chapter 30 Flashcards

Question

Horsetails

Answer 1

All 15 living species are homosporous Constitute a single genus, Equisetum Sporophyte consists of ribbed, jointed photosynthetic stems that arise from branching rhizomes with roots at nodes Scale-like leaves arise from nodes and are nonphotosynthetic Silica deposits in cells – scouring rush

Answer 2

Most abundant group of seedless vascular plants About 11,000 species Coal formed from forests 300 MYA Conspicuous sporophyte and much smaller gametophyte are both photosynthetic True roots, stems and leaves

Answer 3

Produce distinctive sporangia in clusters called sori on the back of the fronds Diploid spore mother cells in sporangia produce haploid spores by meiosis Spores germinate into gametophyte Rhizoids but not true roots – no vascular tissue Flagellated sperm

Answer 4

Seed plants first appeared 305–465 MYA Evolved from spore-bearing plants known as progymnosperms Success attributed to evolution of seed Protects and provides food for embryo Allows the “clock to be stopped” to survive harsh periods before germinating Later development of fruits enhanced dispersal

Answer 5

Embryo protected by integument An extra layer or 2 of sporophyte tissue Hardens into seed coat Also contain food supply for embryo

Answer 6

Female reproductive structure—cone or flower Inside ovule of female—megasporangium (2n) divides meiotically to produce megaspores (n)germinates (mitosis) into megagametophyte (n)egg (n) Male reproductive structure—cone or flower Microsporangium (2n) meiosismicrospores (n) germinate into microgametophytes (n) (pollen grains)mitosisproduce sperm (n) Pollen flies or is carried to female part of plantreleases spermfertilizes eggzygote

Answer 7

``` Plants with “naked seeds” There are four living groups Coniferophytes Cycadophytes Gnetophytes Ginkgophytes All lack flowers and fruits of angiosperms All have ovule exposed on a scale ```

Answer 8

Most familiar gymnosperm phylum Pines, spruces, firs, cedars, and others Coastal redwood – Tallest living vascular plant Bristlecone pine – Oldest living tree Found in colder and sometimes drier regions of the world Conifers are sources of important products Timber, paper, resin, and taxol (anti-cancer)

Answer 9

More than 100 species, all in the Northern hemisphere Produce tough needlelike leaves in clusters Leaves have thick cuticle and recessed stomata to retard water loss Leaves have canals with resin to deter insect and fungal attacks

Answer 10

Male gametophytes (pollen grains) Develop from microspores in male cones by meiosis Female pine cones form on the upper branches of the same tree Female cones are larger, and have woody scales Two ovules develop on each scale Each contains a megasporangium Each will become a female gametophyte

Answer 11

Female cones usually take 2 or more seasons to mature During the first spring, pollen grains drift down between open scales Pollen grains drawn down into micropyle Scales close A year later, female gametophyte matures Pollen tube is digesting its way through Mature male gametophyte has 2 sperm 15 months after pollination, pollen tube reaches archegonium and discharges contents One sperm unites with egg = zygote Other sperm degenerates

Answer 12

Slow-growing gymnosperms of tropical and subtropical regions Sporophytes resemble palm trees Female cones can weigh 45 kg Have largest sperm cells of all organisms! Flagellated sperm carried in pollen grain but swims to egg

Answer 13

``` Only gymnosperms with vessels in their xylem Contain three (unusual) genera Welwitschia--Africa Ephedra--ephedrine Gnetum ```

Answer 14

``` Only one living species remains Ginkgo biloba Flagellated sperm Dioecious Male and female reproductive structures form on different trees Resists pollution ```

Answer 15

Flowering plants Ovules are enclosed in diploid tissue at the time of pollination Carpel, a modified leaf that covers seeds, develops into fruit

Answer 16

Origins as early as 145–208 MYA Oldest known angiosperm in the fossil record is Archaefructus Closest living relative to the original angiosperm is Amborella

Answer 17

Modified stems bearing modified leaves Primordium develops into a bud at the end of a stalk called the pedicel Pedicel expands at the tip to form a receptacle, to which other parts attach Flower parts are organized in circles called whorls

Answer 18

``` Outermost whorl – sepals Second whorl – petals Third whorl – stamens (androecium) Pollen is the male gametophyte Each stamen has a pollen-bearing anther and a filament (stalk) Innermost whorl – gynoecium Consists of one or more carpels House the female gametophyte ```

Answer 19

Single megaspore mother cell in ovule undergoes meiosis Produces 4 megaspores 3 disappear Nucleus of remaining megaspore divides mitotically Daughter nuclei divide to produce 8 haploid nuclei 2 groups of 4 = female gametophyte Integuments become seed coat Form micropyle

Answer 20

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 One of the two pollen grain cells lags behind This generative cell divides to produce two sperm cells No flagella on sperm

Answer 21

One sperm unites with egg to form the diploid zygote New sporophyte Other sperm unites with the two polar nuclei to form the triploid endosperm Provides nutrients to embryo Seed may remain dormant for many years Germinate when conditions are favorable