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Cretaceous Life & Flowering Plants
How did flowers change the world for every living thing?

Flowers changed everything! In the Cretaceous Period, flowering plants burst onto the scene for the first time, and with them came insects, colors, and new partnerships between plants and animals. This is a pivotal moment when Earth began to look more like the world we know today. Your learner will discover how these beautiful new plants and their animal partners created explosive diversity in the ecosystems around them.

S2S_Lesson22 by Selene

Key Ideas

  • Flowering plants (angiosperms) appeared for the first time and spread quickly. They changed land ecosystems.
  • As plants diversified, insects evolved alongside them.
  • Pollinators such as insects helped plants reproduce more efficiently. These plant–animal partnerships reshaped food webs and ecosystems permanently.
  • The Cretaceous Period had the greatest diversity of dinosaurs in Earth's history.
  • Plants and animals depended on one another.

Spines
  • DK's Science as You've Never Seen it Before: Plant Reproduction pg. 174-175
  • Mammoth Science: Flowers pg. 48

✏️  Notebooking Activity
Label the angiosperm (flower) diagram with the appropriate terms: petal, sepal, anther, ovary, stigma, filament, style, and stem. Then answer: why was the development of flowering plants a significant milestone?


Vocabulary
  • Cretaceous — The final period of the Mesozoic Era (about 145-66 million years ago) when flowering plants appeared and dinosaurs peaked.
  • Angiosperm — A flowering plant that produces seeds enclosed in a fruit; angiosperms became dominant plants during the Cretaceous.
  • Pollinator — An animal like an insect or bird that transfers pollen from one flower to another, enabling plants to reproduce.
  • Coevolution — The process by which two species evolve together, each influencing the other's evolution — like flowers and their pollinators.
  • Pollen — Tiny grains produced by flowers containing the male reproductive cells of a plant; transported by wind or animals.
  • Deciduous — A plant that sheds its leaves seasonally; deciduous trees became more common during the Cretaceous.
  • Diversification — A rapid increase in the variety of species; the Cretaceous saw great diversification of both plants and animals.

Cosmic CalendarWhere we are: December 26 to 30
The Cretaceous Period runs from December 26th all the way to December 30th on the Cosmic Calendar, when the extinction event ends it. Read the script below before the lesson.

Read aloud: December 26th on our Cosmic Calendar. The Cretaceous Period, about 145 to 66 million years ago, is just getting started. Dinosaurs are still here, still dominant. But the world is changing around them. Flowering plants are spreading across the continents, and with them come the insects and eventually the birds that depend on those flowers. The Cretaceous will stretch all the way to December 30th on our calendar. We’re going to be here for a few more cosmic days. And during that time, Tyrannosaurus rex and Triceratops will walk the Earth, color will spread across the landscape, and the world will look more alive than it ever has before. What happens at the end of the Cretaceous is coming. But not yet.

Timeline EntriesLabel the next page in your timeline “Cretaceous Life & Flowering Plants: 145 Million Years Ago”. The workbook prompt asks learners to draw the first small flowering plants blooming among ferns and cycads in a Cretaceous landscape, with a bee or early pollinating insect hovering nearby.

Discussion Questions
  1. What is different about flowering plants compared to earlier plants?
    Sample answer: They make flowers and seeds instead of just spores.
  2. How do insects help flowers?
    Sample answer: Insects move pollen from one plant to another.
  3. Why do you think insects liked flowers?
    Sample answer: Flowers gave insects food like nectar.
  4. What might happen if flowers disappeared?
    Sample answer: Insects and animals that depend on them might not survive.

Digging Deeper
  1. How did flowering plants change how plants reproduced
    Sample answer: Flowers allowed plants to use animals instead of wind, making reproduction more reliable and widespread.
  2. Why is the relationship between flowers and insects called mutualism?
    Sample answer: Both organisms benefit—plants get pollinated and insects get food.
  3. How could plant diversity lead to animal diversity?
    Sample answer: More plant types create more food sources and habitats, allowing more animal species to evolve.
  4. Why might the Cretaceous be considered a turning point in Earth’s ecosystems?
    Sample answer: The rise of flowering plants reshaped ecosystems that still exist today.

Species to ResearchThe Cretaceous was rich with diverse life. Here are some species learners can choose to research:
  • Spinosaurus— Possibly the largest carnivorous dinosaur ever; a semi-aquatic predator with a distinctive sail.
  • Triceratops— The iconic three-horned herbivore; one of the last dinosaurs before the mass extinction.
  • Velociraptor— A small, feathered theropod from central Asia; much smaller than its movie portrayal.
  • Mosasaurus— A massive marine reptile (not a dinosaur) that ruled Cretaceous seas.
  • Quetzalcoatlus— One of the largest flying animals of all time; a pterosaur with a wingspan as wide as a small plane.
  • Pachycephalosaurus— A thick-skulled herbivore that may have used its dome for head-butting.

Scientist Connection: Xu XingXu Xing, a Chinese paleontologist at the Institute of Vertebrate Paleontology and Paleoanthropology in Beijing, has described numerous new dinosaur species. His research focuses on feathered dinosaurs from northeastern China’s Cretaceous deposits, a region with significant fossil discoveries in the past thirty years. His work confirms the evolutionary relationship between theropod dinosaurs and modern birds, showing that features like feathers, wishbones, and brooding behavior appeared in dinosaurs before flight evolved. This connects to the lesson’s exploration of how Cretaceous life shaped the world we know today.

Videos
Digging Deeper
Why did so many feathered dinosaur fossils come from northeastern China specifically? Research the Yixian Formation and what made its conditions so unusually good for preserving soft tissues like feathers. Xu Xing has described dozens of species, but scientists debate how many of them truly represent separate species versus individual variation within one species. What makes it difficult to tell the difference from fossils alone?

Sources and More Information:

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