Practical 3- Week 4 (Ch 30)
gametophyte
(1N) the gamete-producing and usually haploid phase, producing the zygote from which the sporophyte arises. eg. dominant form in bryophytes.
sporophyte
(2N) the asexual and usually diploid phase, producing spores from which the gametophyte arises; stalk/seta, capsule containing spores eg. dominant form in vascular plants; the frond of a fern
Pterophytes
(ferns) vasc. plants: have x&p; ferns first to develop complex stems and large leaves; xylem is lignified, have stems, leaves, and roots; ferns reproduce via spores
What does 'alternation of generations' mean?
(metagenesis) the alternation of a sexual phase and an asexual phase in the life cycle of an organism; is a term used to describe the type of life cycle that occurs when they have distinct sexual haploid and asexual diploid stages
male cones
(microstrobilus) are small and inconspicuous and not as 'woody' as female, shorter life span, and produce pollen
bryophytes
(non-vasc. plants) Bryophyta (Byron = moss, phyton = plant) liverworts, hornworts and mosses growing predominantly in moist environments; 1st group to colonize land, most primitive; produce swimming sperm, have no true vasc. system (x&p), have primitive type of conducting cells to transport water and nutrients around the plant, no lignified tissues, roots, stems and leaves
Gymnosperms
(seed plants and pollen) 'Seeds of change', naked or exposed seeds Phylum Gnetophyta - Gnetophytes Phylum Ginkgophyta - Ginkgo Phylum Cycadophyta - Cycads Phylum Coniferophyta - Conifers first to not need water for reproduction, all have pollen, cones and seeds and the dominant gen. is the sporophyte gen.
What adaptations do Pterophytes have for living on the land?
-How do they avoid drying out on land? cuticle, moist environment, stomata, epidermis -How do they support themselves on land? roots and vasc. tissues, cuticle, leaves -Is the plant differentiated into different parts, if so, what are the various parts? yes: stem (short, compressed), rhizomes and roots, and leaves -Do they have differentiated tissue, if so, what are the various types of tissues? vasc. tissue: x&p, epidermal tissue, ground tissue
What adaptations do Lycophytes have for living on the land?
-How do they avoid drying out on land? thick cuticle, moist environment, stomata -How do they support themselves on land? roots and vasc. tissues to get bigger -Is the plant differentiated into different parts, if so, what are the various parts? yes: stem, roots, and microphylls -Do they have differentiated tissue, if so, what are the various types of tissues? vasc. tissue: x&p, root tissue, stem tissue, microphyll tissue
What adaptations do Bryophytes have for living on the land?
-How do they avoid drying out on land? thin cuticle, moist environment, stomata -How do they support themselves on land? rhizoids -Is the plant differentiated into different parts, if so, what are the various parts? yes: rhizoids, gameto. and sporo. -Do they have differentiated tissue, if so, what are the various types of tissues? gameto. and sporo.; rhizoids, seta, leaflike structures
move from water to land
-develop ways to support themselves on land, -develop ways to obtain water and nutrients from the soil -develop transport systems to transport water and nutrients in and around the algae -develop different reproductive structures and strategies (so that their gametes or spores do not dry out and therefore perish).
moss sp.
-gametophyte dom. gen. -spores formed in capsule of sporophyte, less spores -leaflike structure but no vasc. tissue -no true stem (seca) b/c no vasc. tissue, no lignin -rhizoids for roots, unicellular and filamentous
angiosperm success
-incredible structural diversity -more efficient vascular system -mutualistic associations with animals to assist in pollination -relatively short generation times.
fern frond (leaf)
-much larger leaves w/ vasc. tissue -use vasc. tissues -cuticle present -spores in sori under the leaf
moss "leaf"
-not true leaves b/c no vasc. tissue, small -use diffusion/induction -very small, thin cuticle -spores in capsule of sporophyte
Selaginella sp.
-sporophyte dom. gen. -spores formed in stobili, more spores -microphylls w/ only 1 strand of vasc. tissue (1st true leaves) -1st to have true stem b/c have vasc. tissues, lignin in 25% of CW -1st to have true roots
lycophyte adaptions for land
1. 1st group of plants to develop x&p, vascular tissue is organised in steles 2. tracheids are strengthened with lignin for growth & structural support 3. growth in root and shoot from apical meristems 4. have true roots for attachment and water/nutrient absorption 5. have true leaves (microphylls) w/ single strand of vasc. tissue down length of microphylls
to survive on land
1. avoid drying out (dessication): cuticle 2. uptake nutrients from soil: roots 3. body support: stem 4. reproduction: must protect gametes from external environment 5. possess differentiated cells- b/c air and soil differ in composition and resources: xylem & phloem
why algae would not make good land plants
1. do not have vasc. tissues 2. no cuticle (dessication) 3. no stomata (can't avoid dessication) 4. no true roots 5. need water for reproduction
Phylum Cycadophyta - Cycads
140 species remain (representing 11 genera), restricted to (sub)tropical habitats; distinct trunk and a cluster of leaves at the top of the stem; highly toxic containing both neurotoxins and carcinogenic compounds; male and female cycad plants: -Male cycads produce a large strobili (cone) which contains pollen. -Female cycads produce a large strobili (cone) which contains the eggs. The eggs get fertilised and seeds are formed.
fern life cycle (pterophytes)
2 distinct phases: gameto. and sporo., -gameto.: produce the male and female sex cells (gametes), the female of which, when fertilized, develops into a new sporophyte to continue the cycle -sporophyte dom.: The spores land on the substrate and develop into the gametophyte which is small, inconspicuous and short-lived. -spores protected by thick wall and dispersed by wind
How does the moss gametophyte differ from a liverwort gametophyte?
Liverwort: gametophyte body thallose or foliose Moss: gametophyte body differentiate into prostrate, branched filamentous, thalloid protonema and leafy erect; arrangement of leaves?
Lycophytes
P. Lycophyta, Selaginella sp. (heterosporous) and Lycopodium sp. (homosporous), most ancient living phylum of vasc. plants, only 3 living families w/ 1000 sp., usu. in wet environments, gen. small and can be aquatic, terrestrial, climbing and almost half the species are epiphytes; only plant to have microphylls; sporophyte dom. gen., sperm still needs water to swim to egg (like bryophytes)
hornworts
Phylum Anthocerotophyta, 100 sp., gametophytes like thallose liverworts: rosette or ribbon-like; sporophyte with a foot (to attach to gameto.), and a capsule that is long and cylindrical and contains spores
mosses
Phylum Bryophyta; leaves arranged spirally or alternately around a stemlike axis (not a true stem), usu. 1 cell thick (lack vasc. tissue and stomata); gametophyte dominate generation (actively PS) rhizoids, gametophyte, leaf like structures, sporophyte and capsule
liverworts
Phylum Hepaticophyta, 6000 sp., small, green, terrestrial; no true roots, stems, or leaves; single celled rhizoids that aid in absorption (like roots) and also used to attach them to the substrate; leafy gametophyte (clear stem/leaf differentiation) or appear dorsoventrally flattened, without obvious leaves (thallose liverworts)
What does homosporous mean?
Producing spores of one kind only that are not differentiated by sex, grow into bisexual gametophytes (producing both male and female gametes) ex: horsetails and ferns
What does heterosporous mean?
Producing two types of spores differing in size and sex, the male microspore and the female megaspore, which develop into separate male and female gametophytes ex: most seed-bearing plants, as well as some ferns and other seedless plants
similarities and differences between a gymnosperm and an angiosperm
Similar: both produce seeds Different: A- seeds in fruit, pollinated from animals attracted to flowers G- naked see, wind dispersal
how bryophytes are like terrestrial plants
Some have a cuticle and stomata, produce wind-borne spores that are protected from dehydration by a wax-impregnated wall on the outside of the spores, shelter their archegonia and antheridia inside a jacket of protective cells, most have meristems
moss life cycle
The zygote develops into the sporophyte, which when mature produces spores that are dispersed onto the sediment and a gameto. develops from the spore
from flowers to fruit
after fertilization, petals wither, ovary begins to swell, petals drop off, seed develops inside fruit and fruit gets bigger
Phylum Ginkgophyta - Gingko or maidenhair tree
are 'dioecious', (separate sexes), living fossil, Produces male cones, but no female cones. ovules produced at the ends of stalks. female fruit smells bad; herbal supplement to inc. blood flow to brain ex: Gingko biloba
Describe how Pterophytes reproduce on land?
asexual stage makes spores (sporophyte) and sexual stage involved fertilization (gametophyte)
What is differentiated cells/tissue?
cells that have a specific function, specialized
genera Ephedra
desert habitats throughout the world as a highly-branched shrub with jointed stems and much reduced leaves, used medicinally (methampetamines) • Shrub • Minute, scale-like leaves • Green, photosynthetic stems • Male / Female cones produced on nodes of stem
genera Welwitschia
desert regions w/ Most of the plant body is buried in the sandy substrate; a large bowl-shaped structure extends above the surface which produces only two long, strap-like leaves that continue to increase in length throughout life
Explain why a blade is not considered a 'true' leaf. What is the function of a blade?
does not have vascular elements; function still to get nutrients & PS
seeds
embryo and its food supply surrounded by protective coat. embyro can dry out quickly on land, so they developed hard, resilient coats; various seed dispersal
archegonia
female reproductive structure
angiosperms
flowering plants, one phylum, the Anthophyta, 260,000 spp. advanced vascular tissue, a dominant sporophyte stage, a markedly reduced gametophyte stage, and production of seeds enclosed w/in a fruit; two groups: Monocotyledons and the Eudicotyledons
taxol
from Pacific Yew to treat cancer
sexual phase
gametophyte generation, produces gametes (sex cells)
What might be the advantage of having seeds with a dormant but viable state?
if outside conditions aren't suitable for growth of new seed, can just wait until it gets better
lignin
in all vascular plants, provides structural support - allows the plant to grow large
alteration of generations
involves an alternate doubling and halving of chromosome numbers at each phase
sporophyte of Selaginella sp.
is differentiated into root, stem and Microphylls
giant kelp
large algae that do have specialised cells for transporting nutrients throughout the plant
female cones
larger, harder and live for many years and produce the seeds. pollination and fertilization takes place here
spores
located in small cone like structures called strobili or spores attached to stem
antheridia
male reproductive structure
genera Gnetum
moist, tropical regions where they grow as both as trees and vines; Pinnately veined, opposite leaves
Phylum Coniferophyta - conifers
most diverse phyla, pine cones and seeds ex: pines, spruces, firs, yews and junipers; tallest known plant (giant redwood, Sequoia sempervirens) and the oldest known plant (bristlecone pine, Pinus longaeva).
Why are ferns restricted to a moist environment (hint - look at the lifecycle)?
need water for gametophyte reproduction b/c gameto. is fragile
Why you think bryophytes are restricted to moist environments?
no vasc. tissue or roots to uptake water
Why is the thin, upright shoot of a moss gametophyte not considered to be a true stem?
no vasc. tissues
moss leaves have
no vasc. tissues, but do have cuticle
all plants
non-seed plants, non-vascular (Bryophytes- liverworts, hornworts, and mosses) as well as vascular (Lycophytes- Selaginella sp. and Pterophytes- ferns)
Explain why a stipe is not considered to be a true stem. What is the function of a stipe?
not a true stem b/c it lacks tissues specialized for water and nutrient transport, b/c always in water; does have a special region of cells to transport nutrients
monocotyledons
petals in 3 & 6, scattered bundles, parallel leaf venation
eudicotyledons
petals in 4 & 5, organized bundles, branched venation
algae
plant-like organisms that have chlorophyll and other pigments to carry out photosynthesis; no roots, stems, leaves, vascular tissue (xylem and phloem); water provides support for algae and most of their cells have contact with water which has all nutrients that algae needs, nutrients absorbed through cell wall; in water, sperm from algae are able to swim directly to eggs (simple reproductive structures); single celled, colonial, flat like in structure, leaf like sheets, single filaments, microscopic or 50 long
all seed plants have
pollen grains containing sperm
moss sporophyte
produces spores, typically smaller, simpler, shorter-lived; shows defined (determinate) growth; attached to gameto. throughout life and partly dependent on it for nutrition
What are the advantages of dispersing seeds?
reach more broad locations until find a suitable habitat
pine cones often live up to 3 years b/c
seeds need a lot of time to grow and could have a dry year, so bad time to release seeds
flowers
sexually reproductive part of plant; type of modified leaf
stele
solid core of vasc. tissue, fake vasc. tissue, the central core of the stem and root of a vascular plant, consisting of the vascular tissue (xylem and phloem) and associated supporting tissue
Describe how Bryophytes reproduce on land?
spores released, need water for sperm to swim, sex organs, and zygote
reproduction of conifers
sporophyte dom. gen., (the gametophyte form is confined to the cones). produce male and female cones that can be on same tree; male cone produces pollen which is brought by wind to the female cone with produces the seeds. the zygote is produced in female cone after pollination and fertilization via pollen tube and becomes embryo and integumentary enclosure surrounds it, forming the seed. The seeds are dispersed as the matured and now-fertilised cone opens up. Seeds are dispersed by the wind, settle onto the substrate and grow.
asexual phase
sporophyte generation, produces spores asexually
In the lifecycle of plants, what does 'dominant generation' mean?
the generation that the plant spends most of its life in; occupies largest portion of life cycle
cuticle
the outer protective layer of a leaf
Terrestrial plants
thought to have evolved from algae called Charophytes.
Phylum Gnetophyta - Gnetophytes
three genera: Gnetum, Welwitschia, and Ephedra; vessel elements in the xylem and Gnetophyta strobilus (bridge to angiosperms); all produce a megasporangiate (male) and microsporangiate (female) cone; seeds not enclosed
pollen grains
to transport male gametes (sperm) so no longer needed water
Why are ferns able to grow larger than bryophytes?
tough vasc. tissue w/ lignin enables them to grow larger in response to competition for light
energy storage structures
tubers, bulbs, and the cotyledons of seeds
moss gametophyte
usu. have small leaflike structures (no vasc. tissues) but do have water-conducting tissue; anchored to substrate by rhizoids which have conductive tissues
Describe how Lycophytes reproduce on land?
yes still need water to reproduce on land for sperm to swim to egg (ferns need it too)
some algae body parts
• Holdfast - root-like structure that attaches algae to the substrate • Stipe - a stem-like structure • Blade - leaf-like structure