PDS AP Environmental Science 8th Period 2011-12

I’m kind of confused about population momentum. I know it occurs when a population pyramid has a large base, and I know that it’s reflected in “pyramid” shapes, but I’m not exactly sure what it is..

On Tuesday and Wednesday (December 5th and 6th), we talked about population control. For populations that have a pyramid shape and are overpopulated, there are essentially two basic options to decreasing the population size:

1. Decrease Birth Rate
2. Increase Deaths

However, since killing people off/increasing deaths is unethical, a country must instead choose to coerce their members into having less children or give them a choice. One example of a country that chooses to coerce is China because the Chinese government offers incentives to those who only have one child (such as financial benefits) and disincentives to those who have more than one child (For example, those with three or more children face sanctions, and these sanctions can include a sizeable ten percent paycut).  However, since China is only one of three communist countries (along with North Korea and Cuba) that can still legally punish people for the number of children they have, there are other options for countries. The three best options for decreasing population size are:

1. Defeating/Eliminating Poverty - This essentially means helping a country complete their “demographic transition” and increasing their GDP, but this can be extremely difficult, so the next two methods are definitely useful.
2. Offering Opportunities & Education to Women - This basically means shrinking the “window” during which women can give birth because the longer one waits to try to conceive a child, the less likely they are to have a child because, as time passes, one “loses” or “wastes” their eggs and is less likely to be fertile. And, if women work and wait longer to get married and/or have children, they will be less likely to have a child–ultimately decreasing the population size of an area/country.
3. Implementing an Effective Family Planning Program - Family planning can decrease a population’s size via decreasing the number of births in a population. There are five main components to family planning/ways in which family planning can decrease the number of births in a population: allowing women to choose their family size (This will primarily be effective/of use in patriarchal societies where women are forced by their family to keep having children until they get one or two boys. A good example is the woman in the video we watched who was forced by her husband and mother-in-law to keep giving birth until she had a second son.), providing contraceptives to men and women, educating people about how to use contraceptives and other birth-related matters, legalizing abortion in areas, and allowing for voluntary sterilization.

Tags: demographics, population

So I read over the worksheet about the three different types of natural selection, and I understand stabilizing natural selection and diversifying natural selection, but I’m kind of confused about directional natural selection. The worksheet says that the “average shifts,” and I don’t fully understand what that means. Does that just mean that one trait that didn’t occur as frequently before starts to occur more because it’s better adapted to the new conditions?

In class on October 27^th, we talked about the evolution of biodiversity.  Biodiversity is essentially speciation minus extinction because speciation is “the evolution of new species” and extinction is “the death of the last member of a species.” So the difference between the addition of new species and the loss of other species gives one the biodiversity of an area. Literally, “bio” means “life” and “diversity” means “variety,” so biodiversity is essentially the “life variety” in an environment.

There are three types of biodiversity: ecosystem (& biome) diversity, species diversity, and genetic (in a gene pool) diversity. A local example of an ecosystem with diversity is Lake Norman because it has its variety of species. Species diversity has three parts to it: abundance (total # of individuals), richness (# of different species), and evenness (representation). As far as richness is concerned, scientists have names 2 million different species and estimate that there are really about 10 million different species on the planet. And lastly, the genetic type of biodiversity largely encompasses what we learned in biology.

In class, we put together a geological timescale to help explain how we got all of the biodiversity we currently have.

Click to Enlarge

After looking at the timescale, we concluded that we got all of the biodiversity we currently have via biological evolution which can be explained in part by Darwin’s “Theory of Evolution by Natural Selection.”

Tags: biodiversity, evolution

In a review e-mail we received, it said to know “how a temp. line graph can tell you what climatic region a biome may be in (tropical, temperate, polar).” Do you determine what biome it is merely by looking at how high/warm the maximum temperature is? So would you just say that a polar region has a lower maximum temperature than temperate and tropical regions?

So I was going over my notes for the Chapter 3 test, and question 21 on the study guide asks you to give an example of each of the five ecosystem services, but I didn’t really understand the example the book gave for resilience. Can anyone give me another example of resilience or better explain it to me?

In my opinion, the worst environmental problem is habitat destruction because once a habitat is destroyed it’s extremely hard to recreate that habitat or bring back to life the animals who went extinct because of it. Also, it bothers me that people will destroy creatures’ habitats merely for the sake of making money and building fancy schmancy new condo’s or producing items such as the thneeds Dr. Seuss talked about.