Module 9S2 Changes in Populations

Lesson 3—Growth Patterns

Get Focused

How many offspring is a woman capable of having in her lifetime? A woman is capable of ovulating from puberty to menopause - let’s say 30 years. There are approximately 12 opportunities a year to produce an egg, so that’s 30 × 12 = 360 opportunities. However, it takes 9 months of gestation to make an offspring, and if the mother is nursing, she may not ovulate for a few months after the birth – so let’s say she’s capable of having 1 child each year for those 30 years. Therefore, each woman has the potential to produce 30 offspring in her 80 year lifespan. This number doesn’t take many factors into consideration: multiple births, miscarriages, missed ovulations, malnutrition, maternal/child mortality, sterility, etc. However, it is still a very impressive figure. With over 7 billion people on the planet and approximately half female, you can see how human population could get right out of hand if conditions were favorable! A glance at the human population graph may convince you it has. Humans however do not typically produce 30 offspring, and they reproduce at a much slower rate than their biology might permit them to.

As impressive as the biotic potential of humans is, it pales in comparison to a typical female field mouse, which at 1 month is capable of breeding and having a litter of 10 young after a gestation period of 20 days. She is capable of breeding again 24 hours after her litter is delivered. Even though she may only live 5 months in the wild due to predation, the reproductive potential of a wild mouse is staggering: 4 months (120 days) of breeding with one litter of 10 pups every 20 days = a potential to produce 60 offspring in her 5 month lifespan, and achieving this potential is common. (A startling reminder of how necessary predators like coyote, fox, the domestic cat, and possibly poisons like Warfarin (p.691) are to controlling mouse populations.

By the end of this lesson you should be able to answer the following focusing questions:

• What are the different types of population growth patterns?
• How do growth patterns illustrate these types of changes over time?

Module 9: Section 2—Lesson 3 Assignment

After you have completed all of the learning activities for this lesson you can complete the online lesson.

Bio30 4.9.3S2 online assignment

You should also watch the tutorial video for this lesson and submit a summary.  Bio30 tut# 4.9.3S2 Population Types

In addition to your lesson work as listed below, any summary notes, sample problems, diagrams, charts or tables should be stored in the course folder for your teacher’s feedback and study as you prepare for exams.

You must decide what to do with the questions that are not marked by the teacher.

Remember that these questions provide you with the practice and feedback that you need to successfully complete this course. You should record the answers to all of the questions and place those answers in your course folder.