The fossil record indicates that at one time marsupials were common to both Australia and South America, but today most South American marsupials have become extinct. The most probable explanation for marsupials being common to Australia yet not very common to South America today is that
A. South American marsupials were displaced by placental mammals when a land bridge formed between North America and South America about seven million years ago.
B. marsupials were able to flourish in South America because of its isolation from other land masses.
C. placental mammals are less fully developed than marsupials when born and therefore have a better chance of survival after birth.
D. South American and Australian marsupials interbred.
E. marsupials can survive only in warm climates like Australia.
Answer: A. South American marsupials were displaced by placental mammals when a land bridge formed between North America and South America about seven million years ago.
You might also like to view...
Air is the least optimal respiratory medium because ____
a. air flow increases evaporation of water from the respiratory surface b. air contains 30 times as much O2 as water c. air is 1000 times less dense than water d. air requires more energy to ventilate over the respiratory surface e. O2 diffuses more rapidly in air than in water
Resting potential arises from the distribution of charged ____ and small ions inside and outside of a neuron
a. pumps b. channels c. organelles d. proteins e. membranes
Which of the following statements is correctly
related to the opening of stomata?
a. potassium is pumped into the guard cells and water follows by osmosis b. potassium and water are both actively pumped into the guard cells c. potassium is pumped out of the guard cells and water follows by osmosis d. potassium and water are both actively pumped out of the guard cells e. none of these statements is correctly related to the opening of stomata
The p53 protein is critical to the regulation of the cell cycle because it
a. halts cell division when necessary, allowing the cell to repair damaged DNA. b. causes cells with heavily damaged, unrepairable DNA to commit “suicide.” c. prevents the cell from dividing at inappropriate times. d. all of the above