Which of the following statements is true about formation of the primitive streak ?

A. by the cellular dance mechanism, the cells came down the sides of the epiblast to undergo a medially directed intercalation of cells in the posterior margin where primitive streak forms.

B. Cellular dance is mediated by wnt planar cell polarity pathway in the hypoblast cells, at the posterior edge of the embryo.

C. The Wnt pathway activated by fibroblast growth factors (FGFs) produced by the hypoblast.

D. The Wnt planar cell polarity pathway activated by b-catenin produced by the epiblast.

#Question id: 13184

#Unit 10. Ecological Principles

The MacArthur-Wilson equilibrium model of island biogeography predicts the number of species found on islands. The figure below depicts two volcanic islands located off a section of mainland coast.

According to  the  MacArthur-Wilson model, the  number of  bird  species present on  Island 2  at  any  one  time is  a function of the relative rates of

#Question id: 13185

#Unit 10. Ecological Principles

#Question id: 13186

#Unit 10. Ecological Principles

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

This model predicts that recruitment of new individuals into the population should be

#Question id: 13187

#Unit 10. Ecological Principles

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: 13188

#Unit 10. Ecological Principles

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 survivorship curve shown? 

#Question id: 13189

#Unit 10. Ecological Principles