Alice wants to see if she can enhance percent fertilization in her sea urchin experiment. she hypothesizes that depleting calcium (ca2+) from the sea water will increase percent fertilization. alice begins by isolating the eggs from the female in salt water (sw) and calcium-free salt water (cfsw) and then washes the eggs three times in sw or cfsw, respectively. she sees that she has more eggs in her sw group. after doing this, she isolates sperm from the males, dilutes the sperm into equal aliquots and adds a drop of sperm into each of her egg samples. assume that all sperm and eggs were stored under the same conditions. after an hour, under the microscope she observes that her sw eggs has a higher percent fertilization compared to her cfsw eggs. this contradicts her hypothesis. 1a. what confounding variables could account for error in alice’s experiment? (choose three

metamorphism is the change of minerals or geologic texture (distinct arrangement of minerals) in pre-existing rocks (protoliths), without the protolith melting into liquid magma (a solid-state change). the change occurs primarily due to heat, pressure, and the introduction of chemically active fluids. i hoped i !

the oldest known insects are believed to live around 400 millions ago as suggested by the fossil records.   some plants having woody stems also evolved during this time.

after the evolution of insects the first four legged species or the tetrapods evolved in shallow freshwater habitats from the intermediate species approximately 397 million years ago. the tetrapods went on conquering the land giving rise to amphibians, reptiles, mammals and birds.

the major split in tetrapods first occurred 340 million years ago branching off from amphibians.

363 million years ago when the carboniferous period began the insects started roaming on land and taking flights, following which the four limbed tetrapods adapted in the terrestrial habitat.