Download The building blocks of matter (elements and molecules) form the

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The building blocks of matter (elements and molecules) form the basis for increasingly complex substances that
make up living organisms. Single atoms combine to form molecules which in turn are the building blocks for
the organelles that make up living cells. In order of increasing complexity, the list below shows the different
structural elements that together make up an organism – an independently living thing:
atoms – molecules - organelles - cells - tissues - organs - organ systems - organism
The cell is the basic unit of life. It is within
the cell that the chemical reactions necessary
for maintenance and reproduction of life take
place. There are two types of cells,
prokaryotic cells (single-celled organisms
that do not contain a nucleus) and eukaryotic
cells (cells that contain a nucleus).
Eukaryotic cells have the following basic
components: A cell membrane which forms
the outermost boundary layer of the cell,
cytoplasm which consists of a watery
substance, and a nucleus which contains the
chromosomes where DNA is found. Many
eukaryotic cells have other organelles such
as an endoplasmic reticulum, mitochondria,
Golgi bodies, lysosomes, and ribosomes.
During the development of an organism, cells differentiate so they can perform specific functions. Groups of
cells with similar specializations that form a common function are referred to as a tissue. Organs are groups of
several tissues that function together. Examples of organs include kidneys, spleen, liver, heart, lungs and brain.
An organ system is a group of organs that work together to perform a specific function. Examples of organ
systems include skeletal system, muscular system, and digestive
system. The human body is made up of several organ systems that
work together as one unit. The major organ systems of the body work
together, either directly or indirectly, to keep the body functioning
normally.
Circulatory system - The circulatory system transports blood
throughout an animal's body and consists of the heart, blood, arteries,
veins, and capillaries.
Digestive system - The digestive system enables animals to break
down food that they eat and obtain energy and nutrients for other body
processes. It consists of the stomach, intestines, and esophagus.
Endocrine system - The endocrine system is made up of glands (such
as the thyroid and pituitary) and hormones, which are chemicals
released from glands into the bloodstream. These glands and hormones
control or influence various body functions such as metabolism,
growth, and reproduction.
Integumentary system - The integumentary system is an animal’s outer covering, such as skin, scales, feathers,
fur, and other body parts, that protect the animal and prevent it from drying out. This system is the first barrier
to disease and is responsible for controlling body temperature.
Lymphatic system (also called the Immune System) - The lymphatic system helps to filter out diseasecausing organisms and helps to drain fluid waste from in and around tissues. The lymphatic system helps in the
defense against infection and disease. The lymph nodes and white blood cells are part of this system.
Muscular system - The muscular system enables animals to move and control movement. The muscular system
consists of skeletal muscles which help move the skeleton and control movement, smooth muscles which are
involuntary and control the stomach and intestine, and cardiac muscles which include the heart muscles.
Nervous system - The nervous system enables animals to send, receive, and process nerve and sensory
impulses. The nervous system can be broken down into three categories which include the central nervous
system (the brain and spinal cord), the peripheral nervous system (the nerves that branch off of the brain and
spinal cord and carry nerve signals to muscles and glands), and the autonomic nervous system (controls
involuntary actions such as heartbeat and digestion). This system controls all bodily functions. The key parts
of this system are the brain, nerves and spinal cord.
Reproductive system - The
reproductive system enables
animals to produce offspring.
Respiratory system - The
respiratory system includes an
animal's nose, lungs, and
trachea. The respiratory system
brings oxygen into the body
and releases waste carbon
dioxide back into the air.
Skeletal or support system The skeletal or support system
provides internal or external support (such as a skeleton, exoskeleton or shell).
Urinary system (also called the Excretory System) - The urinary system consists of the kidneys and the
bladder. It enables animals to expel waste fluids in the form of urine.