Concentrations of soil mineral ions are greater within the root than in the soil. How do root-hair cells do this?
active transport
Why (by what mechanisms) do cells differ in their responses to hormone signals?
Not all cells contain the receptor, Different cells may have their DNA in different chromatin configurations that allow different genes to be activated by the receptor, Different cells might contain different transcription factors that interact with the receptor to regulate transcription, and Activation of the same gene in different cells might have different effects depending on other proteins expressed in the cells
Tight junctions
Form tight seals that prevent extracellular fluids from leaking between cells
Within an organism, what makes one cell type different from another?
Each cell type expresses different genes
In Drosophila oocytes, concentrations of a gene product called bicoid are high near the head and decline toward the posterior. bicoid is an example of a what?
morphogen
Plasmodesmata
Permit the passage of molecules from the cytoplasm of one cell to another
Stem cells
can undergo mitosis, can differentiate into more than one type of specialized cell, vary in their potency, can sometimes only differentiate into one cell type.
Plants are different from animals because plant development?
involves organ formation in adults
Sexual reproduction
increases genetic variation
In plant reproduction
haploid individuals produce gametes via mitosis
A pollen grain
is a haploid organism, is a male gametophyte, contains 2 sperm cells, and performs double fertilization
Which of the following is NOT true for both male and female mammalian gametogenesis?
gonads.
A. One primary cell produces four mature gametes
Which of the following is NOT TRUE of the placenta
B. Blood of mother and fetus mix
If pregnancy occurs, then
E. A and C
What allows fetal hemoglobin to remove oxygen
from maternal hemoglobin?
Fetal hemoglobin has a higher affinity for oxygen than does maternal hemoglobin
Essentially all exchange of gases and other
materials between the circulatory system and tissues of the body or the outside world (e.g., in the lungs) occurs in the what?
capillaries
Hemoglobin is more likely to release oxygen in metabolically active tissues because why?
CO2 is an allosteric regulator of hemoglobin
Which of the following is NOT an important aspect contributing to water transport through the
xylem?
continuous tubes created by dead vessel and tracheid cells
A. osmosis due to sugar concentrations in source tissues
Which of the following DOES NOT
contribute to the differentiation of stem cells?
C. altered genetic content
Phloem loading occurs through what?
companion cells and plasmodesmata
Alternation of generations in the plant life cycle refers to alternating between what?
haploid and diploid
In Drosophila eyes, photoreceptor cell differentiation
occurs by
