Life Begins at Fertilization with the Embryo’s Conception. “Development of the embryo begins at Stage 1 when a sperm fertilizes an oocyte and together they form a zygote.” “Human development begins after the union of male and female gametes or germ cells during a process known as fertilization (conception).

the general or universal condition of human existence: Too bad, but life is like that. the period of existence, activity, or effectiveness of something inanimate, as a machine, lease, or play: The life of the car may be ten years. a living being, especially a human being: Several lives were lost.

The ankh or key of life is an ancient Egyptian hieroglyphic symbol that was most commonly used in writing and in Egyptian art to represent the word for “life” and, by extension, as a symbol of life itself.

Why is life difficult to define? -Life is difficult to define because there are many properties that make up the definition of life not just one and withing each property there are sub properties. Describe the hierarchical organization of life.

NASA defined life broadly as “A self-sustaining chemical system capable of Darwinian evolution.” While this definition is open enough to include a wide range of potential life forms, it also makes it hard to design a simple test for life. For example, it would be unlikely to observe Darwinian evolution taking place.

Life is a concept that we invented. On the most fundamental level, all matter that exists is an arrangement of atoms and their constituent particles.

Although nonliving things may show some of these characteristic traits, only living things show all of them.

• Organization. Living things are highly organized, meaning they contain specialized, coordinated parts.
• Metabolism.
• Homeostasis.
• Growth.
• Reproduction.
• Response.
• Evolution.

In order for something to be classified as living, it must grow and develop, use energy, reproduce, be made of cells, respond to its environment, and adapt. While many things meet one or more of these criteria, a living thing must meet all of the criteria.

Defining “life” is a very difficult task, and scientists don’t all agree on a common list of the characteristics of life. Some of the other characteristics that the students may discover in their research, and which are often listed in textbooks, include those listed below.

For young students things are ‘living’ if they move or grow; for example, the sun, wind, clouds and lightning are considered living because they change and move.

Mycoplasma genitalium, a parasitic bacterium which lives in the primate bladder, waste disposal organs, genital, and respiratory tracts, is thought to be the smallest known organism capable of independent growth and reproduction. With a size of approximately 200 to 300 nm, M.

Introduction

• An atom is the smallest unit of matter that retains all of the chemical properties of an element.
• An atom consists of two regions.
• Structure of an atom.

Atom