Approximately 65 million years ago, a mass extinction event occurred at the end of the Cretaceous Period. Ammonites and dinosaurs did not survive. Many types of birds and mammals that were alive before the extinction event survived and evolved after the mass extinction.

Question

A scientist is examining layers of rocks containing fossils from during and after the Cretaceous Period. How would the species in the rock layers change?



Move the time quantities into the table to indicate the top, middle, and bottom layers of rock. Then, move the species into the table to indicate which layers each species would be located in.

Response area with 6 blank spaces
Rock

Layer

Number of

Millions of Years Ago

Species Present in Layer
Top
Blank space 1 empty
​

Blank space 4 empty
​

Middle
Blank space 2 empty
​

Blank space 5 empty
​

Bottom
Blank space 3 empty
​

Blank space 6 empty
​


Answer options with 7 options.

A.65
B.Less than 65
C.Ammonites
D.Dinosaurs
E.birds
F.mammals

Answer 1

Here's how the rock layers and species would be organized based on the information provided:

| Rock Layer | Number of Millions of Years Ago | Species Present in Layer | |------------|----------------------------------|--------------------------| | Top | A. 65 | E. birds | | | | F. mammals | | Middle | B. Less than 65 | D. Dinosaurs | | | | C. Ammonites | | Bottom | F. Less than 65 | |

Explanation:

• The top layer (65 million years ago) would contain species that survived the mass extinction, such as birds and mammals.
• The middle layer, which represents a time just after the mass extinction, would consist of species that existed during that period, such as dinosaurs and ammonites but likely are not present in the top layer.
• The bottom layer doesn't contain additional species from before the extinction event, as it's earlier in the geological record and would represent a time with many now-extinct species, including dinosaurs and ammonites.