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Origins of Biodiversity > Plants > Flashcards

Plants Flashcards

Lectures 5-8

1
Q

Create a timeline of when certain plant types evolved.

A
  • First land plants 500 mya
  • First vascular plants 420 mya
  • First seed plants 360 mya
  • Gymnosperms 245 mya
  • Angiosperms 50 mya
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2
Q

How did colonisation of land plants allow for animal life?

A

They reduced the hostility of the land by:
- Increasing oxygen content
- Lowering temperatures
- Habitat provision both physically and via organic matter
- Food source provision

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3
Q

Describe the ancestral relationship of algae.

A
  • Closest related are the Charophytes and Embrophytes (land plants)
  • Then chlorophytes
  • Then red algae
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4
Q

What are the 9 traits charophytes and land plants share?

A
  • Both multicellular and eukaryotic
  • Chloroplasts with chlorophyll a & b shared in plants, green algae
  • Cell walls all contain cellulose with rosette complexes of 6 glucose molecules. Non charophyte algae have linear complexes.
  • Share enzymes that minimise loss of organic compounds using photorespiration. Other algae lack them.
    -Share the structure of flagellated sperm
  • Share the process of phragmoplast formation
  • Similar gene sequences
  • Presence of sporopollenin, a tough polymer protecting exposed zygotes
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5
Q

What are the 4 problems faced by plants colonising land?

A
  • Dessication
  • Lack of structural support
  • Lack of nutrients
  • Access and transport of water
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6
Q

How have land plants overcome these 4 problems?

A

Dessication: Cuticle layer over stomata that opens and closes based on hormones, allowing for gas exchange with minimal water loss
Lack of structural support: Thick cell wall with cellulose and lignin
Lack of nutrients: Root systems, symbiotic association with mycorrhizal fungi
Access and transport of water: Xylem and phloem

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7
Q

What are the 4 main traits land plants posses but charophytes do not?

A
  • Root Apical Meristem and Shoot Apical Meristem
  • Multicellular gametangia (organ/cell in which gametes are formed)
  • Alternation between haploid/diploid in life
  • Walled spores produced in sporangia which is only released in correct conditions.
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8
Q

What are cryptograms?

A
  • Lower plants
  • Seedless plants
  • Spore bearing plants
  • Non flowering plants
    Two types: Vascular (ferns etc) and non vascular (mosses etc)
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9
Q

What are bryophytes?

A

Small plants without vascular systems. They must be kept in moist environments due to the fact they rely on capillary movement of water.

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10
Q

Do bryophytes have leaves or roots?

A

They have neither. They are anchored by rhizoids and have microphylls instead of leaves.

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11
Q

How have some bryophytes evolved to grow up to 2m?

A

Mosses such as polytrichum has conducting tissues in the middle of their stems.

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12
Q

In moss, what produces sperm cells? What does it require?

A

The antheridia releases sperm cells and requires water to release them, such as raindrops.

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13
Q

What produces the egg cell in moss?

A

The egg cell is in the archegonium.

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14
Q

When does the life cycle become diploid?

moss

A

When the sperm and egg cell fuse within the archegonium, creating a diploid zygote.

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15
Q

Describe the process from the zygote to the release of haploid spores.

moss

A

Zygote undergoes mitosis, eventually growing into an embryo. It then forms capsules (sporangium) which undergo meiosis and release haploid spores.

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16
Q

How does the plant grow from these spores?

moss

A

They are blown in the wind away from the parent plant and grow into new male/female gametophytes.

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17
Q

Give a summary of liverworts.

A
  • Hepatophyta
  • Some have simple thallus
  • Similar lifecycle to moss with dominant gametophyte
  • Some have complex gamete bearing structures
  • Some reproduce asexually via budding
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18
Q

Give a summary of hornworts.

A
  • Antherocerophyta
  • Have simple gametophyte thallus
  • Each cell has single large chloroplast
  • Symbiotic with N2 fixing blue-green algae
  • Sporophyte has 2 horns, grows from base
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19
Q

What are vascular cryptograms and their characteristics?

A
  • Ferns, horsetails, club mosses
  • Have vascular tissue
  • Have dominant sporophyte
  • Reduced gametophyte known as a prothallus.
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20
Q

What is the first known vascular land plant?

A

Cooksonia, extinct since the Devonian 380 Mya.
- First plant to show apical dichotomous branching, maximising offspring from one fertilisation.

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21
Q

What is the dominant phase of a fern life cycle?

A

Sporophytic diploid.

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22
Q

What does the prothallus contain?

A
  • Archegonium (egg)
  • Anteridium (sperm)
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23
Q

What is dishiscence?

A

The process in which spores are ejected from sporangium. Dead water filled cells known as annulus loses water via evaporation, is distorted. Annulus peels back, air forms a bubble as water is lost and eventually snaps back and dislodges spores.

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24
Q

Describe the stages of a fern life cycle from a spore to an adult.

A
  • Spores are released from sporangium.
  • Germinate and grow into a prothallus, which houses both the archegonium (egg) and anteridium (sperm)
  • Sperm needs water to travel to egg, they fuse to become a diploid embryo.
  • Grow into adult sporophyte and release new spores after meiosis via dishiscence.
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25
Q

Give a summary of ferns.

A
  • Pteridophyta
  • Large pinnate leaves
  • Sporangia under leaf surface
  • Stem often a rhizome but true roots present.
  • Homosporous (not separated into M and F)
26
Q

Give a summary of whisk ferns.

A
  • Originated in Devonian, known as living fossils
  • Green stems, microphylls, rhizoids
  • Dichotomous branching
  • High chromosome number
  • Gametophyte stage is saprophytic meaning it obtains nutrients from decaying matter
27
Q

Give a summary of horsetails.

A
  • Sphenophyte
  • 4 appendages attached to the spore. In dry conditions this is unfurled, dispersing spores. In wet conditions it is tightly furled and spores are dispersed.
  • Dominant sporophyte, just like ferns
  • Silica rich
  • Distinct strobili (cones) that look very spiky all over
28
Q

Give a summary of club mosses.

A
  • Lycophyta
    -True leaves (megaphylls) and roots
  • Reproductive shoots on sporophyte modified into strobilus (literally just a pinecone)
  • Similar life cycle to fern
  • Some species heterosporous (like moss)
29
Q

What was the significance of the evolution of seedless vascular plants?

A
  • Development of vascular tissues, roots and leaves increased photosynthesis.
    = 5x less co2
    = global cooling and glacial formation
    = generally less death
30
Q

What are gymnosperms?

A

Cone bearing plants with enclosed ovules.

31
Q

Why are seeded plants so successful?

A
  • Embryo is protected from the environment
  • Seed can travel further from parent, increasing areas of colonisation.
  • Seeds retain viability for a long time and can hatch when conditions are right.
32
Q

What is the patterns of life cycles across evolution?

A

As evolution has continued, gametophytic stages have become less dominant - with ferns/seedless vascular plants having macroscopic gametophytes but seeded plants having microscopic gametophytes.

33
Q

Are seeded plants hetero or homosporous?

A

Hetero.
- However closest relative of seed plants are homosporous, meaning they evolved from homosporous ancestors.

34
Q

What determines whether a male or female gamete will be produced?

A

Megasporangia from megaspores = female
Microsporangia from microspores = male

35
Q

How are eggs protected in seeded plants?

A
  • Integuments, which are sporophyte tissue that envelopes the megasporangium (outer later of ovule that holds the egg).
  • Gymnosperms have 1
  • Angiosperms have 2 = more protection
36
Q

What are the main differences between seedless and seeded plants? (you can’t say seeds)

A

Seedless vs seeded:
Flagellated sperm/non flagellated
Require water to move/require animals or wind
Travel few cm/ travel vast distances
Sensitive to dessication/Survive long periods

37
Q

What is the first example of a species transitioning to seeds?

A

Archaeopteris:
- Fern like leaves
- No seeds
But!!!
- Heterosporous
- Up to 30m tall

38
Q

Give a summary of Ginkophyta

A
  • Phyla within gymnosperms
  • 1 extant species that is diecious.
  • Females produce rotting smelling fruit
39
Q

Give a summary of cyadophyta.

A
  • Phyla within gymnosperm
  • 100 extant species, all diecious
40
Q

Give a summary of Gnetophyta.

A
  • Phyla within gymnosperms
  • Closest relative to angiosperms
  • 69 extant species
41
Q

Give a summary of ephedra.

A
  • Phyla within gymnosperms
  • 40 extant species
  • Desert shrub
42
Q

Give a summary of conifera.

A
  • Phyla within gymnosperms.
  • 610 extant species, some up to 5000 yrs old.
43
Q

Are pines hetero or homosporous?

A

Hetero.

44
Q

Describe the process of growth in both male and female pine sporophytes.

A

Female: Ovulate cone contains many ovules which contain megasporocytes (2n), surrounded by a megasporangium and 1 integument.
Male: Pollen cone contains many microsporangia (2n) which undergoes meiosis 2 times to create many pollen grains (n, haploid, gametophytic)
- Megaspore and pollen then fuse

45
Q

What happens to the now fused gametes?

pines

A
  • Undergo meiosis twice to form 4 haploid cells
  • Only 1 survives as a megaspore (n)
  • Female gametophyte develops, containing 2/3 archaegonia which all form eggs.
  • Endosperm forms around now growing zygote, until they are grown enough to fall from the cone and become a new plant.
46
Q

What is an angiosperm?

A

A single phylum known as flowering plants that produce seeds contained within fruits (ovaries).

47
Q

What develops into the male and female gametes in angiosperms?

A

Male: The stamen (made of anther and filament) produce microspores that develop into pollen grains
Female: Carpel (made of stigma, style and ovary) produce megaspores that develop into female gametophytes.

48
Q

Describe the journey from a mature flower to an egg nucleus.

A
  • Ovary in mature flower holds 2n ovules that divide by meiosis. It holds a megasporangium that holds a megaspore.
  • It grows into an egg nucleus inside the female gametophyte after double fertilisation, and eventually into a new zygote.
49
Q

Describe the journey from a mature flower to a new pollen grain with new sperm. Do not describe double fertilisation.

A
  • An anther on the mature flower holds a microsporangium with holds diploid microsporocytes.
  • These have two cell types (generative and tube) and grow to form pollen grains in the stigma.
  • The generative cell divides to form 2 sperm cells during transit along the pollen tube.
  • Double fertilisation occurs, new zygote formed. baby plant.
50
Q

What is an endosperm?

A

Tissue that surrounds and nourishes the embryo in the seeds of flowering plants.

51
Q

What is double fertilisation?

A
  • Pollen tube discharges 2 sperm cells into egg sac.
  • 1 fertilises egg to form diploid zygote (baby).
  • 1 fuses with 2 polar nuclei to form a triploid cell. This divides to form the endosperm.
52
Q

What are the benefits of double fertilisation?

A
  • Co ordinates embryogenesis and endosperm formation
  • Conservation of resources
53
Q

What is a cotyledon? How many do monocots/dicots have?

A

An embryonic leaf in seed-bearing plants, one or more of which are the first leaves to appear from a germinating seed.
- Monocots have 1, dicots 2.

54
Q

What are the differences between monocot/dicot leaves?

A

Monocot leaves: Parallel veins
Dicot leaves: Net/web like veins.

55
Q

What are the differences between monocot/dicot stems?

A

Monocot - Scattered vascular tissue
Dicot - Vascular tissue arranged into rings

56
Q

What are the differences between monocot and dicot roots?

A

Monocot - Fibrous root systems, no main root
Dicot - Have a taproot, a main root with smaller ones coming off it.

57
Q

What are the differences between monocot and dicot flowers and pollen?

A

Monocot - Pollen grain with one opening on a flower with organs of 3x.
Dicot - Pollen grain with three openings with organs in 4 or 5x.

58
Q

How to monocot root caps develop, and what is their purpose?

A
  • Functions as a crash helmet, helping to force its way through soil
  • Constantly replenished with new cells and protects stem cells in root
59
Q

Do all dicots share an ancestor?

A

No, they are paraphyletic.

60
Q

Give a summary of bennetittales.

A
  • Extinct
  • Closer to angiosperm
61
Q

Give a summary of Archaefructus sinensis.

A
  • Transition fossil, around 125 mya
  • Anthers but no pets or sepals
  • Bulbous structure alongside being found with fish bones indicates aquatic species

Origins of Biodiversity (9 decks)

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