Science - Natural Selection Unit

Question 1

What is evolution?

Answer 1

The idea that all species of living things have evolved from simple life-forms which first developed more than three billion years ago.

Question 2

What is Darwin’s thoery of natural selection?

Answer 2

It is based on the fact that natural variation among organisms causes them to differ in ability to survive and reproduce.

Question 3

What are the 3 steps of natural selection

Answer 3

1. Individuals within a species show a wide range of variation because of differences in their genes.
2. Some individuals have characteristics which make them better adapted to the environment. They are more likely to survive and then breed successfully.
3. The genes which have enabled these individuals to survive are then passed on to the next generation.

Question 4

Use Darwin’s theory to explain how giraffes got long necks

Answer 4

Genetic Variation in the population due to mutations and mixing of genes in sexual reproduction Those with longer necks have an advantage can reach more food, can fight better, more attractive to females These long neck animals reproduce and pass on their genes.

Question 5

How are fossils found?

Answer 5

• Relative Dating: Fossils are found in sedimentary rocks. Geologists figure out the relative ages of fossils and sedimentary rock layers, and the fossils they contain. Sedimentary rock typically is layered, with the oldest layers of rock at the bottom and the younger layers nearest the top.
• Radiometric Dating: Until recently, the word “older” or “younger” was the best scientists could do when deciding the ages of fossils. Radiometric dating is based on radioactive decay of radioactive elements in rock samples. It allows scientists to calculate an absolute age (in years) for any fossil or rock layer.
• Putting Both together: For example, a layer of volcanic ash in Wyoming is 73 million years old, and the fossil leaves embedded within it are the same age as the ash - this means they are all from the same period.