Five hundred cockroaches of one species were sprayed with a new insecticide. Twenty-four hours later nearly all the cockroaches were dead. A few, however, survived. This outcome illustrates which one of darwin’s key ideas about natural selection and variation?.

The ancestors of horses possessed feet with five digits. over time, with the development of grasslands, the digits fused and formed hooves. what evolutionary advantage did this transformation serve? a. it allowed them to climb rocky surfaces with ease. b. it allowed them to graze better. c. it enabled them to run faster from predators. d. it let them see clearly through the grasslands. e. it made them taller.

Afarmer began a new method of reducing grain spills. this reduced the number of mice on the farm. the number of snakes in the surrounding area decreased at the same time. the snakes depended on the mice that lived in the field. what’s the likely reason the snake population decreased? a. the number of snake predators increased. b. the number of mice increased. c. the number of mice decreased. d. the pesticides affected the snakes. e. a new breed of mice moved into the field.

What is the amount that shareholders contribute