Life cycles plants Introduction Flashcards
What is vegetative reproduction in marine photosynthetic organisms?
Vegetative reproduction involves the production of genetically identical daughter cells from a parent cell through mitosis.
Describe the process of vegetative reproduction in some unicellular organisms.
In some unicellular organisms, vegetative reproduction occurs through cell division, often referred to as binary fission.
This process results in an increase in the population size if environmental conditions are favorable.
What are adventitious branches, and what is their function?
Adventitious branches are formed in various large thalloid algae and serve as a means of reproduction.
When detached from the parent plant body, they can develop into new individuals.
e.g. in Fucus and Dictyota
What is hormogonia in cyanobacteria?
Hormogonia is a method of vegetative reproduction in cyanobacteria where trichomes within the sheath break up into many-cell segments called hormogonia or hormogones.
What is budding in reproduction?
Budding is a method of reproduction where bud-like structures gradually develop as outgrowths from the parent body.
During this process, the nucleus of the parental cell divides by mitosis, and the daughter nucleus is cut off from the parent cell, growing into a new individual.
How does reproduction occur in filamentous and simple multicellular algae?
Reproduction in filamentous and simple multicellular algae occurs by fragmentation, also known as splitting, where an organism splits into fragments.
Each fragment develops into a mature cell that is genetically and morphologically identical to its parent.
What is asexual reproduction?
Asexual reproduction is the production of offspring without the union of cells or nuclear material.
It is achieved by the production of different kinds of spores.
What are zoospores and how are they produced?
Zoospores are motile unicellular spores produced by most groups of algae.
They may be haploid or diploid, depending on whether they are produced by the gametophyte or sporophyte.
Zoospores can have two, four, or many flagella, and are called bi-, quadri-, or multiflagellate zoospores, respectively.
They are formed within the zoosporangium and are liberated through the disintegration of the zoosporangial wall or the formation of an apical pore on the zoosporangium.
What are aplanospores?
Aplanospores are non-motile spores that some zoospores transform into. They lose their motility during this process.
What is sexual reproduction?
Sexual reproduction involves the production of reproductive cells called gametes.
What are autospores?
Autospores are a type of aplanospores that appear identical to the parent cells.
What is the significance of sexual reproduction?
Sexual reproduction allows for the exchange of genetic material and the formation of new combinations.
Describe the process of sexual reproduction in terms of chromosome sets.
Sexual reproduction involves a complex life cycle where a haploid gamete, containing a single set of chromosomes, combines with another gamete to produce a diploid organism composed of cells with two sets of chromosomes.
What types of sexual reproduction are there?
Depending on the structure, physiological behaviour and complexity of gametes, sexual reproductions are of the following types:
- Hologamous
- Oogamous
- Anisogamous
- Isogamous
Hologamous
Info from slides:
Unicellular member
The vegetative cells of different strains (+ and -) behave as gametes and join together
Info from Google:
In certain unicellular algae whole thallus behaves like gamete and in this process fusion takes place between opposite strained gametes or thalli that after
fusion make diploid zygote. e.g., Chlamydomonas.
Oogamous
Small motile male gamete joins together a large non-motile female gamete
Anisogamous
Gametes are morphologically and physiologically different
Isogamous
Gametes are morphologically and physiologically similar
Overview of differences between vegetative, asexual and sexual reproduction
VEGETATIVE REPRODUCTION:
binary fission, hormogonia, buds, adventitious branches –> production of new individuals
fragmentation –> growth and increase of the sizes of organisms
ASEXUAL REPRODUCTION:
zoospores –> flagellate
aplanospores and autospores –> non-flagellate
SEXUAL REPRODUCTION:
gametes –> flagellate or non-flagellate
they are not able to give rise to a new individual, except after joining two by two
Major types of life cycles in algae
Haplont
Diplont
Heteromorphic diplohaplont
Isomorphic diplohaplont
The kind of life cycle is often important in the delimitation of algal classes.
Algae with only one vegetative phase
Haplontic life cycle
The haploid stage is uni-multicellular and the diploid stage is a single cell
In this case meiosis is zygotic, because the zygote undergoes to meiosis
Unicellular haploid stage (haplontic life cycle)
Multicellular haploid stage (haplontic life cycle)
Diplontic life cycle
The diploid stage is uni-multicellular and haploid gametes are formed
In this case meiosis is gametic, because the diploid cells then undergo meiosis to produce haploid cells or gametes
unicellular diploid stage (diplontic life cycle)
multicellular diploid stage (diplontic life cycle)
What is metagenesis/ heterogenesis?
Some algal species reproduce in a two-cycle pattern called “alternation of generations”
Algae with 2 phases is called…
Haplodiplont: a haploid vegetative phase alternates with a diploid vegetative phase
The alternation of a sexual phase and an asexual phase in the life cycle of an organism.
In the algae with haplodiplontic life cycle meiosis is sporic because it occurs to form spores
Heteromorphic Haplodiplontic or Diplohaplontic Life cycle
There is the succession between two generations, diploid and haploid.
In this life cycle the generations are morphologically different.
Heteromorphic diplohaplontic life cycle
Diploid phase is dominant
The haploid vegetative phase is smaller than the diploid one
Predominance of the Diploid vegetative phase
Heteromorphic Haplodiplontic Life cycle
Haploid phase is dominant
In this case the diploid vegetative phase is smaller than the haploid one.
Predominance of the Haploid vegetative phase
Isomorphic Haplodiplontic or Diplohaplontic Life cycle
There is the succession between two generations, diploid and haploid.
In the isomorphic haplodiplontic life cycle the generations are morphologically identical.
Isomorphic Haplodiplontic or Diplohaplontic Life cycle
Haploid and Diploid vegetative phases are identical
Exospores
are the result of exogenous budding of the cells
What types of reproduction are present in cyanobacteria?
- Asexual
- Vegetative
What are nanocytes and when are they produced?
- Very small cells
- Produced when cell divisions follow each other quickly
- New cells are not able to grow to full size before next division
Exospores and endospores
Asexual reproduction leads to the formation of spores: exospores and endospores
Produced when cells enlarge and each protoplast divides up into a number of daughter cells, surrounded by the mother cell wall.
Exospores and endospores are motile, but not flagellate.
When the conditions are favourable, the spores give rise to new vegetative cells.
Endospores
are produced endogenously, like those in bacteria
How does reproduction occur in some cyanobacteria of the order Pleurocapsales?
Through the formation of a beocyte or baeocyte.
During vegetative growth, the cell increases in size and produces a thick extracellular matrix, known as the F-layer.
After a series of cytoplasmic divisions, the extracellular matrix is broken, leading to the formation of several baeocytes.
Baecytes in Dermocapella
How do filamentous cyanobacteria reproduce?
Filamentous cyanobacteria reproduce through fragmentation of their filaments, known as trichomes.
This division occurs at regular intervals to form short filaments called hormogonia.
What are necridia, and how are they involved in reproduction of filamentous cyanobacteria?
Necridia are particular cells where division occurs during the reproduction of filamentous cyanobacteria.
Necridia picture
