lecture 11 - the success of seeds

Question 1

How did fertilisation and dispersal in plants evolve?

Answer 1

plants evolved from algae which carried out fertilisation and dispersal in water
this evolved into using spores and seeds for dispersal and pollen for fertilisation

Question 2

Describe the evolution of plant reproduction

Answer 2

Land plants evolved with a progressive suppression of the gametophyte generation:
Haploid generation is dominant in mosses (Bryopsida)
Haploid generation is subordinate & free-living in ferns (Pteropsida)
Haploid generation is suppressed & internalised in seed plants (Spermatopsida) the embryo is retained and there are protective layers to megaspore the supply nutrition (seeds appeared by 350 mya)
Evolution of the seed solved the problems of homospory (all spores are identical) & haploid selfing
Heterospory (the evolution of mega and microspores by 360 mya) allowed for the evolution of seed (but created new problems in ensuring fertilisation - which were solved by flowering plants)

Question 3

What features of flowering plant reproduction make it so successful?

Answer 3

Persistence - many plants are successful because they can occupy the same habitat over time - develop a suitable ecosystem
Multiplication - many plants are very good at increasing their numbers (by more than one method) & can conquer new territories
Dispersal - many plants have evolved to colonise new territories by developing sophisticated dispersal mechanisms