PLANTS! And first 2 major transitions of plants Flashcards
Description of Plants
multicellular eukaryotes, evolved from protists(green algae), Primarily terrestrial habitats and some aquatic species; Characteristic cell wall with cellulose and polysaccharides; SIGNIFICATN METABOLIC DIVERSITY(photoautrophs, chemoorganoheterotrophs, and mixotrophs); Plant Complex Life Cycle Alternation of Generations
Plant Photoautotrophs
uses photosynthesis; use chloroplasts leaded with chlorophyll (pigment used in process)
Plant Chemoorganoheterotrophs
primarily parasitic; no photosynthesis or chlorophyll; (Examples: beechdrops, squawroot, Indian pipe)
Plant Mixotrophs
use autotrophy and heterotrophy; Examples are Venus fly traps, pitcher plants; Pitcher plants use lots of photosynthesis and colors(red and green) show this, but flies also option
Plant Complex Life Cycle: Alternation of Generations
Have independent haploid(1n) and diploid(2n) life stages; Haploid Life Stages in Plants are Gametophyte (n chromosomes); Diploid Life Stage in Plants are Sporophyte (2n chromosomes)
Mitosis occurs during haploid gametophyte stage, Fertilization is beginning of diploid sporophyte stage, and Meiosis is the end of diploid sporophyte stage/transitions to beginning of haploid gametophyte stage
Plant Evolutionary transitions
Water to Land-> Vascularization, Plumbing-> Seeds!!-> flowers, fruit
Ancestor to Land Plants
Green algae; Two types, Charophyta and Chlorphyta(phytoplankton); Fossil and DNA evidence suggests that Charophyta are ancestor to land plants
Parka decipiens(400 million yr old fossil) that resemble modern green algae
Transition from water to land
many selective pressures against it, such as structural stability nutrient uptake, and reproduction
Land vs Water: Structural Stability
Water :Lots of support in free-floating in water, Rigid tissues not required to main upright(structural stability)
Land: No support really(structural stability), Natural selection for rigid cell wall, Selection for structures to take up and retain water in environment(water becomes limiting)
Land vs. Water: Nutrient Uptake
where do plants get carbon(C), nitrogen(N), and phosphorous(P), other nutrients?
Water clearly has no issues with this, can absorb nutrients from the water
Land: natural selection for CO2 uptake from air, and roots to extract N, P from soil; also, selection for mutualisms with bacteria and fungi(nitrogen fixers) to get N
Land vs. Water: Reproduction
in water, algae rely on swimming sperm for fertilization
Water have mobile, swimming sperm which can swim to eggs and fertilize them, allows for successful sexual reproduction
Land natural selection for sperm that do not require water to fertilize eggs, and other new modes of reproduction
First Plants on Land
Nonvascular plants
Nonvascular Plants
Means they have no vascular tissue to move water and nutrients around within the plant (no internal plumbing so to speak, no complex plumbing in general)
This limits habitats they can be in; found only in wet, moist, humid habitats; NEED available, stable water source (streams, lakes, consistently dense fog/mist found on mountaintops, rotting logs)
This limits size of plant, Cannot grow taller because they cannot move water and nutrients to increased heights
lack true roots(have rhizoids instead), lack true leaves(have leaf-like spikes/structures instead)
Rhizoids
sponge-like tissue at base of plant that anchors plant and absorbs some water
Leaf-like spikes/structures
have one, long thin cell running down center of spike; draws small amount of water from rhizoids
Alternation of Generations in Nonvascular plants
Nonvascular plants Gametophyte(n) is dominant life stage; it is ALWAYS PRESENT
Nonvascular sporophyte(2n) is present during spore production; die after spore production is complete
In fertilization: mobile, swimming sperm; require water to successfully fertilize egg
In meiosis: spores spread to environment by water, wind; germinate where they land
Three modern groups of nonvascular plants
Bryophyta(mosses), Anthocerophyta(hornworts), Hepaticophyta(liverworts)
**Images of differentiation between groups shown on page 22 of Notes)
Development of Vascularization
2nd major evolutionary transition, All plants beyond this point in evolutionary time have vascular tissues; internal plumbing for moving water/nutrients around the plant
Earliest Evidence of Vascularization
Cooksponia
Sporangia: spore producing structures on sporophyte, 420 Mya, Had single tubes running up center of them, Only fossil sporophytes found
Rhynia
400 Mya, Had extensive vascularization(tubes/vessels) running up stems, Only fossil sporophytes found, Stem cross-section shows extensive vascularization, Sporangia: spore producing structures on sporophytes
Evolution of vascular tissues
Shoots/stem, leaves, roots, etc, Allow movement of water, nutrients(C,N,P) sugars(“food’) dissolved minerals, and hormones; Separate into above ground (shoots, stems, leaves) and below ground(roots); Contained specialized cells known as xylem and phloem for moving substances around the plant
How are substances moved around the plant?
Starting belowground, water absorbed form soil by roots, moved through aboveground tissues(by Xylem; dead cells with thick cell walls that are interconnected)
Xylem moves water/dissolved minerals upwards through all plant tissues(UNIDIRECCTIONAL FLOW); larger “tubes” by themselves
Some water lost in transpiration
Description of Water being Lost in Transpiration
when H20 moves to leaf surfaces, lost to atmosphere when mouth-like opening(STOMOTA) on leaves open, releasing water vapor
Stomata in transpiration open for gas exchange(Open stoma: take Co2 in, and then O2 out, water out as water vapor/lose H20 as water vapor)
CRITICAL TO WATER MOVEMENT: as water vapor is released, water is pulled upward, allowing for continued upward water movement with xylem
All of this above necessary/ relevant for PHOTOSYNTHESIS, without transpiration photosynthesis process does not occur
how do plants protect their water, maintaining high levels in tissue and reducing loss to environment?
Stomata closed when transpiration not occurring to reduce loss of water vapor
Cuticle: avoids further water loss, waxy covering, blocks water evaporation to environment
Photosyntheis
Produces sugars(for growth and reproduction)
How do sugars get to the rest of the plant?
Phloem: living cells; moves sugars, hormones, and nutrients around plant in all directions(to all tissues)(MULTI DIRECTIONAL FLOW); smaller, multiple grouped “tubes”
Benefits of Vascularization
Plants get taller/larger: move materials around whole plant, to great heights
Plants can now live in lower moisture habitats, greatly broadening range of habitats they occupy
**EARLY VASCULAR PLANTS still needed water for reproduction since they had mobile swimming sperm
Vascular Plants
Tracheophyta: group that includes all vascular plants
Major change IN ALL VASCULAR PLANTS in dominant life stage, Shift from gametophyte(n) being dominant life stage(like in nonvascular plants) to sporophyte(2n) being dominant life stage; So sporophyte ALWAYS present, and gametophyte dies after producing haploid sperm and eggs
Four Oldest Vascular Plant Groups
Club Mosses(Lycophyta), Whisk Ferns(Psilophyta), Horsetails(Equisetophyta), True Ferns(Pteridophyta)
**Review images starting on page 25 of notes
Club Mosses(Lycophyta)
No true mosses, Found in moist areas and forests, look like baby pine trees trying to grow in sporophyte stage but they are not obviously
Whisk Ferns(Psilophyta)
NOT true ferns, Found in high mountain habitats, sporophyte stage has sight of green stems with yellow tips, while gametophyte is disgusting orange and clear picture(you know what I am talking about)
Horsetails(Equisetophyta)
Not true horsetails, Found around water; sporophyte appears to be mini conifer tree/baby tree, but is not(pointy-like end with green shoots going upwards, gametophyte looks like green goop)
True Ferns(Pteridophyta)
Have true leaves(enhances photosynthetic ability, transpiration) and true roots(for taking up water and nutrients, etc.); Limited to wet/humid habitats due to mobile sperm needing water to fertilize egg
ALL SPOROPHYTES
Reproduction in True Ferns
fertilization happens on gametophyte(which have special egg and sperm producing structures)
Archegonium: produces eggs
Antheridia: produce sperm
Sperm swim to egg and fertilize it
Fertilized egg leads to sporophyte
Sporangia: release spores which are spread to environment by wind and water, germinate into new gametophytes(when conditions are right)
2 shared characteristics of ancient lineages
Seedless; Still found in primarily wet habitats, since they still rely on mobile swimming sperm that REQUIRE water to swim to eggs to fertilize them
