B3 Flashcards
What are gymnosperms and angiosperms?
Vascular seed plants
What is the life cycle of a fern?
Spore dispersal, spore, young gametophyte, mature gametophyte, antheridium, sperm, archegonium egg. Zygote, new sporophyte, gametophyte, mature sporophyte, fiddlehead, sporangium, sorus, sporangium.
What are some significant feature of seed plants?
Evolution of the ovule and seed were key events for terrestrial plants. The female gametophyte (megagametophyte) is retained within the ovule on the mother sporophyte. The ovule develops into a seed. The seed consist of seed coat, an embryo (next sporophyte generation) and stored in food. The seed replaced the spore as the unit of dispersal
What are all seed plants, and what is a characteristic of seed plants?
Heterosporous, independence from water as a medium of transport of the sperm to the egg. The megaspore develops in the ovule and microspores develop into pollen. Pollen represents the male gametophyte (micro gametophyte).
How do gymnosperms differ from angiosperms?
Gymnosperms do not produce flowers, they do not produce a true fruit. No herbaceous forms. Production of cones. Xylem does not contain vessels, phloem does not contain sieve tube elements. Low biodiversity.
What are the classifications of living gymnosperms?
Coniferophyta, cycadophyta, gingkophyta, gnetophyta.
What are the coniferophyta?
The largest and most widespread group of gymnosperms. 50 genera and 550 species (low biodiversity). Dominate many ecosystems. Included some of the oldest and biggest organisms on the planet. Three native species in the uk Scot’s pine, yew, juniper. More introduced and grown in forest, parks, and gardens, commercially important.
What are pine?
Small to very large, evergreen trees with needle leaves borne on short shoots. Leaves produced in bundles of up to 8. Leaves usually live for 2-3 years but exceptionally for 30 or more years. Leaves have thick cuticle and sunken stomata - suitable for growth under comditions where water is scarce or difficult to obtain.
What is the life cycle of pine?
The pine tree is the mature sporophyte generation. Separate male and female cones on the same tree. Male cones produce pollen grains (microgametophytes). Female cones produce ovules, megagametophytes and seeds. Seed production takes long time e.g. 3 years from pollination to seed.
What are male cones in pine trees?
Found on lower parts, small, clustered. Simple with central axis and microsporophylls that bear microsporangia. Microspore mother cells undergo meiosis to produce 4 haploid microspores. Each microspore develops into a tiny microgametophyte of 4 cells. Pollen grains have 2 air bladders for buoyancy, a tube cell and a generative cell.
What are female cones in pine trees?
Upper part of tree, larger and more complex with ovuliferois scales. Megasporangium on oluviferous scale contains megaspore mother cell which divides by meiosis to give 4 haploid megaspores. Only one megaspore survives. Free nuclear division inside megaspore gives rise to coenocytic cell. Coenocytic cell eventually becomes cellular gametophyte. Each megagametophyte, contains up to 3 archegonia each with a single haploid egg. The ovule is composed of haploid megagametophyte embedded in the diploid megasporangium tissue. The ovule is enveloped in an integument which had an opening called the micropyle at its apex. Integument becomes seed coat after fertilisation. Pollen enters via micropyle.
How does pollination occur in pine trees?
Pollen grains are released from male cones and carried by the wind to female cones
At this time, female cones is small and in its first year. A pollination drop exudes from the micropyle of the ovule, pollen is drawn in towards the nucellus as this evaporates. The pollen germinates to produce a pollination tube, from the tube cell. Pollen tube grows through the nucellus to the egg in the archegonium.
How does fertilisation occur in pine trees?
The generative cell in the pollen divides to produce 2 non-motile sperm. Both sperm are released into the archegonium, but only one unites with the egg cell nucleus to produce the diploid zygote. Each egg in each archegonium may be fertilised, but usually only one zygote develops into an embryo in an ovule.
What happens in the seed in pine trees?
2 ovules on the upper surface of each ovuliferous scale of female cone. Each one develops into a seed. Seed protected by seed coat, which develops from diploid integument. The diploid embryo (the new sporophyte generation) is inside seed. Seed embedded in haploid megagametophyte tissue which serves as a store of food. The embryo consists of a hypocotyl-root axis, an apical meristem, seed leaves and root cap.
What can pine seeds be like?
Short winged
Medium winged
Large vestigial
Large wingless
