Living Thing Biology
Living things make up the world as we know it. Living things are involved in our
life constantly, seeing that we are alive. There are five characteristics that
are common to all living things. Living things are made up of one or more cells.

Each cell is made up of living matter and is separated by a barrier that
encloses the cell from its surroundings. However, there are many different kinds
of cells that make up living things. A single cell can be one organism. These
organisms are known as unicellular. Most of the organisms that we know best such
as people, trees, and dogs are all made up of more than one cell. Organisms made
of more than one cell are said to be multicellular. Another characteristic that
living things share is that they reproduce. They reproduce, or make new
organisms of the same sort. In order for a species to survive, it is a necessity
for them to reproduce because all organisms die eventually. There are two ways
living things reproduce, sexually and asexually. Sexual reproduction needs two
cells from two different organisms to merge and form the first cell of a new
organism. Asexual reproduction is when only one organism can reproduce without
the assistance of another. The third characteristic of living things, is that
all living things need to grow and develop. When an organism is growing, most go
through a cycle called development. The single cell that starts the cell divides
over and over again to make all the cells that the organism has when in
adulthood. As the cycle continues the organism ages. Aging is when the organism
becomes less efficient in the process of life. The organism will not be able to
reproduce, and death comes as finally too. The fourth characteristic of a living
thing is the ability to obtain and use energy. Living things obtain energy from
their environment or their surroundings. All living things require energy to
live and build their cells. This process is anabolism. Anabolism is the process
in a living thing that involves putting together complex substances from simpler
substances. Plants get their energy from the sunlight through a process called
photosynthesis. Animals get their energy from food that is eaten. The food is
then broken down through digestion, resulting in a release of energy called
catabolism. Living things practice anabolism and catabolism through the whole
time they are living. The balance of anabolism and catabolism is called
metabolism. The fifth and final characteristic that all living things share is
that all living things respond to their environment. Response to their
environment can be sudden, through behavior, or gradual, in metabolic process or
growth. Stimulus is anything in the environment that causes a living thing to
react. Stimuli include light, temperature, odor, gravity, sound, water, and
pressure. Plants generally act to stimuli slower than animals. The process in
which living things respond to stimuli in ways to keep conditions in their body
suitable for life is homeostasis. These five characteristics of living things
are just the basics to knowing what makes up living things. Atomic Structure of

Living Things The basic unit of matter is the atom. Atoms are extremely small,
in fact, if you placed 100 million atoms in a row one after the other, it would
be one centimeter long. Even though the atom is small it consists of even
smaller particles, called subatomic particles. Scientists believe that there is
at least 200 subatomic particles. The three main subatomic particles are the
neutron, proton, and electron. In the middle of the atom there is a nucleus. The
nucleus makes up 99.9 percent of the atoms weight even though it is a hundred
times smaller than the atom itself. The nucleus contains two different kind of
subatomic particles, the neutron and the proton. The proton has a positive
charge and the neutron is a electrically neutral subatomic particle. Both are
almost equal in mass, 1 amu (atomic mass unit). Another subatomic particle in
the atom is the electron. It is negatively charged and it's mass is about 2000
times smaller than that of a neutron or electron. Usually the number or electron
in an atom is the same as the number of protons. So, usually the atoms have not
a positive nor negative charge, but they are neutral. Electron are not in the
nucleus like the protons and neutrons are. They travel at very high speeds
throughout the atom in energy levels. The energy levels are like orbits that
surround the nucleus. The number of protons that are in the nucleus of an atom
is