The independent variable is the amount of water consumed by the football players.
The dependent variable is the football players' endurance, measured by how many times they can run up and down the bleachers before catching their breaths.
The coach's hypothesis was that the more water consumed, the more endurance the players will have.
There is not a control group present in this experiment, but it would be the set of players who did not drink a bottle of water before practice.
The experimental group is the set of players who did drink a bottle of water before practice.
The constants in the experiment are the operational definitions of endurance (how he measures their endurance), the amount of water each player drinks throughout the week, and the players used in the experiment.
The lack of a set control group poses a threat to the accuracy of the experiment's results.
Gymnosperms:- non-flowering,exposed seeds,pine or fir fruit.
angiosperms:- flowering,seeds enclosed in fruit,garden flowers and tomatoes
Answer:
(B) Energy transfer between trophic levels is almost always less than 20% efficient.
Explanation:
The ultimate source of energy on the Earth is the Sun. The energy coming from the Sun is captured by green plants by the photosynthesis. During photosynthesis sun energy is fixed into chemical energy (carbohydrate). So, in an ecosystem energy flow is unidirectional (from sun to the green plants). The fixed chemical energy from green plants is transferred to the herbivores then to carnivores through food. When one organism eats another organisms, only 10 % of the energy present in the organism is transferred as a food for the next organism and a large amount of energy is lost as heat into the environment. Thus, energy keeps on decreasing when stored energy moves from producers to top consumers. Thus, less than 20% energy transfer limits the trophic levels in most of the ecosystem.
