3-LS1-1: Modeling Plant and Animal Life Cycles
Also called NGSS 3-LS1-1 · Topic: Inheritance and Variation of Traits: Life Cycles and Traits · Life Science
The Official Wording
Develop models to describe that organisms have unique and diverse life cycles but all have in common birth, growth, reproduction, and death.
Clarification statement: Changes organisms go through during their life form a pattern.
Assessment boundary: Assessment of plant life cycles is limited to those of flowering plants. Assessment does not include details of human reproduction.
NGSS Lead States, 2013 · Read it on nextgenscience.org · checked October 15, 2026
What 3-LS1-1 Means in Plain English
Third graders build models, like drawings, wheels or sequence strips, that show how a living thing changes from start to finish. They see that a butterfly, a frog and a bean plant each change in their own way, yet every one starts life, grows, makes young and dies.
Plant life cycles stay with flowering plants, and the details of human reproduction are not part of this standard. It builds on 1-LS3-1 and leads to inherited traits in 3-LS3-1 and to how plants and animals reproduce in 4-LS1-1.
3-LS1-1 I Can Statements
- I can draw a model of a life cycle.
- I can compare the life cycles of two living things.
- I can name the stages all life cycles share.
3-LS1-1 Worked Example
A four-week observation of painted lady butterflies from a classroom kit, turned into a life cycle model.
What stages does a painted lady butterfly go through, and how long does each one last?
Set It Up: A painted lady butterfly kit with caterpillars in a cup of food, a mesh habitat, and a dated observation journal.
- Measure and sketch the caterpillars every two days.Day 1: about 1 cm. Day 8: about 3 cm
- Record the day each caterpillar hangs in a J shape and forms a chrysalis.Days 9 to 11: chrysalises
- Move the chrysalises to the mesh habitat and keep checking.Days 18 to 20: butterflies come out
- Feed the butterflies sugar water and note what they do.Adults fly and feed, ready to lay eggs
- Draw the stages in a circle with arrows, adding egg as the next step.Egg, caterpillar, chrysalis, adult
The butterflies went from caterpillar to chrysalis to adult in about three weeks, and adults lay eggs that start the cycle again.
Why it works: Every living thing is born, grows, reproduces and dies, though the stages in between look different from one kind to the next.
Common Mistakes with 3-LS1-1
Thinking the butterfly is a new animal
“The caterpillar died and a butterfly came out.”
Try this: Explain that the caterpillar and butterfly are the same animal at different stages. Inside the chrysalis its body is rebuilt.
Drawing life cycles as a straight line
Egg, caterpillar, chrysalis, butterfly, then the end
Try this: Draw the stages in a circle with an arrow from adult back to egg, because adults make young that start again.
Assuming every animal has the same stages
Giving a dog a chrysalis stage
Try this: Compare a butterfly with a dog or a bean plant. All grow and reproduce, but only some change shape completely.
Where 3-LS1-1 Fits
Practice 3-LS1-1
Quick Check
- What stage comes right after the caterpillar in a butterfly's life cycle?
- What do a bean plant and a butterfly life cycle have in common?
- Why is a life cycle drawn as a circle?