How do systems interact to perform the function of regulation in animals? Body systems in animals work together to keep conditions inside their bodies as constant as possible despite changes in external conditions. Animals expend energy to maintain a constant internal environment for their cells and tissues, known as homeostasis. Often homeostasis is regulated by feedback inhibition. Feedback inhibition or negative feedback occurs when an increase in any substance “feeds back” to stop the process that produced the substance in the first place. Notes from CE begin on Slide 5. (contd.)

Complex animals use several body systems to gather and respond to stimuli in their environment. The nervous system collects, processes, and determines how an animal will respond to events in its environment. Animals often respond to information processed in the nervous system by moving. (contd.)

1. Predict Would an animal with a malfunctioning nervous system be able to produce an appropriate muscle response to a predator? Explain. (contd.)

In humans, body temperature is controlled through various feedback mechanisms. 2. Infer Why do you think moving around on a cold day helps to keep you warm?

How do systems interact to perform nutrient absorption in animals? Animals obtain nutrients and energy from food. The different ways that animals obtain food depends on what they eat and their adaptations for getting food. Many carnivores (animal-eaters) have specialized mouth parts to hunt, grab, tear, and slice food. Herbivores (plant-eaters) typically have mouth parts adapted for rasping, grinding, chewing, or sucking. SLIDE 5: (contd.)

3. Contrast How are the teeth of the wolf and horse adapted to their different diets? (contd.)

Some animals digest food mainly inside their cells and pass nutrients to other cells by diffusion. This process is called intracellular digestion. Most animals digest food outside their cells in a digestive system and then absorb it in a process called extracellular digestion. In most animals, the digestive system is a tube with a mouth at one end and an anus at the other end. A digestive tube has specialized areas where food is broken down by enzymes as it moves along the tube by muscular contractions. (contd.)

Carnivores typically have short digestive tubes that produce enzymes to break down meat. Animals don’t produce enzymes that can break down the tough cellulose in plant tissue. Some herbivores, such as cattle, have a four-part stomach, each with a special function. The largest stomach part is a pouch-like extension called a rumen, in which bacteria digest cellulose. Nutrients that are absorbed through the lining of an animal’s digestive system pass into its circulatory system and are carried to cells throughout the body. (contd.)

In many animals, including humans, systems interact to regulate glucose (simple sugar) levels. Animals get glucose from food, and cells use the energy stored in glucose for their life functions. Insulin and glucagon are hormones produced by the pancreas, an organ in the endocrine system. These hormones help to keep the blood glucose level stable. 4. Interpret Diagrams What two hormones regulate blood glucose levels in humans?

How do systems interact to perform reproduction in animals? Animals undergo either asexual or sexual reproduction. Asexual reproduction produces offspring identical to the parent. Sexual reproduction produces offspring with genetic variations, which may increase the ability of a species ability to adapt and survive environmental changes. Proper interactions between the nervous and reproductive systems are critical to successful reproduction. Animals’ reproductive cycles can be affected by their nervous systems’ responses to changes in length of daylight, seasons, tides, or moon phases. (contd.)

In many animals, including humans, the endocrine system produces hormones that regulate the activities of ovaries and testes. In placental mammals, the placenta links the embryo and mother and acts as the embryo’s organ of respiration, nourishment, and excretion. Their blood flows past each other, but does not mix. Oxygen and nutrients diffuse from the mother’s blood to the embryo’s blood; carbon dioxide and wastes diffuse from the embryo’s blood to the mother’s blood.

How do systems in animals interact to defend them from injury or illness? Skin, which makes up a major part of the integumentary system, keeps many pathogens, or disease-causing organisms, from entering the body. If pathogens enter the body through a cut in the skin, the infected area reacts with an inflammatory response. (contd.)

During the inflammatory response, pathogens stimulate cells to release histamines, which increase the flow of blood and nutrients to the infected area. White blood cells from the circulatory system, called phagocytes, move into the infected area and surround and destroy pathogens. (contd.)

The immune system can distinguish between “self” and “foreign” cells and substances, and it can inactivate, or kill, any foreign substance or cell that enters the body. Immune defenses are triggered by antigens, any foreign substance that can stimulate an immune response. The immune system responds to antigens by increasing the number of cells that attack the pathogens or by producing proteins called antibodies. (contd.)

There are two main cells involved in immunity: B cells and T cells. B cells are produced in red bone marrow. T cells are produced in bone marrow, but they mature in the thymus (an endocrine gland). B-cell T-cell (contd.)

B cells discover antigens in body fluids. T cells are released by infected body cells or immune cells that have encountered antigens. Vaccination stimulates the immune system with an antigen. The immune system produces memory B cells and memory T cells that quicken and strengthen the body’s response to repeated infection.