What is evolution of heterospory?
Heterospory evolved due to natural selection that favoured an increase in propagule size compared with the smaller spores of homosporous plants. Heterosporous plants, similar to anisosporic plants, produce two different sized spores in separate sporangia that develop into separate male and female gametophytes.
What is Homospory?
Definition of homospory : the production by various plants (such as the club mosses and horsetails) of asexual spores of only one kind.
What is heterospory give example?
Heterospory : The presence of two kinds of spore in any plant is known as heterospory. Examples: Salvinia, Selaginella. Significance : The microspore and megaspore germinate to form male gametophyte and female gametophyte. The female fametophyte remains attached to sporophytic body.
Why is heterospory of evolutionary significance?
– Heterospory is thus considered an important step in evolution as it is a precursor to the seed habit. – Heterospory evolved first in pteridophytes such as Selaginella and Salvinia. – The seed habit is the most complex and evolutionary successful method of sexual reproduction.
What is evolution of seed habit?
During the course of the evolution of the seed habit, a number of morphological modifications were necessary. First, all seed plants are heterosporous, meaning that two kinds of spores (microspores and megaspores) are produced by the sporophyte. Hence, it is assumed that the ancestors of seed plants were heterosporous.
What is the difference between H * * * * * * * * * * and heterosporous?
A main difference between homosporous and heterosporous pteridophytes is that homosporous pteridophytes produce only one type of spores, which are small in size while heterosporous pteridophytes produce two types of spores; the small microspores and the large megaspores.
What is Diplohaplontic life cycle?
The diplohaplontic life cycle of a seed plant has five defining properties: (1) hetero- spory or separate cell lineages for male and female reproduction, (2) multicellular gametophytes, (3) retention of the female gametophyte within the adult sporophyte, (4) the pollen tube and (5) dispersal of mature embryos.
What do you mean by sporophytes?
Definition of sporophyte : the diploid multicellular individual or generation of a plant with alternation of generations that begins from a diploid zygote and produces haploid spores by meiotic division — compare gametophyte.
What are the three steps in the evolution of seed?
The three steps in the evolution of seed are : soil, water and sunlight.