Gymnosperms

Question 1

what are the spermatophytes?

Answer 1

gymnosperms and angiosperms

Question 2

what developments happened between monilophytes and spermatophytes?

Answer 2

• Heterospory
• Bifacial cambium: Cambium is a layer of meristem tissue (plant stem cells) that forms a sleeve around the trunk under the bark
  Bifacial means that new cells are produced to both sides of the cambial layer
• Seeds (but not the only time seeds evolved but led to present day seeds)

Question 3

what are the features of gymnosperms? reproduction? main groups?

Answer 3

• Woody plants with secondary vascular tissue (stem widening growth)
• Heterosporous
• Retention of megaspores on surface of highly modified sporophylls (similar to amniotic egg)
• Fertilisation by pollen, freed from dependence on external water
• Five main groups: cycads, gingko, pines, gnetophytes, cupressophytes

Question 4

describe cycads

Answer 4

• Mostly tropical or subtropical
• Separate male (microsporangiate) and female (megasporangiate) plants
• Loosely clustered megasporophylls with multiple ovules
• Other cycads have more tightly clustered female clones with 2 ovules per megasporophyll
• Male sporophylls look more like cones
• Female sporophylls can look more like leaves

Question 5

describe gingko

Answer 5

• Currently 1 species: a relict of past diversity
• Gingkophyta appeared in Permian 270 mya
• Dioecious (unisexual sporophytes)
• Deciduous
• Strobili form a fleshy bulb to help with dispersal by animals

Question 6

describe pines

Answer 6

• Leaves needle-like with thick cuticle and hypodermic, sunken stomata, resin ducts
• Can survive dry and cold environments
• Separate male and female cones that can occur on the same plant

Question 7

describe Gnetophytes:

Answer 7

• Three very different genera
• Can have vine-like growth forms or fleshy strobili or only two massive leaves

Question 8

describe Cupressophytes:

Answer 8

A diverse and ecologically and economically important lineage

Question 9

what is the gymnosperm lifecycle?

Answer 9

1. Start with a pine tree (sporophyte generation)
2. Diploid strobili form (small male cones and large female cones)
3. microspores (pollen grains) are produced and dispersed before the megagametophyte develops
4. Pollen then fertilises the eggs in the archegonium in the megagametophyte
5. Zygotes become embryos (then one dies, leaving one) and form sporophytes (seedling and then eventually tree)

Question 10

what is the gametophyte and what is the sporophyte?

Answer 10

gametophyte is the cone, sporophyte is the tree