Biology Homework Chapter 36: Population Structure
Textbook Assignment: Chapter 36: , sections 1-11
- 36.1: Population studies are largely statistical: we look at numbers or percentages of populations and watch how these counts change over time, or with respect to location.
- 36.2: Population density is a function of how many individuals of a species there are in an area. Dispersion patterns can be random, distributed evenly, or clumped around resources (most likely).
- 36.3 Life tables allow us to identify different types of survivorship by comparing how many individuals are born and how long they survive for different species.
- Type I has low birth and infant mortality rates, with parents caring for their young for long periods of time. These patterns are typical of large mammals, whose young require training to survive.
- Type II has moderate birth and death rates. Parents may care for their young for short periods. These patterns are typical of small mammals and birds, whose young require some nurturing in the nest, but not the long training periods used in Type I survivorships.
- Type III has high birth rates and infant mortality, with little care for the young. These patterns are typical of invertebrates and fish, or any species which uses external fertilization methods, or methods where the parent immediately abandons the eggs.
- 36.4: We can use mathematical formula to create models that predict rates of population changes. The simple exponential population growth equation is G = rN, where r = birth rate - death rate. If we take into the account the carrying capacity K, we wind up with the logistic equation G = rN(K-N)/K.
- 36.5: The survival rate r varies between species according to survivorship patterns, but also due to environmental factors, which can include the density of the species own population in a given area. Density-dependent factors include competition for resources, rates of spread of disease, and variations in predator populations. Density-independent factors include abiotic factors like weather conditions.
- 36.6: Boom-and-bust cycles show how prey and predator populations are interdependent.
- 36.7 Life histories contain the major events of birth, reproduction, and death. Type III are r-selection, where the rate of increase is the dominant factor. Type I are K-selection type are indiciatory of type I survivorships, where populations are close to carrying capacity.
- 36.8: Sustainable resource management attempts to harvest renewable resources without damaging the resource base.
- 36.9: Predicting future scenarios from population studies is increasingly difficult, because human populations (like other species) adapt to changing conditions, and in addition, frequently create new factors in the shape of new technologies. Human populations must be compared not only by looking at the total number in a given area, but also by looking at the age and gender distributions in the population.
- 36.10: Age structures show whether a population will be stable, increasing, or decrease, and have social implications as well. Countries with high numbers of children compared to adults are frequently unstable and impoverished, since the few adults must work to provide for the many non-productive children.
- 36.11: Unlike most other species, different human populations change their own environments and use the available energy at different rates. In poorer countries, individuals have low incomes and cannot afford to consume available goods at a high rate.
Read the following weblecture before chat: Studying Populations
Take notes on any questions you have, and be prepared to discuss the lecture in chat.
Perform the study activity below:
Use the Logistic Growth Model at the Virtual Biology Lab to explore how changing the rate r and limiting factor K for two populations can affect their growth and population size.
- Use the default values and run the model by using the Go button (this is a toggle and turns the model off as well, but let the system run until the population graph stops changing).
- Lower the rate value for the red population to 0.5 and rerun the model. What happens?
- Raise the rate value for the red population to 2.0 and rerun the model. What happens?
- Return the rate to 1.0 but change the K carrying capacity to 250. What happens?
Chat Preparation Activities
- Essay question: The Moodle forum for the session will assign a specific study question for you to prepare for chat. You need to read this question and post your answer before chat starts for this session.
- Mastery Exercise: The Moodle Mastery exercise for the chapter will contain sections related to our chat topic. Try to complete these before the chat starts, so that you can ask questions.
- No quiz yet: the Chapter Quiz opens when we finish the chapter.
Read through the lab for this week; bring questions to chat on any aspect of the lab, whether you intend not perform it or not. If you decide to perform the lab, be sure to submit your report by the posted due date.
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