Worksheet 3.7
Student: ................................................................................................................. Class: ...............................................
Use the listed words to complete the sentences below. actual genetic carbon older casts complex relative selection extinct younger
1. Fossils include moulds, ................................., imprints, petrified organisms as well as whole organisms that have been preserved by being frozen or trapped in amber.
2. The absolute age of a fossil is its ............................... age. The .................................. age of a fossil indicates whether it is younger or older than other fossils or rocks.
3. Fossils are found in sedimentary rock. In a cross-section of sedimentary rock the .............................. rock layers are usually on the bottom and the ................................... rock layers are at the top.
4. The age of fossils up to 50 000 years old can be determined by a type of radiometric dating called
.............................. dating.
5. The fossil record shows that over time organisms have become increasingly complex. New species have arisen while others have become ................................. Evolution has occurred.
6. Darwin and Wallace suggested that evolution occurs by natural ............................. According to this theory, organisms that are well suited to their environment are more likely to survive long enough to produce offspring, and also have a better chance of having a larger number of offspring.
7. The fossil record supports the theory of evolution by natural selection in a number of ways. It shows that the organisms living on Earth have become increasingly .............................. over time, and that some species that used to live on Earth have become extinct. There is also fossil evidence of gradual change in particular groups of organisms.
8. Biodiversity at the gene level is important to evolution. In order for evolution to occur, there must be ............................ differences among the members of a species, so that some organisms will be more successful than others.
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