Gymnosperm Girlies

Question 1

Describe in order of greatest to smallest the amount of plants in each phyla

Answer 1

• angiosperms, bryophytes, seedless vascular, gymnosperms

Question 2

is heterospory unique to seed plants?

Answer 2

• nope! seedless vascular have heterospory too

Question 3

What occurs to the ovule after fertilisation?

Answer 3

• it becomes the seed and the integument develops into a seed coat

Question 4

what part of the seed allows pollen entry?

Answer 4

• the micropyle

Question 5

what are the selective advantages of seed plants?

Answer 5

• embryo is nourished and protected
• dispersal from animals
• dormancy periods until they reach ideal conditions
• seed coat acts as a barrier against fungal or bacterial decay

Question 6

what are some adaptations of seed plants that facilitate survival on land?

Answer 6

• the pollen tubes deliver sperm to the egg without the presence of water
• gametophytes are reduced in size, protected and nourished within the sporophyte

Question 7

why is the ginkgo Bilboa so utilized?

Answer 7

• most commercialized medicinal plant in the world

Question 8

Which gymnosperms are used most commonly in medicine?

Answer 8

• ginkgo, ephedra, pacific yew

Question 9

what are progymnosperms?

Answer 9

• arose ~290 million years ago
• intermediate between seedless vascular plants and seed plants
• produced from freely dispersed spores
• probably evolved from more ancient trimerophytes

Question 10

Which is the largest group of gymnosperms? How long do their seeds take to develop and how old are they?

Answer 10

• coniferophyta
• history extends back to at least the carboniferous period
• seeds take 1 1/2 years to develop

Question 11

how long do seeds take to develop in coniferophyta?

Answer 11

• 1 1/2 years

Question 12

where are male and female sporangia located on the conifer tree?

Answer 12

megasporangia on top, microsporangia near bottom
- SOME species are on separate trees

Question 13

at what time of year does the microsporangium undergo meiosis to form the microspore tetrad? What forms from this tetrad?

Answer 13

• early spring the microsporpcyte undergoes meiosis to form the tetrad of microspores
• microspores each develop into a 4 celled pollen grain: has 2 prothallial cells, 1 tube cell, 1 generative cell
  = immature microgametophyte

Question 14

when does the microgametophyte develop sperm?

Answer 14

after pollination

Question 15

Describe the ovulate cones

Answer 15

• larger and more complex than pollen bearing cones
• central axis and modified branches called bract-scale complexes

Question 16

What makes up a bract scale complex?

Answer 16

• ovuliferous scale and sterile bract
• each ovulate scale bears two ovules on its upper surface: grow into cone waiting for pollen

Question 17

describe pollination of the cone and the production of megaspores

Answer 17

• occurs in spring, scales widely open
• pollen lands on drop of water produced by megasporangium
• 1 month after pollination the megasprocyte undergoes meiosis to produce 4 megaspores (the megaspore furthest from the micropyle survives, other 3 degenerate)

Question 18

Describe the production of the megagametophyte

Answer 18

• production of megagametophyte is sluggish
• doesn’t begin until 6 months after pollination, and may take another 6 months for completion

Question 19

Describe what occurs to microspore and the archegonia

Answer 19

• 1 year after pollination the microspore differentiates into a spermatogenous cell (body cell) and sterile cell (stalk)
• 15 months after pollination the archegonia differentiates (primitive characteristic)

Question 20

what occurs before the pollen the reaches the archegonia?

Answer 20

tue spermatogenous cell divides and produces 2 sperm (mature microgametophyte!)
- finally fertilization occurs 15 months after pollination then pollen cell conveys two sperm to archegonium (1 fertilizes and the other degenerates)

Question 21

How many months after pollination does fertilisation occur ?

Answer 21

• 15 months

Question 22

what does polyembryony mean?

Answer 22

• after fertilization ALL eggs are fertilized and begin to develop into embryo
• usually one merry develops but 3-4% have an embryo with 2-3 seedlings

Question 23

What determines gender in the embryo?

Answer 23

proteins

Question 24

what is a suspensor?

Answer 24

• a structure that absorbs all nutrients from the megagametophute and gives to developing embryo, later undergoes programmed cell death

Question 25

How many diploid saprophyte and haploid gametophyte generations are in the conifer seed?

Answer 25

- 2 sporophyte generations, 1 gametophyte generation

Question 26

what provides food for the developing embryo in gymnosperms?

Answer 26

the gametophyte

Question 27

when are seed cones normally shed?

Answer 27

in the autumn of the second year after pollination

Question 28

what allows for seeds to be released?

Answer 28

most cones open and winged seeds exit some species (lodgepole pine) require extreme heat tone released

Question 29

describe the structure of the embryo

Answer 29

- consists of a hypocotyl root axis with a. root cap and apical meristem - apical meristem and ~8 cotyledons (seed leaves) at the other

Question 30

what do seeds look like in yew plants?

Answer 30

- not cones, red fleshy berry like

Question 31

which phyla produces fleshy berry like cones?

Answer 31

conifers

Question 32

describe cycadophyta

Answer 32

- second largest group of gymnosperms - male and ovulate cones on separate plants, both cones large - palm like leaves, mostly found in tropical regions - dominated ~250 years million ago during the permian period (the age of cycads and dinosaurs)

Question 33

Describe the phylum ginkgophyta

Answer 33

- Gingko biloba is the only living member - can grow up to 30m , has fan shaped megaphyllic leaves - deciduous! - living ginkgos seem unchanged for the lat 150 million years - they are diocious - ovules born in pairs on end of short stalks, ripen to produce fleshy coated seeds in autumn - male trees commonly used in parks (pretty), females smell bad

Question 34

Describe the microgametophyes of cycads and ginkgos?

Answer 34

- produces a sperm pollen tube but doesn't directly penetrate the archegonia - they are haustorial: they can live in the nucellus for several months absorbing nutrients - eventually the pollen grain bursts in vicinity of archegonium and the sperm can swim towards the archegonium and fertilize the egg

Question 35

How do the microgametophytes of ginkgos and cycads differ from gnetophytes, conifers and angiosperm?

Answer 35

- the other 3 do not have flagellated sperm (non-motile) to swim to the egg, and sperm are directly Brought to the egg instead

Question 36

what are some similarities between gnetophyta and angiosperms?

Answer 36

- they have vessel elements - do not produce archegonia, produce eggs directly in gnetum and welwitschia - have stroibli similar to those on angiosperm inflorescences - double fertilisation in ephedra and gnetum!

Question 37

what are the 3 kinds of gnetophyta?

Answer 37

- ephedra, gentum, welwitshia

Question 38

Does double fertilisation gnetum and ephedra indicate that it comes form the same evolutionary pathway as angiosperms?

Answer 38

no, since in the gymnosperms the double fertilisation does not yield an endosperm but more embryos