Just need some trying to figure out some of these practice questions. and !

15. 4

16. 1

17. 2

18. 2

Explanation:

15. Consumers in the food chain are ranked according to what they eat. More specifically , they are organised into primary, secondary and tertiary consumers, depending upon what they consume for food. Primary consumers eat mostly plants, and are usually herbivores, tertiary consumers are top predators in the food chain.

16. Decomposers break down dead animals and plants. They are usually bacteria or other small fungi. They play the important role of recycling nutrients from dead matter back into the land. E.g. back into the soil where nutrients can be taken up by plants

17. Food webs are usually extremely complex in nature, with a variety of interactions of different organisms that are of different strengths and importance for the entire food web. Food webs are a good conceptual analysis, but practically are not simple to draw up into a simple web

18. The incorrect statement is that energy travels in both directions in a food web. Energy travel in a food web can be represented in a pyramid, which shows that energy at the bottom of the pyramid is greater than at the top. Energy is lost at every layer of the pyramid from producers up to the tertiary consumers at the top

answer: at 24 february, 2014 the population gets twice of its initial population.

explanation:

since we have given that

the population for alpha city, t years after january 1, 2004 is given as

first we find out the initial population, i.e. t=0,

so, our quadratic equation becomes,

according to question, we have said that if the population has twice its initial population, then it becomes

so, time taken to reach this above mentioned population is given by

now, we know that time can't be negative so, we take t=9.149 years.

hence, at 24 february, 2014 the population gets twice of its initial population.

answer: 2×10^-2kg

explanation: density= mass per volume

vol=mass/density

converting to s.i units we have;

3÷1000kg = 0.003

1.5÷100m = 0.15

0.003/0.15 = 0.02kg