The physical change  of generations, of ferns, or  metagenesis is quite a unique    phenomenon. There are two different phases in one life cycle of            organisms which experience metagenesis. In one phase, spores are produced. In the other phase, sexual cells or gametes are produced. The spore-producing phase is called the sporophyte phase, and the gamete-producing phase is called the      gametophyte phase. The spores produced have a 2n or diploid chromosome         composition and the gametes produced have an n or haploid chromosome           composition.

When you observe ferns, you will see that there are groups of sporangia on the lower surface of the leaves (See Figure 1.8.). It means that the plant is in the sporophyte stage. The fern plants you are observing are members of a sporophyte generation. If the spores in the sporangia fall on a moist place, each will grow and be flatten into a heart-shaped structure called prothallium. it will produce male and female gametes.

In one lifecycle an alternation occurs  sbetween the sporophyte stage, in which spores with diploid chromosomes are produced, and the gametophyte stage, in which gametes with haploid chromosomes are produced. The alternation of the two stages is known as the alternation of generations or metagenesis.

Different species of plants grow differently. Some species grow into short plants with soft stems. They live for only a few weeks or a few months. Some other species grow tall and large, have wooden trunks, and live for years. What part of  the plants controls their growth?

            How do plants become longer? Observe the stem of a plant in Figure 1.11. On the stem you see two types of buds. At the tip there is a terminal bud, which is also known as an apical meristem. It determines the increase of plant length. Along the stem there are lateral buds, which are also known as side buds or             axillary buds. They can finally grow into branches, leaves, or flowers. Buds are the start of new growth and the points where they appear are nodes of growth. Some plant species have stems that keep becoming larger. In fact, some large stems like those found in wooden trees ( teak trees, and some forest trees) are even 1 to 2 meters in diameter. Why do they become so large? Stem enlargement is determined by the presence of a cambium. The cambium is       located between the xylem and phloem  and its function is to form new xylem and phloem .

Figure illustrates the increasing size of the diameter of the stern  stem. It is because the quantity of xylem and phloem increases in the same direction. It means that the cambium keeps producing new xylem and phloem. The stem tip is protected by epidermis on the outside. In any enlarged part of the stem  the epidermis  become               damaged due to the newly produced phloem. To replace it, a new protection is formed in the shape of cork tissues            Why new xylem and phloem arae continously produced? Do you know their function? They are vascular    tissues for transport. Xylem transports water and mineral    solutions from the roots to the sleaves. Phloem transports   photosynthesis products from leaves to all plant organs.      Because their function is important, these tissues are                 continuously produced. The larger the size of the stem, the more xylem and phloem  there are. Besides the stem, the roots’ also grow longer penetrate the soil. Where are the zones that determine root growth? To answer  this question.

Growth and development of  living thing are        influenced by various factors, booth external and internal.         Factor are from  inside the body of the organism and from the environments.

The internal factors are coming from inside the body. There are determined by genes. The work  of  genes is seen in the work of hormones and enzymes. A hormone, auxin, for  example increases  the number and the size of the cells of a tree trunk. It causes the tree grow taller and bigger.  An    enzyme for  example,           digestive  enzymes in mammals enable food to be digested and a bsorbed by the body. The absorbed food is used to           compose new cells to grow and develop.

Environmental factors are related to anything in the environment such as air, water, soil, and sunlight. The sunlight plays an important role in the growth and         development of plants. It affects quantity of chlorophyll, formation of young plants, period of fruition, and the ability to form and store food.

The organisms consist mostly of water. Water is a solvent, or a substance that dissolves various other substances. All nutrients can be utilized by the body of     organisms because they dissolve in water. Similarly, all   substances that must be disposed from the body must also be soluble, or able to dissolve, in water.

            Some organisms can resist extinction because they reproduce and can adapt well. Various changes may occur during the process of producing a new            generation. An alternating succession from one generation to another generation many change physically different characteristics occurs in some organisms. This process is called metagenesis.

1.   Distinguish between growth and development.

2.   Explain the growth and development of plants.

3.   Mention the factors that influence growth and development.

4.   Mention the phases of growth and development in animal.

5.   Compare metamorphosis between meta-genesis.