Which one of the following is necessary for evolution of seeds?

Explanation

All of the options given in the question are correct as there are various steps involved in the evolution of seed habit which are as follows: 1 Evolution of heterospory.2 Retention and germination of megaspore within the megasporangium.3 Development of protective layers around megasporangium.4 Reduction to a single functional megaspore per sporangium.5 Development of an embryo sac within the sporangium.6 Modification of distal end of megasporangium for pollen capture7 Pollen after being trapped in the distal cavity of the megasporangium produces a pollen tube that carries male gametes deep into the embryo sac to fertilize the egg, forming a zygote that forms an embryo. The megasporangium (ovule) after fertilization is transformed into a seed, the integuments becoming the seed coats. The seed offers a maximum degree of protection to a developing embryo under an unfavorable terrestrial environment. The development and evolution of seed habit was a great success and a giant leap that ultimately enabled plants to colonize land permanently.