levels of organization
While cells are the basic units of an organism, groups of cells can perform a job together. These cells are called specialized because they have a special job. Specialized cells can be organized into tissues. For example, your liver cells are organized into liver tissue. Your liver tissue is further organized into an organ, your liver. Organs are formed from two or more specialized tissues working together to perform a job. All organs, from your heart to your liver, are made up of an organized group of tissues. These organs are part of a larger system, the organ systems. For example, your brain works together with your spinal cord and other nerves to form the nervous system. This organ system must be organized with other organ systems, such as the circulatory system and the digestive system, for your body to work. Organ systems work together to form the entire organism. There are many levels of organization in living things ( Figure 1.4). Levels of organization, from the atom (smallest) to the organism (largest). Notice that organelles are inside a cell, and organs are inside an organ- ism.
Although cells share many of the same features and structures, they also can be very different ( Figure 1.3). Each cell in your body is designed for a specific task. In other words, the cells function is partly based on the cells structure. For example: Red blood cells are shaped with a pocket that traps oxygen and brings it to other body cells. Nerve cells are long and stringy in order to form a line of communication with other nerve cells, like a wire. Because of this shape, they can quickly send signals, such as the feeling of touching a hot stove, to your brain. Skin cells are flat and fit tightly together to protect your body. As you can see, cells are shaped in ways that help them do their jobs. Multicellular (many-celled) organisms have many types of specialized cells in their bodies. Red blood cells (left) are specialized to carry oxygen in the blood. Neurons (cen- ter ) are shaped to conduct electrical im- pulses to many other nerve cells. These epidermal cells (right) make up the skin of plants. Note how the cells fit tightly together.
In 1858, after using microscopes much better than Hookes first microscope, Rudolf Virchow developed the hypoth- esis that cells only come from other cells. For example, bacteria, which are single-celled organisms, divide in half (after they grow some) to make new bacteria. In the same way, your body makes new cells by dividing the cells you already have. In all cases, cells only come from cells that have existed before. This idea led to the development of one of the most important theories in biology, the cell theory. Cell theory states that: 1. All organisms are composed of cells. 2. Cells are alive and the basic living units of organization in all organisms. 3. All cells come from other cells. As with other scientific theories, many hundreds, if not thousands, of experiments support the cell theory. Since Virchow created the theory, no evidence has ever been identified to contradict it.
Most cells are so small that you cannot see them without the help of a microscope. It was not until 1665 that English scientist Robert Hooke invented a basic light microscope and observed cells for the first time, by looking at a piece of cork. You may use light microscopes in the classroom. You can use a light microscope to see cells ( Figure 1.1). But many structures in the cell are too small to see with a light microscope. So, what do you do if you want to see the tiny structures inside of cells? In the 1950s, scientists developed more powerful microscopes. A light microscope sends a beam of light through a specimen, or the object you are studying. A more powerful microscope, called an electron microscope, passes a beam of electrons through the specimen. Sending electrons through a cell allows us to see its smallest parts, even the parts inside the cell ( Figure 1.2). Without electron microscopes, we would not know what the inside of a cell looked like. The outline of onion cells are visible under a light microscope.
introduction to cells
A cell is the smallest structural and functional unit of an organism. Some organisms, like bacteria, consist of only one cell. Big organisms, like humans, consist of trillions of cells. Compare a human to a banana. On the outside, they look very different, but if you look close enough youll see that their cells are actually very similar.
This diagram all comes down to one thing; that is cells are the building blocks of life. Cells are the functioning units of living things. All cells share certain common components. These parts are cytoplasm, cell membrane, ribosome and DNA. The DNA is the specific instructions or makeup which explains that specific cell. There are many types of cells. Some cells in this diagram include blood cells, skin surface cells, bone cells, neuron, smooth muscle cells, cardiac muscle cell, skeletal muscle cell and columnar epithelial and goblet cells. These cells all help makeup the human body.
This diagram shows some specialized cells in the human body. The red blood cells carry oxygen to the other cells in the human body. The columnar epithelial cells form the inner lining of the human intestine. The smooth muscle cells are found in the lining of arteries, veins and blood vessels. They help is contraction and relaxation of the body part they are found in. The bone cells are found in the bone tissue and help in building up the human skeleton. The nerve cells are found in the brain, spinal cord and nerves. They process and transmit information through electrical and chemical signals. The ovum and sperm cell help in reproduction. The function of a sperm cell is to swim through fluid to an ovum cell.
most organisms are composed of cells, is part of the cell theory.
a. true --> b. false
a cells function is partly based on its structure.
--> a. true b. false
which of the following is in the correct order?
a) organ system organ organelle - organism b) organism organ organelle - cell --> c) tissue cell organelle - compound d) tissue organelle cell - atom
which of the following is true?
--> a) specialized cells are organized into tissues. b) specialized tissues are organized into an organ system. c) organs work with other organs to form an organism. d) all of the above are correct.
which of the following are parts of the cell theory?
a) all cells come from other cells. b) all organisms are composed of cells. c) cells are alive and the basic units of organization in all organisms. --> d) all of the above are parts of the cell theory.
who developed the idea that all cells come from other cells?
a) robert hooke --> b) rudolf virchow c) rudolf hooke d) robert virchow
when were cells observed for the first time?
a) 1965 b) 1865 c) 1858 --> d) 1665
Which of the following represents better a blood cell?
a. S b. T --> c. N d. C
Which of the followings is referred to a sperm cell?
--> a. U b. W c. T d. Y
Which letter represents the fat cells?
a. J --> b. U c. W d. E
Identify the red blood cells in this picture
a. L --> b. W c. D d. E
Identify the neuron
a. W --> b. U c. X d. M
What is the cell represented with the letter U?
a. RED BLOOD CELL b. WHITE BLOOD CELL --> c. NEURON d. SMOOTH MUSCLE CELL
Please choose which letter indicates 'white blood cells'.
a. U b. W --> c. M d. Y
Can the body function normally without the presence of 'M'?
a. MAYBE b. CANNOT DETERMINE --> c. NO d. YES
Identify the sperm cell in this picture
a. F --> b. P c. U d. V
Which letter represents the Red Blood Cells?
--> a. V b. L c. U d. F
Which cell resembles a starfish?
a. L b. V --> c. F d. U
Which is the muscle cell?
a. F b. L c. V --> d. U
By what letter is the liver cells represented in the diagram?
--> a. T b. U c. M d. L
What kind of cells are represented by the letter C?
a. MUSCLE CELL b. STEM CELL c. BLOOD CELL --> d. NEURON
What type of cell is marked H in this image?
a. BLOOD CELLS b. LIVER CELLS --> c. INTESTINAL CELLS d. CARDIAC CELLS
Which represents muscle cells?
a. T b. H --> c. L d. U
What is the Type Cell labeled V?
a. RED BLOOD CELLS --> b. LEAF CELL c. SPERM CELL d. POLLEN CELL
Which label refers to red blood cells?
a. H b. F c. V --> d. A
Which is the plant root hair cell?
a. V b. A --> c. H d. F
Which letter represents sperm?
--> a. F b. M c. A d. V
Which type of tissues can NOT be differentiated from a fertilized egg?
a. Adipose b. Connective c. Bone --> d. Necrotic
How many cells are there in this diagram?
--> a. 5 b. 7 c. 6 d. 4
How many types of cells are shown in the diagram?
a. 4 b. 3 c. 2 --> d. 5
Which cells are smooth and round?
a. smooth muscle b. striated muscle cells --> c. red blood cells d. fat cells
What are the muscle cells of the heart?
a. Striated (voluntary) --> b. Cardiac c. Nerve d. Smooth (involuntary)
What makes up muscle cells?
a. Sperm --> b. Striated, Smooth, Cardiac c. Red blood cells d. White blood cells
How many blood cells do we have?
a. none b. 4 c. 1 --> d. 6
How many types of muscle cells are there?
--> a. 3 b. 2 c. 1 d. 4
How many types of blood cells are there?
a. 6 b. 2 --> c. 3 d. 4
Which cells make a baby?
--> a. Reproductive cells. b. Muscle cells c. Blood cells d. Nerve cells
From the diagram, identify the cell which carries oxygen to other cells.
a. smooth muscle cell --> b. red blood cell c. neuron d. white blood cell
What shape are the epithelial cells?
--> a. columnar b. neuron c. red d. smooth
How many cells does the human body have?
--> a. 5 b. 4 c. 3 d. 6
How many types of human cells are in the diagram?
a. 3 b. 2 c. 4 --> d. 5
Which cell is part of the nervous system?
a. Smooth muscle cells --> b. Neuron c. White blood cells d. Red blood cells
Which cell has dendrites?
--> a. nerve cell b. blood cells c. sperm cell d. muscle cell
What cells have a square shape?
a. Muscle Cell b. Blood Cell c. Sperm Cell --> d. Skin Cell
How many types of cells are shown in the diagram?
a. 4 b. 8 --> c. 5 d. 3
What is the basic function of a cell?
a. to provide food --> b. ll cells can use energy, respond to their environment, and reproduce c. to provide energy to other cells d. to make plants grow
What cells have a square shape?
a. Blood Cells --> b. Liver cells c. Intestinal Cells d. Muscle Cells
From the diagram, how many cells can stem cells differentiate into?
--> a. 6 b. 7 c. 4 d. 5
How many types of stem cells are there?
--> a. 6 b. 4 c. 3 d. 5
Which of these can stem cells not become?
a. nerve cells --> b. sperm cells c. blood cells d. liver cells
Which cell brings oxygen to other cells?
a. Plant root hair b. Pollen cell --> c. Red blood cell d. Sperm cell
Which of the following cells have the responsibility to transfer oxygen through the body?
a. Pollen Cell b. Plant root hair cell --> c. Red blood cells d. Sperm Cell
Which type of cell has a long tail designed to help with swimming?
a. Plant root hair cell b. Motor neurone cell --> c. Sperm cell d. leaf cell
How many of these cells could be found in a human body?
a. 5 b. 4 --> c. 3 d. 1
Identify the nerve cell
a. X b. D c. W --> d. J
Identify nerve cell
a. E --> b. J c. W d. D