Chapter 2Life Cycles

Pages 62-63

Lesson 1 VocabularyTrait—a form of a characteristic that not all

organisms have in common.

Heredity—the process by which traits are passed from parents to offspring.

Gene—a basic unit of heredity.

What is Heredity?

All Sizes and ShapesAll dogs belong to the same species. Fossils and genetic evidence

show that all are descended from wolves.

Page 64

Lesson 1—Traits (page 66)

• All people have thumbs, but having a hitchhiker thumb is a trait.

• Traits are passed on through heredity.

Lesson 1—Genes (page 67) • Genes carry instructions for how a living thing will grow and

develop.• Each human has the same number and type of genes, but the

instructions on the genes vary.• Different forms of genes cause people to have different traits!

Lesson 1—Genes (page 67)

• Genes work in pairs.

• ½ of your genes come from your mother

• ½ of your genes come from your father

Lesson 1—Traits (page 68)• Traits (such as eye color) are affected by genes

alone.• Nurture (everything in your life) influences many

traits. Example: hair color can be dyed and change.

Lesson 1—Traits (page 68)

• Name some traits:Eye colorHair colorWidow’s peakCleft chinHitchhiker thumb

Rolling tongueAllergiesLonger 2nd toe

Lesson 1—Learned behaviors (69)• The people around you influence your traits, as well.• The language you speak and the words you use are

learned from the people in your life.

Lesson 1—Not learned (69)

• Some behaviors are not learned. Some animals hatch from eggs (never see their parents), but know exactly where to go and what to do to survive.

Lesson 1—Variations (page 70)• Genes affect characteristics such as

height, shape, and color.• Some characteristics are affected by

SEVERAL genes.• For example, eye colors can vary.

They are not simply brown or blue.• Look at the variations in the

Labrador retrievers.

Lesson 1—Variations (page 70)

• You can’t change your eye color, BUT you can change some characteristics.

• For example, how you eat and how much you exercise can determine how tall you grow or how much you weigh.

Review!!!!!• Trait—a form of a characteristic that not all

organisms have in common.

• Heredity—the process by which traits are passed from parents to offspring.

• Gene—a basic unit of heredity.