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