1. Simple optical microscope. One lens.
Disadvantage: Only Van Leeuwenhoek made them, and he's dead.
Advantage: Worked pretty well. With them, Van Leeuwenhoek discovered protozoa and bacteria.
2. Compound optical microscope. Has both an ocular and objective lens.
Disadvantage: limited resolution. Can resolve bacteria, but not smaller things like viruses.
Advantage: can be used with live specimens (using phase contrast or polarized or other special illumination).
3. Binocular dissecting microscope (optic). Has a pair of ocular and objective lenses, and supposedly presents a "3D" view of the specimen to the viewer (I was never able to see in 3D using these darn things).
Disadvantage: Limited magnification
Advantage: Can be used to perform surgery on small but not microscopic specimens, such as fruit flies. Is used in "microsurgery" in hospitals too.
Hope this helps buddy!
Quadrat method is used for estimating the number of individuals in an area. In this method, a large square area on the ground or water surface is marked, call it an enclave. The number of animals present in this enclave is counted. Then by assuming that the animals are less migratory and are uniformly distributed, their number for a large area is estimated by the use of unitary method of calculation. Example a 4 square feet area has 2 snails, then a 1000 square feet area will have (1000 x 2)/4, i.e, 500 snails in it. Fishes can be counted using this method only if they are confined in a small water body like a lake or a pond. Rivers are flowing so the fishes may move along its length which can give us an underestimate or an overestimate of their numbers. Sea has its depth and huge area, and fishes can be moving randomly in it. Hence this method will not work for river and sea fishes.
Answer:
False
Explanation:
Annelids are actually more closely related to species within the mollusk phylum than they are to their worm cousins in the flatworm and roundworm phyla. Although they look quite different on the outside, mollusks and annelids share a more recent common ancestor than roundworms and annelids.
Answer:
A) Any butterfly allele that allowed milkweed toxin storage would be likely to persist because butterflies that had it were more likely to survive.
Explanation:
Butterflies are natural preys to birds. Over time, some butterflies evolved adaptive strategy such as developing an allele which enables storage of toxin from milkweed as a form of defense mechanism. This stored toxins repel birds from eating the butterflies having this allele giving rise to the survival of these butterflies overtime. Butterflies that had it are likely to be highly favored for survival against predatory birds, while those butterflies without this allele are likely to be heavily preyed upon by birds.
