In people who stand for long periods, blood tends to pool in the lower limbs and this may result in varicose veins. what causes the varicose veins?

Why is altruistic behavior not very common?

What is the term for a group of interbreeding organisms that are able to produce fertile young? A. biological species B. ecosystem C. population D. genus

Why does every one have cells

The common edible frog of Europe is a hybrid between two species, Rana lessonae and Rana ridibunda. The hybrids have a wide distribution, from France across central Europe to Russia.

Mention five reason why are usually involved in criminal activities

Which of the following is NOT a pure substance? Question 2 options: Gold Water Helium gas Coffee

Tench fish can't survive salt concentrations beyond 1%. In which two areas can these fish be found? lakes oceans rivers seas

Concerning the presence of the nucleus what is the difference between animal and bacterial cells?

A population of 100 butterflies living on an acre of land loses three-quarters of its members when a sudden freeze in the spring occurs just after they emerge as caterpillars. This population has undergone a reduction in population size due to A.

Do the water bottles need to be full or empty?