Organisms and Populations — Important Questions

Birth rate, Death rate, Sex ratio, Age distribution

Population attributes are characteristics that apply only to groups, not individuals. Birth rate, death rate, sex ratio, and age distribution are all population-level attributes. Individual height is a characteristic of an individual organism, not a population attribute.

Natality, Immigration

Population density increases due to natality (births) and immigration (individuals moving into the habitat). Mortality (deaths) and emigration (individuals leaving the habitat) decrease population density.

Broad base

A growing population has many young individuals, creating a broad base in the age pyramid. A narrow base indicates a declining population, while equal width suggests a stable population.

Parasitic plant

Cuscuta is described as a parasitic plant that grows on hedge plants and derives nutrition from the host plant. It has lost its chlorophyll and leaves during evolution, which fits the parasitic plant category. It is not an ectoparasite or endoparasite as those terms refer to parasites living on the outside or inside of animal hosts.