Midterm 2 Study Guide

Brian McCauley's Bio 6A, Fall 2019.

This study guide has been updated for Fall 2019.

Midterm 2 will be Wednesday, October 30, 2019. You’ll have the whole lecture period. The format will be the same as Midterm 1: mixed, including multiple-choice questions and one long-answer question. Bring a Scantron sheet (one of the long skinny ones with 50 questions per side). On the multiple-choice questions, there might be more than one correct answer; you have to mark all the correct answers and none of the incorrect answers to get credit. There will be no partial credit. Be sure to read the directions on the exam before answering the questions.

The exam will be based on the material I cover in lecture. I will assume that you have read the sections of the textbook that I covered in lecture. If I skipped a section in the book, I won’t ask any questions on that. The exam won’t include material that was covered only in lab (plants, for example), but it will include questions on systematics and gas exchange, which were covered in lab as well as lecture.

This study guide is intended as a guide. It isn’t guaranteed to cover every question that will be on the midterm.

Long-Answer Questions

One of these questions will be on the midterm.

1. Diagram & explain how xylem sap & phloem sap are transported in plants. (Hints: there are several diagrams in the book showing different parts of the overall process; you should try to combine all this information into one big diagram. You don’t need to copy all these figures in your answer, but you should include the information they express. Don’t forget to include water potential.)
2. Explain how the human digestive tract processes food. Include the various organs that help in digestion and absorption, and what happens to each type of food at each stage in the process, including the function of the various categories of digestive enzymes.
3. Compare and contrast the ways that cows and rabbits extract energy from diets consisting largely of cellulose; relate this to the structure of each animal’s digestive tract. If a human received the gut microbiome of a cow, could he live on a diet of grass? (Hint: first you must explain why cellulose is a problem.)

There are only three choices for this midterm!

Important Concepts

Gas Exchange in Plants

• Why gas exchange is important for plants
• Low partial pressure of CO₂; tradeoff between gas exchange & water loss
• Cuticle, stomata, guard cells
• Osmosis; selectively permeable membranes; turgid vs. flaccid vs. plasmolyzed
• Pneumatophores

Transport Systems in Plants

• Why transport is necessary
• Proton pumping creates an electrochemical gradient. Explain how the gradient is chemical and how it’s electrical.
• Proton gradient can be used for cotransport. Why does this work?
• Water potential: solute potential & physical potential
• Osmosis (again) – be sure you can explain it.
• Water exists in 3 compartments in plant tissue
• Water follows 3 paths through plant tissue
• Roots: active transport lowers solute potential.
• Casparian strip
• Root pressure & guttation
• Transpirational pull: roles of evaporation & surface tension (see fig. 36.14). Understand the things that make water potential change in xylem sap transport. How does evaporation generate a force that pulls the water up? Explain this in terms of hydrogen bonds.
• Ascent of xylem sap: roles of root pressure, transpirational pull, cohesion, adhesion.
• Phloem sap: how pressure flow is created.
• Sugar sources & sinks. When sugar enters a sugar sink, why does the solute potential change?
• Why solute potential changes as phloem sap moves through plant
• Why water moves from xylem to phloem in some parts of plant and from phloem to xylem in other parts
• Mycorrhizal fungi

Animal Nutrition

• Heterotrophs & autotrophs
• 2 ways to take food into cell: one molecule at a time, or phagocytosis
• Why size is important
• How do plasmodial slime molds & fungi deal with the problems of being big?
• Intracellular vs. extracellular digestion: compare sponges, cnidarians, and other animals.
• Ingestion, digestion, absorption, elimination
• Gastrovascular cavity vs. complete digestive tract
• Specialization of digestive tract regions: earthworm, insect, bird
• Stomach: enzymes & acid. Why doesn’t the stomach digest itself? How does Helicobacter pylori survive?
• Small intestine: duodenum, liver, gall bladder, and pancreas. Why it’s called the small intestine.
• Digestion means breaking polymers into monomers. Give examples of polymers & monomers.
• Absorption of proteins, carbohydrates, fats
• Blood vessels & lymph vessels near intestine
• Carnivores vs. herbivores
• Cecum
• How termites get energy from cellulose
• Foregut vs. hindgut fermentation
• How cows get energy from cellulose (What do all those chambers do?)
• How rabbits get energy from cellulose. Why coprophagy is popular with rabbits but not cows. Why horses like it, too.
• Gut microbiota; “lean” vs. “obese” microbes in humans and mice.
• Fecal transplants
• Helicobacter pylori. Is it good or bad?
• "Colonocyte metabolism determines gut health." How do microbes affect the metabolism of the colonocytes? How do the colonocytes affect the gut microbiome?