SAT Biology E/M Subject Test

Part II: Subject Review

Chapter 13 Behavior

In this chapter, you will learn that animals exhibit behavior that is present from birth (instinctive behavior) as well as behavior that is learned. Instinctive behavior comes in two forms: as fixed-action patterns and as imprinting. Learned behavior can be the result of habituation, conditioning, or insight.

Instinctive Behavior

Instinct refers to any type of behavior that is not learned—in other words, it exists at the moment of birth; it is inherited behavior. All organisms possess some basic instincts.

Fixed-action patterns are stereotypical behaviors that are triggered by specific stimuli. For example, when a baby bird opens its mouth, a mother bird will put food in it. Another example of a fixed-action pattern is that newly hatched ducks swim when they enter the water. These behaviors are “preprogrammed”; in other words, mother birds don’t have to learn to feed their babies; they just do it. Baby ducks don’t have to learn to swim; they just swim. Other examples of fixed-action patterns are mating rituals, displays of territoriality, and suckling behaviors, and you can probably think of several more.


Konrad Lorenz

A newly hatched bird will follow the first moving object it sees. Because it has no idea what its parent looks like, it will follow a toy, other animal, or a human. Konrad Lorenz, a scientist from Austria, conducted an experiment in which he was the first thing a set of baby ducks saw after they were born. These ducks became imprinted on Lorenz and continued to follow him around, even as they grew into adults.


Imprinting is the recognition of some object as “mother” when it’s seen during a critical time period shortly after birth. Imagine that the first thing a gosling sees when it hatches is its mother. Somehow or another the gosling will decide that this creature is its mother, and will follow it around and treat it as its mother from then on. That’s good, because the creature usually is its mother.

Suppose, though, that instead of its mother, the first thing the gosling saw when it hatched was you. Believe it or not, the gosling will decide that you are its mother. It will follow you around and treat you as its mother. Even if it sees its real mother after that, it will ignore her and continue to think you are its mother.

An interesting thing about both of these behaviors (fixed-action patterns and imprinting) is that they occur even if the stimulus is not the “real” stimulus encountered in nature. A mother bird will attempt to feed anything that has a gaping mouth, even a decoy. Baby goslings will imprint on anything seen in that critical period, even balloons and ticking clocks.

Learned Behaviors

Learned behaviors are those that require interaction with the environment or with other organisms in order to occur. The simplest form of learning is called habituation. Habituation occurs when a non-harmful stimulus is repeated over and over again and the organism learns to ignore it. If you gently poke a dog on the back with a stick, it will turn around to see what’s going on. But if you keep on poking it, the dog eventually learns to ignore the poke. Interestingly though, if you poke the dog in a new place, or if you wait a couple of days and poke it in the back again, it will again turn around to see what’s going on. In other words, the basic response (turning around, in this case) isn’t lost, it’s just temporarily modified by learning.


Ivan Pavlov

You may have heard of Pavlov’s dogs. His classical conditioning experiment involved training a dog to associate a ringing bell with food. Soon the dog would salivate whenever he heard a bell, even if no food was available. You probably react in the same way sometimes.


Conditioning is a type of learning in which a stimulus is associated with a particular behavior. Because it involves associations, conditioning is sometimes referred to as associative learning.

Imagine some fish in a tank. If we tap on the tank at the same time we drop some fish food into the water, and we do this for several days, the fish learn that a tap on the tank means food. They will swim to the top of the water when they hear a tap even if there is no food present. They have associated tapping with food. This is called classical conditioning.

Another form of conditioning is called operant conditioning. Imagine that every time a cat starts scratching on the couch, its owner squirts it with a water gun. The cat soon learns not to scratch on the couch because it knows it will get squirted. Or imagine that a rat learns to press a button because every time it presses the button it gets a food pellet. Learning that occurs because of a reward and punishment system is operant conditioning.

The highest form of learning is insight learning. Insight refers to the ability to approach new situations and figure out how to deal with them. As animals go, human beings are pretty good at insight, and so are some other animals, like cows. Another word for insight is reasoning.

Quick Quiz #1

For each of the situations described below, write:

(A)  if it represents a fixed-action pattern,

(B)  if it represents imprinting,

(C)  if it represents classical conditioning,

(D)  if it represents operant conditioning, or

(E)  if it represents insight learning.

1. ________ A dog learns that if it brings the newspaper into the house each evening, it gets a bone.

2. ________ A bird treats the human it saw when it first hatched as its mother.

3. ________ A frog squeezes the swollen belly of a female frog to release eggs.

4. ________ A cockroach learns to run from light because every time a light comes on someone tries to step on it.

5. ________ A man wishes to turn a screw and, having no screwdriver, realizes that he can use the edge of dull knife as a substitute.

6. ________ A cat runs into the kitchen and looks for food when it hears the electric can opener.

7. ________ A bird puffs up its brightly colored chest to attract a mate.

Correct answers can be found in Chapter 15.

Turning Behavior in Plants: The Tropisms

The word tropism is derived from the Greek word tropos, which means “to turn,” so tropisms are all turning behaviors in response to particular stimuli. There are three stimuli that can cause turning: light, gravity, and touch.

Plants need light. If a plant sits in a room in which sunlight comes in through one window, the plant will, on its own, bend toward the window. When a plant bends toward light, we call it phototropism (photo = light).

Plants need minerals and water from the earth. Plant roots therefore like to grow downward, in the direction of the gravitational pull. When roots grow downward, toward the earth, it’s called positive gravitropism. Plant stems and leaves, on the other hand, grow up, away from the earth. This is called negative gravitropism. Gravitropism is sometimes referred to as geotropism.

Lastly some plants will grow along a wall or trellis. The physical touch of the plant on the object causes it to grow in that direction. This is known as thigmotropism (thigmo = touch).

Also, these turning behaviors are induced by plant hormones, called auxins. So remember:


Phototropism means …

growth of a plant toward light.

   

Positive gravitropism means …

growth of the roots downward, toward the earth.

   

Negative gravitropism means …

growth of the plant stem upward, away from the earth.

   

Thigmotropism means …

growth of the plant along a surface.


Animals and Plants Can Tell Time: Biological Clocks

Imagine that a plant predictably opens its leaves at 6 A.M., closes them at noon, opens them again at 6 P.M., and closes them again at midnight. Imagine, furthermore, that the plant does this even if it is kept in the dark all day and all night. This plant seems somehow to know when to open and close its leaves, even without being exposed to changing conditions of sunlight. Something in the plant keeps time.

Circadian Rhythm

Daily cycles of light and 
dark set an organism’s 
biological clock to 
approximately 24 hours.

We don’t know how plants, animals, or individual cells keep time, but they seem to do it. In other words, living things have biological clocks. The behavior that arises from biological clocks is instinctive; it isn’t learned.

When a biological clock makes an organism do something on a daily basis, it is referred to as a circadian rhythm. The plant that opens and closes its leaves predictably several times daily exhibits a circadian rhythm. A plant that loses its leaves in the fall and regrows them in the spring does NOT reflect a circadian rhythm. The pattern is seasonal, not daily.

Organisms Communicate: Pheromones

Many animals communicate with other members of their species by releasing chemicals called pheromones. A pheromone is any chemical that (1) is released by one member of a species and (2) affects the behavior of other members of the species in a predictable way.

Suppose an ant discovers a food source and wants others of her colony to know about it. She lays down a trail of chemicals, leading from the ant colony to the food source. The other ants know to follow the chemical trail, and so they’re led to the food. This chemical is a pheromone.

Some female animals release chemicals that attract males, and these chemicals are also pheromones. On discovering danger, some animals release chemicals that signal others of their species to stay away, and these chemicals, too, are pheromones. In some species, an animal’s dead body releases a chemical that causes survivors of the species to bury it. That chemical is a pheromone as well.

Be careful! Do not confuse pheromone with hormone! Hormones are also chemicals, but they are released into the blood of an organism and affect only that organism. Here’s a comparison table:

Plants and Animals Coexist: Symbiosis

Organisms of different species sometimes share living space, in arrangements referred to as symbiosis. Moss grows on tree trunks, and bacteria live in our intestines. These are both examples of symbiosis. For the SAT Biology E/M Subject Test, you should know the three types of symbiosis: mutualism, parasitism, and commensalism.

In mutualism, both organisms in the symbiotic relationship benefit from the association. Humans and their intestinal bacteria are an example of mutualism. The bacteria get a food source (our indigestible material), and they, in turn, provide us with vitamin K.

In parasitism, one organism benefits from the association, while the other organism is harmed. Intestinal tapeworms are parasites. The tapeworms benefit—they get food—but the host is harmed, often suffering from nutritional deficiencies.

In commensalism, one organism benefits from the association, and the other organism is neither harmed nor helped. In fact, the other organism couldn’t care less about the first organism. An example of commensalism is the relationship between buffalo and egrets (birds that live with the buffalo). As the buffalo walk through tall grass, they flush out bugs, which the egrets eat. The egrets benefit from the relationship, and the buffalo don’t really care one way or the other.

Quick Quiz #2

Fill in the blanks and check the appropriate boxes:

  1. A chemical released that causes an organism’s own heart rate to increase is an example of a [  pheromone  hormone ].

  2. Roots growing toward the earth is described as [  positive  negative ] gravitropism.

  3. A rooster crowing in the morning is an example of a _________________________ rhythm.

  4. A fruit tree flowering in the spring is an example of a _________________________ rhythm.

  5. Growth of a plant toward light is called _______________________.

  6. Bacteria that release chemicals to draw other bacteria toward a food source are releasing [  pheromones  hormones ].

  7. Athlete’s foot is the common name that describes a fungal infection of the skin of the feet, especially between the toes. The skin becomes cracked and sore. This is an example of a [  mutualistic  commensalistic  parasitic ] relationship.

  8. Epiphytes are small plants that grow on the branches of big trees. The epiphytes are exposed to sunlight, and the big tree is neither helped nor harmed. This is an example of a [  mutualistic  commensalistic  parasitic ] relationship.

  9. Any two organisms living in an intimate association with each other are said to be in a _________________________ relationship.

10. An ivy growing along a trellis is an example of __________________.

Correct answers can be found in Chapter 15.

Key Words

instinctive behavior

fixed-action patterns

imprinting

learned behaviors

habituation

conditioning

associative learning

classical conditioning

operant conditioning

insight learning

reasoning

tropism

phototropism

positive gravitropism

negative gravitropism

geotropism

thigmotropism

auxins

circadian rhythm

pheromones

symbiosis

mutualism

parasitism

commensalism

Summary

•   Animals have some behaviors that are present at birth. These are instinctive behaviors.

•   Instinctive behavior can be fixed-action patterns or imprinting.

•   Animals also have learned behaviors, which can be the result of habituation, conditioning, or insight.

•   Plants respond to different stimuli. Specifically, these stimuli are light, gravity, and touch.

•   Animals can communicate by the release of pheromones, chemicals that are released and cause a reaction in another animal.

•   Plants and animals can coexist in arrangements called symbiosis. This includes mutualism, para-sitism, and commensalism.