Lecture 10 Plants 2: Non-vascular plants & transition to land Flashcards
Acquisition of photosynthesis in plants and other photosynthesizers
Archaeplastids acquired photosynthesis ability by primary endosymbiosis (2 membranes)
Other photosynthesizers did secondary endosymbiosis of red/green algae (>2 membranes)
Describe viridiplantae (2) and major divisions (3)
Viridiplantae: green plants.
500k species, monophyletic.
Includes green algae (dominant photosynthesizers in fresh water);
Land plants (dominant photosynthesizers on land):
non-vascular (Bryophytes) & vascular plants (Tracheophytes)
Key innovations for plants proliferation of new lineages with more complex chara. and access to habitats: (5)
Chloroplasts with chlorophyll a+b and beta-carotene: present in all descendants unless lost
Ability to live on land: land plants (bryophytes, ferns, gymno/angiosperms)
Vascular tissues: vascular plants (ferns, gymno/angiosperms)
Seeds (versus spores): seed plants (gymno/angiosperms)
Flowers: angiosperms
Describe green algae (5)
Can have flagella and swim.
8k species, uni/multicellular;
90% in freshwater, main primary producers in freshwater;
Produce sexual/asexual
Limited presence on land: watermelon snow, lichens, non-photosyn. animal parasites
Timeline of life with a focus on plants: (9+5)
Plants transtion to land and beyond (4)
Land plants are monophyletic: only one successful transition from freshwater to land
Nonvascular: earliest branch, most ancient living group of land plants
Vascular: monophyletic. Evolved only once
Seed: monophyletic. Evolved only once
Advantages plants moving to land (4)
Huge uncolonized area, abundant light, available CO2, less herbivory at the time
Challenges plants moving to land (5)
UV radiation,
dehydration,
dispersal,
gravity,
nutrients
Describe Bryophytes (5)
14k species (mosses, liverworts, hornworts)
No xylem/phloem/true roots, can grow on rocks/shallow soil
Absorb nutrients & water thru leaves
Thin leaves w/ rudimentary cuticle, few to no stomata
Small, short, slow-growing: limited by diffusion, generally grow in damp habitats
Describe plants innovation of “sunscreen” (4)
UV lights damages DNA; water absorbs UV light, less problem for algae
Algae survived on land made compounds that absorb UV light
Most plants accumulate flavonoids, anthocyanins to absorb UV
Maple leave: green (chlorophyll)-yellow (carotenoids & flavonoids)-orange (carotenoids)-red (anthocyanins & carotenoids)
Describe plants innovation of cuticle (4)
Watertight sealant covering aboveground plant parts
Hydrocarbons + lipids + wax, produced by epidermal cells
Prevents water loss, inhibits gas exchange
Earliest nonvascular have rudimentary cuticle, no stomata
Describe plants innovation of reproduction (3)
Harsh conditions for gametes (reproductive cells) thus three instrumental innovations:
Spores encased in tough coat:
Resist drying (desiccation); survive fairly long time; dispersed by wind (light)
Gametes produced in complex multicell structure;
Fossilized early plants have specialized reproductive organs
Protect gametes from drying & physical damage
Present in all modern land plants except angiosperms (flowers)
Individuals produce male/female organs
Embryos retained on and nourished by parent plant
Not shedding their eggs into water or soil, retain them
Zygotes begin development on parent plant; form multicell embryos
Embryo retention: key innovation in land plants
Alternation of plants generations: (multicellular has 1n/2n stages) (9)
As land plants became more complex, sporophyte became dominant.
Describe bryophytes reproduction (3)
Gametophyte phase dominant; can be uni/bisexual (either/both male and female)
Need water for reproduction: thin layer on plant allows sperm to move
