Plant Kingdom 1 Flashcards
why do plants have life cycles
In plants, both haploid and diploid cells can divide by
mitosis. This ability leads to the formation of different
plant bodies - haploid and diploid. The haploid plant
body produces gametes by mitosis. This plant body
represents a gametophyte. Following fertilisation the
zygote also divides by mitosis to produce a diploid
sporophytic plant body. Haploid spores are produced
by this plant body by meiosis. These in turn, divide by
mitosis to form a haploid plant body once again.
why are plant life cycles also called as alternations of geenrations
during the life cycle of any sexually reproducing plant,
there is an alternation of generations between gamete
producing haploid gametophyte and spore producing
diploid sporophyte
explain haplontic life cycle
Sporophytic generation is represented only by the
one-celled zygote. There are no free-living
sporophytes. Meiosis in the zygote results in the
formation of haploid spores. The haploid spores
divide mitotically and form the gametophyte. The
dominant, photosynthetic phase in such plants is
the free-living gametophyte. This kind of life cycle
is termed as haplontic. Many algae such as Volvox,
Spirogyra and some species of Chlamydomonas
represent this pattern
explain diplontic life cycle
On the other extreme, is the type wherein the diploid
sporophyte is the dominant, photosynthetic,
independent phase of the plant. The gametophytic
phase is represented by the single to few-celled
haploid gametophyte. This kind of life cycle is
termed as diplontic. An alga, Fucus sp., represents
this pattern (Fig. 3.7b). In addition, all seed bearing
plants i.e., gymnosperms and angiosperms, follow
this pattern with some variations, wherein, the
gametophytic phase is few to multi-celled.
explain life cycle of bryophytes
A dominant, independent, photosynthetic, thalloid or erect phase is
represented by a haploid gametophyte and it alternates with the shortlived multicelluler sporophyte totally or partially dependent on the
gametophyte for its anchorage and nutrition. All bryophytes represent
this pattern.
explain life cycle of pteridophytes
The diploid sporophyte is represented by a dominant, independent,
photosynthetic, vascular plant body. It alternates with multicellular,
saprophytic/autotrophic, independent but short-lived haploid
gametophyte. Such a pattern is known as haplo-diplontic life cycle. All
pteridophytes exhibit this pattern
algae usually show haplontic life cycle. but thr are some exceptions what are they?
Interestingly, while most algal genera are haplontic, some of them
such as Ectocarpus, Polysiphonia, kelps are haplo-diplontic. Fucus, an
alga is diplontic.
explain division thallophyta
According to two kingdom classification, all the algae, fungi were placed in
thallophyta, because their plant body is thallus(not differentiated into stems,roots and leaves).
(2) In thallophyta the male sex organs are called as Antheridia and female sex organs are
called as Oogonia. Sex organs are unicellular & jacket less [Jacket - layer of sterile
cells]
(3) The sexual reproduction in thallophyta is isogamous, anisogamous and oogamous.
(4) In thallophyta, sexual reproduction takes place through zygotic meiosis, therefore
embryo is not formed.
Absence of embryo formation is unique character of thallophyta so they are
also known as “nonembryophytes”
classify various plant divisions based on:
(i) formation of embryo
(ii) presence of vascular tissue
(iii)visibility of sex organs
(iv)presence of seed
(i)present- embryophyte(bryo/pterido/gymno/angiio)
absent- non embryiphyte
(ii) present- tracheophyte(pterido/gymno/angio)
absent-attracheophyte(bryo/algae)
(iii) visible- phanerogams (angio/gymno)
hidden-cryptogams( bryo/pterido/algae)
(iv) present- spermatophyte( angio/bryo)
absent- non spermatophyte ( algae/bryo/pterido)
explain the different types of vegetative and asexual repro in algae
Vegetative reproduction :-
It is of following type
(a)
Binary fission - Cell is divided into two parts.
eg. Found only in Unicellular algae
(b) Fragmentation - Filaments break down into small pieces & form new filaments.
eg. All filamentous algae
(ii) Asexual reproduction :-
Zoospores are formed in favourable conditions and aplanospores, hypnospores and
akinetes etc. are formed in unfavourable condition.
explain sex organs of algae
Male sex organ is called antheridium and female is called oogonium. The sex
organs of algae are unicellular & jacketless. But exceptionally sex organs of
green algae Chara (Chara - green algae - known as stone wort) are
multicellular and jacketed.
The male sex organ of Chara is known as globule and female is known as
nucule.
life cycle of algae
Plant body of algae is haploid so sexual reproduction take place through
zygotic meiosis. So their life cycle is haplontic.But exceptionally brown algae
are diploid. [Ex. In Fucus, life cycle is diplontic]
(c)
Algae reproduce by zygotic meiosis i.e. first division in zygote is meiosis so
embryo is not formed.
different types of sexual repro in algae
(1) Isogamous - Cladophora, Ulothrix, Ectocarpus, Spirogyra
(2) Anisogamous - Chlamydomonas braunii
(3) Oogamous - Sargassum, Volvox, Fucus and Chara
different body forms of chlorophyceae
(i) Unicellular :-
(a) Chlamydomonas - Motile unicellular algae. These algae move with the help of
flagella.
(b) Chlorella - Non motile unicellular alga.
(c) Acetabularia - It is the largest unicellular plant.
Note : According to five kingdom system the algae described above should be
placed in Protista but because their life cycle is similar to green algae so they are
studied in Plantae.
(ii) Colonial - Some green algae are found in colonies. They form colony of cells. The number
of cells in a colony is fixed. Colony with fixed number of cells is called coenobium.
eg. Volvox - Motile colony
(iii) Multicellular filamentous - Mostly the green algae are multicellular and filamentous.
eg. Ulothrix, Spirogyra
(iv) Multicellular thalloid or Parenchymatous - Some algae are multicellular in length and
width.
eg. Ulva
what are the different pigments presentin chlorophyceae
Chlorophyll – a and b
Carotene – Beta
Xanthophyll – Luteaxanthin and Violoxanthin
