2ArthropodsThe evolution of arthropods, by natural selection and other processes, has led to fewer body segments and highly specialized appendages for feeding, movement, and other functions.Arthropods have exoskeletons. When they outgrow their exoskeletons, arthropods undergo periods of molting.Reproduction can occur both internally or externally.
3ArthropodsCrustaceans typically have two pairs of antennae, two or three body sections, and mandibles.Chelicerates (spiders and such) have mouthparts called chelicerae and two body sections, and nearly all have four pairs of walking legs.Uniramians (insects and such) have jaws, one pair of antennae, and unbranched appendages.The growth and development of insects usually involve metamorphosis, which is a process of changing shape and form. Insects undergo either incomplete or complete metamorphosis.
4EchinodermsEchinoderms are characterized by spiny skin, an internal skeleton, a water vascular system, and suction-cuplike structures called tube feet.The water vascular system carries out many essential body functions in echinoderms, including respiration, circulation, and movement.Echinoderms reproduce by external fertilization.
5EchinodermsAn amphibian is a vertebrate that lives in the water as a larva and on land as an adult.Early amphibians evolved several adaptations that helped them live at least part of their lives out of water. Bones became stronger. Lungs and breathing tubes enabled them to breathe air. The sternum formed.
6ChordatesA chordate is an animal that has, for at least some stage of its life, a dorsal, hollow nerve cord; a notochord; pharyngeal pouches; and a tail.Most chordates are vertebrates.Fish have adapted to aquatic life by various modes of feeding, specialized structures for gas exchange, and paired fins for locomotion.
7MammalsMammals have hair, the ability to nourish their young with milk, breathe air, have four-chambered hearts, and are endotherms.As mammals evolved, the form and function of their jaws and teeth became adapted to eat foods other than insects.Similar ecological opportunities on the different continents have produced some striking examples of convergent evolution in mammals.
8PrimatesPrimates have binocular vision, a well-developed cerebrum, relatively long fingers and toes, and arms that can rotate around their shoulder joints.Hominids, which include humans, developed into a bipedal species, with opposable thumbs.
9DiseasesSome diseases are produced by agents, such as bacteria, viruses, and fungi. Some are caused by materials in the environment, and some are inherited.Disease causing agents are called pathogens.Viruses are tiny particles that invade and replicate within living cells.
10How are they spread?Some infectious diseases are spread from one person to another through coughing, sneezing, or physical contact.Others are spread through contaminated food or water, or infected animals.
11Fighting DiseaseThe function of the immune system is to fight infection through the production of cells that inactivate foreign substances or cells.Skin is the body’s most important, nonspecific defense against disease.The inflammatory response is a nonspecific defense reaction to tissue damage caused by injury or infection.
12Fighting DiseaseA fever is advantageous because many pathogens can only survive within a narrow temperature range.Antibodies are proteins that recognize and help destroy pathogens.
13Immune System Problems Allergies are an overreaction to certain things. Allergens activate chemicals called histamines.When the immune system makes a mistake and attacks the body’s own cells, it produces an autoimmune disease. (MS, RA, TIdiabetes)Immunodeficiency diseases attack the immune system itself, leaving the body defenseless against other diseases.
14Other Health FactorsEnvironmental factors that can affect your health include air and water quality, poisonous wastes in landfills, and exposure to solar radiation.Healthful behaviors include eating a healthful diet, getting plenty of exercise and rest, abstaining from harmful activities, and having regular checkups.
15StimuliA stimulus is any kind of signal that carries information and can be detected.A response is a single, specific reaction to a stimulus.When an animal responds to a stimulus, body systems—including the sense organs, nervous system, and muscles—interact to produce the resultant behavior.
16Behaviors Innate behaviors are instinct. Innate behaviors appear in fully functional form the first time they are performed.Learning is altering behavior as a result of experience.
17LearningThe four main types of learning are habituation, classical conditioning, operant conditioning, and insight learning.Habituation is when an animal decreases or stops its response to a repetitive stimulus that neither rewards nor harms the animal.Classical conditioning is a mental connection between a stimulus and a response.Operant conditioning is learning to behave in a certain way through repeated practice.Insight learning is reasoning.
18BehaviorsMany animals respond to periodic changes in the environment with daily or seasonal cycles of behavior.Migration is the periodic movement from one place to another.Circadian rhythms are the daily behavioral cycles.To pass along its genes to the next generation, an animal needs to locate and mate with another member of its species at least once.
19Social BehaviorsSocial Behavior is the interaction between individuals or groups.Competition and Aggression can fall into this category.Animals may use visual, sound, touch, or chemical signals to communicate with one another.