Bio 140: Chapters 29-31

all green algae and land plants shared a common ancestor a little over a billion years ago

DNA sequences data

helped overcome desiccation (water loss) and protect from harmful effects of the sun

helped maintain gas exchange

fungi helped plants colonize land made nutrients available

chlorophytes and charophytes

never made it to land

sister to all land plants

all land plants have multicellular haploid and diploid stages trend toward more embryo protection and smaller haploid stage

how water is moved, consists of xylem and phloem

multicellular diploid stage produces spores by meiosis

diploid spore mother cells (sporocytes) undergo meiosis in this form produces four haploid spores of gametophyte generation

multicellular haploid stage spores divide by mitosis produces gametes which fuse to form the diploid zygote of the sporophyte generation

large gametophyte, small dependent sporophyte

small dependent gametophyte, large sporophyte

closest living descendants of the first land plants called non-tracheophytes, lack tracheids or other conducting spells

simple but highly adapted to diverse terrain 16,000 species in 3 clades conspicuous gametophytes and small sporophytes

liverworts, mosses, and hornworts

flattened gametophytes with liverlike lobes (80% look like mosses)

umbrella shaped structures

small leaflike (not leaves because of no vascular tissue) structures around a stemlike axis --> gametophytes

how mosses are anchored to the substrate

female gametangia of mosses

male gametangia of mosses sperm must swim in water

puzzling origins due to no fossils until cretaceous photosynthetic sporophytes cells have one large chloroplast

first vascular land plant, appeared 410 MYA short with no roots or leaves and homosporous

only one type of spore produced

conducts water and dissolved minerals upward from the roots

conducts sucrose and hormones throughout the plant

xylem and phloem, enable enhanced height and size develop sporophyta but not gametophyte

lycophytes, pterophytes, and seed plants reduced gametophyte size and gametangia

early fossils reveal stems but no roots or leaves contain food supply for young plants

provide transportation and support, lycophytes diverged before true roots appeared lack of roots limited early tracheophytes

increase surface area for photosynthesis evolved twice

found in seed plants with a singular vein

true leaves, found in ferns and seed plants with branched veins

worldwide distribution but abundant in tropics lack seeds (resemble mosses) sporophyte dominant

phylogenetic relationships among ferns and relatives is still unknown form antheridia and archegonia, require free water for flagellated sperm

whisk ferns and horsetails

found in tropics, sporophyte is evenly forking green stems without true leaves or roots some gametophytes develop elements of vascular tissues

all 15 species are homosporous one single genus, Equisetum sporophyte is ribbed, jointed photosynthetic stems arising from branching rhizomes with roots at nodes

silica deposits in cells

most abundant group of seedless vascular plants (11,000 species) coal formed from ferns conspicuous sporophyte and smaller gametophyte (photosynthetic)

different from mosses, greater development and independence in sporophytes, gametophyte lacks vascular tissue

sporophytes have rhizomes and not true roots leaves (fronds) develop at the tip of the rhizome as fiddleheads

distinctive fern sporangia in clusters on the back of leaves

began to diversify from seedless ancestors 319 MYA

protects and provides food for the embryo allows the clock to be stopped to survive harsh environments before germination later fruit development enhanced dispersal

an extra layer or two of sporophyte tissue that hardens into the seed coat and protects the embryo

divides meiotically inside ovule to produce haploid megaspore, which then produces the egg that combines with sperm

pollen grains dispersed by wind or a pollinator, no need for water

develop within an ovule, enclosed within diploid sporophyte tissues in angiosperms

ovule and protective tissue that develops into fruit

plants with "naked seeds" lack flowers and fruits ovule exposed on a scale

coniferophytes, cycadophytes, gnetophytes, ginkgophytes

pines, spores, firs, cedars, etc. found in colder and sometimes drier regions sources of important products like timber, paper, resin

tallest living vascular plant

oldest living tree

more than 100 species in the northern hemisphere produce needlelike leaves in clusters leaves with thick cuticle and recessed stomata to slow water loss

pines have leaves with this to deter insects and fungal attacks

male gametophytes are pollen grains formed from microspores by meiosis female pine cones form on the upper branches (larger with woody scales)

each ovule of a pine contains a megasporangium with a specific name, and is then surrounded by the integument

small opening at the end of the integument

1. During the first spring, pollen grains drift down between open scales

2. Pollen grains are drawn down into the micropyle and scales close

3. 12 months later, female gametophyte matures as the pollen tube is digesting its way through and mature male gametophyte has 2 sperm

4. 15 months after pollination, pollen tube reaches the archegonium and discharges content

5. One sperm unites with the egg to form a zygote and the other sperm degenerates

slow growing gymnosperms of tropical and subtropical regions, sporophytes of this clade resemble palm trees and female cones can weigh up to 45 lbs

only gymnosperms with vessels in their xylem, composed of linking vessel element cells rather than tracheids cells join end to end in xylem tissue and are common in flowering plants

only one living species remains dioecious species

male and female reproductive structures form on different trees

flowering plants that have ovules enclosed in diploid tissue at the time of pollination

a modified leaf that covers seeds and develops into fruit

changed earth's terrain that was previously dominated by ferns, cycads, and conifers unique features include flower production, insect pollination, and broad leaves with thick veins

oldest known in the fossil record is archaefructus 125 million years old but unlikely to have been the first lack sepals and petals

modified stems bearing modified leaves

primordium develops into a bud at the end of a stalk

pedicel expands at the tip creating the place where other parts attach

flower parts are arranged into circles

sepal --> outermost petals stamens (androecium) gynoecium --> innermost

pollen bearing anther and a filament (stalk)

consists of one or more carpels, houses the female gametophyte

ovary, stigma, and style

swollen base containing ovules that later develops into the fruit

tip of carpel where pollen lands

neck or stalk of the carpal

1. A single diploid megaspore mother cell in ovule undergoes meiosis to produce four haploid megaspores of which one survive

2. The daughter nuclei divide to produce eight haploid nuclei in two groups of four

3. Two nuclei (one from each group) migrate toward the center

4. Cell closest to the micropyle becomes the egg

5. Two other cells are synergids

6. Antipodals are the three cells at other end with no function

7. Integuments become the seed coat

occurs in the anthers similar but less complex than female gametophyte formation diploid microspore mother cells produce four haploid microspores binucleate microspores become pollen grains

mechanical transfer of pollen from anther to stigma may or may not be followed by fertilization pollen grains develop a pollen tube that is guided to the embryo sac the grain cell that lags behind produces the two sperm cells

one sperm unites with egg to form the diploid zygote --> new sporophyte the other sperm unites with the two polar nuclei to form the triploid endosperm that provides the embryo with nutrients seed may remain dormant for many years

1. They maintain dormancy under unfavorable conditions

2. They protect the young plant when it is most vulnerable

3. They provide food for the embryo until it can provide its own food

4. They facilitate dispersal of the embryo

cease once the seed coat forms germination cannot take place until water and oxygen reach the embryo

specific adaptations ensure that seeds will germinate only under appropriate conditions ex: some seeds lie within tough cones that do not open until exposed to fire

mature ovaries often formed from the flower ovary but sometimes occurs without seed development

the ovary wall containing three layers

exocarp, mesocarp, and endocarp determine the fruit type

three in one package fruits and seed coat from prior sporophyte generation remnants of gametophyte generation produced egg embryo represents next sporophyte generation

occurs through a wide variety of methods ingestion and transportation by birds/vertebrates hooked spines on birds or mammals blowing in the wind floating and drifting on water

1.5 million species single celled/multicellular sexual/asexual unusual mitosis

blastocladiomycota, neocallistigomycota, chytridiomycota, glomeromycota, basidiomycota, and ascomycota

zygomycota, sometimes microsporidia

long slender filaments in multicellular fungi, some continuous and some divided by septa cytoplasm flows throughout for rapid growth

mass of connected hyphae grows through and digests substrate