Biology Midyear Review

Rafael lives near a road at the bottom of a hill. His parents are concerned that soil will wash off the hill and rocks will fall onto the road. Rafael conducts an investigation to find out if grass growing on a hillside will help stop soil erosion.

 

He collects two samples of the same size and type of soil. One sample of soil has grass growing on it and the other does not. He places each sample of soil in a small tray. For his investigation, Rafael pours the same amount of water onto both samples of soil. He uses a large tray to collect water that may flow through the soil.

 Which practice shows the best way for Rafael to set up this investigation?

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Answer explanation

In this experiment, the independent variable (aka manipulated variable), is whether the soil has grass or not since Rafael wants to test whether the grass will prevent soil erosion.

Remember you may only have one independent variable in your experiment. The rest (controlled variables) must stay the same.

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Why should experiments be replicable?

• So that the materials used can be validated.

• So that scientists can gain popularity in the community.

• So that fewer errors will be made and the data appear to be more correct.

• So that others can repeat the experiment and obtain similar results.

Answer explanation

Remember "replicable" means "repeatable."

Scientists repeat their experiments to validate their results. If you follow the same steps but get different results each time, you might be doing something wrong!

Which of the following is the smallest unit of life that can carry out all life functions?

• the mitochondria

• the vacuoles

• the nucleus

• the cell

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In what part of the plant cell does the process of photosynthesis take place?

• nucleus

• mitochondria

• chloroplasts

• vacuoles

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What is RNA?

• A nucleic acid that processes all steps of protein synthesis in all living cells.

• A molecule that contains the genetic code of organisms.

• The process in which cells make proteins.

• A gene that is damaged or changed in a way to alter the genetic message carried by that gene.

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A student noticed that the freshwater plant, Elodea, produced bubbles when placed in direct light. What could the student most likely conclude?

• Bubbles of carbon dioxide were produced as a result of photosynthesis.

• Bubbles of oxygen were produced as a result of photosynthesis.

• Bubbles of carbon dioxide were produced as a result of cellular respiration

• Bubbles of oxygen were produced as a a result of cellular respiration

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Plant cells are able to produce their own food. This process happens in which structure?

• cell wall

• chloroplast

• mitochondrion

• vacuole

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These diagrams show a variety of cells from the same organism. How can cells from the same organism have such different shapes and functions?

• As each cell differentiates, the DNA changes so that each type of cell has different DNA once it reaches maturity.

• Mutations in the cells' nuclei lead to new combinations of DNA, resulting in different shapes and functions in the different types of cells.

• During differentiation, different parts of the DNA in each type of cell are activated, resulting in the different structure and function of the cells.

• During differentiation, different types of cells produce proteins which destroy the nonactive DNA, leading to cell specialization.

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Which statement best explains why animals are considered heterotrophic?

• They are able to produce food through the process of photosynthesis.

• They are able to produce food through the process of respiration.

• They are able to obtain nutrients by decomposing plant and animal tissue.

• They are able to obtain nutrients by consuming other organisms or their products.

Enzymes are proteins that help increase the rate of chemical reactions inside cells. These proteins are composed of many simpler molecules called amino acids. Which of the following suggests that the shape of an enzyme determines the enzyme’s function?

• Enzymes are specific to a substrate

•  Enzymes can operate in a wide range of conditions.

• Enzymes are activated by neighboring molecules.

• Enzymes can be found in all life-forms.

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