Plants and Their Needs — Answer Key
Part A: Multiple Choice
Circle the best answer for each question.
1. What do leaves use sunlight, water, and carbon dioxide to make?
A) soil
B) food
C) seeds
D) flowers
Leaves mix these three ingredients together in a process called photosynthesis to make sugar, which is the food that keeps the whole plant alive.
2. Where does a plant get most of its water?
A) from the air
B) from its leaves
C) from the soil through its roots
D) from its flowers
Rain and watering soak into the soil, and the roots pull that water up like thousands of tiny straws, which is how most of a plant's water gets in.
3. What gas do plants take in from the air to make food?
A) oxygen
B) carbon dioxide
C) nitrogen
D) helium
Plants breathe in carbon dioxide through the tiny holes in their leaves; this gas is a key ingredient they mix with sunlight and water to make sugar.
4. A cactus lives in the desert. How does it store water?
A) In its thick, fleshy stem.
B) In its flowers.
C) In its thin, flat leaves.
D) In the sand around it.
Because the desert gets so little rain, a cactus stores water inside its plump stem like a built-in water bottle, which lets it survive long dry spells.
Part B: Fill in the Blank
Write the correct answer on each line.
1. During photosynthesis, plants give off oxygen that people breathe.
When plants make food, they release oxygen into the air as a leftover gas, and that oxygen is exactly what people and animals need to breathe.
2. A cactus has spines instead of flat leaves to save water.
Flat leaves lose lots of water to the hot desert air, so a cactus grew sharp, skinny spines instead — they lose almost no water and also scare away animals.
3. Water moves from the roots up through the stem to the leaves.
Inside the stem there are tiny tubes that work like an elevator, lifting water from the roots all the way up to feed every leaf.
4. Plants that live in very wet places have large leaves to catch light.
Rainforest plants grow huge leaves because sunlight is often blocked by taller trees, so big leaves give them more surface to soak up whatever light sneaks through.
5. The green color in leaves comes from chlorophyll.
Chlorophyll is a green coloring inside leaf cells that grabs sunlight and turns it into energy for making food, and it is what gives plants their green color.