Flashcards in Quiz #2: labs 3,6,11,12 Deck (32)
Use beams of electrons to magnify a specimen. Capable of magnifying objects many more times than the human eye can.
When should an oil-immersion objective be used?
For observing small organisms and the fine detail of specimens
Why do many biologists prefer a phase contrast microscope?
It has a special condenser for accenting tiny differences in a specimen, which is good for cellular components and microscopic organisms
Advantage of parfocal objectives
Parfocal objectives only need small adjustments in focusing
depends on design and quality of objective lenses
movement of protozoans in pond water in relation to movement of the slide
when the slide goes left, the protozoans move right, a mirror image.
relationships between plane of focus, depth of field, illumination, and magnification
-a plane of focus puts the specimen at optimal distance
-depth of field is the thickness of the specimen-
-illumination lights the object
-magnification is the product of the power of the ocular and the power of the objective.
-all these things are used to examine a specimen
what is the magnification of a microscope with a 10 x ocular and a 95 x oil-immersion objective?
ocular: 100x; oil-immersion: 950x
three rules when focusing a microscope
1. adjust the oculars
2. raise the stage all the way up and position the specimen under the objective
3. use the focus adjustment knobs to get a clear view of the specimen
Prokaryotic vs. eukaryotic cells
Prokaryotic cells do not have membrane-bound nucleus and organelles, while eukaryotic cells do. Prokaryotic organisms are in Archeabacteria and Eubacteria kingdoms; eukaryotic cells are in kingdoms protista, plantae, fungi, and animalia
unicellular, colonial, multicellular organisms
-One cell: unicellular.
-colonial organisms: composed of loosely connected groups of cells
-multicellular: made from many cells
What factors prevent cells from becoming the size of giant blobs that consume city blocks in science fiction movies
cells can only come from pre-existing cells
compare and contrast plant and animal cells
plant cells: cell wall provides protection in shape. animal cells: plasma membrane provides the protection. in animal cells, lysosomes are used for digestive enzymes
what is the significance of the S phase of interphase?
each chromosome replicates to produce two sister chromatids
differences between animal and plant mitosis
animal cells: have abstula and during cytokinesis, a cleavage furrow develops.
plant cells: cell growth occurs in meristematic region and a cell plate is formed during cytokinesis
how do the events that occur in interphase prepare the cell for prophase?
the chromosomes and the volume of the cell have doubled, allowing prophase to begin the process of cell replication
difference between karyokinesis and cytokinesis
karyokinesis: division of genetic material
cytokinesis: division of the cytoplasm
function of cell division
1. asexual reproduction
2. formation of gametes
3. growing and repairing tissues in animals
what is meiosis?
the process of dividing sex cells
what cells undergo meiosis?
define and describe diploid (2n)
total number of chromosomes in the nucleus of a cell
define and describe haploid (n)
one-half the number of pairs of chromosomes
define and describe synapsis
process where homologous chromosomes pair up
define and describe crossing over
physical exchange of genetic material between homologous pairs
describe each stage of meiosis
meiosis I and meiosis II. In meiosis I, homologous chromosomes pair up in prophase I and exchange genetic material before the cell divides. Meiosis II is much like mitosis in that it has the same stages and processes like mitosis.
events of spermatogenesis
A sperm cell undergoes meiosis I, which creates two sperm cells, then undergoes meiosis II, where the two cells divide and become sperm.
where does spermatogenesis occur?
seminiferous tubules in the testes
events of oogenesis
a primary oocyte divides in meiosis I into a secondary oocyte and a polar body. a sperm contacts the secondary oocyte, and meiosis II begins. it becomes a zygote
where does the process of oogenesis begin?