Plant Diversity Flashcards
1
Q
Bryophytes
A
- Seedless and non-vascular
- Earliest diverged Embryophytes arose ~475-430 million years ago
- Mosses have the greatest extant diversity (~10,000 species)
2
Q
Gametes are “soft” so they require:
A
water for finding each other and for fusion/fertilization and are difficult to disperse when relying on both water and compatible mate
3
Q
spores are “hard” therefore:
A
- Easy to disperse (promotes outcrossing and reduces competition with parent)
- Greater production of spores leads to a greater chance of having a nearby mate and water for the new gametophytes = higher reproductive potential and expansion/invasion of territory
4
Q
Mosses
A
- highly dependent on water
- Lack of vasculature keeps them close to their water sources (thrive in rainforests and marshy or wet areas)
- Serve many purposes in the ecosystem (water retention, insulation, carbon sink, nutrient balance)
- Various anthropomorphic uses (fuel source, packing/storage material, medicinal properties)
5
Q
Poikilohydry
A
- Bryophytes are known as poikilohydric meaning they have little control over their water content (Poikilo = variable, Hydry = water)
- Great at absorbing water and surviving in very wet/moist conditions but have poor control over water loss when the surrounding area is drying out
- Basically, they do not restrict water loss
6
Q
Bryophytes are Drought Tolerators
A
- May not be able to be active during dry periods but can withstand periods of drought and then resume when moisture returns
7
Q
Drought Tolerator
A
maintain cell wall elasticity and control osmotic balance
8
Q
Drought Avoider
A
Actively resist water loss
9
Q
Moss Life Cycle
A
- Life cycle is highly dependent on water (required for gamete release/ejection and fertilization)
- Sporophytic stage is retained on the female gametophyte
- Spore dispersal is aided by a lengthening of the sporophyte
- Spores are released when dry and carried by the wind
10
Q
Moss Reproductive Organs
A
- Gametangia are the gamete producing organs
- Archegonia produce egg cells
- Antheridia produce sperm cells
- The embryo develops into the sporophyte which gives rise to the sporangia (the spore producing organs)
11
Q
Moss - Protonema
A
- Instead of 1 spore germinating to form a single gametophyte, moss spores germinate to develop a branched, filamentous, multicellular network = protonema
- Single protonema can give rise to several buds which develop into individual Gametophytes
- This clustering of Gametophytes helps provide structural support and increases the amplification of offspring from a single successful reproductive event
12
Q
Moss Life Cycle Key Points
A
- Water is critical to complete the life cycle
- Gametophyte (n) is the dominant phase
- Eggs are produced in Archegonia
- Sperm are produced in Antheridia
- Flagellated sperm, after being dispersed by active water, swim to the egg
- Sporophyte retained on the female gametophyte
- Sporangia produce haploid spores through meiosis -> dispersed (when dry) by wind
- Spores are coated with sporopollenin
- Protonema produces multiple buds that develop into gametophytes
13
Q
Bryophyte Importance
A
- Reduce soil erosion along streambanks, aid in the retention of water in tropical forests and soil formation in the desert and polar regions, and can reduce nutrient loss from soils
- Some have medicinal properties
- Can be grown in bioreactors for harvesting of recombinant proteins
- For studying plant evolution, development and physiology
- For soil and garden water rentention
14
Q
Bryophyte Summary
A
- Non-vascular plants
- Have no control over water loss = Poikilohydric
- Water is critical for survival and reproduction
- Gametophyte is the dominant phase
- Flagellated sperm swims to the egg
- Sporophyte retained on the female gametophyte
- Key members of the ecosystem
- Various anthropomorphic uses
15
Q
Seedless Vascular Plants
A
- Arose ~425 million years ago
- First to develop vasculature and true leaves
- The sporophytic phase becomes dominant
- Pteridophytes (ferns and allies) have the greatest extant diversity (~9,000 species)
16
Q
Major Adaptations Added With Seedless Vascular Plants
A
- Vascular tissue
2. Root system
17
Q
Vasculature
A
- Vascular tissue evolved in a series of gradual steps with progressively more lignin deposition
- Provide an increasing level of structural support and efficient water transport
- Main support comes from the lignification of the secondary cell walls (Xylem and Sclerenchyma)
- Allowed for improved conductance of water and continued upright growth
18
Q
Vasculature in Ferns and Seed Plants = Tracheids
A
- Closely packed elongated cells
- Cells are dead at maturity
- Thickened secondary cell walls with lignin deposits have gaps = Pits
- Better structural support
19
Q
Vasculature in Angiosperms = Vessels
A
- Similar to tracheids, but shorter and wider
- Both walls have gaps, more efficient water transfer through the Pits
20
Q
Non-vascular plants only possessed rhizoids
A
which act to anchor the plant but do not behave as true roots
21
Q
Often >50% of overall biomass is below
A
ground level in vascular plants
22
Q
Root Systems
A
- Can act as a nutrient reserve and as a backup plant stock
- The use of stomatal conductance and transpiration allows for negative pressure to create a vacuum to draw up water from the roots into the stem tissue
- ~90% of the water absorbed by the root is lost through transpiration but allows for sufficient water to be translocated throughout the plant and intake of necessary soil nutrients
- Drought avoiders
23
Q
Evolution of Microphylls (an offshoot of the main vertical axis)
A
- Vasculature largely exists as a single strand (xylem, phloem, sclerenchyma, and parenchyma in one bundle)
- Modification of stems to increase photosynthetic surface area
- Narrow leaves with one strand vasculature (vein)
24
Q
Lycophytes (Club Mosses, Spike Mosses and Quillworts)
A
- Highly diverse around 350 mya = Carboniferous Period
- Present-day lycophytes are small and grow on forest floors in moist conditions
- Some are poikilohydric
- All have microphylls
25
Q
Carboniferous Period (350-300mya)
A
- Oxygen levels raised to ~30% (currently ~21%)
- Microphylls and megaphylls evolved
- Tree sized Lycophyte forms inhabited swamps
- Arthropods are still the dominant animal on land
- High oxygen levels allowed for massive arthropods (2m in length)
- First seed plants begin to emerge
26
Q
Evolution of Megaphylls
A
- Broader leaf with multiple veins within a web of photosynthetic tissue
- Much greater photosynthetic area with efficient nutrient transfer capabilities
- Shared among all of the Pteridophytes and the Seed plants
27
Q
Pterophyta (Ferns)
A
- The most abundant group of seedless vascular plants
- Familiar plant body is sporophyte stage (2n)
- Finely divided leaves (fronds)
- Sporangia often grouped together as Sori on lower surface or margins of fronds
- Spores develop into gametophytes
- Antheridia and archegonia develop on the underside of gametophytes
- Have well-developed vasculature and roots
- Can survive without continuous moisture
- Drought Avoiders
28
Q
Sporangia
A
- Found on the underside of the fern frond
- Groups of sporangia known as Sori
- Often have a protective covering while developing known as an Indusium
29
Q
Fern Life Cycle
A
- Sporophyte phase is dominant
- Incredibly high production of spores within the sporangia
- Gametophytes produced are often hermaphroditic
- Archegonia + Antheridia
- The sporophyte is retained on the gametophyte but quickly outgrows it
30
Q
Fern Life Cycle – Key Takeaways
A
- Single spore develops into a single gametophyte
- Gametophyte is photosynthetic
- Archegonia are often formed first = dictate neighbouring gametophyte development
- Antheridia release flagellated sperm
- Sporophyte lives for a long time and produces new fronds, most will produce sporangia
31
Q
Importance of Seedless Vascular Plants
A
- Well equipped to survive in the understory, establish ground cover
- Common in tropical areas
- Can be used in cooking
- Efficient N2 fixation = biological fertilizer in rice fields
- Medicine and remedies for kidney problems
- Ornamental plants
32
Q
Seedless Vascular Plants –Summary
A
Lycophytes and Pterophytes
- Have vasculature, plants are larger and upright
- Sporophytes dominant
- Sporophytes produce plant bodies with leaves and roots
- Small gametophytes (most often hermaphroditic) -> Antheridia and Archegonia
- Produce flagellated sperm
- Sporophyte initiated on the gametophyte but quickly outgrows it
- The gametophyte is often retained
- Very diverse and persistent
- Greatest diversity during the Carboniferous period
33
Q
Land Plant Classification
A
Nonvascular plants: lack vascular tissue, gametophyte (haploid) generation is dominant = Bryophytes (mosses)
Vascular seedless plants: well-developed vascular tissues, do not make seeds, sporophyte (diploid) generation is dominant = Lycophytes and Pterophytes
Vascular seed plants: well-developed vascular tissues and produce seeds, diploid generation is dominant = Gymnosperms and Angiosperms
34
Q
Selection for Sporophytes – Genetic Load
A
- Mutations constantly arise (necessary for variation, most are deleterious)
- Haploids have no chance of complementing deleterious mutations (mutations have a higher chance of affecting fitness)
- Diploids have more room to accumulate mutations (complemented by sister chromosome (masking))
- The haploid phase helps purge deleterious mutations and allows favourable mutations to be passed on
35
Q
Vascular Seed Plants
A
- Gymnosperms and Angiosperms
- Arose ~300 mya
- Account for the vast majority of all extant species
- Dominate the land
- Dominant phase = sporophyte
- Gametophyte extremely reduced
36
Q
Major Reproductive Changes as Seed Plants Dominate Land
A
Non-vascular and seedless vascular vs. vascular seed plants
- Both have pores with a resistant coat for protection
- Spores are released to produce gametophyte vs not released to produce gametophyte
- Spores identical in shape/size vs not identical, male and female
- Flagellated sperm vs non-flagellated sperm
- External water required for fertilization vs not required for fertilization
- Embryos not protected vs embryos protected (seeds)
37
Q
Gymnosperms ~1000 species
A
- Naked seed plants (Gymno = naked, Spermae = seed)
- Produces reproductive organs that contain the haploid spores = Male: microspores, Female: megaspores
- Fertilized ovule becomes the seed
- Seeds desiccate to attain dormancy prior to dispersal
38
Q
Pollen
A
male gametophyte developed from the microspore on the sporophyte prior to dispersal
39
Q
Ovule
A
Sporophyte structure that houses and protects the megaspore that gives rise to the female gametophyte
40
Q
Conifers: Cone Bearers
A
- Reproductive structures/organs that contain the haploid spores = cones
- Spores are not released: Pollen (male gametophyte) is released
- Male cones house the Microspores = produce male gametophytes (pollen)
- Female cones house the Megaspores = produces female gametophytes inside the ovule
41
Q
Conifer Life Cycle
A
- Sporophyte dominant
- Reproductive organs that contain the haploid spores = Cones
- Pollen – developed from the microspore on the sporophyte prior to dispersal
- Pollen develops within protective spore coat and produces non-motile sperm
- Ovule – Sporophyte structure that houses and protects the megaspore
- Female gametophyte develops within the ovule to form the archegonia
- Pollen is deposited in the female cone, a pollen tube grows and releases sperm cells
- Fertilized ovule becomes the seed
42
Q
Conifer Reproduction – Pollen Tube Growth
A
- Matured pollen is in a quiescent and dry state = allows for dispersal by wind
- The mature pollen are winged and are carried to female cones
- Once it hydrates on the pollination drop of the ovule and is brought to the megasporangium tissue it produces the pollen tube = Grows for several months
- Archegonium releases pollen attractant chemicals to guide pollen tube growth towards the egg cell
- Pollen tube ruptures when it has reached the archegonium to release: 1 Tube nucleus, 2 Sperm Cells, and a Sterile Cell
Only 1 Sperm Cell will fuse with the egg in each archegonium
43
Q
Conifer Reproduction Length
A
- Whole process takes about 2 years
44
Q
Conifer Reproduction – The Ovule and Fertilization
A
- Female Cone: Many Scales -> 2 Ovules per scale = 4 megaspores per ovule -> 1 survives
- 1 megaspore develops into female gametophyte = 2-4 archegonia per gametophyte
- 4 embryos per archegonium -> <16 embryos compete = mature seed with only one embryo
45
Q
Gymnosperm Seed
A
- Following fertilization, the ovule housing the embryo and matures into a seed
- Egg cell + Sperm cell -> Zygote -> 1 dominant embryo (2n)
- Female Gametophyte -> nutritive tissues (n)
- Integument -> Protective seed coat (2n)
46
Q
Seeds are major adaptations for uncertain environments
A
- Long distance transport – reduces parent-offspring competition, promotes outcrossing, and expansion of territory
- Dormancy – Embryo protected until the right conditions are perceived
- Protection from predation
47
Q
Conifer Life Cycle –Key Takeaways
A
- Spores that produce the gametophytes are no longer dispersed
- Microsporangia -> Microspores that produce male gametophyte (pollen)
- Pollen desiccates prior to dispersal
- Ovule houses the megasporangium
- Megasporocytes undergo meiosis -> 4 Megaspores (1 survives) -> female gametophyte -> archegonia -> egg cells
- Pollen tubes grow through the megasporangium to reach archegonia
- Only 1 sperm cell is used
- Only 1 of <16 embryos will survive per seed
- Pollination + Fertilization takes up to 2 years
- Fertilized ovule becomes the seed, female gametophyte becomes nutritive tissue
- Seed desiccates prior to dispersal
48
Q
Extant Gymnosperms
A
- The majority of living gymnosperms are woody species
In order of extant diversity, the major groups are:
1. Conifers = 550 species, all cone-bearing
2. Cycads = 185 species
3. Gnetophytes = 70 species
4. Ginkgophytes = 1 species - All possess vasculature, megaphylls, pollen, seeds, and a dominant sporophytic phase
49
Q
Gymnosperms – Summary
A
- Gymnosperms: Vascular seed plants with naked seeds
- Sporophyte dominant phase
- Evolution of the ovule – houses the megasporangium/female gametophyte
- Evolution of the pollen – male gametophyte, develops on the sporophyte and grows the pollen tube to release sperm cells
- Dry pollen are winged and dispersed through wind
- Embryo retained on the female gametophyte
- Female gametophyte retained on the sporophyte
- Seed dries prior to dispersal
50
Q
Angiosperms ~260,000 species
A
- Covered Seeds (Angio = vessel/container)
- Incredibly important to humans
- Sporophyte dominant
- Produces reproductive organs that contain the haploid spores -> flowers
- Microspores = Anthers, Megaspores = Ovules
- Pollen – male gametophyte developed from the microspore on the sporophyte prior to dispersal
- Ovule – Sporophyte structure that houses and protects the megaspore that gives rise to the Embryos sac (female gametophyte)
- Ovules develop inside of an ovary
- After fertilization, the ovule becomes the seed, and the ovary becomes the fruit
51
Q
Angiosperms – Key Adaptations
A
- Efficient transport of water and nutrients
- Flowers
- Double fertilization
- Ovaries
52
Q
Angiosperm Reproduction –
Flowers
A
- Compact reproductive organs
- Often hermaphroditic/bisexual
- Attractive to pollinators
53
Q
Angiosperm Reproduction – Double Fertilization
A
- Utilize both sperm cells
- Produces embryo and nutritive tissue = Endosperm
- Nutritive tissue only develops if pollination is successful
54
Q
Angiosperm Reproduction – Ovaries
A
- Houses and protects the ovules
- The base of the carpel
- Following fertilization, becomes the fruit
- Can aid in dispersal and nourishment of the seeds
55
Q
Double Fertilization
A
- Pollen attractant released from the embryo sac -> guides pollen tube growth
- One sperm cell from the pollen fuses with the egg, forming the zygote. The other unites with the diploid central cell of the embryo sac to form a triploid cell that gives rise to endosperm
- Egg cell (haploid, n) + sperm cell (haploid, n) -> Zygote (diploid, 2n) -> Embryo
- Central Cell (diploid, 2n) + sperm cell (haploid, n) -> Endosperm (Triploid, 3n) -> Nutritive Tissue
56
Q
Angiosperm Reproduction – Animal Pollinators
A
- Many angiosperms have specific pollinators instead of just wind
- Pollinators undergo coevolution with angiosperms
- Plants have evolved to attract pollinators (showy, mimicry, scent, nectar)
- Animals have evolved various behaviours and body parts for pollination (proboscis/tongues, different mouthparts)
- Highly specific flowers for pollinators
57
Q
Angiosperm Seeds
A
- Following fertilization, the ovule housing the embryo, matures into a seed
- Egg cell + Sperm cell -> Zygote -> Embryo (2n)
- Central cell + Sperm cell -> Endosperm nutritive tissues (3n)
2 Integuments -> Protective seed coat (2n) - The remaining female gametophytic cells either degenerate or remain as part of the nutritive tissue
- Seeds will fully dry prior to dispersal to attain dormancy
58
Q
Extant Angiosperms – Major Classes
A
- Monocots (single cotyledon/seed leaf) ~ 60,000 species
- Eudicots (True Dicots, 2 cotyledons) ~200,000 species
59
Q
Monocots (single cotyledon/seed leaf)
A
- Grasses, palms, lilies, orchids, bulbs, pineapple, banana
- Parallel-veined leaves common
- Floral parts in groups of 3
- Bundles of vascular tissue scattered in stem
- Fibrous root system
- Pollen grain with 1 aperture -> monocolpate
60
Q
Eudicots (True Dicots, 2 cotyledons)
A
- Most fruit trees, roses, beans, tubers, squashes, asters, cacti, succulents
- Reticulate veins
- Floral parts in groups of 4 or 5
- Bundles of vasculature arranged in a ring
- Branching roots with a strong tap root
- Pollen grain with 3 apertures -> tricolpate
61
Q
Major Developmental Differences Between the Seed Plants
A
Gymnosperms vs. Angiosperms
- Reproductive organs: unisexual cones vs. bisexual flowers
- Seeds at maturity: exposed/naked vs. covered/contained
- Integument(s) covering ovule: single vs. 2
- Female gametophyte: 100s of cells vs. 7 cells
- Microsporangia housed: on male cones vs inside anthers
- Primary mode of pollen dispersal: wind vs. animal pollinators + wind
- Pollination + fertilization length: ~2 years vs. minutes-hours
- Sperm cell(s) used during fertilization: 1 vs. 2
- Nutritive tissue for young embryos: remnant female gametophyte (n) vs. endosperm (3n)
- Xylem is composed of: tracheids vs. vessels +tracheids
- Phloem composed of: sieve elements vs. sieve tubes + companion cells
62
Q
Angiosperms – Summary
A
- Angiosperms: Vascular seed plants
- Have vasculature and covered and protected seeds
- Sporophyte dominant phase
- Hermaphroditic flowers are the reproductive organs
- Pollen microscopic, developed in anthers
- Female gametophyte small/microscopic and retained on the sporophyte within the ovules, housed in the ovaries
- Fertilization creates the embryo and the nutritive tissue
- The embryo is still retained on the female gametophyte
- More efficient vasculature and faster growing
- Flowers co-evolved with animal pollinators for cross-pollination
- The largest groups are the monocots and the eudicots
- Key Differences: venation/vasculature, floral parts, seed leaves
- Survive in dry conditions with less water
63
Q
Seeds – Breaking Dormancy
A
- Seeds are dry and dormant prior to their dispersal from the parent plant
- Seeds will germinate when they are in suitable conditions (i.e. when they have sufficient water and access to resources)
- The absorbance of Red Light activates Phytochrome B
- Repeated/extended Red Light exposure converts sufficient amounts of Phytochrome to the active state to initiate seed germination
- Reabsorption of far-red light inactivates the Phytochrome
- Lack of light also causes Phytochrome to revert to the inactive form
64
Q
Seeds need to sense whether or not they will receive
A
enough light to photosynthesize
65
Q
Germination will use up all of the:
A
nutritive tissue present in the seeds
66
Q
If the plant is unable to photosynthesize:
A
once it emerges then it will quickly die
67
Q
Far-red light is not absorbed well by plants
A
reception of Far-red light alone indicates plant coverage overhead (Red light absorbed above) and not enough light for photosynthesis
68
Q
Requirement of water for fertilization and the availability of water
A
From high to low
Aquatic algae -> mosses -> ferns -> gymnosperms
69
Q
Length of Gametophyte (n) generation
A
From long to short
Aquatic algae -> mosses -> ferns -> gymnosperms
70
Q
Relative size of Gametophyte (n) generation
A
From large to microscopic
Aquatic algae -> mosses -> ferns -> gymnosperms
71
Q
Length of Sporophyte (2n) Generation
A
From short to long
Aquatic algae -> mosses -> ferns -> gymnosperms
72
Q
Relative size of Sporophyte (2n) Generation
A
From small to large
Aquatic algae -> mosses -> ferns -> gymnosperms
73
Q
Protection of the zygote/embryo
A
From none to very high protection
Aquatic algae -> mosses -> ferns -> gymnosperms
74
Q
Key trends observed as plants dominate the land
A
- Longer time spent as diploid sporophyte -> Greater production of spores, handle greater genetic loads
- Increasing protection of the embryo
- Decreasing water availability (moving further away from sources) and lower requirement for external water during fertilization
