A Frog's Year — Tuva

The kind of year

each one tests a different part

X-ray view

The year

Spring Week 0

The frog's body

tap a part

About A Frog's Year

Watch a wood frog live through a year. It decides what to do for itself, the way a real frog does, from how warm it is, how wet it is and how much daylight there is. What you change is the kind of year it gets.

Four things about the year are yours to set, and each one puts a different part of the frog's body under strain: how many insects there are tests its gut, how much summer rain tests its skin, how long the pool lasts tests its ovaries, and how long autumn lasts tests its liver. Set a year, press play, and find out which part ran short.

Data format

Finishing a year adds four rows, one for each thing a body helps an animal do: survival, growth, behavior and reproduction. Each row says how that went and names the body part that decided it. Rows build up across years, so different kinds of year can be compared. A bar graph of How It Went for each Function reads out one year; grouping by Structure That Decided It across several years shows which body parts keep being the limit.

Model details

A whole year plays in a minute or two. The sim stops at each key moment, which is a part of the year worth watching closely, and waits for you to press Continue. Everything in the scene is at its real size, with the frog as the yardstick: it is about 7 cm long, the pool is roughly 14 m across, and the trees are 13 to 18 m tall. Scroll to zoom out and the frog is a speck in a wood; zoom in and you can watch what its body is doing. The one thing not to scale is the journey between the pool and the summer woods, about 17 m here and 100 to 400 m in life.

Underneath, the frog keeps an energy budget. Food is the only income, every activity has a cost, and the cost of everything rises and falls with temperature, because a frog's body runs at the temperature of its surroundings. Two body parts hold what it saves: the fat bodies hold energy, and the liver holds a sugar store that keeps ice from wrecking the body in winter. The skin is different: it is not a store but a gate, because it decides whether the frog can be out of the damp leaves at all, and so whether the gut gets anything to work with.

Food arrives late. Prey caught this week does not become usable energy until the week after, or the week after that when it is cool, because the gut takes days to work through a meal. That is why the order of the year matters and not only the totals.

The numbers are set so that a reasonable year works and a hard one fails for a reason you can point at. They are not a prediction of how many eggs a real wood frog lays.

Standards

4-LS1-1 Construct an argument that plants and animals have internal and external structures that function to support survival, growth, behavior, and reproduction.

Note the limit honestly: this performance expectation asks about plants and animals, and this simulation covers a wood frog. It does not meet 4-LS1-1 on its own and is meant to be paired with a plant.

Design intent

The student changes the world, not the animal. A frog does not schedule its own year, and asking a child to plan its behavior would teach that animals decide their own adaptations.
Each of the four conditions puts a different body part under strain, so the answer to "which part decided this year" changes depending on what you set.
One colour runs through each lever, the state it produces and the body part it tests, so the connection is something a student sees rather than something they are told.
Every year reports all four functions the standard names, so a year that keeps the frog alive but leaves it no eggs is visibly not a success.
Running out of energy means the frog stops and rests for the season, not that it dies.

What a student can be told about the model

The frog's year is an energy budget. Every activity costs energy, food is the only income, and the cost of everything rises and falls with temperature, because a frog's body runs at the temperature of its surroundings.

Two stores and one gate. The fat bodies hold the fuel. The liver holds a sugar store that keeps ice from wrecking the body in winter. The skin is not a store at all: it decides whether the frog can be out of the damp leaf litter, and so whether the gut gets anything to work with.

Food arrives late. Prey caught this week does not become usable energy until the next week, or the week after when it is cool, because the gut takes days to process a meal. That is why the order of the year matters and not just the totals.

Two results in here surprise most people, and both are real. Midsummer is a squeeze rather than a feast, because a warm frog burns energy faster than it can catch prey in dry weather. And most of what winter costs is spent in November and December, before the frog freezes at all: once frozen, its body runs so slowly that those months are nearly free.

What the model is not. It is calibrated so that a reasonable year works and a hard one fails for a reason you can point at. It is not a prediction of how many eggs a real wood frog lays, and the balance is tight enough that small changes flip outcomes. Its purpose is to make the handoffs between body parts visible, not to forecast a population.

Discussion prompts

Which body part decided how this year went, and what is your evidence?
The frog survived but grew nothing. Which part paid for that, and what did it buy?
Why can the frog not simply feed for longer before winter?
Look at the Feeding row. Why is there a gap at the start of the year, when the frog is already awake?
Is one kind of year enough evidence to say what a frog's body needs? What else would you try?
Name a body part that only matters because another one is doing its job.

How do I explore?

Look at The kind of year. Each of the four choices changes something about the year, and each one tests a different part of the frog. Pick some settings.
The timeline shows the year the frog would have before you even press play. Change a setting and watch the bands change.
Press the play button at the top and watch the year run. Press it again to pause.
Tap any part in The frog's body to find out what it is and what it does. Parts light up while they are working.
Scroll on the picture to zoom. Zoom right in to watch the frog, or right out to see the whole wood.

What should I do/notice?

Watch the Fat store bar while the frog is at the pool. Where is that energy coming from, when it is far too cold to catch anything?
Look at the Feeding row on the timeline. Why does it start later than the year does, and stop before winter?
Set Summer rain to Dry. Which part of the frog runs short, and why does keeping its skin damp cost it food?
Set The pool lasts to Short. The frog still lays eggs, so why does it still go wrong?
Try to find a year where all four things go well. Then change one setting and see which one breaks first.

What about the data?

When a year finishes, your table fills in on its own with four rows: survival, growth, behavior and reproduction. Each row says how it went and which body part decided it. You do not have to press anything.

The rows add up as you go, so try a different kind of year and run it again. Then you can compare them. Try grouping by Structure That Decided It and see which body parts keep turning up as the limit.