CK-12 Life Science

by CK-12 Foundation

  Figure 15.30

  These geese are flying south for the winter. Flocks of geese migrate in V-shaped formations.

  Some animals migrate very long distances. The map in Figure below shows the migration route of a species of hawk called Swainson’s hawk. About how many kilometers do the hawks travel from start to finish? Are you surprised that birds migrate that far? Some species of birds migrate even farther.

  Figure 15.31

  The migration route of Swainsons hawk starts in North America and ends in South America. Scientists learned their migration route by attaching tiny tracking devices to the birds. The birds were then tracked by satellite. On the migration south, the hawks travel about 8,000 kilometers from start to finish.

  Birds and other migrating animals follow the same routes each year. How do they know where to go? It depends on the species. Some animals follow landmarks, such as rivers or coastlines. Other animals are guided by the position of the sun, the usual direction of the wind, or other clues in the environment.

  Daily Cycles

  Many animal behaviors change at certain times of day, day after day. For example, most animals go to sleep when the sun sets and wake up when the sun rises. Animals that are active during the daytime are called diurnal. Some animals do the opposite. They sleep all day and are active during the night. These animals are called nocturnal. Animals may eat and drink at certain times of day, as well. Humans have daily cycles of behavior, too. Most people start to get sleepy after dark and have a hard time sleeping when it is light outside. Daily cycles of behavior are called circadian rhythms.

  In many species, including humans, circadian rhythms are controlled by a tiny structure called the biological clock. This structure is located in a gland at the base of the brain. The biological clock sends signals to the body. The signals cause regular changes in behavior and body processes. The amount of light entering the eyes controls the biological clock. That’s why the clock causes changes that repeat every 24 hours.

  Lesson Summary

  Communication is any way that animals share information.

  Social animals live together in groups and cooperate with one another.

  Some of the most important animal behaviors involve attracting mates and caring for offspring.

  Some animals defend the area where they live from other animals.

  Many animal behaviors occur in cycles that repeat yearly or daily.

  Review Questions

  List two ways that animals communicate.

  Describe how ants in a colony cooperate.

  What is courtship behavior?

  Why do male dogs urinate on fire hydrants and other objects?

  Give an example of a circadian rhythm.

  How do ants use chemicals to communicate?

  Explain how courtship behaviors could evolve.

  How do adult animals increase their own fitness by teaching skills to their young?

  What is the advantage of animals using display behavior instead of fighting to defend their territory?

  What is migration, and why do animals migrate?

  Further Reading / Supplemental Links

  Bernard Stonehouse and Esther Bertram. The Truth about Animal Communications. Tangerine Press, 2003.

  Betty Tatham. How Animals Communicate. Franklin Watts. 2004.

  Etta Kaner. Animal Groups (Animal Behavior). Tandem Library, 2004.

  Pamela Hickman. Animals and Their Mates: How Animals Attract, Fight for, and Protect Each Other. Kids Can Press, Ltd., 2004.

  Susan Glass. Staying Alive: Regulation and Behavior. Perfection Learning, 2005.

  http://news.nationalgeographic.com/news/2003/07/0709_030709_socialanimals.html

  http://www.ninds.nih.gov/disorders/brain_basics/understanding_sleep.htm

  http://www.usatoday.com/news/science/aaas/2002-04-05-coop-behavior.htm

  http://www.wjh.harvard.edu/~mnkylab/media/vervetcalls.html

  http://en.wikibooks.org

  Vocabulary

  biological clock

  Tiny structure in the brain that controls circadian rhythms.

  circadian rhythms

  An organism's daily cycles of behavior.

  communication

  Any way that animals share information.

  cooperation

  Working together with others for the common good.

  courtship behaviors

  Special behaviors that help attract a mate.

  display behavior

  Fixed set of actions that carries a specific message.

  hibernation

  State in which an animal’s body processes are slower than usual.

  language

  Use of symbols (or sounds) to communicate.

  mating

  Pairing of an adult male and female to produce young.

  migration

  Movement of animals from one place to another; often seasonal.

  social animals

  Animals that live in groups with other members of their species.

  Points to Consider

  The biological clock located just below the human brain controls behaviors such as the sleep-wake cycle.

  The brain is part of the nervous system. What other body system are found in humans?

  Which body system includes the bones? Which system includes the muscles? What do bones and muscles do?

  Chapter 16: Skin, Bones, and Muscles

  Lesson 16.1: Organization of Your Body

  Lesson Objectives

  List the levels of organization in the human body.

  Identify the four types of tissues that make up the body.

  Identify 12 organ systems.

  Describe how organs and organ systems work together to maintain homeostasis.

  Check Your Understanding

  What is a cell?

  What are some of the differences between a prokaryotic cell and an eukaryotic cell?

  What are some of the basic functions of animal cells?

  Introduction

  The men in Figure below have just jumped into freezing icy water. They are having fun, but imagine how cold they must feel! One minute their bodies were wrapped in warm clothes, the next, they were dunked in freezing water. Their bodies are now working hard to adapt to the sudden great change in temperature. The ability of the body to maintain a stable internal environment in response to change is called homeostasis. Homeostasis allows your body to adapt to change, such as jumping into cold water, running in hot weather, or not getting enough food when you are hungry. Homeostasis is an important characteristic of living things.

  Figure 16.1

  The bodies of these swimmers are working hard to maintain homeostasis while they are in the icy pool water. Otherwise, their life processes would stop working as soon as they got into the water.

  Cells, Tissues, and Organs

  Cells are the most basic units of life in your body. They must do many jobs to maintain homeostasis, but each cell does not have to do every job. Cells have specific jobs to maintain homeostasis. For example, nerve cells move electrical messages around the body, and white blood cells patrol the body and attack invading bacteria. There are many additional different types of cells. Other cells include red blood cells, skin cells, cells that line the inside of your stomach, and muscle cells.

  Groups of Cells Form Tissues

  Cells are grouped together to carry out specific functions. A group of cells that work together is called a tissue. Your body has four main types of tissues, as do the bodies of other animals. These tissues make up all structures and contents of your body. An example of each tissue type is shown in Figure below.

  Figure 16.2

  Your body has four main types of tissue; nervous tissue, epithelial tissue, connective tissue, and muscle tissue. They are found throughout your body.

  Epithelial tissue is made up of layers of tightly packed cells that line the surfaces of the body. Examples of epithelial tissue include the skin, the lining of the mouth and nose,
and the lining of the digestive system.

  Connective tissue is made up of many different types of cells that are all involved in structure and support of the body. Examples include tendon, cartilage, and bone. Blood is also classified as a specialized connective tissue consisting of cells and an abundant extracellular interstitium.

  Muscle tissue is made up of cells that have filaments that move past each other and change the size of the cell. There are three types of muscle tissue: smooth muscle, skeletal muscle, and cardiac muscle.

  Nervous tissue is made up of the nerve cells that together form the nervous system. Nervous tissue is found in nerves, the spinal cord, and the brain.

  Groups of Tissues Form Organs

  A single tissue alone cannot do all the jobs that are needed to keep you alive and healthy. Two or more tissues working together can do a lot more. An organ is a structure made of two or more tissues that work together. The heart, shown in Figure below, is made up of four types of tissues.

  Figure 16.3

  The four different tissue types work together in the heart as they do in the other organs.

  Groups of Organs Form Organ Systems

  Your heart pumps blood around your body. However, your heart needs to be able to get blood to and from every cell in your body in order to do its job. So, your heart is connected to blood vessels such as veins and arteries. Organs that work together form an organ system. Together, your heart, blood, and blood vessels form your cardiovascular system.

  Organ Systems Work Together

  Your body’s 12 organ systems are shown in Table below. Your organ systems do not work alone in your body. They must all be able to work together to maintain homeostasis. For example, when the men in Figure below jumped into the cold water, their integumentary systems (skin, hair, nails), cardiovascular systems, muscular systems, and nervous systems worked quickly together to ensure the icy-cold water did not cause harm to their bodies. The nervous system sent nerve messages from the skin to tell the cardiovascular system to reduce the blood flow to the skin. Blood flow is then increased to the internal organs and large muscles to help keep them warm and supply them with oxygen. The nervous system also sent messages to the respiratory system to breathe faster. This allows for more oxygen to be delivered by the blood to the muscular system which is shivering and moving about to keep the body warm. Feedback loops in the nervous and endocrine systems regulate conditions in the body. A feedback loop is a path that leads from the initial generation of the signal to the subsequent modification of the initial event. For example, the men that jumped into the cold water did not need to continue to breathe faster and faster. Feedback loops return the respiratory system to "normal." One of the most important functions of organ systems is to provide cells with oxygen and nutrients and to remove toxic waste products such as carbon dioxide. A number of organ systems, including the cardiovascular and respiratory systems, all work together to do this.

  Major Organ Systems of the Human Body Organ System Major Tissues and Organs Function Example

  Cardiovascular Heart; blood vessels; blood Transports oxygen, hormones and nutrients to the body cells, and wastes and carbon dioxide away from cells

  Lymphatic Lymph nodes; lymph vessels Defense against infection and disease, transfer of lymph between tissues and the blood stream

  Digestive Esophagus; stomach; small intestine; large intestine Processing of foods and absorption of nutrients, minerals, vitamins, and water

  Endocrine Pituitary gland, hypothalamus; adrenal glands; Islets of Langerhans; ovaries; testes Communication within the body with hormones; directing long-term change over other organ systems to maintain homeostasis

  Integumentary Skin, hair, nails Protection from injury and fluid loss; physical defense against infection by microorganisms; temperature control

  Muscular Cardiac (heart) muscle; skeletal muscle; smooth muscle; tendons Movement, support, heat production

  Nervous Brain, spinal cord; nerves Collecting, transferring and processing information; directing short-term change over other organ systems in order to maintain homeostasis

  Reproductive Female: uterus; vagina; fallopian tubes; ovaries Male: penis; testes; seminal vesicles Production of gametes (sex cells) and sex hormones; production of offspring

  Respiratory Trachea, larynx, pharynx, lungs Delivery of air to sites where gas exchange can occur between the blood and cells (around body) or blood and air (lungs)

  Skeletal Bones, cartilage; ligaments Support and protection of soft tissues of body; movement at joints; production of blood cells; mineral storage

  Urinary Kidneys; urinary bladder Removal of excess water, salts, and waste products from blood and body; control of pH; regulates water and electrolyte balance

  Immune Skin; bone marrow; spleen; white blood cells Defending against microbial pathogens (disease-causing agents) and other diseases

  Figures in table above: Each body system works together to maintain homeostasis of other systems and of the entire organism. No system of the body works alone, and your well-being depends upon the well-being of all the body systems. A problem in one system usually affects other body systems.

  Homeostasis and Feedback Regulation

  Homeostasis refers to stability, balance, or equilibrium within a cell or the body. It is an organism’s ability to keep a constant internal environment. Homeostasis is an important characteristic of living things. Keeping a stable internal environment requires constant adjustments as conditions change inside and outside the cell. Because the internal and external environments of a cell are constantly changing, adjustments must be made continuously to stay at or near the set point (the normal level or range).

  The endocrine system plays an important role in homeostasis because hormones, which are the messengers of the endocrine system, regulate the activity of body cells. The release of hormones into the blood is controlled by a stimulus, or signal. For example, the stimulus either causes an increase or a decrease in the amount of hormone released. Then, the response to the signal changes the internal conditions and may itself become a new stimulus. This self-adjusting mechanism is called feedback regulation.

  Feedback regulation occurs when the response to a stimulus has an effect of some kind on the original stimulus. The type of response determines what the feedback is called. Negative feedback occurs when the response to a stimulus reduces the original stimulus. Positive feedback occurs when the response to a stimulus increases the original stimulus.

  Thermoregulation: A Negative Feedback Loop

  Negative feedback is the most common feedback loop in the body. The system acts to reverse the direction of change, keeping things constant. For instance, when the concentration of carbon dioxide in the human body increases, the lungs are signaled to increase their activity and exhale more carbon dioxide, so your breathing rate increases. Thermoregulation is another example of negative feedback. When body temperature rises, receptors in the skin and the brain sense the temperature change. The temperature change (signal) triggers a command from the brain. This command, causes a response (the skin makes sweat and blood vessels near the skin surface dilate), which helps decrease body temperature. Figure below shows how the response to a stimulus reduces the original stimulus in another of the body’s negative feedback mechanisms.

  Figure 16.4

  Control of blood glucose level is an example of negative feedback. Blood glucose concentration rises after a meal (the stimulus). The hormone insulin is released by the pancreas, and it speeds up the transport of glucose from the blood and into selected tissues (the response). Blood glucose concentrations then decrease, which then decreases the original stimulus. The secretion of insulin into the blood is then decreased.

  Positive feedback is less common in biological systems. Positive feedback acts to speed up the direction of change. An example of positive feedback is lactation (milk production). As the baby drinks its mother's milk, nerve messages from the mammary glands cause a hormone, prolactin, to be rele
ased. The more the baby suckles, the more prolactin is released, which stimulates further milk production.

  Not many feedback mechanisms in the body are based on positive feedback. Positive feedback speeds up the direction of change, which leads to increasing hormone concentration, a state that moves further away from homeostasis.

  Lesson Summary

  The levels of organization in the human body include: cells, tissues, organs, and organ systems. A tissue is a group of cells that work together. An organ is made of two or more tissues that work together. Organs that work together make up organ systems.