T7- Systematics (not included) Flashcards
What was the first direct evidence of plants ?
Cooksonia
- had no leaves, no roots, no flowers
- vascular tissues to conduct water
- was liberating spores
- had cell specialized in gas exchanges (stomata)
What were disadvantages and advantages of living above the water line ? (colonization of land by plants)
D;
- dry environment
- strong effect pf gravity
- no nutrients in the atmosphere (nitrogen fixation - aquatic plants could capture nitrogen directly from water)
- rapid changes in temperature
A;
- brighter sunlight, unfiltered by water and phytoplankton (direct access to sunlight)
- more CO2 in atmosphere than in water
- abundance of nutrients on the shoreline
What adaptations of plants allowed them to colonize land?
- the protecting of the spores, gamaetes, zygote and the embryo
- protecting against dryness
- maximizing photosynthesis (large leaves, presence of stomata, evolution of specia pigments)
- growth to compensate the lack of movement towards resources (allows them to exploit the environment)
What are some key innovations made by land plants?
Alternation of generations (haplo-diplontic life cycle)
- multicellular 2n indiv (sporophyte) - diploid
- multicellular n indiv (gametophyte) - haploid
Embryo retained in the maternal gametophyte tissues
- for protecting and nutrition
- stage that comes after the zygote
Spores protected by a wall of highly resistant polymer (sporopollenin)
Spore dispersion occurs in the air independently from water
Egg is non motile but the sperm can often swim in water
Apical meristem = region of stem division at the tip of roots and shoots (allows for branching)
Stem cells (undifferentiated cells) allow indeterminate growth to maximize its exposure to resources
Presence of cuticle to protect against dessication (resisting dryness with this thin waxy layer)
Presence of stomata = pore surrounded by guard cells to allow gas exchange and water loss regulation
What are bryophytes?
Paraphyletic group of all non-vascular plants
- do not produce seeds or flowers
- absence of specialized tissue to conduct water and nutrients (no vascular system)
- life cycles are dominated by gametophytes
- water flows through the tisue (spore germination and sperm swimming depends on water)
- contain rhizoids = filament that attaches to the substrate (no absorbtion of water/minerals)
What are tracheophytes?
Monophyletic group of all vascular plants
- life cycle dominated by sporophyte
- gametophyte is reduced in size
What is vascularization?
Presence of lignified (made of lignin = made of phenyl) tissues that transport water, nutrients and sugars through the plant
What are the 2 specialized transport tissues of vascular plants?
- xylem = water and minerals to the leaves
- phloem = sugar, the products of photosynthesis
What is lignin?
Polymer in cell walls that is impermeable to water and structural support for gravity
- allows plants to have ability to grow tall, dispere farther and compete for light
- forms plant rigid walls so plant can stay upright
How can leaves be specialized to produce spores?
- Only 1 type (homosporous) producing a bisexual gametophyte
- most seedless vascular plants
- lychophytes, monilophytes
- Producing 2 types (heterosporous) producing either a female gametophyte (megasporangium) or a male gametophyte (microsporangium)
- all seed plants
- gymnosperms, angiosperms
What are some advantages of heterospory?
- for each spore there is specfic selection with specific functions (increase in specialization)
- a separate female gametophyte can better nourish the embryo (no energy spent producing male gametes)
- male and female gametophytes can mature at different times (no self fertilization = higher genetic diversity)
What is a seed? What are seed plants called
Embryo surrounded by nutritive substances and a protective coat
Spermatophytes
What are 5 key innovations of seed plants?
1) Extremely reduce gametophyte is protected from environmental stresses (UV and dessication) and is directly nourished from the sporophyte
2) Ovule; structure containing the megaspore - fertilization without requiring water from the environment
3) Heterosporous; microspore - male gametophyte (n) which can dispere farther, megaspore - female gametophyte (n) which nourishes the developing embryo
4) Pollen grain; male gametophyte enclosed within a pollen wall and can disperse very far via wind, animals…
5) Production of a seed; increases the survival of plants during reproduction
- embyro is nourished and can resist drought or low temperatures
- seed germination happens during favourable conditions
- can have adaptations to many new environments
What are gymnosperms?
Seed plants (not enclosed in chambers) but produces no flowers
Non flowering seed plants
Seed is exposed on sporophylls and can survive years before germination (leaf with hard tissue)
What are angiosperms?
Flowering plants that produce seeds (enclosed in chambers;ovaries)
- seed enclosed in a chamber (carpel) that matures into a fruit
- flower = modified leaves (sporophylls) specialized in reproduction
carpel produces female
stamen produces male - fruit = mature ovary of flower that helps with seed dispersal
wind (anemochory)
animals (zoochory)
