Levels of plant organization:
To explain this diagram we start with Algae.
There are three different types of algae: Brown (Heterokontophyta), Red (Rhodophyta) and Green (Chlorophyta). evolution wise, brown came first, then evolved into red, which evolved into green. The reason that scientists believe tat algae evolved into plants is mainly because of Green Algae and what it does. first of all, many species of Green Algae are multicellular, while most Brown and Red Algae are either singlecellular or colonial. The other main reason they believe plants were born from Green Algae is because they preform photosynthesis.
Once this Green Algae landed on, well... land, the next stage was Bryophyta.
When Green Algae got to land, there were some things it needed to do, it needed to keep from losing all its water by growing a waxy cuticle, it had to grow some kind of roots to keep itself from washing away, so it evolved ryzoids. for reproduction, it evolved spores.
Bryophytes however, still needed surface water to live, so the next step in plant evolution was the addition of vascular tissue. This new stage is called Pteridophyta.
Pteridophytes, or Ferns developed Xylem (water and minerals from roots to shoots) and Phloem(photosynthetic materials from shoots to roots) but only in the stem. this vascular tissue allowed the ferns to grow in places without surface water, but still need very wet soil as the fake roots (hyphae) don't actually pick up water from the ground. These ferns still use spores for reproduction.
The next evolutionary step for land plants was the development of seeds, these seeds may grow in two ways, either in cones (Gymnosperms) or in fruits by flowers (Angiosperms)
Gymnosperm means 'naked seed' and represents all coniferous trees. Angiosperms on the other hand mean 'covered seed' and represents all plants that flower and make fruit. This stage meant the addition of true roots allowing for the plants to grow in places where water isnt close to the surface, as these true roots can 'search' through the ground for water and transport it via xylem to the shoots. the Gymno and Angiosperms also evolved seeds as the new means for reproduction through pollination. Gymnosperms go about it by air dispersal from their pollen cones to the female cones which hold the seed. Angiosperms use flowers as means for seed production: a flower blooms with both the Stamen (male) and carpel (female) sex organs on it the pollen from the Stamen is brought from it to the female Stigma, the sticky tip of the Carpel and fertilizes the egg within the ovary. The fertilized egg become seeds and a layer of fleshy fruit covers it.
This is only a summary of how plants have evolved from Algae to Angiosperms.
There are three different types of algae: Brown (Heterokontophyta), Red (Rhodophyta) and Green (Chlorophyta). evolution wise, brown came first, then evolved into red, which evolved into green. The reason that scientists believe tat algae evolved into plants is mainly because of Green Algae and what it does. first of all, many species of Green Algae are multicellular, while most Brown and Red Algae are either singlecellular or colonial. The other main reason they believe plants were born from Green Algae is because they preform photosynthesis.
Once this Green Algae landed on, well... land, the next stage was Bryophyta.
When Green Algae got to land, there were some things it needed to do, it needed to keep from losing all its water by growing a waxy cuticle, it had to grow some kind of roots to keep itself from washing away, so it evolved ryzoids. for reproduction, it evolved spores.
Bryophytes however, still needed surface water to live, so the next step in plant evolution was the addition of vascular tissue. This new stage is called Pteridophyta.
Pteridophytes, or Ferns developed Xylem (water and minerals from roots to shoots) and Phloem(photosynthetic materials from shoots to roots) but only in the stem. this vascular tissue allowed the ferns to grow in places without surface water, but still need very wet soil as the fake roots (hyphae) don't actually pick up water from the ground. These ferns still use spores for reproduction.
The next evolutionary step for land plants was the development of seeds, these seeds may grow in two ways, either in cones (Gymnosperms) or in fruits by flowers (Angiosperms)
Gymnosperm means 'naked seed' and represents all coniferous trees. Angiosperms on the other hand mean 'covered seed' and represents all plants that flower and make fruit. This stage meant the addition of true roots allowing for the plants to grow in places where water isnt close to the surface, as these true roots can 'search' through the ground for water and transport it via xylem to the shoots. the Gymno and Angiosperms also evolved seeds as the new means for reproduction through pollination. Gymnosperms go about it by air dispersal from their pollen cones to the female cones which hold the seed. Angiosperms use flowers as means for seed production: a flower blooms with both the Stamen (male) and carpel (female) sex organs on it the pollen from the Stamen is brought from it to the female Stigma, the sticky tip of the Carpel and fertilizes the egg within the ovary. The fertilized egg become seeds and a layer of fleshy fruit covers it.
This is only a summary of how plants have evolved from Algae to Angiosperms.