Lab #25 Protists

How does the stigma help chlamydomonas survive?The stigma helps Chlamydomonas survive, by detecting light. The organ is photosynthetic.

In Chlamydomonas, the eyespot is part of the chloroplast and takes on the appearance of a membranous sandwich structure. It is assembled from chloroplast membranes (outer, inner, and thylakoid membranes) and carotenoid-filled granules overlaid by plasma membrane

Chlamydomonas Life Cycle Protist Life Cycle (Chlamydomonas)

• REPRODUCTION:

It takes place either by asexual or sexual method.

(1) Asexual reproduction

(i) by Zoospore formation: This type of reproduction occurs in favourable conditions. Active cells of organism comes to rest, the flagella re withdrawn, and the ell contents divide into four, eight or sixteen parts, which become zoospore. These daughter individuals develop their individual cell wall and flagella. The parent cell wall is lost and the new individuals attain independent existence. They grow and develop into new chlamydomonas.

(ii) Palmella stage: Under favourable conditions the pond becomes dry. Zoospores remain enclosed within the parent cell wall, it grows in size and divides and large number of zoospores without flagella may be found in clusters inside an envelope of mucilage. This aggregation of cells is called palmella stage. On approach of favourable condition cell change to motile condition.

(2) Sexual Reproduction:It takes place by fusion of gametes and is isogamous. Inchlamydomonas sexual reproduction is variable from isogamy to anisogamy and oogamy. Some species are monoecious and others are diocious.In clamydomonas media and C debaryana the sexual reproduction is isogamous. In this case contents of cell divide to form 2 to 64 biflagellate gametes (like zoospores). Gametes may be naked or may have a cell wall. These are identical in shape and size and are called isogametes. They unite in pairs from their anterior end and form quadric-flagellate zygospore. It then loses cilia and becomes rounded.In chlamydomonas braumi sexual reproduction is of amisogamous type. One cell divides twice to form four big biflagellate gametes (female gametes) and other cells divide 3 to 4 times to form 8 or 16 small biflagellate gametes (male gametes). In this way gametes of different sizes are formed one big and one small gamete unit together which result in the formation of zygospore.

In chlamydomonas coccifera and Coogamum the sexual reproduction is of oogamous type. In male cell produces 16 or 32 small biflagellate male gamete and the female are produced singly non motile female gamete. Male and female gamete fuse together to form zygote.Germination of Zygote: Zoospore of zygote is formed by fusion of gametes. When favourable conditions come, the zygote nucleus which is diploid (2n) divides by meiotic (reduction) division and then divides mitotically to form four zoospores which are biflagellate and contain haploid nucleus. They come out by the burting of zygote wall and develop into new individuals.

If brown algae contain chlorophyll. why, then, do they appear brown ...

• Carotenoids are usually red, orange, or yellow pigments, and include the familiar compound carotene, which gives carrots their color. These compounds are composed of two small six-carbon rings connected by a "chain" of carbon atoms. As a result, they do not dissolve in water, and must be attached to membranes within the cell. Carotenoids cannot transfer sunlight energy directly to the photosynthetic pathway, but must pass their absorbed energy to chlorophyll. For this reason, they are called accessory pigments. One very visible accessory pigment is fucoxanthin the brown pigment which colors kelps and other brown algae as well as the diatoms.

Protists (Lab 26)

foraminiferan• The Foraminifera ("hole

bearers", or forams for short) are a phylum or class of amoeboid protists.

foram

• Foraminifera have many uses in petroleum exploration and are used routinely to interpret the ages and paleoenvironments of sedimentary strata in oil wells.[25] Agglutinated fossil Foraminifera buried deeply in sedimentary basins can be used to estimate thermal maturity, which is a key factor for petroleum generation.

Forams are the principal microfossil used to age-date and correlate marine sedimentary rocks — they areinvaluable to the oil industry. It is u nusual to drill an oil well without a paleontologist onsite. Based on foram recovery the paleontologist determines the age of the sediments drilled through and howmuch deeper to drill to reach the oil the bearing layer characterized by a particular microfossilassemblage.

Paramecium: transverse fission

• Paramecium may reproduce by transverse fission (called asexual) or by conjugation (called sexual). The reference to 'sexual' is not quite appropriate as Paramecium has no sexual organs or sexual dimorphism whatsoever.

Paramecium

Transverse fission

• Reproduction by transverse fission takes place in favorable conditions, with plenty of nutrients and space. This is the only way in which Paramecium can increase its numbers. A transverse constriction takes place at the mid section, dividing the organism into two daughter units which are different. The 'lower' unit must regenerate an anterior end, and the 'upper' unit must regenerate a posterior end. During transverse fission the micronucleus divides first by mitosis, and the macronucleus divides later by amitosis, a simple constriction.

Paramecium

What requirements might make culturing parasitic zoomastigotes diffiult?

• Why do some scientists call conjugation "sexual reproduction" and others do not?

• Genetic recombination occured, but no increase in cell numbers

• is the cell fundamental unit of life in plasmodial slime molds

• why are unicellular organisms that reproduce by mitosis considered immortal