Which form of life first appears in the fossil record approximately 175 million years ago?

• A. Mammals
• B. Dinosaurs
• C. Flowering plants (angiosperms)
• D. Birds

Answer: (A)

Verified step by step guidance

1. Step 1: Begin by understanding the timeline of life on Earth. The fossil record provides evidence of when different forms of life first appeared. Familiarize yourself with the major evolutionary milestones.
2. Step 2: Recall that mammals, dinosaurs, flowering plants (angiosperms), and birds all emerged at different points in Earth's history. Use your knowledge of paleontology and evolutionary biology to place these groups in chronological order.
3. Step 3: Focus on the approximate time frame given in the problem: 175 million years ago. This corresponds to the Jurassic period, which is part of the Mesozoic era. Identify which of the listed groups first appeared during this time.
4. Step 4: Consider the evolutionary history of each group: Mammals evolved earlier, around 200 million years ago; dinosaurs dominated the Mesozoic era and were already present; flowering plants (angiosperms) appeared later, around 125 million years ago; birds evolved from theropod dinosaurs during the Jurassic period, approximately 150-160 million years ago.
5. Step 5: Based on this analysis, determine which group aligns most closely with the 175-million-year timeframe. Use the fossil record and evolutionary context to confirm your answer.