Dictyostelium discoideum is an unusual organism, one that straddles the boundary between the unicellular and the multicellular. Its feeding phase consists of individual amoeba-like cells that move independently, feeding on bacteria by phagocytosis. When the food runs out, cells begin to aggregate into a multicelled structure that migrates toward light. The cells differentiate into a base, stalk, and spores; only the spores survive to colonize a new habitat. What is the advantage of forming spores?
A. Spores can mate with other species.
B. Spores are smaller and can be transported to new habitats.
C. The spores will eat the other cells.
D. Spores have flagella and can swim to new habitats.
E. The spores are photosynthetic.
B. Spores are smaller and can be transported to new habitats.
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Viruses may not be cultivated in
A. live organisms. B. embryonated chicken eggs. C. tissue culture. D. blood agar.
Mechanoreceptors for touch and pressure are located in numerous locations in the vertebrate body
Which of the following is NOT a location of such mechanoreceptors in vertebrates?
a. skin b. skeletal muscles c. internal organs d. walls of blood vessels e. bones
Connective tissue includes adipose tissue, tendons, bone, cartilage, and blood. What do all these tissues have in common?
A. They all consist of few cells sparsely distributed in large amounts of extracellular material. B. They all provide structural support to the body. C. They all physically bind other tissues together. D. They are all hard tissues.
Scientists may compare similar genes in different species and determine what percentage of base pairs is identical. From this, it can be estimated how long ago the two species shared a common ancestor. The validity of this conclusion depends on an
important assumption. This assumption is that: A) all living things use the same genetic code. B) both species belong to the same kingdom. C) the gene codes for a functional protein. D) mutations occur at a fairly constant rate in all evolutionary lines.