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
What is the dominate life stage of ferns/horsetails?
Sporophyte dominates life cycle
- larger than gametophyte
- independent (photosynthetic) most visible
- protects small photosynthetic gametophyte
List the 3 parts of ferns/horsetails
- Fronds (divided into smaller units called pinnae)
- Stems grow underground (invasive)
- Vascular tissue allows plants to grow larger (size limited by lack of secondary vascular tissue)
How did seeds change plant evolution?
- Allowed them to become dominate producers on land
- Seed plants do bot require external water source for fertilization
- Seeds consist of embryo and endosperm (nutrients)
- Pollen also important (dispersal of male gametes)
What are the two groups of vascular seed plants?
Angiosperm (seeds and fruit)
Gymnosperm (seeds)
Gymnosperms
- divided into 4 groups
- have naked seeds (not enclosed by ovaries)
- adapted to drier conditions
- cone bearing-Conifers
Have large cones and palm-like leaves Can live in nutrient-poor conditions Few species exist today Have insect pollination/animal dispersal Most are on endangered species list WHAT AM I?
Cycads
Only one living species (Ginkgo Biloba)
High tolerance for air pollution
Ornamental tree with health benefits
WHAT AM I?
Ginkgos
Most are evergreens
Continue photosynthesis year-round
Tolerate cold dry conditions
Have xylem consisting of unique cells called tracheids
Have secondary xylem growth (produces wood for support/strength)
Produce chemicals to deter insects/fungi
WHAT AM I?
Conifers
What are the 3 key features of gymnosperm life cycles?
- Dominance of sporophyte generation
- Development of seeds from fertilized ovules
- Transfer of sperm to ovules by pollen (wind)
Gymnosperms VS. Angiosperms
Gymnosperms can outcompete angiosperms in cold and dry climates (freeze/thaw cycles)
Fewer problems with gas bubbles in xylem tracheids
Comprised of three genera-vary in appearance
Some are tropical but others live in deserts
Have traits similar to angiosperms (multicellular xylem vessels and double fertilization)
WHAT AM I?
Gnetophytes
Characteristics of angiosperms
- have protected seeds (enclosed by ovaries)
- better suited to life on land
- most widespread diverse group
Why is the diversity of angiosperms still a mystery/what is a theory?
May be due to slower rates of species loss rather than faster rates of species formation
What is 1 of the 3 innovations evolved by angiosperms, then explain
- Flowers
- specialized shoot structure for sexual reproduction
- to attract animal pollinators
- contribute to diversity (reducing likelihood that rare species go extinct) - Double fertilization
- more efficient use of energy for reproduction - Fruits
- forms after fertilization
- consist of mature ovary (may include other flower parts)
- evolved to protect seeds/aid in dispersal
- can be either fleshy or dry (nuts)
What are the 3 rare groups of angiosperms?
AM or Ella
Water lilies
Star anise and relatives
Magnoliids
Include magnolias, laurels, black pepper, avocados
Common in early angiosperm evolution in tropics
Monocots
- 25% of angiosperms
- food crops (rice, wheat, corn)
- other economically important plants (bamboo, orchids, tulips)
Eudicots
- 75% of angiosperms
- economically important plants (food, forests, gardening, health)
- interesting plants (carnivorous, parasitic, epiphytes)
Monocot characterisitcs
Scattered vascular tissue Parallel veins One cotyledon Floral organs in multiples of 3 Pollen grain with 1 opening Fibrous root system (no main root)
Eudicot characteristics
Vascular tissue arranged in a ring Netlike veins Two cotyledons Floral organs in multiples of 4 or 5 Pollen grain with 3 openings Taproot (main root)
