Lesson 17

17

The Carboniferous Period

What happens to life when the whole world is covered in enormous forests?

Vast swamp forests, high oxygen levels, and large insects characterized the Carboniferous Period. The lesson also covers the formation of coal and the amniotic egg, which allowed vertebrates to reproduce away from water.

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Key Ideas

  • The Carboniferous Period lasted from about 359 to 299 million years ago, and was defined by vast swamp forests, high oxygen levels, and giant insects.
  • Amphibians were the first land vertebrates, but they stayed tied to water for reproduction. They solved most land problems, but not the egg problem.
  • The amniotic egg was one of evolution's greatest inventions: a sealed, portable aquatic environment that let animals reproduce anywhere on dry land.
  • The first reptiles evolved the amniotic egg and spread rapidly across the land. Waterproof skin, stronger limbs, and more efficient lungs came with them.
  • When Carboniferous forests died in the swamps and compressed over millions of years, they became coal. When we burn coal, we release energy from ancient sunlight.

Spines

  • DK's Science as You've Never Seen it Before: Carbon Fossil Fuels pg. 37
  • Visual Timelines: Life on Earth pg. 40-45
  • Alternative: Kiddle: Carboniferous

Vocabulary

  • Carboniferous: The period 359-299 mya of vast swamp forests that eventually became coal.
  • Amphibian: A vertebrate that can walk on land but must return to water to reproduce.
  • Amniotic Egg: An egg with a protective membrane and shell; allowed reptiles to reproduce on dry land.
  • Reptile: A vertebrate with scales and amniotic eggs; could live fully on land.
  • Arthropod: An invertebrate with a hard exoskeleton and jointed legs, like an insect or spider.
  • Adaptation: A feature or behavior that helps an organism survive, shaped by natural selection.
  • Spore: A tiny reproductive cell released by early land plants like ferns.
  • Swamp: A wetland with standing water and dense vegetation; Carboniferous swamps were filled with giant ferns.
  • Coal: A fossil fuel formed from compressed Carboniferous plant material buried over millions of years.

Discussion Questions

  1. How did plants help animals move onto land?
    Sample Answer: Plants made food and homes for animals to live on land.
  2. Why were insects so much bigger during the Carboniferous than they are today?
    Sample Answer: There was more oxygen in the air, so insects could grow bigger.
  3. Why did higher oxygen levels allow larger animals and insects to exist?
    Sample Answer: Insects breathe through tiny holes called spiracles, and oxygen spreads passively into their bodies. With more oxygen in the air, it could reach deeper into a bigger body.
  4. The amniotic egg has been called one of evolution's greatest inventions. Do you agree? What would the world look like without it?
    Sample Answer: Answers will vary. The amniotic egg let animals reproduce away from water, so without it, land animals like reptiles, birds, and mammals would have stayed tied to water.

Digging Deeper

  1. Find Argentina on a map. Then look up where Argentina would have been on the supercontinent Gondwana during the Permian Period (about 270 million years ago). Why do you think the location of a fossil matters for understanding how animals spread across the ancient world? Research one therapsid fossil found in South America and write a brief description of what it tells us.
    Sample Answer: Answers will vary.
  2. Can you think of modern examples of plants changing the environment for animals? Think about rainforests, coral reef algae, or grasslands. How do plants create habitats that other living things depend on? How is this similar to what Carboniferous plants did?
    Sample Answer: Rainforests create homes and food for many animals, and coral algae support reefs and the animals that live there.
  3. Light a candle and observe how long it burns in open air. Talk about how oxygen feeds a flame, and how higher oxygen in the atmosphere would have affected everything from fires to insect body size. What might a Carboniferous forest fire have looked like compared to a modern one?
    Sample Answer: Answers will vary.