Seedless Plants - Ch. 25 Flashcards
how many years ago did the green algae and land plants share an ancestor; what supergroup are they included in?
1 billion years ago; supergroup archaeplastida
what two lineages did ancestral green algae give rise to?
chlorophytes and streptophytes
what did the chlorophytes give rise to?
aquatic algae
what did the streptophytes give rise to?
gave rise to land plants. group includes the charophytes, which includes the pond plants, and the embryophytes which includes the embryophytes
chlorophytes
microscopic, 2 anterior flagella, most are haploid, reproduces both sexually and asexually, not haplodiplontic, always unicellular
streptophytes
eukaryotic, autotrophic, starch food storage as cellulose, alternations of generations life cycle, asexual and sexual reproduction, capture light and fix CO2
did chlorophytes make it to land?
no
did the charophytes make it onto land?
yes, they are the sister group to all land plants
charophytes
clade of the streptophytes, also green algae, distinguished from chlorophytes by close phylogenetic relationship to land plants, have haplontic life cycles, has 2 clades: charales and colechaetales
what traits do charophytes share with land plants?
homologous chloroplasts, meaning they utilize chlorophyll a and accessory pigments chlorophyll b and carotenoids, cellulose in cell wall, and store excess sugars as starch
characteristics of embryophyes
waxy cuticle, gametes protected in sex organs (gametangia), embryo protected by the parent
what are the adaptations to terrestrial life?
protection from desiccation with the addition of a waxy cuticle and stomata, moving water using tracheids, dealing with UV radiation caused mutations, haplodiplontic life cycle
what are the ecological roles of bryophtes?
contribute to biodiversity in all terrestrial ecosystems, carbon storage, and the colonization of rocks and soil
what do soil crusts do?
provide micro-habitats, the crust communities are algae, lichen, moss, and bacteria. the soil crusts stabilize soil, reduce erosion, and provide a nitrogen fixing bacteria and micro-organisms
bryophytes
closest living descendants of first land plants, called nontracheophytes because they lack tracheids, they uptake nutrients and water through diffusion, mycorrhizal relationships to enhance water uptakes, highly adaptable, 3 clades: liverworts, mosses, and hornworts, gametophyte is haploid and sporophyte is diploid, require water for sexual reproduction
thallus
A plant body that is not differentiated into stems and leaves, and lacks true roots and a vascular system. The plant body may be round with extended leaves or may be flat and ribbon-like.
rhizoids
anchor the plant, Hair-like structures on the thallus similar to roots
dichotomous branching
Branching into two arms, or forking into two
antheridium
Male sex organ -club shaped which contains androcytes. Each androcyte changes to a small, motile, biflagellate antherozoid (spermatozoid).
archegonium
Female sex organ – flask-shaped. Contains an egg or oosphere.
zygote
The result of fertilization by the penetration of the large, non-motile oosphere by the small, motile antherozoid
Liverworts
marchantiophyta/hepaticophyta
have flattened gametophytes with liverlike lobes, form gametangia in umbrella-shapped structures, also can undergo asexual reproduction, no stomata - takes up water on the surface and no cuticle
haplodiplontic life cycle
diploid stage: sporophyte, produces haploid spores by meiosis, the diploid spore mother cells (sporocytes)undergo meiosis in the sporangia and will produce 4 haploid spores and the first cells of gametophyte generation
haploid stage: gametophyte
spores divide by mitosis, produces gametes, gametes fuse to form diploid zygote, first cell of next sporophyte generation
hornworts
anthocerotophyta
no fossils until the cretaceous period, sporophyte is photosynthetic and embedded in gametophyte tissue, cells have a single large chloroplast, narrow sporophyte, stomata are present, many form symbiotic relationships with cyanobacteria and fix nitrogen in the air
mosses
bryophyta
gametophytes consist of small, leaflike structures around a stemlike axis, anchored to substrate through rhizoids, multicellular gametangia form at the tips of gametophytes, most numerous species, live in a variety of habitats like tundras or tropics, slow down erosion, store moisture and nutrients, provide shelter and food,, sensitive to air pollution, only have a stomata on sporophyte
tracheophyte plants
cooksonia was the first vascular land plant, appeared 420 mya, phylum rhyniophyta, no roots or leaves, homosporous
xylem
conducts water and dissolved minerals upwards from the roots
phloem
conducts sucrose and horomones throughout the plant
vascular tissues
enable enhanced height and size in the tracheophytes, developes in sporophyte but not gametophyte, cuticle and stomata are found in vascular seedless plants
tracheophytes
three clades: lycophytes, pterophytes, and seed plants, gametophyte reduced in size relative to sporophyte during their evolution, reduction in multicellular gametangia,
lycophytes
club mosses, abundant in the tropics, lack seeds, resemble true mosses but are not actually, sporophyte dominant, earliest group of seedless, can be heterosporous or homosporous
pterophytes
Phylogenetic relationships among ferns and their relatives is still being sorted out, All form antheridia and archegonia, All require water for flagellated sperm
whisk ferns
phylum monilophyta, class psilotopsida, found in tropics, Sporophyte consists of evenly forking green stems without true leaves or roots, Some gametophytes develop elements of vascular tissue–Only one known to do so, branched dichotomously, have small yellow nodes that are sporangia
horsetails
phylum monilophyta, class equisetopsida, all 15 living species are homosporous, Sporophyte consists of ribbed, jointed photosynthetic stems that arise from branching rhizomes with roots at nodes, Silica deposits in cells – scouring rush
ferns
Most abundant group of seedless vascular plants–About 11,000 species, Coal forests and swamps 300 MYA, Conspicuous sporophyte and much smaller gametophyte are both photosynthetic
fern reproduction
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, Fern life cycle differs from that of a moss, Much greater development, independence and dominance of the fern’s sporophyte, Gametophyte lacks vascular tissue
evolution of seed plants
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, 400 million years between appearance of vascular tissue and true leaves–Natural selection favored plants with higher stomata densities in low-CO2 atmosphere–Higher stomata densities favored larger leaves with a photosynthetic advantage –Seeds–Highly resistant–Contain food supply for young plant–Lycophytes and pterophytes do not have seeds
sporophyte
diploid, then results in syngamy (fusion) of two gametes
sporangia
vessel for spores
microspores
male spores
megaspores
female spores
male gametangium
antheridium
female gametangium
archegonia
stoma
pores within the cuticle that open and close to regulate traffic of gases and water vapor (not all plants have stoma)
when did land plants appear?
during the ordovician period (500 mya)
nonvascular plants
lack vascular tissues that trasnport water and nutrients
vascular plants
developed 500-435 mya, have vascular tissues, divided into lycophytes and monilophytes
lifecycle of liverworts
- haploid spores germinate into flattened thalli attached to a substrate
- stalk like structures grow from the thallus and carry male and female gametangia
- male gametes swim with their flagella to the female for fertilization
- zygote grows into a sporophyte inside the archegonia
- disseminated by wind or water, spore dispersal aided by elators
- can reproduce asexually though gemmae cups
lifecycle of hornworts
- follows alternation of generations
- gametophytes grow as flat thalli on the soil with embedded male and female gametangia
- flagellated sperm germinate archegonia
- zygote develops into a long and slender sporophyte and splits open to release spores
- thin branched cells surround spores to propel them further
- will germinate and give rise to the next generation
lifecycle of mosses
- follows alternation of generations
- haploid gamete, which germinates from a haploid spore
- cells akin to an apical meristem actively divide and give rise to a gametophore
- male and female gametangia develop at the top of different gametophores
- males produce alot of sperm, females make only one egg
- sperm swims down neck into ventor
- sporophyte is dependent upon gametophyte
when did vascular plants appear?
present in silurian period, about 430 mya
microphylls
small and simple vascular system, 350 mya in silurian period, may have originated from flattening of lateral branches or sporangia that lost their reproductive capabilities
megaphylls
large leaves with a pattern of multiple leaves, seen in ferns and more derived vascular plants
sporophylls
leaves that were modified structurally to bear sporangia
strobili
cone-like structures that contain sporangia, like pine cones
true ferns
phylum monilophyta, class polysodiosida
- considered the most advanced seedless plants
- live in shaded areas
- in denovian period - 420 mya
- dominant stage of lifecycle is the sporophyte
- fronds have sporangia underneath called sori
