Answer to Question 1
Descriptive studies are designed primarily to document what is going on or what exists. Public opinion polls that seek to describe the proportion of people who hold various opinions are primarily descriptive in nature. For instance, if you want to know what percentage of the population would vote for a Democrat or a Republican in the next presidential election, you are simply interested in describing something.
Relational studies look at the relationships between two or more variables. A public opinion poll that compares the proportion of males and females who say they would vote for a Democratic or a Republican candidate in the next presidential election is essentially studying the relationship between gender and voting preference.
Causal studies are designed to determine whether one or more variables (for example, a program or treatment variable) causes or affects one or more outcome variables. If you performed a public opinion poll to try to determine whether a recent political advertising campaign changed voter preferences, you would essentially be studying whether the campaign (cause) changed the proportion of voters who would vote Democratic or Republican (effect).
Answer to Question 2
a
Invasive species provide an example of predator pressure.
Animal carcasses like this South African wildebeest provide important nutrition for both hunters and
Examples of Declarative and Nondeclarative Memory Tasks
Examples of waste and hazard containers.
Examples of Primary (Congenital) Forms of Immunodeficiency
The RecA strand exchange reaction as shown from single-molecule studies