In the early days of germ theory, contagious diseases were thought to be caused by fungi or bacteria. in the 1890s, dmitri
ivanovski filtered extracts from diseased tobacco plants and discovered that the disease could be transmitted to new plants
through the filtrate. he concluded that the disease was caused by particles smaller than bacteria: the tobacco mosaic virus.
which best explains how ivanovski's work led to a change in the germ theory?
he tried to promote his hypothesis as a law.
he used a new experimental method to test his hypothesis.
he used a more powerful bacterial strain than other scientists had.
he obtained results that confirmed what other scientists were thinking

advantage of using stem cells in medical research:

1.       it provides medical benefits in the fields of therapeutic cloning and regenerative medicine.

2. it provides great potential for discovering treatments and cures to a variety of diseases including parkinson disease, spinal cord injuries, diabetes, alzheimer’s disease and many more.

3. limbs and organ could be grown in lab from stem cells and then used in transplant or treat illness.

black

lasagna

lunch

math

cells use diffusion to get substances in and out of themselves. that diffusion will occur across the cell membrane or the outer covering of the cell. because we are talking about the surface of the cell, surface area and volume are  important factors here. as a cell increases in size, its surface area and volume increase as well.  we call that the surface area to volume ratio (sa: vol).  but the catch is that  volume increases at a greater rate than surface  area. in other words, as a cell gets bigger, the sa: vol gets smaller. so a really small cell like bacteria is mostly cell membrane (surface) with very little contents (volume). a really big cell like an egg, is mostly insides with a super thin membrane. so what ends up happening is that the cell cannot efficiently diffuse all of the stuff it needs in/out to survive. therefore cell size is limited to about 100mm. so how do we make organisms bigger than 100mm? cells divide! by dividing and becoming multicellular, organisms are able to grow!   check out the diagrams i attached to see the effect of sa: vol. i hope this ! good luck!