  • Composed of tracheids and vessel elements, strengthened by lignin
  • Phloem -> transports photosynthates
  • Composed of sieve tube elements and companion cells
48
Q

What does the transport of nutrients in (seedless) vascular tissues allow for?

A
  • Allows plants to grow tall and still get nutrients to leaves
  • Allows plants to outcompete shorter plants for light
49
Q

Describe the evolution of roots in seedless vascular plants

A
  • Vascular tissues are also found in roots

* Roots absorb water and nutrients from the soil, anchors the plant

50
Q

Describe the evolution of leaves in seedless vascular plants

A
  • Leaves increase surface area for photosynthesis
    • Megaphylls
    • Megaphylls
51
Q

Megaphylls

A

larger, more evolutionarily advanced

- leaves that increase SA for photosynthesis

52
Q

Microphylls

A

smaller, supported by a single strand of vascular tissue (Lycophytes)
- leaves that increase SA for photosynthesis

53
Q

What is the Shoot System of Seedless Vascular Plants comprised of?

A

is comprised of the above ground organs of the plant (leaves, stems)

54
Q

What is the Root System of Seedless Vascular Plants comprised of?

A

is comprised of the below ground organs (roots)

55
Q

How are seedless vascular plants diverse?

A
  1. Modified leaves allow for reproduction
  2. Most seedless vascular plants are homosporous
  3. Some seedless vascular plants are heterosporous
56
Q

In seedless vascular plants, modified leaves allow for reproduction. Explain

A

• Sporophylls bear sporangia

  • Fern sporophylls produce SORI (sing. sorus)
  • Lycophytes (clubmosses and allies) produce STROBILI (sing. strobilus), which are little “cones”
  • Angiosperms (covered later) have modified sporophylls called carpels and stamens
57
Q

In seedless vascular plants, most seedless vascular plants are homosporous. Explain

A
  • One type of sporangium that produces one kind of spore
  • Develop into a bisexual gametophyte
  • Ex. Ferns
58
Q

In seedless vascular plants, some seedless vascular plants are heterosporous. Explain

A

• Two types of sporangia that produce two kinds of spores
- Megasporophylls
- Microsporophylls
• Develop into single sex gametophytes

59
Q

Describe the two types of sporangia that produce two kinds of spores

A
  • Megasporophylls (“female spore leaves”) which produce megasporangia (“female spore bearing structures”)
  • Microsporophylls (“male spore leaves”) which produce microsporangia (“male spore bearing structures”)
60
Q

Seedless vascular plants evolved many adaptations like what?

A
  • Lycophyta

- Monilophyta

61
Q

Describe Lycophyta

A
  • Club mosses, spike mosses, quillworts
  • Most ancient group
  • Carboniferous period (359-299 million years ago)
  • Used to be massive (2m wide!), but changing drier climate meant only the small ones were able to survive
62
Q

Describe Monilophyta

A
  • Ferns, horsetails, whisk ferns
  • Devonian origins
  • Ferns are most diverse, ~12,000 species
  • More closely related to seed plants than lycophytes
  • Have leaves, roots
  • ~15 species of horsetails exist today (Equisetum spp.)
  • Whisk ferns (Psilotum sp.) are considered “living fossils”
63
Q

Describe Spike Moss

A

Phylum: lycophyta*

Habitat: marshy areas or as submerged aquatic plants*

Sporophytes: upright stems

Leaves: many small leaves*

Types of sporangia: heterotrophs

64
Q

Describe Quillwort

A

Phylum: lycophyta

Habitat: aquatic

Sporophytes: *

Leaves: single sporophyll

Types of sporangia: heterosporous*

65
Q

Describe Club Moss

A

Phylum: lycophyta*

Habitat: *

Sporophytes: horizontal stems

Leaves: strobili

Types of sporangia: homosporous

66
Q

Describe Fern

A

Phylum: monilophyta

Habitat: tropical to temperate

Sporophytes: megaphylls

Leaves: large leaves called fronds, often divided into leaflets*

Types of sporangia: most homosporous

67
Q

Describe Horsetail

A

Phylum: monilophyta*

Habitat: marshy places & along streams*

Sporophytes: vegetative & reproductive stems

Leaves: rings of leaves

Types of sporangia: homosporous with cones releasing spores that typically give rise to bisexual gametophytes*

68
Q

Describe Whisk Fern

A

Phylum: monilophyta*

Habitat: species of the genus Timesipteris, closely related to whisk ferns are found only in the South Pacific*

Sporophytes: dichotomously branching, lacks roots

Leaves: reduced

Types of sporangia: homosporous

69
Q

Describe the process of Homosporous spore production (most seedless vascular plants)

A

sporangium on sporophyll -> single type of spore -> typically a bisexual gametophyte -> eggs OR sperm

70
Q

Describe the process of Heterosporous spore production (all seed plants) FOR EGGS

A

MEGAsporangium on MEGAsporophyll -> MEGAspore -> female gametophyte -> eggs

71
Q

Describe the process of Heterosporous spore production (all seed plants) FOR SPERM

A

MICROsporangium on MICROsporophyll -> MICROspore -> male gamete -> sperm

72
Q

Cuticle

A

waxy layer on the outer epidermis to help prevent desiccation

73
Q

Stomata (pores)

A

allow exchange of carbon dioxide and oxygen

• Can close in periods of hot, dry conditions to prevent water loss

74
Q

What did development of lignin allow for?

A

allowed for super rigid cell walls to support upward growth

- in Megouasag (Micmac for “red cliffs”)

75
Q

What is the function of having fern-like leaves?

A

surface area allowed more efficient photosynthesis to compete with early plants
- in Megouasag (Micmac for “red cliffs”)

76
Q

peat

A

• Preserves organisms from decaying due to the low temps, pH, and oxygen levels of peatlands

- Important fuel source (Finland and Ireland uses a lot of it!)    - Horticultural nutrient to help retain  moisture in soils    - Carbon sink -> 30% of the world’s carbon is stored in peatlands comprising 3% of Earth’s surface

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