Intro to Biology

According to the data the average pulse rate immediately after exercise was higher than the average resting pulse rate.

Which procedure would increase the validity of the conclusions from this experiment?

• Decreasing the number of students participating in the activity

• Increasing the number of times the activity is repeated

• Eliminating the data where resting pulse rate is taken

• Changing the temperature in the room before & after exercise

Answer explanation

Repeating the experiment makes it less likely that wrong conclusions will be made due to random variation

Which statement best describes a hypothesis?

• A hypothesis is the correct answer to a scientific question

• Defects collected from an experiment written in the form of a hypothesis

• A hypothesis is a possible testable explanation for a scientific question

• A hypothesis is the process of making careful observations

Answer explanation

A hypothesis is a possible explanation for a scientific question. It can be tested to see if it is correct or if we need to revise it and make a new hypothesis

Write the steps of the scientific method in the correct order from beginning to end

• Make an observation.

  Ask a question. ·

  Propose a hypothesis. ·

  Make predictions. ·

  Test the predictions. ·

  Iterate.

• Propose a hypothesis. ·

  Make predictions. ·

  Test the predictions

  Iterate

  Make an observation.

  Ask a question.

• Make predictions. ·

  Test the predictions

  Iterate

  Make an observation.

• Iterate

  Make an observation

  Hypothesis

  Make predictions

  Guess an answer

Scientists want to perform an experiment to see if poison ivy grows taller when exposed to more carbon dioxide

How should the control group in this experiment be treated?

• The control group should have plants growing at normal carbon dioxide level

• The control group should have plants growing at higher oxygen levels

• The control group should have plants growing at different carbon dioxide levels

• The control group should have plants growing in different amounts of water

Answer explanation

Scientists would grow plants at a normal carbon dioxide level to see if increasing carbon dioxide has an effect on the experimental group

Which of the following best explains water's ability to dissolve certain substances but remain separate from others?

• Water molecules can form ionic bonds with polar molecules, such as glucose

• Due to hydrogen bonding, water is more dense as a liquid than a solid

• Water has an overall negative charge, which allows it to easily dissolve nonpolar substances like glucose

• Water molecules are polar, consisting of two partially positive hydrogen atoms, and one partially negative oxygen atom

Answer explanation

Water's polarity allows it to attract and interact with other polar molecules like glucose. However, oils are non polar and cannot attract water to form a solution

Which of the following describes the most likely way in which 2 water molecules will interact?

• An iconic bond will form between the oxygens in each water molecule

• A covalent bond will form between the hydrogen of one water molecule and the oxygen of the other water molecule

• A hydrogen bond will form between the hydrogen atom of one water molecule and the oxygen atom of the other water molecule

• A metallic bond will form between the hydrogens in each water molecule

Answer explanation

Because water molecules are polar, a hydrogen bond will form between the partially positive hydrogen end of one water molecule and a partially negative oxygen atom of the other water molecule

Which of the following observations is best explained by waters high surface tension?

• A local pond is slow to freeze despite low air temperature

• A leaf floats on the surface of a puddle

• A human sweats in order to cool down

• A tree takes up water from its roots

Answer explanation

Water molecules on the surface of the puddle form hydrogen bonds with one another allowing them to resist the external force of the leaf

Which statement best describes why water is an effective solvent?

• Water is an ironic compound that attracts other like molecules

• Water's relatively small size allows it to fit between individual atoms, driving them apart

• Water's polarity allows it to dissolve ionic and polar compounds

• Water's hydrophobic nature separates polar and nonpolar substances

Answer explanation

Water is a polar molecule. The partially positive and partially negative ends of water interact with polar molecules and ions, helping disperse the molecules and irons in the solution

Which of the following statements explains why ice floats on the surface of a pond?

• As water freezes iconic bonds form between water molecules preventing the ice from sinking below the surface

• The crystalline structure of solid ice makes it less dense than liquid water

• The increased number of hydrogen bonds in ice compared to liquid water causes the water molecules in ice to be closer together

• The ice molecules have higher kinetic energy than the liquid water molecules causing them to float

Answer explanation

When water freezes, it forms a crystalline structure with each water molecule hydrogen bonded to 4 other water molecules. This structure keeps the water molecules further apart then they would be in liquid water. As a result ice is less dense than liquid water

Which of the following biological activities best demonstrates water's adhesive properties?

• The vacuole of a plant cell swells as water enters and dilutes its contents

• Water travels through vascular tissue from the roots to the leaves of a plant moving against the force of gravity

• Water evaporates from leaves through openings called stomata, which open and close in response to environmental conditions

• A leaf's cuticle or waxy outer coating repels water droplets

Answer explanation

The movement of water in a plant's vascular system relies on the adhesion of water to the walls of the xylem