Traits
Explanation:
Students will explore the difference between physical appearances passed down as inherited traits, and responses to the environment that are learned, not inherited.
Key Concept 1: Some traits are inherited from parent to offspring, while other behaviors are learned during an organism’s lifetime.
Organisms resemble their parents and have behaviors that help them survive within their environments. Physical likenesses between parents and offspring are inherited, passed from generation to generation, such as feather color or shapes of leaves in plants. Other likenesses are learned, such as table manners, reading a book, or seals balancing balls on their noses. Organisms that have well-adapted bodies and useful behaviors are the ones to survive.
Key Concept 2: Inherited characteristics are things such as hair color, the shape of a beak, and spines on a cactus.
Most of the physical characteristics of an organism are inherited from its parents through reproduction. The genetic code (cell blueprint) from parents is transferred to the cells of the offspring as part of its heredity. A tiger kitten will resemble its parents’ four legs, two ears and eyes, a tail, and fur. It will breathe air and need water and food just like its parents. Some characteristics will not be physically evident, but are inherited just the same. The tiger kitten will also inherit being a carnivore (meat eater) and being an instinctive hunter.
A new crop of flowers in a flowerbed will be easily identifiable because they will reflect the traits they inherited from the parents. A young daffodil plant will have the same root system, stem, leaf form, and flower color as its parents that supplied the seed from which it grew. It will have the same needs for sunlight, water, and soil, and possess about the same life span. All of these genetic characteristics are calledinherited traits, having been passed from generation to generation.
Key Concept 3: Acquired characteristics can include learned behaviors, such as a child riding a bicycle or animals learning tricks, but can also include physical characteristics, such as a scar.
Acquiredmeans to obtain a characteristic after an organism is born by learning the behavior, such as riding a bike, or being affected physically after birth, such as getting a cut that leaves a scar. Beyond the inherited traits that an organism receives from its parents, nature has given an organism the ability to respond to changes in an environment. These changes by organisms to the surrounding environment are not physical changes, but are changes in behavior. These changes in response to the environment are called “learned or acquired characteristics.”
Learned characteristicsin animals can be taught or come through experiences in the environment. The tiger kitten is an instinctive hunter and carnivore, but it does not know how to hunt from birth. Many animal parents, such as lions, tigers, and wolves, teach their young how to hunt and how to work in packs to bring down prey. A human infant has all the physical characteristics of the parents, but has to be taught a language, proper human behavior, and how to ride a bicycle. Other learned characteristics can come through interaction within the environment. A bear, hunting for salmon along a river, learns the best place to catch fish and will fight to keep other bears away from his favorite spot. Yellowstone National Park in Wyoming has a continual problem with bears that invade campsites. Once a bear discovers scrap food in a trashcan in the campground, it can abandon its usual foraging and rely on campers for food. Yellowstone has had to implement a policy of capturing the bears and transporting them miles into the wilderness away from campers to get them to return to their usual feeding habits. Bear-proof garbage bins are used in many parks to avoid teaching bears that human trash is a food source.
Acquired traits in plantsare responses to the environment. In hydrangea flowers, soils of different pH (acidity) will cause the plant to produce different colored flowers, ranging from pink to blue. The structures of the hydrangea are inherited, but the specific color of the flowers is a response to soil conditions. When a plant responds to its environment and grows in a certain way, that response is an acquired trait. For example, gravity pulls roots to grow downward and the plant stems respond and grow upward. If a plant is tipped on its side, the stem will still curve to grow upward. Some plants, such as sunflowers, respond to the direction of sunlight and have learned to grow toward the light.