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Plants and colonization of land.docx

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Dalhousie University
BIOL 1011
Mark Johnson

Plants and colonization of land - nicotine, caffine, THC and asprin among other drugs are secondary products produced by plants to defend from bugs, fungi, and nematodes - importance of plants: clothing, energy, food, medicine ect - botany – the study of plants - plants split from red algae 1.5 billion years ago o deep time is weird shit - cyanobacteria were first plants to photosynthesize o first bits of oxygen were used up by chemical processes in oxidization of iron - 2.4 billion years ago Cambrian explosion (oxygen revolution o another smaller one at 700 million years ago - plants colonize land bout 500 million years ago What makes plants plants - plants use starch to store energy instead of sugar o sugar would be great but absorbs= water too easily - chlorophyll B accessory protein - presence of cellulose in the cell wall - thylakoid (little stacks of pancakes) o part of photosynthesis Charophytes and land plants - charophytes are the closest relatives of land plants o a type of green algea o cell division  form cell plate in center of cell o Plasmodesmata  Interconnections between cells o Sperm structure o Peroxisome enzymes o Rose shaped cellulose synthesizing complexes Features of land plants - cuticle - sporopollenin - multicellular jackted sex organs - embryophyte condition o the offspring stay on the plant that produced the egg to develop for a time Major groups of land plants - Plants can often have 2 mating type o Chlamydomonas for example has a + and – cell which come together to form a diploid zygote - How did alt. of gen. originate? o Zygote delays meiosis instead divides and grow resulting in multicellular diploid o Every single land plant has alt. of gen. - There are 10 different divisions of land plants, o Mosses o Ferns o Conifers o Angiosperms - Life cycle of land plants o Meiosis in land plants make spores  A spore is a single cell which can grows without joining with another cell  Spores develop into gametophyte  Gametophyte produce either an egg or sperm  Fertilized eggs become sporophytes  Gametophytes produce gametes  Sporophytes produce spores - Moss o Low growing o 15000 ish species o confined to damp areas o swimming sperm o no vascular tissue o no true leaves o gametophyte dominant o homosporous o sporophytes grow out of gametophytes (the little brown globs on stems) - Ferns o Vascular plants first showed up 410 milion years ago o 20 000 species o vascular tissues o swimming sperm o sporophyte dominant o homo and heterosporous o sporangium grow on underside of leaves, each have spores inside (little brown spots) o gametophyte are heart shaped and contain both make and female sex organs - spores o homosporous one type of spore vs hetreosporous 2 types of spores o mega makes big, egg o micro makes small, sperm - 5 divisions of seed plants o for us conifers and angiosperms Types of plant cells - Epidermal cells o Cuticle o Formed by epidermal cell o Protects from ultraviolet radiation, fungi, insects o Prevents water loss o Secretory cells o Tricomes, special name for hairs o nettle stinging cells, sage, spearmint, mint, thyme, lavender o the “spice” part of spices comes from tricomes o THC gathers on cannabis tricomes o Floral nector forms on flower tricomes - Parenchymal cells o Have a primary cell wall - Collenchyma o Stiff o Supports in young growing tissues o Very thick but uneven primary walls o Celery stack for example - Sclerenchyma o Secondary cells walls o Ligin, woody fibre o Fibers in a bunch o Jute, burlap, hemp o Sclereids  Shorts rounded cells  Acorns - Tracheids and vessel elements o Xylem transport water and minerals o Long and thin o Dead when mature o Very strong, strong secondary walls o Do not stack, more so overlap ends o Vessel elements also stack but more like soup can - Sieve elements o Main elements is phloem, transport sugar water Plants growth - plants grow from there tips - primary cell growth o meristems, apical and lateral o o apical (AM)  root AM and shoot AM  primary growth o Lateral  Vascular cambrium and cork  Secondary cork - 3 tissue systems produced by AM o dermal, vascular, ground o AM shoot (SAM)  Primary growth of both root and shoot  Makes 3 other meristems  Protoderm  Procambrium  Ground meristem  Roots also have an AM (RAM)  Cap of dead tissue on tip to protect the root  RAM found just behind the cap  Core of root called stele  Root hairs increase surface areas  4 month old rye grass o 14 billion root hairs o surface area 400 sq feet - Secondary growth o Forms wood o Trees are almost all dead o Plants that become woody differentiate some of there cells o Vascular cambium produces secondary xylem (wood) on the inside of it and phloem on the outside - SO both primary and secondary growth are occurring in trees o Primary at the tips, buds o Secondary on the inside expanding are turning into wood - The darker wood in the centre on the tree is called heart wood o Plants move toxins and gunk to the center - Lighter wood around the edge is called sapwood Photosysnthesis: Light and dark reactions - transportation o movement of water in an upwards direction o movement of sugar water in all directions o gasses absorbed through leaves o water get absorbed by the root hair through 2 methodes  symplastic: with the cytoplasm  apoplastic outside the cell
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