lecture 8 Seed plants Flashcards
(68 cards)
1
Q
What is the first step in the life cycle of lower land plants?
A
Multicellular vegetative haploid plant(gametophyte)
2
Q
What is the second step in the life cycle of lower land plants for males?
A
Male sex organ (gametangium)
3
Q
What is the third step in the life cycle of lower land plants for males?
A
antherozoids
4
Q
What is the Fourth step in the life cycle of lower land plants ?
A
FUSION
5
Q
What is the fith step in the life cycle of lower land plants?
A
Zygote
6
Q
What is the Sixth step in the life cycle of lower land plants?
A
Multicellular vegetative diploid plant(sporophyte)
7
Q
What is the Seventh step in the life cycle of lower land plants ?
A
Sporangium
8
Q
What is the Eight step in the life cycle of lower land plants?
A
MEIOSIS
9
Q
What is the Nineth step in the life cycle of lower land plants?
A
SPORES
10
Q
What is the second step in the life cycle of lower land plants for females?
A
Female sex organ (gametangium)
11
Q
What is the third step in the life cycle of lower land plants for females?
A
egg
12
Q
What does the introduction of genetic material from another individual during sexual reproduction adds to?
A
Variation among offspring
13
Q
Alternation of generations is most clearly seen in?
A
Bryophytes – sporophyte shows a number of pre-adaptations to successful life on land
14
Q
In Pteridophytes the sporophyte is?
A
predominant in the LC
15
Q
What is the most important reproductive & dispersal unit of Bryophyta (haploid)?
A
Spores
16
Q
Describe seeds
A
a reproductive structure Composed of a protected embryo plant
17
Q
How are Embryo’s developed in seed plants?
A
develops from a fertilised oosphere of a gametophyte which is at all times structurally attached to, and physiologically dependent upon, a sporophyte
18
Q
List the features of Gymnosperms
A
•Naked seeds (not protected) •Winged seeds •Wind pollinated •Conifers produce cones –Female cones are larger contain ovules –Male cones are smaller contain pollen •Needle like leaves •Evergreen, leaves are continually replaced
19
Q
List the features of Angiosperms
A
- Protected seeds in fruit
- Produce flowers
- Colourful to attract pollinators
- Broad shaped leaves
- Deciduous – lose all leaves once per year; remain dormant in the winter
20
Q
What species of plants became dominate with time?
A
sporophyte
21
Q
What types of gametophyte plants became dominate?
A
•From single gametophyte plant
–To small male gametophyte
–Large female gametophyte
22
Q
Explain Heterospory
A
–Microspores producing male gametophyte
–Megaspores producing female gametophyte
23
Q
Progressive changes in the life cycle of land plants cont: Development of gametophyte within the spores before?
A
dispersal
24
Q
Progressive changes in the life cycle of land plants cont: Retention of female megaspore in the?
A
megasporangium
25
Progressive changes in the life cycle of land plants cont: development of the female?
gametophyte
26
Development of male gametophyte within what female organs?
–Carpel = megasporophyll
–(NB a carpel = ovary, style & stigma)
27
Seed plants (spermatophytes) – show the?
phenomenon of alternation of generations
28
What the 2 types of spores produced by sporophytes?
* Microspores
| * Megaspores
29
Sporophyte produces 2 types of spores,this is known as?
heterosporous
30
Megasporangium – undergoes?
meiosis to produce megaspores (female gametophyte)
31
Microsporangium – undergoes?
meiosis to produce haploid microspores, germinate to produce male gametophyte (pollen)
32
Many gymnosperms use wind for?
pollination and seed dispersal
33
Microspores (pollen grains) ,Produced in the?
microsporangia (anthers)
34
microsporangia (anthers) Give rise to vestigial male gametophytes & 2 male nuclei which?
1 ) fertilises the female nucleus
–Other joins with the 2ndry nucleus to make the triploid endosperm nucleus
–NB. only in angiosperms
35
Megaspores (ovules) Produced within?
each megasporangium (embryo sac)
36
Megaspores Produces a?
vestigial female gametophyte & a single female sex cell
37
What are the advantages of seed habit?
–Development of pollen grains which may be transferred by wind or animals (usually insects) from 1 plant to another
–Female gametophyte is retained on the sporophyte where it is protected & nourished
After fertilisation the whole gametophyte & the surrounding integument becomes the seed
In Angios (as distinct from Gymnnos) the seeds are surrounded by a modified ovary wall, the carpel, which often plays an important part in the successful dispersal of the seed
38
What do Gymnospermae have?
* Have naked seeds – no carpel is present
* No vessels in their xylem tissue
* Major surviving group is the Coniferae
* Characterised by needle-like leaves & cones
39
What do Angiospermae have?
Have seeds which are enclosed in the carpel – which becomes modified to aid dispersion
* Double fertilisation takes place & an endosperm tissue forms within the ovule
* Vessels are present
40
Compare Tracheids and Vessels
* Both are tubes that allow water & minerals to move around the plant
* They give support to the plant
* Water & minerals go in and out through pits on the sides of the tubes
* Vessels form continuous tubes
* Tracheids are tapered at one end and allow one cell to overlap around another at their ends
41
WHat are Gymnosperms in relation to seeds?
* After fertilisation - young sporophyte is liberated as the seed
* Members show a tendency to a reduction in leaf size
•Xylem is composed of tracheids
–(*except Gnetales – vessels)
•Microspores pass down the micropyle & come in direct contact with the nucellus during the pollination process
42
Describe Cycadophytes
* Short unbranched trunk
* Terminal crown of long, leathery fern-like pinnate leaves
* Mostly less than 6 feet tall
* Large conspicuously developed pith and cortical zones in the stem
* Found across much of tropical & subtropical parts of the world
43
Describe Cycadophytes in relation to seeds
* Relatively little development of 2º xylem
* All dioecious (male & female strobili on separate plants)
* Pollen sacs on scale like micosporophylls in compact cones (microsporangia)
* Megasporophylls also in cones•Pollination by wind
44
Describe Gnetales
* Long micropylar tube formed by the integument of the ovule
* Leaves opposite
* Dicotyledonous embryo
* Absence of resin canals
* Presence of vessels in xylem
* Both staminate & ovulate structures show a compound strobilus
45
Describe Ginkgoales
* One living species Ginkgo biloba
* Deciduous tree with fan-shaped leaves
* Male strobilus in short pendant paired microsporophylls
* Female ovules develop into yellowish, cherry-like seeds
* Seed coat decomposes at maturity for dispersal
46
Coniferophytes comprise gymnosperms with?
* Simple, often needle-shaped or scale leaves
* Tall often profusely branched trunks
* Relatively small pith & cortex zones in stem
* Conspicuous development of 2ndry xylem
47
Describe coniferales
* Strobili modified into cones
* Cone scales are modified sporophylls
* Xylem contains tracheids but no vessels
* Wind pollination
48
Describe coniferales in relation to seeds
* Seeds unprotected by sterile tissue
* Female cones contain megasporangium
* Each megasporangium produces an ovule with an integument
* Male cones contain microsporangium in strobilus containing a microspore – pollen grain•e.g. Pinus, Abies, Picea, Tsuga
49
List the features of Cycads
Ciliated antherozoids
2degrees thickening not vigorous
Wood manoxyllic
Comparatively small plants
Stems unbranced
leaves pinnate
Dioecious
Dicotyledonous
Ovules have radial symmetry
Originated from seed ferns
Limited tropical and sub-tropical distribution
50
List the features of conifers
Passive male gametes
Massive 2 degree thickening
Wood pycnoxylic
Mostly large plants
Stems profusely branched
Leaves simple, 4 types
Monoecious
Polycotyledonous
Ovules have bilateral symmetry
Originated from Cordaitales
Still successful. More or less global distribution
51
Ecological importance of gymnosperms
* Provide food & habitat for wildlife
* Forests prevent soil erosion
* Reduce greenhouse effect gases
52
Economic & commercial importance of gymnosperms
* Lumber for wood & paper
* Resins – wood, furniture
* Ornamental plants (trees, landscaping)
* Food - pine nuts (pesto)
53
Angiosperms undergo an alternation of?
generations in which the diploid, or sporophyte, generation is dominant
54
The haploid, gametophyte generation is exceedingly?
reduced & vestigial (more so than in the gymnos)
55
Explain Angiosperm reproduction
* Starts with the development of the anther & the carpel in the flower
* Meiosis gives rise to microspores & megaspores – which germinate to produce reduced gametophyte plants
* Give rise to gametes which fuse & the resulting zygote has divided to form the new embryo sporophyte plant
* Process is completed with the shedding & germination of the seed, which contains the new diploid sporophyte plant as the embryo
56
Angiosperms Seed is an?
integumented megasporangium with a single megaspore (the ovule) & within this a vestigial female gametophyte generation develops
* It is retained & nourished by the sporophyte during its development
* The microspore or pollen grain is transferred to the proximity of the ovule by wind or insects
57
Explain Microsporogenesis reproduction in Angiosperms
–pollen grains are the microspores
–Occurs within the pollen sacs of the anther & involve spore mother cells
–Pollen sacs are microsporangia
–Each spore mother cell gives rise (via the two divisions of meiosis) to a group of 4 pollen grains
•Usually separates into four distinct grains
58
Megasporogenesis–Meiosis takes place within the?
ovule
59
Explain Microgametogenesis
–Process whereby the microspore (pollen grain) gives rise to a vestigial male gametophyte plant
–& eventually to 2 male gametes
–Greatly shortened gametophyte generation
–Non-flagellate male gametes
60
Megaspore nucleus divides mitotically to give?
Gives rise to the 8 nucleate embryo-sac
61
Explain Fertilisation
* When in contact with the stigma the pollen grain germinates
* Pollen tube grows from the stigma down through the style into the ovary
* Ovule is penetrated via the micropyle, then the nucellus & finally the embryo sac
* Once the pollen tube has penetrated into the embryo sac the tip breaks down & both male gametes are discharged
* Fertilisation involves the fusion between one of the male gametes with the single female gamete of the embryo sac
62
The unique feature of fertilisation in angiosperms is that a?
2nd fertilisation also takes place when a 2nd male gamete fuses to form the endosperm
63
The endosperm gives rise to nutritive tissue in the seed which?
–Provides nutrition for the embryo & young plant
–Often filled with food materials – carbs, fats & proteins present in labile form
64
What is the sequence in which Female Gametophytes are developed
Parent Diploid sporophyte -> Flower -> Stamen -> Pollen sac -> MEIOSIS -> Many micro-spores -> Female Gametophye (Embryo sac)
65
What is the sequence in which male Gametophytes are developed
Parent Diploid sporophyte -> Flower -> Carpel -> ovule -> Meiosis -> One mega spore -> Male Gametophyte (Plant).
66
What happens after the sequence which Female Gametophytes are developed?
2 gametes developed -> Double fusion -> the sequence then splits. The one gamete goes to -> Zygote -> embryo -> Seed dispersal and germination. The second gamete goes to -> Primary endo-sperm nucleus -> Endosperm.
67
nuclei are derived from
the pollen grains
68
Explain double fertilization
One sperm nucleus fertilizes the egg, generating a 2Ndiploid zygote.Another sperm nucleus fertilizes a polar cell with two 1N nuclei, generating a 3N triploid endosperm, which provides nutrients to the developing embryo.
