Kingdom Plantae
Alternation of generations life cycle in plants
A plant goes through two stages in their life.Starting at the sporophyte stage, the plant is a multicellular diploid (2n, or contains two sets of chromosomes). Then the sporophyte goes through meiosis, and the plant divides into unicellular haploid (n, contain one set of chromosomes) spores.The spores then undergo mitosis and grow into a mature gametophyte. From the gametophyte stage, male and female gametes are produced and when the plant goes through fertilization and creates a zygote. The zygote contains chromosomes from the male sperm and the female egg making it diploid. The zygote goes through mitosis and grows into a sporophyte, completing the cycle.
Describe the characteristics of the following plant phylums
Bryophyta: Bryophytes were the first plants to evolve onto land. They are non-vascular plants with no water transport system and no true roots. They also have swimming (flagellated) sperm. The life cycle for Bryophytes is dominated by the haploid gametophyte stage and they use spores to reproduce.
Pteridophyta: Known as the seedless vascular plants as they do not produce seeds. Pteridophyta uses the alternation of generations life cycle but is dominated by the sporophyte stage. Pteridophytes are more advanced than Bryophytes as they have evolved vascular tissue. This allows Pteridophytes to transport water using xylem and nutrients using phloem, making them better adapted to a drier climate. Spores are used to reproduce. The sperm would swim from the antheridium to the egg in the archegonium then later produce spores to reproduce.
Gymnosperm: Known as the seeded vascular plants and the "naked seed". They are vascular, heterospory (male vs female gametophytes) plants with a life cycle dominated by the sporophyte stage. Pollen is used for reproduction. Their evolution of the seed has helped protect their embryo from drought and UV radiation. Their leaves became needles to prevent water loss. They have male cones that contain pollen grains that are used to protect and transfer the pollen grains that are used to protect and transfer the pollen by wind or animals. They also have female cones containing the female gametophyte, the egg, and protects the embryo until after fertilization.
Angiosperm: Angiosperms are the flowering plants and are covered seeds. Their major advancement is the flower and it is also their reproductive structure. Most angiosperms are vector pollinated or pollinated by animals. They have four organ systems, the roots, the stem, the leaves and the flower. These plants are also dominated by the sporophyte stage completely and are vascular. The flower part of the plant contains the petals, sepals, stamen and carpel and is used to attract pollinators. The covered seed offers the embryo nutrients and protection to enable it to grow. Some angiosperms contain fruit that protect the seed and can be used to transfer it (through the digestive system of animals). Angiosperms are divided into monocots that have only one cotyledon (seed leaf) and dicots with two cotyledons.
Life cycles
Bryophyta
In the Bryophyta lifecycle the haploid gametophyte stage is dominant. Starting with the haploid spores, the spores grow into a protonemia and grow into a male gametophyte (antheridia) and a female gametophyte (archegonia). Once at this stage the sperm inside the antheridia swims to the egg inside the archegonia with the help of water and the egg goes through fertilization. Once fertilized, the embryo grows into a diploid (2n) zygote and into a young sporophyte, and eventually becoming a mature sporophyte. The capsule on the mature sporophyte releases spores continuing the life cycle. |
Pteridophyta
In the Pteridophyta life cycle the diploid sporophyte stage. The life cycle begins with the haploid spores (n) that go through meiosis to grow into a young gametophyte and then into a mature gametophyte known as a prothallus. The prothallus has male antheridia and female archegonia that together go through fertilization and become a diploid sporophyte. The sporophyte grows through mitosis and then goes through meiosis to produce spores inside a sporangia and in clusters called sori. When ready the sporangia opens and releases its spores to germinate and continue the life cycle. |
The Gymnosperm life cycle is dominated by the diploid sporophyte stage (2n). Beginning with a mature sporophyte (2n, adult tree) the tree contains both male, containing pollen grains, and female, containing an egg, cones. The male pollen grains make its way to the embryo, female cone, and land on the female cone resulting in the female cone growing a pollen tube that attaches to the ovary allowing the pollen to fertilize the embryo. The female cone opens up to release the seeds to germinate and the life cycle continues.
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The gymnosperm lifecycle is dominated by the diploid stage of the flower (2n). Starting with the mature flower, the lifecycle repeats. The flower contains both haploid pollen grains (male gametophyte) from the anther, and haploid embryo sac (female gametophyte) containing the egg. The pollen grains travel down the style in a pollen tube and into the ovule, then to the egg. Fertilization then occurs and forms a diploid zygote. Mitosis occurs and fruit develops from the ovary, producing seeds which grow into mature flowers through mitosis.
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Parts of a flower
Anther: Produces male gametophyte, pollen.
Stigma: It provides a receptacle for pollen to land on.
Filament: Supports the anther
Petals: The petals are the colourful part of the flower that is used to attract pollinators
Pistil: The female part of the flower used in reproduction. Contains the stigma, style, ovary and ovule. Inside the ovule is where the egg is and where fertilization occurs.
Stamen: The male reproductive part of the flower containing the anthers and the filaments. This is where sperm is produced.
Sepals: Protect the bud of the flower and provide support for the petals.
Stem: Provides support and structure for the plant. Also used to transfer water and nutrients throughout the plant.
Leaves: Makes the process of photosynthesis possible. The leaves take in sunlight used to make nutrients for the plant.
Roots: Take in water and nutrients for the plant from the ground. Also help stabilize the plant in one spot.
Stigma: It provides a receptacle for pollen to land on.
Filament: Supports the anther
Petals: The petals are the colourful part of the flower that is used to attract pollinators
Pistil: The female part of the flower used in reproduction. Contains the stigma, style, ovary and ovule. Inside the ovule is where the egg is and where fertilization occurs.
Stamen: The male reproductive part of the flower containing the anthers and the filaments. This is where sperm is produced.
Sepals: Protect the bud of the flower and provide support for the petals.
Stem: Provides support and structure for the plant. Also used to transfer water and nutrients throughout the plant.
Leaves: Makes the process of photosynthesis possible. The leaves take in sunlight used to make nutrients for the plant.
Roots: Take in water and nutrients for the plant from the ground. Also help stabilize the plant in one spot.
Microscope lab
Analysis:
1. What forms of Chlorophyta did you view?
Unicellular, multicellular, and colonial
2. What are the antheridium and archegonium? Function?
The antheridium is the male reproductive structure that makes sperm, and the archegonium is the female reproductive structure that makes eggs.
3. How are bryophytes and pteridophytes similar and different?
The both make spores, both have an alternation of generations life cycle. In moss, the gametophyte stage is dominate and in ferns the sporophyte stage is dominant. Pteridophytes also have developed vascular tissue which is a major advancement over bryophytes.
4. What is a prothallus and what is its function?
A fern gametophyte (n). It is thin, heart shaped structure that aids in reproduction.
1. What forms of Chlorophyta did you view?
Unicellular, multicellular, and colonial
2. What are the antheridium and archegonium? Function?
The antheridium is the male reproductive structure that makes sperm, and the archegonium is the female reproductive structure that makes eggs.
3. How are bryophytes and pteridophytes similar and different?
The both make spores, both have an alternation of generations life cycle. In moss, the gametophyte stage is dominate and in ferns the sporophyte stage is dominant. Pteridophytes also have developed vascular tissue which is a major advancement over bryophytes.
4. What is a prothallus and what is its function?
A fern gametophyte (n). It is thin, heart shaped structure that aids in reproduction.