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Bio 29, 30, 38, 39

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Overview of Plant Evolution
Plants appeared on land 475 million years ago. The evolutionary history of plant kingdom reflects increasing adaptation to their terestrial environment
Evolution of Plants
Evolved from a group of green algae; charaophyceans
Plant Kingdom Characteristics
chloroplasts containing chlorophyll a and b, photosynthetic autotrophs, eukaryotic cells containing a nuclei, cell wall --> cellulose
Terristrial adaptations
cuticle, gas exchange, lignin, meristem, vascular tissue
Cuticle
waxy outer covering prevents water loss
lignin
provide structure to cell walls
meristem
elongates and exploits resources
vascular tissue
eventually
gas exchange
.
Why would plants want to live on land?
niches that are available for occupation, nutrient rich soil base, more co2, more sunlight, no predators
Alternation of generations
two alternate multicellular forms, each one produces the other
Review of the process
Fertilization->Zygote (2n)->Mitosis->Sporophyte (2n)->Meiosis->Haploid Spores (n)->Mitosis->Gametophyte (n)->Gametes (n)->Fertilization
Hetomorphic
sporophyte and gametophyte difer in morphology
Sporophyte is....than the gametophyte
LARGER (except in bryophytes)
there tends to be a .... of the haploid gametophyte generation and ... of the diploid sporophyte
REDUCTION, DOMINANCE
Classification of plants
Major taxonomic category of plants is the division, comparable to phylum in the animal kingdom
Bryophytes
Nonvascular, Seedless Plants (first to evolve from the charophyceans)
Characteristics of the bryophytes
rely on diffusion to move h20 throughout plant, requires h20 for reproduction, dominant gametophyte, sporophyte is reduced
Life cycle of the bryophytes
Zygote->sporophyte->spores->sperm in antheridea, ovule in archegonia (bisexual gametophyte)->fertilization in the presence of H20->Zygote
Mosses
Brophyta, 1200 species
3% of the land is covered in mosses, usually in teh tundra, absorbs 20x their weight in water
Liverworts
Hepatophyta, 6500 species
Tropics
Hornworts
Anthocrophyta, 100 spcies
Cells contain only one large chloroplast
Pteridophyta
Vascular Seedless plants, formed the vast "coal forests" during the Carboniferous Period
Coal forests
decaying organic plant material collected at the bottom of immense swamps located in forests predominantly composed of ferns. These deposits were covered with sediments ande exposed to heat and pressure transforming them into coal.
Adaptations of the "vascular seedless plants"
Vascular Tissue (transport nutrients throughout plant), structural support, regional specialization (roots for obt. water, leaves, and shoots for sugar prod.), sporophyte is DOMINANT
Life cycle
zygote->sporophyte (fern)->haploid spores->archegonia, antheridea on heart-shaped bisexual gametophyte->fertilization->zygote
Classifications (3 divisions)
club mosses, ferns, horsetails
Seed plants
The emergence of seed plants further transformed the Earth. Seeds and other adaptations of gymnosperms and angiosperms heightened the ability of plants to survive and reproduce in diverse terrestrial environments; these plants became the principal producers in the food webs of most terristrial ecosystems
Adaptations conributing to the success of seed plants
origin of the seed (embryo w/ a food supply w/in a protective coat), pollen (male gametophyte, no longer dependant upon h20 fertilization), reduced gametophyte (dominant sporophyte)
Gymnosperm characteristics
Reproductive structure is the cone, cones consist of clusters of scales, scales contain the ovules and this is the site of fertilization, naked seed (the seed is exposed)
Four divisions of gymnosperms
Cycadophyta (tropical palms), Ginkgophyta (bibko biloba, memory enhancement), Gnetophytes (very diverse in structure), Coniferphyta
Coniferphyta
conifers ("evergreens"), needle-like leaves, lumber industry, redwoods are the tallest, giant sequoia=largest, oldest
Life cycle of a pine (gymnosperm) demonstrates key reproductive adaptations of seed plants
female gametophyte consists of nutritive tissue, male pollen (gametophyte), most bear female and male cones, extended life cycle (3+ years)
Pine tree life cycle
pollen cone->meiosis->microsporangium->pollen grains
ovulate cone->ovule (single scaled sporophyle->megaspore
pollen grain->micropyle, megaspore ->meiosis, 1 survives
megaspore->mitosis->archegonium, pollen spore->pollen tube
Fertilization->zygote (seedling)
Anthophyta
one division of angiosperms (most dominant plant form today); consists of the rose, petunia, apple, orange, banana tree
Monocots
one cotyledon, veins parallel, complexly arranged vascular bundles, fibrous root system, floral parts in multiples of 3
Dicots
Two cotyledoms, netlike veins, vascular bundles arranged in a ring, taproot present, floral parts in multiples of 4/5
Monocot examples
corn, rice, wheat
Dicot examples
carrot, cacti, oat, shrub, daisy
Characteristics of angiosperms
rely on insects and nimals to transfer pollen, defining reproductive structure for angiosperm is the flower
Flower
reproductive structure generally consisting of a compressed shoot system with four sets of modified leaves; petals, sepals, stamens, carpels
Petals
attract pollinators and provide a wind breaker
Sepals
ringed leaves at base of flower
Carpal
top=stigma, style=middle, bottom=ovary (cont. ovules)
Stamen
top=anther, bottom=filament
Complete flower
contains all four sets of modified leaves (carpals, stamens, petals, sepals)
Incomplete flower
missing one of the 4 sets
Perfect flower
contains both carpals and stamens (it is posible to be an incomplete perfect flower)
Imperfect flower
unisex; contains either carpals or stamens
monoecious
Plants that have both carpallic and stametic flowers
dioecious
plants having either carpallate or stamellate flowers, but not both

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