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BIOL371 Comparative Biology of Plants and Animals > Plant Origins > Flashcards

Plant Origins Flashcards

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1
Q

Endosymbiosis

A

Engulfing without digestion

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2
Q

Primary Endosymbiosis

A
  • resulted in the retention of: Mitochondrion = Alpha Proteobacterium, and Plastid/chloroplast = Cyanobacterium
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3
Q

Plastids within the eukaryotic cell allowed for photoautotrophs (algae)

A
  • Reduces requirement for phagocytosis

- Increases need for cellular water

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4
Q

Secondary Endosymbiosis occurred across:

A

various lineages of aquatic algae

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5
Q

Secondary Endosymbiosis

A

Subsequent uptake of a red and/or green alga by other non-photosynthetic eukaryotes gave rise to several aquatic algal lineages and phytoplankton

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6
Q

Chloroplasts

A
  • utilize the energy from light to break H2O molecules into O2 and H+ ions
  • H+ ions are used to generate ATP by pumping through an ATP synthase on the thylakoid membrane into the stroma
  • An electron transport chain caused by the splitting of the water molecules allows for the reduction of NADP to NADPH
  • The high energy compounds ATP and NADPH aid in the fixation of CO2 into polysaccharides through the Calvin Cycle starting with Rubisco in the stroma
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7
Q

Heterotrophic Plants – Alternative Nutrition

A
  • Some plants have lost the ability to photosynthesize in favour of alternative nutrient acquisition strategies
  • These are and represent <1% of all plant species – All ancestral lineages were photoautotrophs
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8
Q

Mycoheterotrophs

A

– obtain carbon source from fungal associations with other plants

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9
Q

Parasitic plants/heterotrophs

A

obtain carbon source directly from other plants

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10
Q

Plant Cell Walls

A
  • Reduced requirement for phagocytosis allows for the development of cell walls
  • quite porous and allows for nutrients and water to pass-through
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11
Q

Primary Plant Cell Walls

A
  • Provide support and protection but allow for flexibility
  • Rigidity is highly dependent on turgor pressure, which is dictated by the surrounding environment and maintained by vacuole
  • Deposited outside of the plasma membrane
  • Composition is largely the same among all plants
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12
Q

Cellulose

A
  • The most abundantbiopolymer in the world/known universe
  • Long, unbranched microfibrils made up of β1-4 glucose linkages
  • major component of dietary fibre (hard to digest)
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13
Q

Osmotic Pressure

A
  • Vacuoles have higher solute concentration and the osmotic flow of water occurs from outside the cell (lower solute concentrations) to into the vacuoles
  • The turgidity of the vacuole pushes the plasma membrane outwards and this pushes against the cell wall
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14
Q

Turgid State

A

The ideal state for plant cells, helps maintain the structure of the plant and maintains osmotic balance

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15
Q

Effects of Osmotic Pressure

A
  • Rapid and concerted movements of solutes can quickly divert water from the cell and force some cells to contract
  • Pressure sensors or mechanosensors can activate ion channels that change the osmotic potential of the cell
  • Actually causes an action potential similar to animal cells and can trigger coordinated events in nearby tissues or organs
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15
Q

Effects of Osmotic Pressure

A
  • Rapid and concerted movements of solutes can quickly divert water from the cell and force some cells to contract
  • Pressure sensors or mechanosensors can activate ion channels that change the osmotic potential of the cell
  • Actually causes an action potential similar to animal cells and can trigger coordinated events in nearby tissues or organs
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16
Q

Multicellularity in Eukaryotic Algae

A
  • True multicellularity involves the specialization of cells to perform different functions
  • Allows for coordinated behaviour of different tissues to aid in the fitness of the organism as a whole
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17
Q

We know that all land plants are descended from the same clade of Eukaryotic Green Algae because:

A
  • Multicellularity arose multiple times in algal lineages, completely separate from the animal/fungal ancestral lineage
  • End products are similar but the processes are unique and can be used to distinguish evolutionary trends
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18
Q

All land plants display:

A

multicellularity

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19
Q

Plant Cell Multicellularity – Cell Division

A
  • Critical importance to the multicellularity of Land Plants
  • Land plant cell division progresses through the production of the Phragmoplast
  • This arrangement of the microtubules allows for cell wall deposition between the two separated nuclei prior to the complete division of the cytoplasm
  • Deposition of the cell wall materials also involves the fusion of vesicles from the ER and Golgi to form the new plasma membranes
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20
Q

Plasmodesmata

A
  • are intercellular connections between plant cells
  • These connections are formed cell division
  • Secondary plasmodesmata can develop through the degradation of the cell wall but do not occur in all cells
  • Analogous to the gap junctions seen in animal cells
  • These connections allow for easier cell-to-cell transport of cytoplasmic contents
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21
Q

Passage of materials through the plasmodesmata is regulated by:

A

the ER within the cavity (desmotubule)

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22
Q

Defining Characteristics of Land Plants

A
  • Are sessile
  • Are photoautotrophic (vast majority)
  • Have primary cell walls (largely composed of cellulose and hemicellulose)
  • Are multicellular
  • Have Cuticles
  • Have Stomata for gas exchange
  • Have an alternation of generations -> Diphasic life-cycle
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23
Q

True colonization began with

A

fungi, early embryophytes (~475mya), and then animals (arthropods first)

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24
Q

Vascular plants develop:

A

Around 425mya and proceed to dominate to the end of the Carboniferous (~300mya)

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25
Q

Tetrapods arise

A

~400mya, first to come on land ~360-380mya

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26
Q

Seed plants arise

A

~300mya, arthropods and amphibians dominant animals on land, reptiles begin to radiate, last common ancestor between reptiles and mammals ~285mya

27
Q

Why Move Out of the Water?

A
  • NO competition
  • Unlimited and untapped mineral resources
  • Unlimited space for establishment and growth
  • Full access to light
  • No predators
  • Any organisms that could become accustomed to life on land had room to radiate
28
Q

Freshwater algal mats would have been the first to:

A

begin photosynthesizing on land, would have to withstand wet-dry cycles but were still largely aquatic.
- Likely formed symbiotic relationships with fungi -> established the first soils and allowed for further diversification

29
Q

First truly terrestrial plants were the first of the:

A

Embryophytes -> Bryophytes (475mya)

30
Q

Plants established habitable regions, acting as the:

A

primary producers

31
Q

Challenges with Life on Land

A
  • Desiccation
  • Respiration
  • Reproduction
  • Locomotion and support
  • Nutrients
  • Senses
32
Q

Desiccation Challenges

A
  • Protection from drying out (resistant coat or skin to prevent body fluids from evaporating) and dealing with scarce water
33
Q

Respiration Challenges

A
  • In water, dissolved oxygen and carbon dioxide are exchanged.
  • Organisms had to deal with the exchange of atmospheric gases. (e.g. Stomata, Lungs)
34
Q

Reproduction Challenges

A
  • In water, eggs and sperm could be released into the water or broadcast
  • Land organisms had to develop successful reproductive strategies under desiccating conditions. (i.e. tighter control over the dispersal of “soft” propagules/gametes) (e.g. alteration of generations in plants, the evolution of amniotes in animals)
35
Q

Locomotion and Support Challenges

A
  • No more propulsion through a viscous medium, no more support or buoyancy from the water
  • Now require new locomotive systems and supports (e.g. Limbs/appendages, types of joints, reinforced tissues)
36
Q

Nutrient Challenges

A
  • Mineral nutrients and ions are diffused in the water and are readily taken up through diffusion and maintaining osmotic balance.
  • On land, mineral nutrients are held in the substrate.
37
Q

Senses Challenges

A

Organisms on land had to adapt to the changes in light, sound, and smell which were perceived very differently in water.

38
Q

Major Early Adaptions of Land Plants

A
  1. Waxy Cuticles
  2. Stomata
  3. Alternation of generations
39
Q

Waxy Cuticle

A
  • is a waxy layer that prevents water loss from stems and leaves
  • Protects the plants from drying out and also from pathogen attack
  • Wax is deposited outwards by the epidermal cell layers (upper and lower)
  • Thickness varies depending on the perception of heat and light
  • Wax is not easily permeable to gases
40
Q

Stomata

A
  • are pores that allow the exchange of gases across photosynthetic surfaces
  • Opening and closing of the pore is controlled by specialized cells called Guard cells
  • The guard cells themselves are still covered by the cuticle but create a pore when they swell and pull apart
  • Regulation of the release of gases only when water is plentiful greatly reduces unnecessary water loss
41
Q

Jigsaw puzzle growth pattern of epidermal layers allows for

A

complete and intricate seals between neighbouring cells regardless of swelling/contracting

42
Q

The guard cells are able to swell and contract quickly in response to:

A
  • the accumulation of solutes -> changes their osmotic potential:
  • Water moves in (plentiful) -> swell to sausage shape -> pore opens
  • Water moves out (lacking) -> contract to flaccid straight-sided shape -> pore closes
43
Q

Alternation of Generations

A
  • Instead of one “body”, the plant life cycle progresses through two multicellular growth forms:
  • Diploid (2n) Phase = Sporophyte -> makes spores (n) through meiosis
  • Haploid (n) Phase = Gametophyte -> makes gametes (n) through mitosis
44
Q

Sporophyte

A
  • Diploid (2n)
  • multicellular body/form
  • produces spores (n) through meiosis
45
Q

Spores

A
  • Haploid

- Unicellular but will germinate to produce Gametophyte (n) through mitosis

46
Q

Gametophyte

A
  • Haploid
  • multicellular body/form
  • produces haploid, unicellular gametes (n) through mitosis
47
Q

Gametes

A

Sperm and egg cells fuse (fertilization) to form a unicellular zygote (2n) that will quickly develop into an embryo through mitosis

48
Q

Embryo

A
  • Diploid (2n)
  • multicellular
  • will develop into a sporophyte through mitosis
49
Q

The embryo of land plants is retained on the

A

Female gametophyte

50
Q

Why Alternate Generations?

A

Amplifies of gametes and their chances of successful fertilization events and offspring

51
Q

Algae reproduction was entirely water-mediated

A
  • Long gametophyte phase
  • Zygote immediately undergoes meiosis to produce spores
  • Haploid spores give rise to gametophytes which produce haploid gametes through mitosis (very difficult on land)
52
Q

Alternation of generations (Embryophytes)

A
  • Retention of the zygote on the female gametophyte and allowing it to develop into an embryo -> Diploid Sporophyte
  • Localized dispersal of gametes for greater certainty
  • Allows for greater production of spores (“hard” propagules) for dispersal and amplification of offspring from a single fertilization event
53
Q

In the simplest form, the land plants are separated by the presence of 2 features alone:

A
  1. Presence of Vasculature

2. Presence of Seeds

54
Q

Plant Vasculature

A
  • No muscles or moving pumps are involved in moving the solutes
  • Vascular tissues are commonly grouped together in either 1 or several bundles (xylem, phloem, parenchyma, fibre (sclerenchyma))
  • Complex network that connects the entire plant from root/anchoring system to the photosynthetic surface
  • Allows for the transfer of water and nutrients throughout the plant
  • Contributes to the overall structure and support of the plant
55
Q

Xylem cells transport:

A

Water and dissolved nutrients

56
Q

Phloem cells transport:

A

Sugars and other nutrients

57
Q

Secondary Cell Walls

A
  • Not present in all plant cells
  • Develop in areas that require additional support and in the vasculature
  • Composed of cellulose, hemicellulose, and pectin BUT all the gaps are filled in with Lignin
58
Q

Lignified parenchyma =

A

Sclerenchyma (fibre cells)

59
Q

Xylem cells also develop from lignified parenchyma but are

A

dead at maturity

60
Q

Lignin

A
  • A highly complex phenolic polymer that covalently binds the cellulose and hemicellulose and is extremely resistant to degradation
  • Creates a hydrophobic and impermeable barrier to water
  • Rigidity of cell is reliant on lignin
61
Q

Xylem Tissue

A
  • The pits that develop along the xylem cells are not blocked by secondary cell walls
  • Pits of vessels even lack primary cell walls
  • Water can transit through xylem cells from bottom to top and into the next or exit the xylem into the surrounding tissue
62
Q

Vasculature – Transport

A
  • The taller plants grow = more room with less competition for light but are further from their resources
  • Becomes harder to distribute those products throughout the plant and they become top-heavy
  • Require long-distance transport mechanisms: xylem + phloem
  • Require substantial supportive tissues: xylem + sclerenchyma
63
Q

Seeds

A
  • Seeds are housings for the young embryo
  • Comprised of maternal sporophytic tissue and female gametophytic tissue
  • A derived feature shared by the Gymnosperms (conifers and others) and the Angiosperms (flowering plants)
64
Q

Extant diversity:

A
  • Bryophytes: ~19,000 species
  • Pterophytes: ~10,000 species
  • Gymnosperms: ~1000 species
  • Angiosperms: ~260,000 species

BIOL371 Comparative Biology of Plants and Animals (10 decks)

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