Why are there so many species of living things alive on earth now, more than at any time in earth's history?
What will be an ideal response?
The end of the Paleozoic era was a time of warm, moist climates and a dominance of large dinosaurs. A meteor hit the earth, and the dinosaurs became extinct. The small mammals of that time no longer had to fear dinosaur predators and could expand their niches into those previously occupied by the dinosaurs. Then the earth began a cooling phase, further favoring the development of many and diverse mammals. Arthropods became adapted to every extreme environment imaginable on the earth. Deserts expanded as the climate became drier, making it difficult for tropical forest species to make it to the far reaches of their previous domain. The diversity of habitat was greater than at any time in earth's history, making possible the evolution of many regionally distinct groups.
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In which plant cell or tissue would the pressure component of water potential most often be negative?
A) leaf mesophyll cell B) stem xylem C) stem phloem D) root cortex cell E) root epidermis
A method of identification using immobilized, known antigens to identify unknown antibodies and vice versa, where the presence of the agent being tested for immediately brings about a color change is called ________.
A. immunochromatography B. Western blotting C. ELISA D. radioimmunoassay
How does radiometric dating work?
1.Cooling of molten rock produces particular mineral structures that can be used to determine when a crystal formed. 2.Radioisotope decay speeds up over time, so a graph can be made to predict the date. 3.Although ratios of atoms cannot be determined precisely, their half-lives can be used to predict an approximate date that a crystal formed. 4.Fossils older than 60,000 years can only be dated using carbon 14 since all other atoms will have decayed since then.
The eastern indigo snake often makes its home in abandoned gopher tortoise burrows. How would you characterize this relationship and its effect on each member?
A. amensalism: neutral for snake, negative for tortoise B. commensalism: neutral for snake, neutral for tortoise C. commensalism: positive for snake, neutral for tortoise D. parasitism: positive for snake, negative for tortoise E. amensalism: negative for snake, neutral for tortoise