fossil
Reading Passage 1
Clues from the Past
Texas has not always looked the same. Long ago, a shallow sea covered parts of Texas. In that water, many living plants and animals lived and grew. These organisms left behind clues for scientists to study.
When a plant or animal died, it sometimes sank into mud. Over time, layers of mud and sand covered it. The soft parts of the organism broke down, but the harder parts or shapes stayed. Sometimes, an imprint of the organism was left in the mud. Over many years, the layers turned into rock and formed fossils.
Later, the environment changed. Swampy forests covered Texas. Scientists have found fossils and imprints of reptiles, turtles, and tree ferns from that time.
Different fossils can show what the environment was like. Even though the living organism is gone, these clues help scientists learn about the past.
Reading Passage 2
Clues from the Past
Texas has not always been covered in grasslands like it is today. About 100 million years ago, a shallow sea covered parts of Texas. In that water, many living plants and animals grew, moved, and survived. How do we know? These organisms left behind clues that scientists study today.
When an animal or plant died, its remains sometimes sank to the bottom of the water. Over time, layers of mud and sand covered the remains. As more layers built up, the soft parts of the organism broke down, but harder parts or shapes stayed. In some cases, an imprint of the organism was left behind in the sediment. Over many years, the layers hardened into rock, preserving what was once part of a living thing and creating fossils.
Eventually, the environment changed, and swampy forests covered Texas. Fossils and imprints of crocodile-like reptiles, turtles, and tree ferns have been found from this time.
Different types of fossils can show whether the environment was wet, dry, warm, or full of plants. Even though the original living organism is gone, these clues remain. They help scientists understand how organisms lived and what their environments were like long ago.
Reading Passage 3
Clues from the Past
Texas has not always had the same environment it has today. Around 100 million years ago, a shallow sea covered parts of the region. In this setting, many living plants and animals thrived. These organisms left behind important evidence that scientists still study.
When a plant or animal died, its remains often settled into layers of sediment. Over time, more layers of mud and sand built up on top. As pressure increased, the soft parts of the organism decayed, while harder parts or shapes remained. In some cases, an imprint of the organism formed in the sediment. Over long periods of time, these layers hardened into rock, creating fossils that preserve evidence of past life.
As time passed, the environment in Texas changed. Swampy forests replaced the shallow sea. Scientists have discovered fossils and imprints of crocodile-like reptiles, turtles, and large tree ferns from this period.
By studying different types of fossils, scientists can infer details about past environments. Even though the original living organism no longer exists, these preserved clues provide valuable information about how organisms lived and how their environments changed over time.