This science worksheet challenges students to complete sentences about animal groups using a provided word bank.

Let's solve the missing words problem step by step using the provided word bank. Here is the solution with explanations:

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Word Bank:

- invertebrate
- vertebrate
- four
- five
- birds
- fish
- reptiles
- mammals
- amphibians
- insects
- mollusks
- octopus
- squid
- gills
- lungs
- warm
- cold
- exoskeleton
- sea-urchin
- starfish
- worms

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1. An animal that has a backbone is called a ________ and an animal without a backbone is called an _________.

- Explanation: Animals with backbones are classified as "vertebrates," while animals without backbones are classified as "invertebrates."
- Answer:
- vertebrate
- invertebrate

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2. There are ______ main groups of vertebrates and ______ main groups of invertebrates.

- Explanation:
- Vertebrates are divided into five main groups: mammals, birds, reptiles, amphibians, and fish.
- Invertebrates are divided into four main groups: insects, mollusks, arthropods, and echinoderms (among others).
- Answer:
- five
- four

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3. The five main groups of vertebrates are m________, r________, f________, a________, and b________.

- Explanation: The five main groups of vertebrates are:
- Mammals
- Reptiles
- Fish
- Amphibians
- Birds
- Answer:
- mammals
- reptiles
- fish
- amphibians
- birds

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4. ______ like ants and bees are invertebrates.

- Explanation: Ants and bees belong to the group of invertebrates known as "insects."
- Answer:
- insects

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5. Slugs and snails are _______ that live on land and o________, s________, and cuttlefish are mollusks that live in the sea.

- Explanation:
- Slugs and snails are mollusks that live on land.
- Octopuses and squids are mollusks that live in the sea.
- Answer:
- mollusks
- octopus
- squid

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6. Mammals breathe using ______ and fish breathe using ______.

- Explanation:
- Mammals use lungs for breathing.
- Fish use gills for breathing.
- Answer:
- lungs
- gills

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7. Most reptiles and fish are ______-blooded.

- Explanation: Reptiles and fish are typically "cold-blooded," meaning their body temperature changes with the environment.
- Answer:
- cold

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8. Mammals and birds are ______-blooded.

- Explanation: Mammals and birds are "warm-blooded," meaning they maintain a constant body temperature regardless of the environment.
- Answer:
- warm

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9. ______ and ______ lay eggs. All invertebrates lay eggs.

- Explanation: Among vertebrates, reptiles and birds are known to lay eggs. All invertebrates also lay eggs.
- Answer:
- reptiles
- birds

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10. Scorpions, spiders, crabs, and insects are called ______ because they have hard bodies called an ______ and jointed legs.

- Explanation: Scorpions, spiders, crabs, and insects are all arthropods. They have a hard outer covering called an "exoskeleton" and jointed legs.
- Answer:
- arthropods
- exoskeleton

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11. Animals like the s________ and s________ are called echinoderms.

- Explanation: Sea urchins and starfish are examples of echinoderms, which are marine animals with spiny skin.
- Answer:
- sea-urchin
- starfish

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12. ______ are annelids because they have segmented bodies covered in bristles.

- Explanation: Worms, such as earthworms, are annelids. They have segmented bodies and are often covered in tiny bristles called setae.
- Answer:
- worms

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Final Answer:

1. vertebrate, invertebrate
2. five, four
3. mammals, reptiles, fish, amphibians, birds
4. insects
5. mollusks, octopus, squid
6. lungs, gills
7. cold
8. warm
9. reptiles, birds
10. arthropods, exoskeleton
11. sea-urchin, starfish
12. worms

Boxed Final Answer:
\boxed{
\begin{array}{l}
1. \text{vertebrate, invertebrate} \\
2. \text{five, four} \\
3. \text{mammals, reptiles, fish, amphibians, birds} \\
4. \text{insects} \\
5. \text{mollusks, octopus, squid} \\
6. \text{lungs, gills} \\
7. \text{cold} \\
8. \text{warm} \\
9. \text{reptiles, birds} \\
10. \text{arthropods, exoskeleton} \\
11. \text{sea-urchin, starfish} \\
12. \text{worms} \\
\end{array}
}