Unit 6 Lesson 5: Modeling Evolution

Question 1

The process of evolution can be broken down into four significant factors:

Answer 1

• Genetic variation, caused by factors such as mutations and genetic flow, leads to variation in traits within a population.
• Those individuals with traits that give competitive advantages are better adapted to their environments, making it more likely that those individuals will survive and reproduce.
• Individuals that survive and reproduce at a higher rate will pass along their competitive advantages to their offspring.
• Over many generations, groups of individuals with traits that provide competitive advantages can evolve into a different species.

Question 2

adaptation

Answer 2

any trait that can be passed on to subsequent generations that increases the organism’s ability to survive in its environment and reproduce

Question 3

fitness

Answer 3

how well an individual survives and reproduces in its environment

Question 4

natural selection

Answer 4

the process that results in an organism having favorable adaptations to its environment, which are passed on through reproduction and thus change the genetic makeup of future generations

Question 5

How does the example of the evolution of the horse provide insight into the process of natural selection? Provide specific examples to support your answer.

Answer 5

The example of the horse shows how those individual animals with advantageous traits were able to survive, reproduce, and pass those advantageous traits on to their offspring. Over time, the process of natural selection led to a series of evolutionary changes such as stronger teeth and hooves. In addition, the example of the horse shows how changes in environment required animals to evolve and adapt to new circumstances. For example, when grasslands became more plentiful than forests, horses’ feet, teeth, and digestive organs adapted and evolved.

Question 5

hich of the following is an important process that leads to evolution?

changing environment

advantageous traits

fitness

genetic variation

Answer 5

genetic variation; Genetic variation leads to advantageous traits that allow individual animals to survive, reproduce, and pass those traits on to their offspring.

Question 6

Select one species that went extinct and another that evolved and survived. Develop a possible explanation for why one species was more successful than another.

Answer 6

Tyrannosaurus rex went extinct while the horse evolved and survived. It is likely that the T. rex went extinct because its extinction was caused by a sudden event (an asteroid impact) that gave it too little time to adapt and evolve. The horse, by contrast, was suited to live through the asteroid strike and, through the process of natural selection, evolve to thrive in a new environment. Those species that evolve develop and pass along advantageous traits that allow them to adapt to a changing environment. Those that go extinct cannot evolve fast enough to adapt.

Question 8

At earlier points in Earth’s history, animals such as dinosaurs were much larger than they are today. What is one possible explanation for why animals are so much smaller today than in the past?

Answer 8

One possible explanation is that very large animals like dinosaurs required a great deal of food, and during the time of the dinosaurs, food may have been more plentiful. When food became scarce, however, the larger animals didn’t have enough to eat. Those that were smaller had the competitive advantage. They were able to survive, reproduce, and pass along genes that made their offspring smaller. Over time, new smaller species evolved.