The treeʹs horizontal axis is a timeline that extends from 100,000 years ago to the present; the vertical axis represents nothing in particular. The labeled branch points on the tree (V—Z) represent various common ancestors. Letʹs say that only since 50,000 years ago has there been enough variation between the lineages depicted here to separate them into distinct species, and only the tips of the lineages on this tree represent distinct species.

According to this tree, what percent of the species seem to be extant (i.e., not extinct)?

#Question id: 11763

#Unit 9. Diversity of Life Forms

What makes certain red algae appear red?

#Question id: 11764

#Unit 10. Ecological Principles

The mathematical model for geometric growth of a population is identical to the model for exponential growth, except that __________ in the geometric model.

#Question id: 11765

#Unit 10. Ecological Principles

The population density of a particular insect species was determined to be 15,000 adults per hectare in the summer of 1996, 21,000 adults per hectare in the summer of 1997, and 29,400 adults per hectare in the summer of 1998. Based on these population estimates, what is your estimate of λ, the annual rate of geometric growth?

#Question id: 11766

#Unit 10. Ecological Principles

The population density of a particular insect species was determined to be 15,000 adults per hectare in the summer of 1996, 21,000 adults per hectare in the summer of 1997, and 29,400 adults per hectare in the summer of 1998.

What would you expect the insect population to be in the summer of 2000, assuming no change in λ?

#Question id: 11767

#Unit 10. Ecological Principles

If a population has a stable age distribution, which of the following statements is true?

#Question id: 11768

#Unit 10. Ecological Principles

As documented by peter and rosemary grant, the population of the medium ground finch on the tiny island of Daphne major in the Galápagos archipelago responded how to changes in food resources associated with climate changes: