The following figure is a model of seedling establishment as a function of distance from a parent tree. Initial seed density measures the number of seeds falling to the ground. Seed survivorship measures the proportion of seeds that survive to the adult stage at each distance

Which of the following factors is most likely to generate the seed density curve shown? 

#Question id: 5649

#Unit 5. Developmental Biology

From earliest to latest, the overall sequence of early development proceeds in which of the following sequences?

#Question id: 5648

#Unit 5. Developmental Biology

Use the following information to answer the question. In order to test how sea urchin sperm bind to eggs, scientists isolated the egg receptor protein that binds to the sperm acrosomal protein called bindin. Plastic beads were coated with egg receptor for bindin (ERB1) from eggs of the sea urchin Strongylocentrotus purpuratus, and then the beads mixed with sperm from S. purpuratus or from the related species, S. franciscanus. The researchers counted how many sperm were bound to each bead. The results are shown in the graph below. Treatments:

A: S. purpuratus sperm mixed with S. purpuratus ERB1 beads

B: S. purpuratus sperm mixed with beads containing no ERB1 protein

C: S. franciscanus sperm mixed with S. purpuratus ERB1 beads

D: S. franciscanus sperm mixed with beads containing no ERB1 protein

 What is a broader implication from the observations of the experiment?

#Question id: 5035

#Unit 5. Developmental Biology

 A fertilized egg is called a:

#Question id: 5036

#Unit 5. Developmental Biology

 The experiments of Spemann and Mangold first defined what feature of amphibian embryos?

#Question id: 5037

#Unit 5. Developmental Biology

Genes control development by:

#Question id: 5038

#Unit 5. Developmental Biology

The folding of sheets of cells, the migration of cells, and cell death are all mechanisms of