Tutor profile: Amanda P.

Are there mammals that lay eggs?

Yes! A group of mammals called the "monotremes" are mammals that lay eggs! Monotremes include the echidna and the platypus. The monotremes are older than both placental mammals and marsupial mammals.

What is the law of superposition?

The law of superposition states that the oldest rock layers (or strata) will be at the bottom of a sequence, while the youngest layers will be at the top. This can be compared to a basket of laundry. If you put your dirty clothes in the basket each day, you will find that the oldest clothes will be at the bottom of the basket, while the newest will be at the top. This same principle applies to geology!

The pronghorn antelope is found in western North America today. The pronghorn can reach speeds of up to 60 mph, much faster than any predators that are present today. Why is the pronghorn seemingly "over-engineered" for its environment? In other words, why can the pronghorn travel at such a fast rate of speed when its predators don't even come close?

This could be due to a phenomenon termed "antagonistic coevolution". In the past, the pronghorn evolved alongside an animal known as the American Cheetah (there were cheetahs in America until around 12,000 years ago!). Today, African cheetahs can reach speeds of up to around 60 mph. So, if American cheetahs could run at a similar speed, we can predict that the American cheetah might have evolved alongside the pronghorn. The two might have pushed each other to be faster and faster until eventually the American cheetah went extinct, leaving the pronghorn over-engineered for its current environment!