Animal Growth and Heredity Chapter 4

How Does Cell Division Affect Growth? All organisms start life as a single cell. Then, the cell divides. Body cells make exact copies of themselves as they divide. Bone cells divide and build more bone cells Each cell has a special function. Some organisms, like bacteria and protists, are mature as soon as they are formed. They reproduce immediately.

Mammals, birds, reptiles, and many fish spend months or years growing and developing before they reach maturity. They do not change much as they grow. The young resemble the adults.

Butterflies and frogs have one kind of body when they they’re young and a very different kind of body when they are mature. (metamorphosis) Life Cycle of a Frog Life Cycle of a Butterfly

Mitosis and Meiosis

Zygote Gamete cells with ½ the DNA of each parent. Each parent contributes ½ the DNA needed (called gametes) to have a fertilized cell (called a zygote) Contains the same number of chromosomes as the parent cells Zygote – the fertilized cell that develops into a new being (baby)

How Are Characteristics Inherited? An inherited trait is a characteristic passed from parents to their offspring. Hair color, facial shape, eye color, skin color, freckles, hair texture, earlobe shape are inherited. If this is the mother dog, what do we know about the father dog?

Heredity interested Gregor Mendel, a 19th century Austrian monk. He noticed some pea plants were tall and others were short. He did controlled experiments and learned that some plant traits were directly passed to the next generation and some skipped a generation. In people, blue eyes can pass to a generation even when both parents have brown eyes, but only if there are blue eyes in previous generations.

Dominant and Recessive Traits A dominant trait is a strong trait. A recessive trait is a weak trait. The offspring need TWO recessive genes (one from each parent) to show the recessive trait. In people, blue eyes can pass to a generation even when both parents have brown eyes, but only if there are blue eyes in previous generations.

Genes Mendel’s factors are now known as genes. All inherited traits are controlled by genes. You probably have some genes for dominant traits. You probably have some genes for recessive traits.

Human Behaviors Most human behaviors are learned, like walking, talking, and eating politely. Some behaviors, such as sleeping and waking, are inherited.

Instincts An instinct is a behavior that an organism inherits. They are passed from the parents to their offspring. Squirrels instinctively collect and store nuts and other seeds for the winter. Ants instinctively “herd” aphids to fresh leaves. The aphids eat the leaves and make a sweet liquid that the ants eat. The ants defend the aphids against predators. What instincts were you born with? You were able to eat and sleep when you needed to. AND, you were able to communicate with your parents when you needed things – your CRYING was instinctive!!

Learned Behaviors I don’t wanna!! A learned behavior is a behavior an animal or human acquires through experience. You were born with the instinct to cry, but you learned to vary the pitch and loudness of your crying, depending on your needs. As you grew and developed, you learned many other behaviors. You learned how to walk and talk. You learned how to dress yourself, how to bathe, and how to brush your teeth. Even though you had the instinct to eat, you learned table manners and how to use spoons, forks, and knives. Sometimes animals learn “human” behaviors like a parrot speaking or a dog shaking hands.

Environmental Influences An organisms environment is everything in its surroundings that affects it, including water, soil, air, weather, landforms, and other living things. Sometimes, changes in the environment force animals to change their behavior. In areas where food becomes less plentiful, some animals may learn to eat different foods. Environmental Influences