Alternation of Generation:
Plants have two phases in its life cycle, gametophyte and sporophyte. The gametophyte is a haploid in which the organism only contains 1set of chromosomes from one parents. While the gametophyte stage is a haploid, the sporophtye is a diploid, where it contains two sets of chromosome from two parents. While the embryo is growing and in the fertilization process of the cycle the organism participates in mitosis, the growing part of the cycle. After fertilization, when the egg and sperm are introduced to each other, the organism undergoes meiosis to grow one organism that becomes a haploid. Meiosis occurs when the spores are released to become new individuals. Mitosis occurs when the zygote is formed with both the parents' chromosomes. The zygote is created by the antheridium, male gametophyte and the archegonium, the female gamtophyte.
Characteristics:
Bryophyta
-mosses, liverworts, hornworts
-gametophyte is dominant
-lacks vascular tissue
-simplest/first land plants after green algae
-depends on water for reproduction
Pteridophyta
-horsetails, ferns, clubmosses
-vasvular plant: xylem-conducts water from roots and phloem-conducts product of photosynthesis
-swimming sperm- flagellated sperm
-sporophyte is dominant
-water absorbed through roots
-seed present
Gymnosperm
-gingko, cycad, gnetophyte
-naked seeds
-sporophyte dominant
-seeds
-not as dependent on water
-pollen- pollination
-true roots
-needles act as natural anitfreeze
Angiosperm
-flowering plants
-specialized reproductive structure
-pollination
-parallel evolution between angiosperms and animals
-sporophyte is dominant
-leaves, stems, roots, flower
-seed protection gor embryo
-monocots and dicots
-mosses, liverworts, hornworts
-gametophyte is dominant
-lacks vascular tissue
-simplest/first land plants after green algae
-depends on water for reproduction
Pteridophyta
-horsetails, ferns, clubmosses
-vasvular plant: xylem-conducts water from roots and phloem-conducts product of photosynthesis
-swimming sperm- flagellated sperm
-sporophyte is dominant
-water absorbed through roots
-seed present
Gymnosperm
-gingko, cycad, gnetophyte
-naked seeds
-sporophyte dominant
-seeds
-not as dependent on water
-pollen- pollination
-true roots
-needles act as natural anitfreeze
Angiosperm
-flowering plants
-specialized reproductive structure
-pollination
-parallel evolution between angiosperms and animals
-sporophyte is dominant
-leaves, stems, roots, flower
-seed protection gor embryo
-monocots and dicots
Life Cycles:
Bryophyta
In the life cycle of a Bryophyta the gametophyte is dominant, carrying out most of plants photosynthesis. It is dependent on water for fertilization where sperm must swim to the egg. A Moss is an example of Bryophyta. It grows into a mass of tangled green filaments called protonema. As protonema grows, it forms rhizoids, like roots. Grows into the green moss that is the gametophyte stage of a moss life cycle. The sperm is produced in the antheridium, and the egg cells are produced in the archegonium. Fertilization produces diploid zygote beginning of sporophyte stage. The mature sporophyte is a long stalk ending in a capsule, in it the haploid spore produced by meiosis. When capsule ripens, it will then open and haploid spores scattered to wind to scatter to restart the cycle again and grows with mitosis.
Pteridophyta
Ferns are sporophytes dominant, which makes them diploids for most of their cycle. The sporophyte develops haploid spores on the underside of fronds in the tiny containers called sporangia. They group into clusters called sori and develops into haploid gametophytes. The small gametophyte first grows into a set of rootlike rhizoids. Mature gametophyte is a thin heart-shaped green structure. The antheridia and archegonia are found on the underside of the gametophyte The diploid zygote is produced by fertilization and then develop into a new sporophyte plant. When the sporophyte grows, the gametophyte slowly goes away, whereas the sporophyte lives for a long time.
Gymnosperms
Reproduction is in cones, produced by sporophyte plant. Gymnosperms produce two types of cones, pollen cones which are the male gametophyte, pollen grains and seed cones which are the female gametophyte. Within the ovules, the ovules undergo meiosis and will produces haploid cells that grow and divide to produce female gametophyte. The life cycle begins when the pollen cones release large amounts of pollen grains which gets carried by the wind and if a pollen grain reaches a seed cone, it will then get caught in the sticky secretion of a scale of the female cone. The pollination will drop and it will ensure that the pollen grains will stay on the ovule. Once the pollen grain splits open, it then begins to grow a structure called pollen tubes that will contain two haploid sperm nuclei. The fertilization produces a diploid zygote, that will then grow into an embryo. The embryo is encased within what will later will grow into a seed.
Angiosperms
In angiosperm the reproduction takes pace within the flower. The seed develops inside protective structures after fertilization. Each flower contains an ovary and anthers, and inside the anthers which is the male part, each cell undergoes meiosis and will then produce haploid spore cells. Haploid spore cells become a single pollen grain and the walls thicken to protect the contents of the pollen grain from dryness and any physical damage when released from inside the anther. In the pollen grain, the nucleus undergoes mitosis division to produce haploid nuclei. The Female gametophyte is the ovary of the flower that contains ovules. The rest of the cells go through mitosis while meiosis is used in getting the diploid cells into a haploid by division. Surrounding the membrane is the embryo sac. In the nuclei is the egg nucleus and when fertilization occurs this cell becomes the zygote which grows into a sporophyte.