CK12 Earth Science

Figure 12.9: Meteor crater in Arizona was formed about 40,000 years ago by the impact of a meteorite that was about 50 meters in ...

Figure 12.11: The Earth formed at the same time as the other planets in our solar system about 4 1/2 billion years ago. ( 17 ) c ...

Formation of Earth’s Atmosphere The early Earth was very different from our Earth today. The early Earth experienced frequent im ...

Oxygen in the atmosphere is important for life for two main reasons. First, oxygen makes up the ozone layer. The ozone layer is ...

in Australia. Besideschangesinlifeandtheatmosphere, otherchangeshavealsohappenedsincetheEarth was first formed. Early volcanic e ...

Suppose that the Earth had been much cooler when it first formed. How would the earth’s interior be different than it is today? ...

Introduction In the summer of 1909, an American scientist named Charles Doolittle Walcott (Figure 12.15) was in the Rocky Mounta ...

Figure 12.16: This bizarre animal with five eyes lived during the Cambrian. Fossils of it were discovered by Charles Walcott. ( ...

Figure 12.17: There is an amazing diversity of organisms on Earth. ( 5 ) ...

Figure 12.18: Many animals, like this polar bear, have special body features that help them live in a certain environment. ( 20 ...

Figure 12.19: An explanation of how adaptations develop. ( 14 ) are very different from their ancestors and may become a whole n ...

Figure 12.20: The horse has evolved over the last 60 million years. Horses today are much larger than earlier horses. ( 3 ) Phan ...

Table 12.1: (continued) Era Millions of Years Ago Major Forms of Life 200 First mammals on Earth 251 Age of dinosaurs begins Pal ...

Table 12.1: (continued) Era Millions of Years Ago Major Forms of Life 500 First fish on Earth The eras of the Phanerozoic Eon ar ...

Figure 12.21: Just before the Phanerozoic, many parts of Earth were covered with glaciers. After the Earth began to warm and man ...

Lesson Summary Adaptations are favorable traits that organisms inherit. Adaptations develop from variations within a population ...

variation Having many differences. Image Sources (1) http://en.wikipedia.org/wiki/Image:Geologica_time_USGS.png. GNU-FDL. (2) ht ...

(16) http://commons.wikimedia.org/wiki/Image: Temperate_rainforest_2004-04-09.jpg. GNU-FDL. (17) http://commons.wikimedia.org/wi ...

Chapter 13 Earth’s Fresh Water 13.1 Water on Earth Lesson Objectives Describe how water is distributed on Earth. Describe what ...

Figure 13.1: Earth, the “Blue Marble,” can be seen in this photograph to be mostly covered with liquid water. ( 16 ) ...