Question

which of the following questions is testable in a scientific investigation?
are dogs better pets than cats?
are dogs happy when they are walked?
are cats more active at night than during the day?
are cats easier to take care of than dogs?

in the 18th century, carolus linnaeus classified organisms based on their structural similarities. modern classification determines relationships more accurately because it is based on genetic and other biochemical similarities. this change in classification method best illustrates that
multiple trials are required to increase the validity of a scientific explanation
scientific explanations are subject to the ethical view of the scientist proposing them
peer review is required to validate the results of scientific investigations
all scientific explanations are tentative and subject to change and improvement

an experiment is described below.
a large field at the base of a mountain becomes flooded when heavy rains in the mountains cause a stream to overflow. each time the flooding occurs, more soil washes away.
the owners of the land want to perform an experiment to see if different types of plants could help reduce the soil erosion. they choose five areas of ground that are the same size, the same distance from the stream, have the same slope and the same kind of soil, and receive the same amount of sunlight. the type of plant planted in each area is different for each of the five areas. measurements of soil erosion will be made each time flooding occurs. the results will be compared after six months.
which hypothesis is being tested in this experiment?
soil erosion is affected by the strength of the wind.
flooded areas have greater soil erosion than areas that are not flooded.
some types of plants reduce soil erosion more than others.
some types of soil are more easily eroded.

base your answers to the following questions on the information below and on your knowledge of biology.
an experiment was carried out to answer the question \does the ph of water affect the growth of radish plants?\ two groups of ten radish plants were set up. one group was watered with water having a ph of 3.0, and the other group was watered with water having a ph of 7.0. both groups of plants received the same amount and intensity of light, the same amount of water, and they were grown in the same type of soil. the heights of the radish plants were measured every 2 days for a period of 2 weeks.
which activity might help to increase the validity of this experiment?
repeating the experiment several times
using two different types of radish seeds in each group
using the same ph for both groups of plants
placing one set of plants in sunlight and one in darkness

Explanation:

1. A testable question in a scientific investigation must be measurable. "Are cats more active at night than during the day?" can be measured by observing cat activity levels at different times. "Better pets", "happy" (emotional state not easily measured), and "easier to take care of" (subjective) are not as objectively testable.
2. The change from structural - based to genetic/biochemical - based classification shows that scientific explanations (classification methods) are not fixed. They are tentative and can change as new evidence (like genetic knowledge) emerges. It's not about multiple trials (no mention of repeating experiments here), ethical views (not the focus), or peer - review (not the key point).
3. The experiment has different plant types (independent variable) and measures soil erosion (dependent variable). So the hypothesis is about plant types affecting soil erosion. Wind strength (not part of the experiment), flood comparison (not the variable tested), and soil type (kept the same) are not relevant.
4. Repeating an experiment several times helps to account for random errors and increases the validity (how well the experiment measures what it's supposed to). Using different radish seeds (introduces another variable), same pH (removes the independent variable), and different light (introduces another variable) would all decrease validity.

Answer:

1. Are cats more active at night than during the day?
2. all scientific explanations are tentative and subject to change and improvement
3. Some types of plants reduce soil erosion more than others.
4. repeating the experiment several times