8.Pioneer species such as lichen and moss inhabit an area after a major disturbance such as a volcanic eruption. Over time, other species are found in the disturbed area and the number of pioneer species decreases. Why does the number of pioneer species decrease?The amount of available sunlight is reduced. The pioneer species can no longer thrive. The area has more soil to support complex plants. The competition increases between organisms. The area is more susceptible to the wind. Seeds are captured in the pioneer plants and germinate at a higher rate. The temperature is not as extreme as it was following the disturbance. Fewer of the pioneer species reproduce.

Over the past 60 years, many amphibian species have experienced significant population declines and some species have become extinct. scientists suspected that local human activities such as the destruction of wetlands, regional pollution, and deforestation were the main reasons for these losses. however, research over the past 20 years reveals significant amphibian population declines in protected areas of the world, such as nature preserves and parks. these global declines suggest widespread problems including increased ultraviolet radiation, acid rain, and disease. in switzerland, for example, 14 of the 20 native amphibian species are threatened with extinction. chytridiomycosis is a fungal disease first identified in 1998 as a cause of massive amphibian deaths. in some severely impacted populations, a few individuals have survived, perhaps because of some natural resistance. if these resistant individuals continue to survive and prosper, new resistant populations might emerge. this would be an example of the founder effect artificial selection genetic drift natural selection sexual selection

1) strawberry plants typically reproduce by making runners, which are miniature versions of themselves, that grow off of the roots and stems of the parent. this type of vegetative reproduction is known as a) pollination. b) fragmentation. c) binary fission. d) vegetative propogation.

Aresearcher designed an investigation to test what effect eating different types of food would have on blood insulin levels. she selected 10 male subjects who were all 25 years of age and in good health. the experiment took place over 3 days. at 8: 00 a.m. on each day, the subjects ate a meal consisting of only 1 type of food. they had their blood insulin levels measured after consuming the meal. on day 1 they ate a high fat diet, on day 2 they ate a high protein diet, and on day 3 they ate a high sugar diel what is the independent variable in this experiment? a the age of the subjects b the blood insulin level c the type of food consumed d the time of day the meal was consumed