Interpreting Timelines The e timeline below shows some of the physical events th

Question

Interpreting Timelines The e timeline below shows some of the physical events that have helped to shape fe on Earth. Some major advances in the evolution of life are also shown. Use e timeline and the "Life Events" (a-d) listed below the timeline to complete li items 1-4. In each numbered space in the timeline, write the letter of the most appropriate event from the "Life Events" below the timeline. Timeline of Life on Earth Number of years ago 4.6 billion 25 billion Life events Physical events Earth forms and surface cools Oxygen gas is released into seas, then enters atmosphere. 1.5 billion 700 million 440 million 430 million The first eukaryotes evolve. The first multicellular organisms evolve. First mass extinction 2. Amphiblans are the first vertebrates Protective ozone shield in place in upper atmosphere 370 million on land 360 million Second mass extinction 360 million Widespread drought 245 million 210 million 65 million 60 million 3. Third mass extinction Fourth mass extinction Fifth mass extinction Earth's climate becomes moist 4. The first humans appear. More than half of tropical rain forests and many species destroyed 2 million Present Life Events a. Reptiles evolve from amphibians and become dominant on land. b. Birds and mammals become dominant on land. c. Plants and fungi invade land for the first time. d. Cyanobacteria first begin to carry out photosynthesis.

Explanation / Answer

1. Option D. is the answer. Cyanobacteria first began to carry out photosynthesis around 2.5 billion years ago.

2. Option C. is the answer. Plants and fungi invaded the land around 430 million years ago.

3. Option A is the answer. Reptiles evolved from amphibians and became dominant on the land around 350 million years ago. The repltiles evolved in the late carboniferous period and became dominant in the permian period.

4. Option B is the answer. Birds and mammals became dominant on land around 65 million years ago after the fifth mass extinction which wiped all the dinosaurs from the land.

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