Higher plants: spore-bearing and seed

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2018-03-20 08:57:08

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Higher plants-these are plants that came onto land and adapted to their new habitat. There are over 300 thousand species. Higher plants are distinguished by the presence of vegetative organs such as root and escape, and have the same photosynthetic pigments: chlorophyll and carotenoids.

The Higher plants in the majority have complex transport system of substances, can regulate the evaporation of water through leaves. Plant cells form a tissue. The sporophyte dominates the life cycle (except bryophytes).

Postpone Gametophyte reduced to a few cells. Organs sexual and asexual reproduction multicellular. Fertilization with the increasing complexity of types is no longer dependent on water. The zygote gives rise to a multicellular embryo.

Higher terrestrial plants make up the bulk of the biomass of the Earth – about 90%.

Systematics of higher plants

In higher plants, include ferns and higher seed plants.

Ferns: enjolras (only fossils), psilotales (there are about 20 species), bryophytes (23 to 27 thousand species), lunoobraznye (about 1300 species), hvoscheobraznyh (about 30 species), ferns (12,000 species).

Higher plants that reproduce by spores, nerds unite General title – the highest spore. These include both existing and extinct species. The Supreme body of the spore is divided into overground and underground part, the development of vegetative organs. The life cycle consists of alternation of generations: sporophyte and gametophyte. The sporophyte is well developed, lives a long time (except for bryophytes). It develop multicellular sporangia, of which after meiosis haploid spores are formed of real. They are unicellular, small in size, are distributed mainly by the wind and germinate into a gametophyte.

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The Fertilization of ferns occurs only in the presence of water. The location of the reproductive organs distinguish male and female plants (which have both male and female cells) and same-sex (with male or female cells).

Disputes may be different and the same size. Higher spore-bearing plants that have the same disputes, call Ravnoparavie, and those that have spores different – raznoplanovye. Depending on the size distinguish microspores (small size) and megaspores (large).

It is believed that the seed plants came directly from the spore, in particular from the ferns.

Higher seed plants: pinophyta (gymnosperms) – about 800 species, magnoliophyta (angiosperms) - 300 thousand.

The Higher seed plants flourished in the Mesozoic era, when the climate became more arid and cold, there was a change of seasons. Currently, the most common angiosperm species.

Seed plants have several advantages over ferns. They consist of the same organs: the root, the escape of the seed. The trunk is significantly stronger than the spore as it grows the cells of the wood. If this is the main part of the cells of the wood – dead.

Seed plants are extremely raznoplanovye. The gametophyte on the sporophyte develops and eats at his expense.

The Reproduction takes place through seeds, which represent multicellular formed embryos, which include the supply of nutrients. The highest seed fertilization precedes pollination-transfer of pollen grains in seed beginnings with the egg. Pollination is via wind, water, animals, insects. Fertilization ceases to depend on water, how high the spore. It is due to vegetative cell of pollen, which germinates in the pollen tube.

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