Science Grade 9 Quiz
Questions: 16 · 10 minutes
1. A blood vessel carries blood directly away from the heart. What type of vessel is it?
A capillary
A venule
An artery
A vein
2. A rabbit population grows for several years and then remains close to the same size. What is the most likely explanation?
Every rabbit has reached the same age
Mutations have stopped occurring in the population
Limited resources are keeping the population near its carrying capacity
The rabbits no longer compete with one another
3. A persistent pesticide enters a lake food web in very small amounts. Which organism is likely to develop the highest pesticide concentration over time?
The algae that absorb the pesticide from the water
The small crustaceans that eat the algae
The fish-eating bird at the top of the food web
The aquatic plants growing near the shore
4. An enzyme works fastest at 37°C, but its activity drops sharply at 70°C. What is the best explanation?
The substrate has gained too little kinetic energy to collide with the enzyme
The enzyme's active site has changed shape because the protein denatured
The enzyme has been used up during the reaction
The reaction has changed the enzyme into a different substrate
5. On a hot, dry day, a plant closes many of its stomata. What is a likely immediate effect?
More water vapor leaves the leaf, increasing water loss
Less carbon dioxide enters the leaf, which can reduce photosynthesis
More glucose enters the leaf from the atmosphere
Less oxygen reaches the roots through the soil
6. Which cell structure is directly responsible for assembling proteins from amino acids?
Nucleus
Ribosome
Mitochondrion
Cell membrane
7. Which process produces new, genetically similar body cells during growth and wound repair?
Natural selection
Meiosis
Fertilization
Mitosis
8. Which gas is released as a product of photosynthesis?
Oxygen
Nitrogen
Methane
Carbon dioxide
9. Which combination of features makes lung alveoli effective surfaces for gas exchange?
Thin walls, large surface area, and a rich blood supply
Rigid walls, dry surfaces, and large internal pressure
Thick walls, small surface area, and low blood flow
Muscular walls, digestive enzymes, and a narrow cavity
10. What is the main ecological role of decomposers such as many fungi and bacteria?
They break down dead material and return mineral nutrients to ecosystems
They convert all atmospheric nitrogen directly into oxygen
They prevent consumers from competing for food
They create energy that producers can absorb
11. A plant cell is placed in a concentrated salt solution. What is most likely to happen?
Salt leaves the cell by osmosis, causing it to swell
The cell wall dissolves because salt breaks down cellulose
Water enters the cell by active transport, making it burst
Water leaves the cell by osmosis, causing the cell membrane to pull inward
12. During vigorous exercise, muscle cells increase their rate of cellular respiration mainly to do what?
Stop carbon dioxide from entering the blood
Produce glucose for storage in the muscles
Convert oxygen directly into protein
Release more usable energy in the form of ATP
13. After an antibiotic treatment, a few resistant bacteria survive and reproduce. Why may the bacterial population later become harder to treat with the same antibiotic?
Resistant bacteria pass heritable traits to their descendants
The antibiotic teaches individual bacteria how to resist it
All bacteria intentionally change their DNA when exposed to medicine
The surviving bacteria stop reproducing until the antibiotic disappears
14. A mutation occurs in one of a person's skin cells after exposure to ultraviolet radiation. Why is this mutation unlikely to be inherited by their children?
All mutations are repaired before cells divide
The mutation occurred in a body cell rather than a reproductive cell
Skin cells do not contain DNA
Ultraviolet radiation causes only temporary changes to proteins
15. A microscope has a 10× eyepiece lens and a 40× objective lens. What is the total magnification?
50×
30×
4,000×
400×
16. In pea plants, tallness (T) is dominant over shortness (t). A Tt plant is crossed with a tt plant. What percentage of the expected offspring will be short?
25%
75%
50%
100%