Animal Growth and Heredity

Growth and Development All living things start life as a single cell. One cell divides into 2, 2 into 4 and so on. All living things grow and most pass through stages. The stages an organism pass through make up a life cycle. A life cycle starts with a fertilized egg.

Cell Division Mitosis is the process by which most cells divide. Changes first take place in the nucleus. Chromosomes are the threadlike structures found in the nucleus. During mitosis a new cell gets an exact copy of chromosomes.

How are characteristics inherited? An inherited trait is a characteristic passed from parents to offspring. In humans, hair, eye color, skin, freckles, and the shape of our earlobes are inherited.

Gregor Mendel In 1857 Mendel began experimenting with pea plants to learn how traits were inherited. Through experimentation, Mendel learned that each parent passes one pair of its factors to an offspring. He learned that traits can skip a generation. He also learned that the height of pea plants depended on the factors they inherited from their parents.

Dominant & Recessive Traits Dominant traits are strong traits. If an organism has 1 factor for a dominant trait, that trait will appear. Recessive traits are weak traits.

Genes A gene is the part of a chromosome that contains DNA. A combination of about 20,000 different genes that we inherit from our parents make us unique.

Instincts A behavior that organisms develop. They are passed from parents to offspring. Behaviors for building homes and caring for young are usually instinctive. Birds know how to instinctively build their nests. Instinctively animals know that they must hunt for food.

Learned Behaviors Some animals instinctively know that they must hunt. They must learn how to hunt. A learned behavior is a behavior obtained through experience. Most behavior is learned through the teaching by adults of the same species.

Environmental Influences Some behaviors and characteristics are a result of environmental influences. All living and nonliving things that affect an organism make up its environment. Changes in the environment can cause animals to change their behaviors.

Video

Video

Questions How does cell division affect growth? What characteristics are inherited? What other factors affect characteristics?