Lecture 2

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Liv

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In land plants, meiosis produces spores
A spore is a single cell that can divide by mitosis to produce a multicellular organism often with a protective coat
A gamete is a single cell that can unite with another gamete to produce a diploid zygote
There are 10 divisions (phyla) of land plants (the Embryophytes)
The 4 major divisions for us are mosses, ferns, conifers, and angiosperms
There are about 15,000 species of mosses
Mosses are low growing and confined to damp areas
Mosses are confined to damp areas because they have swimming sperm and no true vascular tissue
Mosses have no true leaves
Mosses are gametophyte dominant
Mosses are homosporous
There are about 20,000 species of ferns and most are tropical
Ferns appeared about 400 million years ago
Ferns have vascular tissue, xylem and phloem
Xylem and phloem provide support and supply plants
Ferns have swimming sperm
Ferns are sporophyte dominant
Ferns can be homosporous or heterosporous
Homospory is when there is one size of spore from meiosis
Heterospory is when there are two sizes of spore from meiosis
There are five divisions (phyla) of seed plants
Seed plants have both seeds and pollen
A seed is the embryo, with some nutrition, surrounded by a seed coat
Seeds develop from the ovule
An ovule is the site of female meiosis
An ovule contains the female gametophyte, female sex organs, egg and embryo
Pollen is the mature male gametophyte
Pollen is only a few cells in size
There are about 550 species of conifers
Conifers have their reproductive organs in cones
Conifers are sporophyte dominant
Conifers are heterosporous
The microgametophyte is pollen in conifers
In conifers the megagametophyte is within the ovule and it makes the egg and nourishes the embryo
In conifers, the nutrition in the seed is the megagametophyte
Conifers have separate male and female cones
Male cones release pollen
Female cones collect pollen and release seeds
Conifers have naked seeds called gymnosperms
Conifers have very slow reproduction