LECTURE 8 STUDY GUIDE (GYMNOSPERMS)

what is an embryophyte?

land plants

which four shared derived characters underlie most of their evolution?

dependent embryos, vascular systems, seeds, and flowers

which plant taxa are: nonvascular (avascular) plants, seedless vascular plants, seed plants, and flowering plants?

nonvascular plants: bryophytes (liverworts, mosses, hornworts)

seedless vascular plants: lycophytes and monilophytes

seed plants: gymnosperms and angiosperms

flowering plants: angiosperms

which five characters define seed plants (spermatophytes)?

1. microscopic gametophytes (haploid) which are protected by sporophyte (diploid) tissues

2. heterospory but spores do not disperse as in ancestral plants

3. ovules protect megasporangia

4. male gametophyte encased in pollen grain for dispersal which aids in pollination (tube cell grows towards ovule) then generative cell dives into two sperm

5. seeds (embryo, food, and integument) disperse

which five phyla are all seed plants classified within?

1. cycandophyta

2. ginkgophyta

3. gnetophyta

4. coniferophyta

5. angiophyta

what is an ovule? where would you find an ovule in a gymnosperm?

ovules are like “eggs” in large ovulate cones

what is pollen? where is the pollen-producing tissue in a gymnosperm?

pollen is like “sperm” in small staminate cones

how does gymnosperm pollen typically disperse? how does its shape differ from angiosperm pollen? how does this difference in morphology relate to dispersal mechanisms?

typically wind dispersed

angiosperm is more circular with spikes and gymnosperm looks like mickey mouse

gymnosperm is smoother and angiosperms are sticker and more prickly which attaches to animals better

what is the difference between ovulate and staminate cones and their role in the life cycle of gymnosperms?

ovulate cones are megastrobili (large) and they make ovules (eggs)

staminate cones are microstrobili (small) and they make pollen (sperm)

how is a seed made from an ovule?

1. ovule encases a megasporangium (diploid) which produces a megaspore (haploid)

2. megaspore grows into a female gametophyte (haploid)

3. the female gametophyte produces an egg (haploid)

4. an ovule is pollinated by a pollen grain (male gametophyte)

5. pollen produces two sperm (haploid) and only one fertilizes the egg which turns into a zygote (diploid)

6. the zygote turns into an embryo (diploid) encased in a female gametophyte (haploid) and sporophyte integument (diploid) to form a seed

a seed consists of an embryo (2n), nutritive material (n), and an integument or seed coat (2n). why do these different parts of a seed differ in nuclear ploidy?

embryo comes from sperm and egg

nutritive material is made out of the female gametophyte

integument or seed coat is made from the zygote

how does the life cycle of seed plants compare to spore-bearing plants?

most of them are monoecious where individuals produces both ovulate and staminate cones and spore-bearing plants either produce female or male gametophytes

which life stage dominates the life cycle in each type of plant?

sporophytes

in which structures must one look to find the gametophyte stage of seed plants?

cones or flowers

do seed plants bear spores (i.e. disperse them)? which life stages of seed plants do disperse? are seed plants homo- or heterosporous?

no

pollen stage

heterosporous, produce micro and macrospores

what does the term gymnosperm mean?

seed plant that reproduces by exposing their seed

in which four phyla/divisions are gymnosperms classified? recall the brief information reported for each phylum?

1. ginkgophyta: monotypic, only a single extant species (ginkgo biloba)

2. cycadophyta: includes 130 spp. sago palm (cycas revoluta) common in las vegas landscapes

3. gnetophyta: includes a few species classified within just 3 genera that inhabit either tropics or desert habitat

4. coniferophyta: largest taxon, ¾ of all gymno species.

which phyla have representatives that live in the southern U.S?

cycadophyta, ginkgophyta, gnetophyta

what is dioecious?

produces male OR female

what are examples of conifers?

pine, fir, cedar, redwood, sequoia, spruce, hemlock, larch, cypress, and juniper species

how do humans use douglas-fir?

used for lumber to frame walls in homes

which tree is the most: massive, tallest, and oldest? where do they live?

oldest tree is bristlecone pine, nevada

massive is giant sequoias, california

tallest is coastal redwood, california

what are local gymnosperms listed during class and at what elevation, relatively, would you find them?

indian tea (ephedra spp.) found at lower elevations

single leaf pinyon (pinus monophyla) lower elevations

white fir (abies concolor) found at mt. charleston elevations

ponderosa pine (pinus ponderosa) also found at mt. charleston elevations

bristlecone pine (pinus longaeva) high elevation

what is the generalized gymnosperm life cycle?

1. microsporocytes (diploid) divide by meiosis to form microspores (haploid) that divide by mitosis to form male gametophytes (haploid) dispersed as pollen. pollination occurs

2. megasporocytes (diploid) divide by meiosis to form megaspores (haploid) that divide by mitosis to form female gametophytes (haploid)

3. gametophytes produce gametes (haploid) by mitosis. sperm fertilizes egg to form a zygote (diploid). it grows into an embryo

4. embryo (diploid) + food (haploid) + integument (diploid) = seed. two seeds can form on each scale

5. seeds disperse sporophyte (diploid) offspring

what is the difference between pollination and fertilization?

pollination happens when male gametophytes form by mitosis from microspores

fertilization happens when gametophytes produce gametes (haploid) and the sperm fertilizes egg to form a zygote (diploid)

which life stage(s) disperse?

pollen stage

seed stage

why is dispersal important for a seed plant?

plant reproduction, population distribution, increases the chance that the seed will land into a better environment for gemination

how are gymnosperms seeds dispersed?

via wind

about how long does it take for a pine tree to undergo its life cycle?

requires two seasons

1. pollen dispersal and pollination

2. gamete formation and fertilization THEN seed dispersal

which gymnosperm sperm are flagellated and which are not?

cycands, ginko, and conifers

gnetophytes sperm are not flagellated

how do sperm get to the ovules to fertilize the egg?

rupture from pollen tubes and wiggles to the egg

do you appreciate the difference between pollination, fertilization, and seed dispersal?

pollination: transfer of pollen to ovules required for fertilization

fertilization: fusion of gametes to form a zygote

seed dispersal: to form new plants

when do these processes occur relative to each other and within the typical time span of a pine life cycle?

first is pollen dispersal and pollination

second is gamete formation and fertilization

then seed dispersal happens after both

happens in 2 seasons