Plants Flashcards
How did plants evolve?
Plant ancestors diverged from protists about 1.5 billion years ago with a branch shared with animals and fungi
The transition to land for plants was hard, list 3 problems and their solutions
Greater temperature extremes–stomata controlled by guard cells
Reduced water availability–development of xylem, roots/rhizoids and presence of sporopollenin (in spores), protected gametangia/gametes
Variable nutrient availability–development of xylem/phloem, seeds with food reserves, apical meristems
Light fluctuation–apical meristems/reinforced cell walls
Exposure to UV radiation–protective flavonoids/pigments, protected gametangia
Higher evaporation rates (wind)–waxy cuticle, stomata controlled by guard cells
What is a common ancestor of all plants?
Group of green algae called Charophytes
What is the most diverse group of plants?
Angiosperms = flowering plants
Approximately how many species of plant are there?
400,000
What to plants do?
Supply O2 and use CO2
Provide food source
What are five key traits that appear in plants?
- Alternation of generations (multicellular, dependent embryos)
- Walled spores
- Multicellular gametangia (produce gametes)
- Apical meristems
- Development of vascular tissue (xylem and phloem)
What other characteristics allowed plants to survive?
Cuticle and secondary chemical defence compounds
Symbiotic associations with fungi
Explain the process of alternation of generations
Gametophytes (haploid) produces gametes (haploid) in mitosis
Gametes fuse to produce sporophyte (diploid) which produce spores (haploid) in meiosis
Explain the process of walled spores produced in protective sporangium
Sporophyte produces spores in sporangium (multicellular)
Diploid cells in sporangium undergo meiosis to generate spores (haploid) that germinate into gametophyte
Spore walls contain sporopollenin that resists harsh environments
Explain the process of multicellular gametangia producing gametes
Gametes produced in gametangia (multicellular)
Female gametangia = archegonia: produce eggs/site of fertilization
Male gametangia = antheridia: sperm production and release
In apical meristems plants sustain…
Cells from apical meristems can…
Continual growth (tips of shoots and roots) Differentiate into various tissues
Development of vascular tissue
Xylem contains…
Phloem contains…
Water
Sugars
Plant that lacks vascular tissue
Nonvascular plant
- liverworts
- mosses
- hornworts
Plants that have vascular tissue
Vascular plants
- lycophytes
- ferns and horsetails
- gymnosperms
- angiosperms
Define Bryophytes
- first to diverge after move to land (unique life cycle)
- small, simple, tough
- Small size due to constraints on fertilization (sperm requires water and can only move short distance)
- Simple structure–flattened photosynthetic structures (thallus) – only a few cells thick, lack internal air spaces, no water conducting system
What stage dominates the life cycle of Bryophytes?
Haploid gametophyte stage–larger than sporophyte
Independent (photosynthetic) and most viable
Supports non-photosynthetic sporophyte (less conspicuous)
How to Bryophytes work?
- Diffusion-absorb water and CO2
- Lack waxy cuticle to reduce water loss
- Require moist/wet environment (can tolerate some desiccation)
- Poor competitors (small size)
- Ecological importance
Explain Sphagnum
- Peat bogs
- found in boreal forest
- key role: creating acidic/wet conditions that slow decomposition
- produce phenols
- store large amounts of organic carbon
- vulnerable to climate change
List 3 characteristics to vascular plants
- Diploid sporophyte stage dominates life cycle
- Evolved vascular tissue (xylem and phloem)
- Less dependent on water for reproduction
Explain the dominate life cycle stage of vascular plants
Diploid sporophyte stage
- larger/independent
- supports smaller dependent gametophyte
What are the seedless vascular plants?
Lycophytes
Ferns/horsetails (Pterophytes)
Fossil ancestors show leaf-like structure and xylem cylinder
Grew to considerable size during wet period (400 million years ago)
Disappeared when climate change and swamps dried up
Decomposed slowly-buried forming coal deposits
Currently much smaller
Have simple veneration, roots and can tolerate desiccation
WHAT AM I?
Lycophytes
Ex. Selaginella-resurrection plant
What is the other name for ferns and horsetails?
Pterophytes or pteridophyte = monophyletic group
Most members are ferns –have coiled leaves that uncoil during growth/development