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Why land plants evolved from Algae.
The first land plants are believed to be Bryophytes, which include mosses, hornworts, and liverworts and they are thought to have developed from multicellular green algae. Algae and Bryophytes share many of the same characteristics. Evidence to show this is that Bryophytes don't have any vascular tissue, which means that they cannot transport water and nutrients throughout the plant, they must use diffusion and osmosis. These characteristics are shared by algae, which leads scientists to believe that algae evolved into Bryophytes. Another piece of evidence is that mosses life cycle is dominted by the gametophyte stage, which is also the same as algae. and lastly, another piece of evidence is that they both perform photosnthesis with chlorplasts to obtain energy.
The first land plants are believed to be Bryophytes, which include mosses, hornworts, and liverworts and they are thought to have developed from multicellular green algae. Algae and Bryophytes share many of the same characteristics. Evidence to show this is that Bryophytes don't have any vascular tissue, which means that they cannot transport water and nutrients throughout the plant, they must use diffusion and osmosis. These characteristics are shared by algae, which leads scientists to believe that algae evolved into Bryophytes. Another piece of evidence is that mosses life cycle is dominted by the gametophyte stage, which is also the same as algae. and lastly, another piece of evidence is that they both perform photosnthesis with chlorplasts to obtain energy.
Bryophytes
Bryophytes are believed to be the first land plants. They do not have vascular systems, so they cannot transport water throughout the plant. This means they must live close to the ground and in areas with lots of water. Their lifecycle is dominated by the gametophyte stage, which is haploid and that gametophyte is the moss we are familiar with. When the gametophyte is fertilized, it creates a sporophyte that releases spores, which then turn into a gametophyte and the cycle is repeated. Other examples of Bryophytes include liverworts and hornworts.
Life Cycle of a moss
Bryophytes are believed to be the first land plants. They do not have vascular systems, so they cannot transport water throughout the plant. This means they must live close to the ground and in areas with lots of water. Their lifecycle is dominated by the gametophyte stage, which is haploid and that gametophyte is the moss we are familiar with. When the gametophyte is fertilized, it creates a sporophyte that releases spores, which then turn into a gametophyte and the cycle is repeated. Other examples of Bryophytes include liverworts and hornworts.
Life Cycle of a moss
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Pteridophyte lifecycle
-A haploid gametophyte is formed. It is heart shaped, with the male part at the pointed end, and the female part at the rounded end.
-The sperm from the male end of the gametophyte is carried through water to the female end of another gametophyte, and fertilizes the egg.
-a diploid sporophyte begins to grow out of the fertilized egg.
-the sporophyte is now a full grown fern.
-the bottoms of the fronds form sori, which are clusters of sporangium, and the sporangium contains the spores.
-eventually, the sporangium capsule opens and haploid spores are released and blown by the wind.
-these spores land on the ground and begin to germinate
-the spores grow into a gametophyte and the cycle continues.
Examples of Pteridophytes
Ferns- live all around the world, and are especially abundant in tropical rain forests.Can grow anywhere from a few inches tall to 30 feet tall.
Horsetails- are found all over the world, in wet areas such as swamps and marshes, and are commonly used in medicine.
Club mosses- evergreen herbs with needlelike or scalelike leaves, and look like a small branch of a pine tree
-A haploid gametophyte is formed. It is heart shaped, with the male part at the pointed end, and the female part at the rounded end.
-The sperm from the male end of the gametophyte is carried through water to the female end of another gametophyte, and fertilizes the egg.
-a diploid sporophyte begins to grow out of the fertilized egg.
-the sporophyte is now a full grown fern.
-the bottoms of the fronds form sori, which are clusters of sporangium, and the sporangium contains the spores.
-eventually, the sporangium capsule opens and haploid spores are released and blown by the wind.
-these spores land on the ground and begin to germinate
-the spores grow into a gametophyte and the cycle continues.
Examples of Pteridophytes
Ferns- live all around the world, and are especially abundant in tropical rain forests.Can grow anywhere from a few inches tall to 30 feet tall.
Horsetails- are found all over the world, in wet areas such as swamps and marshes, and are commonly used in medicine.
Club mosses- evergreen herbs with needlelike or scalelike leaves, and look like a small branch of a pine tree
Bryophytes vs. Pteridophytes
Bryophytes and Pteridophytes have many similarities, but also many differences. They are similar in that they both have alternation of generation lifecycles, where they switch between a haploid gametophyte and a diploid sporophyte. Which means that they both have a part of the cycle where spores are forms and released, and another part of the cycle where a sperm gametophyte fertilized an egg gametophyte.They also both must live in a moist area because their gametophytes are carried through water, so without a good source of water, they both would die. Differences between the two are that Pteridophytes have vascular tissue, xylem and phloem, that transport water and nutrients throughout the plant. Bryophytes do not have this, as the must transfer water and nutrients through diffusion and osmosis, which is why they are low lying. The vascular tissue also gives structure and support to the plant, so they can grow larger. Another difference is that the pteridophytes life cycle is dominated by the diploid sporophyte stage, whereas the bryophytes life cycle is dominated by the haploid gametophyte stage. Also, pteridphytes have fronds, which are like leaves, and the bryophytes do not.
Other Facts
-Ferns are a major contributor to the fossil fuels that we use today. Long ago they were alive and formed large forests, and as these forests decomposed, fossil fuels were created.
-Liverworts and mosses can be found on every continent, including Antarctica.
-Not all ferns are green, they can be multiple different colours, such as yellow, red, orange, and purple.
Bryophytes and Pteridophytes have many similarities, but also many differences. They are similar in that they both have alternation of generation lifecycles, where they switch between a haploid gametophyte and a diploid sporophyte. Which means that they both have a part of the cycle where spores are forms and released, and another part of the cycle where a sperm gametophyte fertilized an egg gametophyte.They also both must live in a moist area because their gametophytes are carried through water, so without a good source of water, they both would die. Differences between the two are that Pteridophytes have vascular tissue, xylem and phloem, that transport water and nutrients throughout the plant. Bryophytes do not have this, as the must transfer water and nutrients through diffusion and osmosis, which is why they are low lying. The vascular tissue also gives structure and support to the plant, so they can grow larger. Another difference is that the pteridophytes life cycle is dominated by the diploid sporophyte stage, whereas the bryophytes life cycle is dominated by the haploid gametophyte stage. Also, pteridphytes have fronds, which are like leaves, and the bryophytes do not.
Other Facts
-Ferns are a major contributor to the fossil fuels that we use today. Long ago they were alive and formed large forests, and as these forests decomposed, fossil fuels were created.
-Liverworts and mosses can be found on every continent, including Antarctica.
-Not all ferns are green, they can be multiple different colours, such as yellow, red, orange, and purple.
References-
http://www.eoearth.org/view/article/150791/
http://www.seaweed.ie/algae/rhodophyta.php
http://www.britannica.com/plant/club-moss
http://gandha.weebly.com/uploads/1/3/3/6/13367253/pteridophytes.pdf
http://www.eoearth.org/view/article/150791/
http://www.seaweed.ie/algae/rhodophyta.php
http://www.britannica.com/plant/club-moss
http://gandha.weebly.com/uploads/1/3/3/6/13367253/pteridophytes.pdf