Grade 3
Life Cycles and Traits
Life cycles, inherited traits, environmental influence on traits, and advantages of variation.
3-LS1-1, 3-LS3-1, 3-LS3-2, 3-LS4-2
4 lessons
100 quiz questions
Lesson 1: Life Cycles
Compare life cycles and the shared pattern of birth, growth, reproduction, and death.
Learning goals
- Describe common stages in organism life cycles.
- Compare life cycles of different organisms.
- Use a model to show a life cycle pattern.
Life cycles have patterns
A life cycle is the series of stages an organism goes through during its life. Organisms have different life cycles, but they share a pattern: birth, growth, reproduction, and death.
Different organisms, different stages
A flowering plant may begin as a seed, grow into a plant, make flowers, and produce new seeds. A butterfly begins as an egg, becomes a caterpillar, forms a chrysalis, and becomes an adult butterfly.
Models show life cycles
A model can show the order of life cycle stages. Arrows are often used to show how one stage leads to the next and how the pattern repeats in a new generation.
Lesson 2: Inherited Traits and Variation
Analyze patterns in traits shared between parents and offspring.
Learning goals
- Identify inherited traits in plants and animals.
- Explain that offspring resemble parents but are not exactly the same.
- Describe variation among similar organisms.
Traits can be inherited
A trait is a characteristic of a living thing. Many traits are inherited from parents. For example, young plants may have leaf shapes similar to parent plants, and young animals may have body features similar to their parents.
Variation exists
Offspring often look similar to their parents, but they are not exactly the same. Members of the same kind of organism can vary in size, color, shape, or other traits.
Data can show patterns
Students can collect and compare data about traits. Patterns in the data can provide evidence that traits are inherited and that variation exists in a group.
Lesson 3: Environment and Traits
Use evidence to explain how the environment can influence traits.
Learning goals
- Identify environmental factors that can affect growth or traits.
- Explain that inherited traits can be influenced by conditions.
- Use evidence to support an explanation.
The environment can affect organisms
The environment includes living and nonliving surroundings. Water, sunlight, food, temperature, space, and exercise can affect how an organism grows and develops.
Traits can be influenced
A plant may inherit the ability to grow tall, but if it does not get enough water or sunlight, it may stay short. A pet dog may become overweight if it gets too much food and little exercise.
Evidence supports explanations
A good explanation connects evidence to a science idea. If two similar plants grow differently because one got more sunlight, that evidence can support the idea that environment influenced growth.
Lesson 4: Variation and Survival
Explore how differences among individuals can provide survival advantages.
Learning goals
- Describe variations among individuals of the same species.
- Explain how some variations can help organisms survive.
- Use cause-and-effect reasoning about survival and reproduction.
Individuals vary
Individuals of the same species may have different characteristics. Some may be larger, faster, better camouflaged, or better protected than others.
Some traits provide advantages
A variation can give an organism an advantage in a certain environment. A plant with larger thorns may be less likely to be eaten. An animal with better camouflage may be harder for predators to see.
Survival and reproduction
Organisms with helpful traits may be more likely to survive, find mates, and reproduce. Their offspring may inherit similar helpful traits.