Answer the question using the accompanying figure. What is occurring in step 6?
a. fission
b. fusion
c. fertilization
d. the first meiotic division
e. the second meiotic division
ANSWER: b
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The most distinctive characteristic of leaf mesophyll cells is that they are filled with
A. central vacuoles. B. many chloroplasts. C. oxygen bubbles. D. veins. E. stomata.
Specificity refers to ____
a. the ability of MHC markers to identify foreign cells b. the ability of macrophages to destroy bacteria c. the ability of the complement system to form membrane attack complexes d. the formation of specific receptors on T and B cells e. the formation of specific memory cells after an infection
Evolution can be observed and tested
a. true b. false
On a trip to the Southwest United States, you and a friend collect some seeds from a piñon, a type of pine tree. Your friend also gathers a small bagful of soil from under the piñon tree. Back home, both of you plant your seeds in commercial sterilized
potting soil, but your friend adds a spoonful of the collected dirt to each of her pots. Her seedlings do better than yours. What is the likeliest explanation for your differences? A) Pine seedlings are better adapted to the sandy soil of the Southwest than to commercial potting mix. B) The soil from the Southwest probably contained macronutrients missing from the potting mix. C) The soil from the Southwest probably contained nitrogen-fixing bacteria that colonized the seedlings' root nodules. D) The soil from the Southwest probably contained fungi able to establish a mycorrhizal association with the seedlings' roots.