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Evolution and development of reproduction in plants

-- Define and briefly discuss both siphonogamy and the seed.
-- Which do you think came first?

I have a good start on the definitions, but please reword or (briefly) add to them to make them complete:

A seed is: a fertilized, integumented, (Sterile covering/coating. Provided by diploid parent) undehiscing (non-splitting. Does not split open for sperm) megasporangium. (Place where meiosis takes place to produce female eggs).

Siphonogamy: the process of getting a sperm to an egg without water

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This question has a lot to do with the evolution/ development of different plant species.
Think of algae, mosses, and ferns as being simple (non-seed producing) plants and conifers and flowering plants as being seed bearing plants. The latter more advanced than the former.
The first three are limited in their ability to colonise all areas, indeed at some stage in their development they are truly water bound. (These plants have a life cycle that involves alternation of generations between different phases in their life cycle but that is another story) and therefore in biological terms cannot be considered truly successful.
Gymnosperms i.e. Conifers and Angiosperms i.e. flowering plants however are considered much more advanced plants. A seed is quite an advancement on spores in terms of complexity, survival, adaptation etc.
Gymnosperms are said to have naked exposed seeds and Angiosperms develop seeds within a developed ovary that biologists call a fruit.
To manage to break free from water dependence, plants evolved a number of strategies over millions of years.
All Sexual reproduction is about sex, say no more! Sex is about getting ...

Solution Summary

The solution explains in a logical easy to follow way, with the minimum of complex botanical vocabulary, how plants have evolved from the simplest water dependent mosses to the complex advanced flowering plants. The emphasis is on the reproductive mechanisms and how advances in the way that the male gamete developed to fertilise the female gamete independently of water as a vector.