chapter 1.5 // lab 1 Flashcards
hypothesis testing is a two step process
- State the hypothesis as precisely as possible and list the predictions it makes
- Design an observational or experimental study that is capable of testing those predictions.
Food Competition Hypothesis (Giraffes)
long-necked giraffes survive better and produce more young as they can reach food that is unavailable to other species or short-necked giraffes.
food competition hypothesis found to be false because
found giraffes generally eat food at 60%, on average, of their height so prediction that giraffes feed high in trees does not hold true.
hypothesis not abandoned completely though, in extreme droughts giraffes may look to higher places for food.
Sexual Competition Hypothesis (Giraffes)
idea that giraffes with long necks are able to strike harder blows during combat for mating than short-necked ones, resulting in more offspring and increasing the frequency of long necks.
experiments allow researchers to…
test the effect of a single, well-defined factor on a particular phenomenon.
Pedometer Hypothesis (Ants)
idea that ants always know how far they are from the nest because they track the number of steps they have taken and their stride length. Idea is that they can make a beeline back toward the burrow because they integrate info on the angles they have traveled and the distance they have gone.
null hypothesis
species what should be observed when the hypothesis being tested isn’t correct (so stride length and step number having no effect on the ant’s ability to get back to the nest).
ant experiment results
o Ants had shorter legs, normal legs, and legs with stilts. Ants with stumps stopped short by about 5 m from the nest, normal ants went the correct distance of 10 m, and ants with stilts went about 5m too far.
ant experiment repeated again
it was found that there was then no difference between the ants when they stopped to look for the nest opening.
good scientific hypotheses
make testable predictions that can be supported or rejected by collecting and analyzing data.
control groups are important because
they check for factors, other than the one being tested, that might influence the experiment’s outcome.
experimental conditions must be
as constant or equivalent as possible.
repeating the experiment is essential
to reduce uncertainty
Biologists practice evidence-based decision making
They ask questions about how organisms work, pose hypotheses to answer those questions, and use experimental or observational evidence to decide which hypotheses are correct.
