Throughout millions of years plants have acquire specific adaptation that have helped them to survive harshness and stresses of the environment
Plants have been very important to human as that are widely used around the globe. You can be thankful to plants for the bananas, oranges, nuts you often eat.There are many types of plants. There are seed plant, seedless plants, vascular plants and non-vascular plants. There will be further explanation on this later on.
 
Seed plant have common adaptations. They have reduced gametophytes, they are heterosporous and have an ovule and pollen. The gametophytes are reduced in gametophytes as they are so tiny that they are microscopic. This is really different to the seedless plants which can be seen with a naked eye. Seedless plants lack these adaptation except for some who exhibit hererospory.

SEED PLANTS:




Look underneath a fern frond, and you will often see small clumps, spots or patches that look like they are stuck onto the under surface of the pinnae (small leaflets). These patches are where you find the spores. The spores grow inside casings called sporangia.

Gametophytes is single cell structure that contians a single set of chromosome that produce female gametophyte or male gametophytes. The reason seedplant have reduced gametophytes is to keep it protectes. Because of their tiny size they can develop from the spores that are inside the sporongia of the sporophyte. The sporophyte is used like a something t o cover and protect the gametophyte from unfavorable conditions such as drought and UV radiation. This is also an advantage for the the gametophyte as the sporongia provides it nutrients.
Seed plant are heteresporous. Seed plants have megasporangia in megasporophylls that produce megaspores that give rise to female gametophytes, and microsporangia in microsporophylls produce microspores that give rise to male gametophytes. This plants have female and male gametophytes rather than a bisexual one, which is the case of seedless plant that are homosporous.


Seed plants are also unique at retaining the megaspores within the sporophyte. The megaspore are enclosed by layers of sporophyte, integuments. The way the ovule is made is by the megaspores making the females gametophytes that then produces egg cells.An ovule of a plant will have a megasporangium, the megaspore and the integuments.

The pollen grain is made from the microspores. Inside the pollen grain there are male gametophytes that are protected as well by a tough layer. Pollen grains can travel great distance and still be unharmed. They can also be carried away by animal who eat them and then deposits them somewhere far. Others, can be carried away by the wind or get stuck on the fur of animals. When the pollen grains get to the ovule tha is called pollination.Pollen grains when  they star growing they form or gice rise to a pollen tube which then puts two sperms into the ovule.

GYMNOSPERMS

These type of plants have "naked" seeds. They are called "naked" seed because their seeds are not enclosed in ovaries like in angiosperms. Gymnosperms are so rare now as 90% of all plants on earth. They are in restricted places and there are four most known gymnosperms phylums, cycadophytas,gynkophyta, gnetophyta, and coniferophyta.

Cycadophytas- they the largest group after the coniferophyta phylum. They have large cones and palmlike leaves.

Gynkophyta- The ginkgo tree (Ginkgo biloba) is the only living species of the early gymnosperm phylum Ginkgophyta. These type of plants are popular as ornamental because they can tolerate air pollution

THE LIFE CYCLE OF A PINE:

Pines. like is all seed plants, they are heterosporous. This mean there is a female gametophyte and male gametophyte. In pines, however, the sporophytes or the spores are separated. The large one is the ovule cone and the small one is the pollen grain cone. In the small cone microspores are produced which then develop into pollen grains that contain male gametophytes. In the ovulate cone megaspores are produce which then develop into female gametophyte. As the process of pollination is completed and the new plant is ready to germinate a good three years have to pass by.

ANGIOSPERMS

They are moslty know as "flowering plants" such as roses and other types of flowers. They produce two different types of reproductive structures, fruits and flowers.
Right now on earth,  angiosperms are very abundant as they make 90% of all plants. The angiosperms in flowers are composed of carpel,stamen, petals and sepal The ones most involved in the reproductive process are the stamen and the carpel. the stamen has the microsporophylls, where the microspores are developed and the stamen include the ovary of the flowers where the megaspores are produced.

As you can see in this flowers there is the megasporophyll in the ovaries that produce the female gametophytes and there is the stamen which has the anther, where inside are microsporophylls that produce the male gmaetophytes.


The other reproductive structure in angisperma are fruits. They consist of mature ovaries. Once the transfor of pollen to the ovule has happened the developing of the seed starts. As th seed developed the ovary thickens, this is called pericarp. In fruits there are two types the juicy and the dry fruits. Some juicy fruits ofr example are watermelon,apple,oranges and dry one would be nuts, walnuts,etc. 

Some angiosperms have adaptations that allows them to disperse their seeds. For example, dandelions, coconuts, barbs of cockleburs,etc. These type of seed are mande in a way that they can be dispersed to far distances. Dandelion and other plants with similar traits are dispersed by the air. Coconuts traveled by the water and when they split open the seed gets spread over the water releasing those seeds in different places. Cockleburs get stuck on animals fur and are in that dispersed to further distances from the origin. Ohter angiosperms make edible fruits that can be eaten by animal and when they deposit their feces the tough seeds are undamaged and ready to make a new plant. It must be noted that animals played an important roel not only on the dispersal of seed plants but also in pollination besides form bees, bats, butterflies and other animals help on the pollination process.


EXAMPLES:

 
The cycle of angiosperms is very different from the gymnosperms. It produces a diploid cell rather than a haploid. Angiosperms do cross pollination, this meaning that there is transfer of the pollen form one plant to the other. This really crucial for the ongoing diversity of plants.In the angisoperm there is microspores that produce male gametophytes and megaspore that produce female gametophytes. The male gametes are found in the pollen grain while the female gametes are found in the ovaries.Pollen grains have two haploid cells that give rise to two sperm and the pollen tube. One of those sperm reaches the egg and combines with it making a diploid cell. The other sperm goes with nuclei of female gametophytes. Having two sperms fertilizing a same plant is called double fertilization. Double fertilization has somebenefits. One is that the development of the embryo and the development of food storage happen at the same time.

 

In temrs of evolution, angiosperms have been on earth for about 140 million years. Fossils of a 140 million year angiosperm was found but did not have sepals or petals. We can see here evolution taking palce as the angiosperms now have sepals and petals. Because this fossil was found close to a fish fossil, scientist think that angiosperm may have start up in aquatic areas.

 

 

the "evolution development" hypothesis was suggested by the scientist Frolich who said that millions of year ago the ovules and the pollen were separated but due to mutations or change on genes the ovules develop in microsporophylls which evolved into carpels.  

 

Angiosperm species with one cotyledon, seed leaves, are call monocots and those with two eudicots.

 

 

 

Plant have played an important role in our lives. Everything we eat come from some kind of plants. Starting from the cereal we eat everyday in the morning and ending with snacks like apples and oranges. Plants have also been used as medicine for headaches, used as cancer treament and many other other diseases and pains humans deal with in a daily basis.  

Some examples of these medicines are: