Biodiversity and keystone species

Science · Animals of the World · ages 9-11

Name ______________________ Date ____________

Which place has the least biodiversity?
- A forest edge with birds, bushes, and insects
- A farm field with only one kind of crop
- A pond with fish, frogs, and water plants
Which of these places has the most biodiversity?
- A lawn with just one kind of grass
- A coral reef full of many kinds of fish, corals, and crabs
- A parking lot with no plants or animals
What is a keystone species?
- The biggest animal in an ecosystem
- The most common plant in an ecosystem
- A species that many others depend on, even if its numbers are small
Which animal is a keystone species in kelp forests?
- Seagull
- Clownfish
- Sea otter
A beetle pest kills every oak tree it touches. Forest A has only oak trees. Forest B has oaks, pines, and maples. What most likely happens when the pest arrives?
- Forest B survives, because its pines and maples keep the forest going
- Both forests lose every single tree
- Forest A recovers faster, because oaks grow back quickly
Mia counts the kinds of birds in two places. She finds 3 kinds at a city park and 9 kinds in a forest. Which place has higher biodiversity?
- They are equal, because both places have birds
- The forest, because 9 kinds is more variety than 3 kinds
- The city park, because city birds are rarer
Bees are considered a keystone species mainly because they
- carry pollen between flowers so plants can make seeds and fruit
- are the biggest insect in most gardens
- eat all the other insects nearby
A keystone species is always the biggest animal in its ecosystem.
Circle one: True False
Zara wants her school garden to stay healthy through hot, dry summers. Which plan uses the idea of biodiversity?
- Dig up all the plants and cover the garden with gravel
- Plant many different kinds of flowers and bushes, so some will thrive even if others struggle
- Plant just one kind of flower, so the garden looks tidy
After wolves returned to Yellowstone, young trees grew back along the rivers. Why did beavers return too?
- More trees gave beavers food and wood for their dams
- Beavers chased the elk away from the rivers
- Wolves carried the beavers back to the park

Answer key

For grown-ups. Fold this page away before handing over the rest.

Biodiversity and keystone species W1-mt_NDZYiLvApW-s1

A farm field with only one kind of crop · Fewer different kinds of life means less biodiversity. A field with one crop has very low variety.
A coral reef full of many kinds of fish, corals, and crabs · Biodiversity is about variety. The reef has many different kinds of life, so it has the most biodiversity.
A species that many others depend on, even if its numbers are small · A keystone species has a huge effect on the life around it, far bigger than its size or numbers suggest.
Sea otter · Sea otters eat sea urchins that would otherwise destroy the kelp, so the whole forest depends on them.
Forest B survives, because its pines and maples keep the forest going · Forest B has backup: even if the oaks die, the pines and maples remain and hold the ecosystem together.
The forest, because 9 kinds is more variety than 3 kinds · Biodiversity is the variety of species, so the place with more kinds of birds has higher biodiversity.
carry pollen between flowers so plants can make seeds and fruit · Pollination lets plants reproduce, so bees support far more of the ecosystem than their small size suggests.
False · A keystone species is known by its effect, not its size. Bees are tiny, but whole farms and gardens depend on them.
Plant many different kinds of flowers and bushes, so some will thrive even if others struggle · Many different kinds of plants give the garden backup plans: if one kind struggles in the heat, the others keep it going.
More trees gave beavers food and wood for their dams · The chain reaction reached the beavers: wolves changed the elk, the trees grew back, and the beavers had what they needed again.