One tiny disc-shaped unit floating in the blood picks up oxygen in the lungs and carries it through a narrow vessel. On its own, what level of organization is this one unit?

The heart sits in the chest and pumps blood out to the body without stopping. What level of organization is the heart itself?

A thin sheet inside the stomach wall is made of many muscle cells of the same kind, joined together and squeezing at the same moment. What level of organization is this sheet?

A rabbit hops across a meadow, breathing, digesting grass and pumping blood all at once. What level of organization is the whole rabbit?

A biologist views one neuron under a microscope and traces its long thin fiber. Where does that single neuron belong in the levels of organization?

Skin covers the outside of the body, holds water in and keeps germs out. What level of organization is skin?

A maple leaf takes in sunlight and air and makes food for the tree. What level of organization is one whole leaf?

The inside of the small intestine is lined by a layer of absorbing cells of the same kind, packed side by side along the whole tube. What level of organization is this lining?

In a kidney, filtering tissue, connective tissue and nerve tissue all work together to clean wastes out of the blood. What level of organization does this working group form?

The mouth, the esophagus, the stomach and the intestines each do one job, and together they break food down and absorb nutrients. What level of organization do these parts form together?

In the wall of an artery, many muscle cells of one kind lie side by side and tighten at the same time to narrow the vessel. What do these cells form when they work together?

In a horse, the digestive, circulatory, respiratory, muscular and nervous systems all work at the same time in the same body. What do all of them together make up?

A student sorts the kidneys, the bladder and the tubes joining them into one group because they all help remove liquid waste. What level of organization has the student grouped?

Deep inside the brain, huge numbers of nerve cells of the same kind are packed into one layer that passes signals as a unit. What level of organization is that layer?

In a multicellular organism, the organ is one level of organization. What is the very next level up from the organ?

Moving downward through the levels of organization, what level comes directly below the tissue?

A poster lists the levels of organization of a multicellular organism from smallest to largest. Which order is correct?

Order these parts of a mammal from the smallest level of organization to the largest: the heart, a muscle cell, the circulatory system, muscle tissue. Which order is correct?

A flat sheet of connective tissue in an athlete's back is far wider and heavier than the appendix, a small organ near the intestines. Which one sits at the higher level of organization?

A wall chart runs organism at the top, then organ system, then organ, then cell at the bottom, but one level was left out. Where does tissue belong on the chart?

A scientist lifts one tiny living unit from the skin onto a slide. It has its own membrane and nucleus and is not joined to any others. Where does this single unit belong in the levels of organization?

A layer of fat lies under the skin of a seal, built from many storage cells of the same kind packed together and acting as one layer. What level of organization is that layer?

The lungs sit inside the chest, are built from several kinds of tissue, and do the single job of moving gases in and out of the blood. What level of organization are the lungs?

An oak tree takes in water through its roots, makes food in its leaves and moves material through its trunk, all at the same time. What level of organization is the whole tree?

Bone contains many bone cells of one kind surrounded by the hard material they build, all acting together as one solid mass. What level of organization is that mass of bone material?

Under a microscope a scientist studies one long, thin muscle fiber taken from a frog's leg and measures its length. At what level is the scientist working?

In the levels of organization of a multicellular organism, which level sits directly above the cell?

Moving downward through the levels of organization, which level comes directly below the organ system?

A poster lists four groups of body parts. Which group contains only organs?

Order these parts of a bird from the smallest level of organization to the largest: the respiratory system, one lung, a single lung cell, lung tissue. Which order is correct?

A student writes the sequence cell, tissue, organ system, organism and is told one level is missing. Where does organ belong in that sequence?

Counting from cell up to organism, how many levels of organization are named in a multicellular organism?

A student says an organ system is larger than an organism because it holds so many organs. What is wrong with that reasoning?

Several kinds of tissue are joined together in the eye, each doing a different job so the eye as a whole can detect light. What level of organization does this joined group form?

The nose, the windpipe, the lungs and the diaphragm all work together so a body can take in air. What level of organization do these parts form together?

A layer of nerve tissue in the spinal cord is made of many nerve cells. Why is this layer at a higher level of organization than one nerve cell?

A frog's heart pumps blood through its body. Which organ system is the heart part of?

A sheet of muscle tissue on its own cannot pump blood or digest food. What must be added to muscle tissue for it to become an organ?

A student groups the mouth, the esophagus and the stomach together and calls the group an organ. What is wrong with calling it an organ?

Two students compare a single blood cell with a whole heart. Which statement about their levels is correct?