Written Report in Mechanics of Life

Topics: Cellular differentiation, Cell, Reproduction Pages: 10 (2629 words) Published: May 28, 2013
College of the Immaculate Conception
Sumacab Este, Cabanatuan City
Summer 2013

Graduate School Department
Developmental Biology

Mechanics of Life

Prepared by:
Christina Miranda Baldazo
MAEd—General Science

Prepared for:
Dr. Agnes Aquino

Developmental Biology
Mechanics of Life
1. Development from Egg to Organism
* Fertilization
* Development of Human Embryo
* Development of a Flowering Plant
2. Differentiation in Plants and Animals
3. Coordination
4. Senses
5. Movement
6. Defense Strategies
7. Reproduction
1. Development from Egg to Organism
* Fertilization
In fertilization, the nuclei of the sperm and the ovum fuse to form a zygote. This event occurs in the oviduct. A single ejaculation of semen during sexual intercourse can release about 150 to 350 million sperm. But only 300 to 400 sperm reach the upper part of the oviduct within an hour. Contractions along the tract help them move up the female reproductive tract.

If the sperm arrive 1 to 2 days before or after ovulation, fertilization can occur. The oocyte remains viable for about 24 hours after ovulation while the sperm are viable up to 48 hours after ejaculation.

In the oviduct, sperm surround the oocyte but only one sperm penetrate and fertilize it. The high number of sperm increases the chances of successful fertilization. The throng of sperm loosens the follicle cells that envelop the secondary oocyte by releasing digestive enzymes. Fusion with one sperm triggers the secretion of a membrane that prevents other sperm from entering. It also stimulates the oocyte to complete meiosis II and form the ovum.

* Development of Human Embryo
Embryonic and Fetal Stages
Pregnancy takes about 38 weeks to complete from the time of fertilization. The fertilized ovum begins to divide by mitosis as it slowly travels from the oviduct to the uterus. At day 7, the embryo is ready to implant on the uterine lining. The organ called placenta develops between the embryo and the mother’s uterine wall. It is made up of blood-engorged vessels and membranes that nourish the growing embryo with oxygen and nutrients. During the embryonic period, which starts on week 3 and continues until week 8, major organs start to take shape. Human features can now be identified in the fetus. The fetal period, during which organs increase in size and tissues become specialized, is from week 9 up to birth.

* Development of a Flowering Plant
Parts and Function of a Flower
A typical flower has two main parts—the essential and the accessory parts. The essential parts of a flower are those directly involved in sexual reproduction. These include the pistil and the stamen. The accessory parts are those that are not involved in sexual reproduction but facilitate it. These parts include the sepals, petals, bracts, receptacle, and peduncle.

The pistil is the female reproductive part of a flower. It consists of the stigma, style, and ovary. The ovary contains the ovule. The stamen is the male reproductive part of a flower. It consists of the anther and filament. The anther contains the pollen grains.

A flower may be complete or incomplete; perfect or imperfect; regular or irregular.
The transfer of pollen from the anther to the stigma is called pollination. Pollination may occur in two ways: by self-pollination or by cross-pollination. In self-pollination, pollen is transferred from the anther to the stigma of the same flower. Cross-pollination involves transfer of pollen from one flower to the stigma of another flower of the same plant or another plant of the same kind.

A fruit is ripened ovary. A fruit that develops mainly from the ovary is a true fruit. If it develops from the sepals, petals, or receptacle as well as from the ovary, it is an accessory fruit.
A seed is a mature ovule. It contains the plant embryo, and consists of the following parts—seed coat, hilum, silk scar,...
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