CSCredit Sprint
Sign upStart free

Credit Sprint / Study guides / Organismal biology

Credit Sprint's Guide to Organismal Biology for CLEP® Biology

About 34% of the CLEP® exam

CLEP® Biology spends a third of the exam on how whole plants and animals work: plant structure and transport, reproduction, and animal organ systems such as the nervous, endocrine, immune, circulatory and digestive systems. AP® Biology touches these only as examples, so CLEP® students need extra practice here.

Water and sugar transport in a plant xylem: water up(transpiration pull) phloem: sugarsource → sink stomata release water vapor

What you need to know

  • Plants: roots absorb water and minerals; xylem carries them up, pulled by transpiration and cohesion. Phloem carries sugar from sources (leaves) to sinks (roots, fruits).
  • Stomata let CO₂ in and water vapor out. Guard cells close them when water is scarce.
  • Plant hormones: auxin (growth toward light, phototropism), gibberellins (stem growth, germination), abscisic acid (closes stomata, dormancy), ethylene (fruit ripening).
  • Flowering plants have alternation of generations and double fertilization: one sperm makes the zygote, the other makes endosperm.
  • Nervous system: neurons fire action potentials (Na⁺ in, then K⁺ out) and release neurotransmitters across synapses.
  • Endocrine system: hormones travel in the blood. Most are regulated by negative feedback, such as insulin and glucagon controlling blood glucose.
  • Immune system: innate defenses (skin, inflammation, phagocytes) are fast and general; adaptive defenses (B cells make antibodies, T cells kill infected cells) are specific and have memory.
  • Circulation and gas exchange: the four-chambered heart separates oxygen-rich and oxygen-poor blood; alveoli exchange gases by diffusion.
  • Digestion breaks food down by hydrolysis; the small intestine's villi absorb nutrients; kidneys' nephrons filter blood and regulate water.

Practice questions

1. Water climbs up thin xylem tubes in a tree partly because water molecules stick to each other and to the tube walls. These properties are
  1. hydrolysis and dehydration
  2. cohesion and adhesion
  3. polarity and specific heat
  4. evaporative cooling and density
Show answer

cohesion and adhesion. Cohesion is water-to-water; adhesion is water-to-surface.

2. Digestive enzymes break starch into glucose by
  1. dehydration synthesis
  2. denaturation
  3. hydrolysis
  4. oxidation of glucose
Show answer

hydrolysis. Water is added to break each glycosidic bond.

3. Cellulose gives plant cell walls strength because
  1. β linkages let its long straight chains hydrogen-bond into tough fibers
  2. it is branched like glycogen
  3. it is made of amino acids
  4. it is hydrophobic like a lipid
Show answer

β linkages let its long straight chains hydrogen-bond into tough fibers. Parallel chains bonded side by side form microfibrils.

4. A cell secretes large amounts of digestive enzymes. Which organelles would you expect to be especially abundant?
  1. Rough ER and Golgi complex
  2. Chloroplasts and vacuoles
  3. Smooth ER and lysosomes
  4. Peroxisomes and centrioles
Show answer

Rough ER and Golgi complex. Rough ER makes secreted proteins; the Golgi packages them.

5. Lysosomes digest worn-out organelles. If a lysosome burst, the cell would most likely be damaged because
  1. the cell wall would dissolve
  2. ATP production would stop immediately
  3. its hydrolytic enzymes would break down molecules in the cytoplasm
  4. the cell would lose its DNA
Show answer

its hydrolytic enzymes would break down molecules in the cytoplasm. The enzymes are normally sealed away.

6. Cells lining the small intestine have many microvilli. The main advantage is
  1. a smaller volume
  2. protection from stomach acid
  3. a greater surface area for absorbing nutrients
  4. more DNA per cell
Show answer

a greater surface area for absorbing nutrients. More membrane surface means faster exchange.