Pteridophytes: Sporophyte, Gametophyte and Heterospory
Pteridophytes — the ferns and horsetails — hold a decisive place in the story of plant life on land. They are evolutionarily the first terrestrial plants to possess vascular tissues, namely xylem and phloem, and this single innovation allowed the plant body to grow larger, to conduct water and food across real distances, and to stand upright away from permanently wet ground.
In this quiz you will examine:
- The vascular tissues and the evolutionary position of pteridophytes
- Microphylls and macrophylls, sporophylls and strobili
- The free-living prothallus and the water requirement for fertilisation
- Homosporous and heterosporous conditions
- Retention of female gametophytes and the precursor to the seed habit
Where bryophytes placed the gametophyte at the centre of the life cycle, pteridophytes reverse the emphasis: the main plant body is a sporophyte differentiated into true root, stem and leaves. Keep that inversion in mind as you work through the twenty questions below.
Q1. Evolutionarily, pteridophytes are best described as the first terrestrial plants to possess which feature?
The lesson states that pteridophytes are evolutionarily the first terrestrial plants to possess vascular tissues – xylem and phloem. Flowers, fruits and enclosed seeds belong to later groups.
Q2. In pteridophytes, which generation is the main plant body?
In pteridophytes the main plant body is a sporophyte, differentiated into true root, stem and leaves. The gametophyte is reduced to a small, inconspicuous but multicellular structure.
Q3. Which contrast correctly describes the shift in dominance from bryophytes to pteridophytes?
In bryophytes the dominant phase in the life cycle is the gametophytic plant body, whereas in pteridophytes the main plant body is a sporophyte. This inversion of dominance is the central contrast between the two groups.
Q4. The sporophyte of a pteridophyte is differentiated into which set of organs?
The lesson states that the pteridophyte sporophyte is differentiated into true root, stem and leaves, and these organs possess well-differentiated vascular tissues. Foot, seta and capsule describe the moss sporophyte.
Q5. Small leaves, as found in Selaginella, are called:
The leaves in pteridophytes are small (microphylls) as in Selaginella or large (macrophylls) as in ferns.
Q6. Large leaves, as found in ferns, are termed:
The lesson states that the leaves in pteridophytes are small (microphylls) as in Selaginella or large (macrophylls) as in ferns.
Q7. The leaf-like appendages that subtend the sporangia of a pteridophyte sporophyte are called:
The sporophytes bear sporangia that are subtended by leaf-like appendages called sporophylls.
Q8. When sporophylls form distinct compact structures, these structures are called:
In some cases sporophylls may form distinct compact structures called strobili or cones, as in Selaginella and Equisetum.
Q9. In which pair of genera are strobili or cones formed?
The lesson names Selaginella and Equisetum as the genera in which sporophylls form distinct compact structures called strobili or cones. Funaria and Polytrichum are mosses.
Q10. By what process are spores produced in the sporangia of pteridophytes?
The sporangia produce spores by meiosis in spore mother cells.
Q11. The spores of a pteridophyte germinate to give rise to which structure?
The spores germinate to give rise to inconspicuous, small but multicellular, free-living, mostly photosynthetic thalloid gametophytes called prothallus.
Q12. Which set of conditions do pteridophyte gametophytes require for growth?
The lesson states that these gametophytes require cool, damp, shady places to grow, and that this specific restricted requirement limits their spread.
Q13. Why is water required during the sexual reproduction of pteridophytes?
Water is required for transfer of antherozoids – the male gametes released from the antheridia – to the mouth of the archegonium.
Q14. The male and female sex organs borne on the pteridophyte gametophyte are respectively:
The gametophytes bear male and female sex organs called antheridia and archegonia, respectively.
Q15. Fusion of the male gamete with the egg present in the archegonium results in the formation of:
Fusion of male gamete with the egg present in the archegonium results in the formation of a zygote, which thereafter produces a multicellular well-differentiated sporophyte.
Q16. In the majority of pteridophytes, all the spores are of similar kinds. Such plants are called:
In majority of the pteridophytes all the spores are of similar kinds; such plants are called homosporous.
Q17. Which genera are named in the lesson as heterosporous, producing macro (large) and micro (small) spores?
Genera like Selaginella and Salvinia, which produce two kinds of spores, macro (large) and micro (small) spores, are known as heterosporous.
Q18. In heterosporous pteridophytes, the megaspores and microspores germinate to give rise to which gametophytes respectively?
The megaspores and microspores germinate and give rise to female and male gametophytes, respectively.
Q19. In heterosporous pteridophytes, the female gametophytes are:
The female gametophytes in these plants are retained on the parent sporophytes for variable periods, and the development of the zygotes into young embryos takes place within the female gametophytes.
Q20. The retention of the female gametophyte on the parent sporophyte, with the zygote developing into a young embryo within it, is regarded as:
The lesson states that this event is a precursor to the seed habit, considered an important step in evolution.