Help please about Plants.?

Question

I need to have 3 reasons each for these questions. Why do we know that mosses are the most primitive of all plants on earth? Why are ferns less primitive? Why are gymnosperms more advanced than mosses and ferns? Why are flowering plants the most advanced?

Answer 1

1) Mosses are primitive because they lack efficient structures and mechanisms that would otherwise make the plant grow larger:

a) they lack vascular tissue - therefore depend on diffusion

b) the dominant phase of moss is that having a halved chromosome number(known as the gametophyte). The haploid condition is known to be quite primitive because any mutation in the DNA will show up in the organism.

c) they lack a cuticle and are suscepltible to drying

d) this is extra - they only have rhyzoids which are not real roots. they are chains of cells which cannot penetrate deep in the soil.

2) ferns are less primitive because they have evolved advantages over mosses:

a) the phase having double the chromosome number is dominant(sporophyte)

b) they have vascular tissues i.e can grow larger

c) the sporophyte has true roots and true leaves

3)Gymnosperms have made major adaptations over ferns.

a) their haploid phase has been enclosed within the diploid phase and therefore it is not susceptible to drying up.

b)they have developed seeds which can survive unfavourable conditions

c) they can grow larger

d) they produce 2 types of spores

4) Flowering plants are the most advanced because:

a) they have true roots, true leaves, vascular tissues and cuticles.

b) the generation having double the chromosome number is dominant whilst that with half the number is very reduced and enclosed.

c) they have flowers which are very efficient reproductive structures.

d) they produce seeds.

I know its a little long! Hope I helped!

Answer 2

We don't really say "advanced" anymore, but moss lacks vascular tissue (xylem and phloem). The others are vascular. Gymnosperms have seeds and pollen, ferns only have spores (and their sperm have to swim in wet soil all the way to the vicinity of a female plant. Flowering plants have flowers, and hence are pollinated more efficiently than gymnosperms. They also have more elaborate seeds.

Answer 3

Just to corroborate Pseudo Obscure: basal and derived are preferred over primitive and advanced, respectively. The former are objective statements about order of origin, whereas the latter are subjective calls about presumed function (or apparent lack thereof). To say that an angiosperm is more advanced than a fern glosses over the fact that ferns have managed to persist for 350 MY or so -- presumably, then, the adaptations in ferns have served them rather well.