2. 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
4. •
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Active cells of organism comes to rest, the flagella re withdrawn, and the ell contents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 quadricflagellate 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.
5. 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.
8. 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 are
invaluable 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.
9. Paramecium: transverse
fission
Paramecium
• 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.
10. Transverse fission
Paramecium
• 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.
12. • Why do some scientists
call conjugation "sexual
reproduction" and others
do not?
• Genetic recombination
occured, but no increase in
cell numbers
13. • is the cell fundamental unit
of life in plasmodial slime
molds
14. • why are unicellular
organisms that reproduce
by mitosis considered
immortal
Editor's Notes
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 chlamydomonasbraumi 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 chlamydomonascoccifera 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.
any unicellular organism of the rhizopodan order Foraminiferida (formerly Foraminifera), characterized by long, fine pseudopodia that extend from a uninucleated or multinucleated cytoplasmic body encased within a test, or shell. Depending on the species, the test ranges in size from minute to more than 5 cm (2 inches) in diameter and varies in shape, number of chambers, chemical composition, and surface orientation. Tests of a South Pacific species are large enough to be used as jewelry by oceanic islanders; Nummulite specimens from the Eocene limestones of the Egyptian pyramids often exceed 5 cm in diameter. Foraminiferans inhabit virtually all marine waters and are found at almost all depths, wherever there is protection and suitable food (microscopic organisms).An important constituent of the present-day planktonic (floating) and benthic (bottom dwelling) microfaunas, foraminiferans have an extensive fossil record that makes them useful as index fossils in geological dating and in petroleum exploration. The word foraminiferan does not refer to the external pores found in some species but to the foramina (openings or apertures) between adjacent chambers after a new chamber envelops a previous one. When the foraminiferans die, their empty calcareous tests sink and form the so-called foraminiferal ooze that covers about 30 percent of the ocean floor. Limestone and chalk are products of the foraminiferan bottom deposits.The major factors governing the growth, reproduction, and distribution of foraminiferans are water temperature, depth, and salinity; availability of suitable food; nature of the substratum; and oxygen supply. The present-day foraminiferan population of the seas consists of six recognizably different faunas; four occur in warmer waters, two in colder waters.Although some species of foraminiferans reproduce exclusively by asexual means (multiple fission, budding, fragmentation), for most species there is a regular or an occasional sexual generation. Reproduction usually occupies one to three days, depending on the size and complexity of the species. Small species may complete both the sexual and asexual generations within a month, but larger species often require a year or two. Reproduction normally terminates the life of the parent, since all its cytoplasm is generally devoted to formation of the young.
