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There are several cells in body of sponges and they are responsible to perform different functions.


Archaeocytes are totipotent cells which can differentiate into other cell types within the body of sponge. Moreover choanocytes also give rise to germ cells.

Choanocytes are flagellated cells which line the spongocoel and form the so called 'choanoderm': the layer represents endoderm of a diploblastic poriferan organism. The flagella help in creating a unidirectional flow of water around the body of sponge. Choanocyte also has a collar made of microvilli. These cells capture microcopic food particles. Digestion is also intracellular, taking place within choanocyte.


Porocytes are unique, elongated, tubular cells . Each porocyte allows water to flow inside the spongocoel from surrounding aquatic habitat. The pore through which water flows in is called ostium (singular). There are innumerable ostia (plural).


There are several other cells in Porifera. Ectodermal or outer layer of sponge body is made up of pinacocyte cells. Then there are spongocytes which secrete skeletal material. Contractile myocyte cells are present around osculum, a large pore for throwing out water from spongocoel.



Streptococci are a genus of coccus (spherical bacteria) that occur in pairs or chains.


Streptococci (singular: Streptococcus) are bacteria that are spherical in shape (cocci; singular: coccus) and they exist in pairs or chains.

This peculiarity of streptococci is because they divide along a single axis, thus forming continuous chains instead of separating or clumping (as in staphylococci).

Many of them are part of the normal flora of the human mouth, upper respiratory tract, intestine and skin; but some of them are pathogenic.

Streptococci are gram positive, mostly aerobic with some facultatively anaerobic.

The image below is a 3D model of a common streptococcus: S. pyogenes.





There is a category of bacteria called obligate anaerobes . These are bacteria which are actually poisoned by oxygen.

They generate all of the energy they need using glycolysis. The pyruvate formed in glycolysis is not broken down by the Kreb's cycle and electron transport chain. The pyruvate is broken down using fermentation pathways such as lactic acid fermentation.


Anaerobic respiration only produces 2 ATP molecules for every glucose molecule, that is definitely less than the 36-38 ATP produced by aerobic cellular respiration , but cells can survive on this.

This video provides more information about cellular respiration.

Hope this helps!


First and foremost is mutation , then there is natural selection . Other than these gene flow, genetic drift, sexual recombination are some of important factors which influence evolution of living organisms.


  • Mutation is source of variation, and all individuals of a population vary among themselves because of presence of different variations in each of them.
  • Variations could be helpful in survival of an organism. Then there are higher chances of those variations being inherited by the progeny.
  • Favourable variations are thus selected by nature through generations, which eventually help in evolution of a well adapted organism.



  • Living organisms benefit from crossing over and random fertilisation , which help in producing unique combinations of different variations.
  • Generally a population remains naturally divided in subpopulations/demes. Each subpopulation may have some variations which is unique to them. When gene flow between subpopulations stop (exchange of variations no longer take place between subpopulations), then one subpopulation may evolve into one species. (Organisms must interbreed to remain in a single species)





  • Genetic drift is another important factor that randomly changes allele frequency and hence affect evolutionary potential of a group of organisms.


Synaptic terminal is axonic end of presynaptic neuron.



Presynaptic neuron sends message to postsynaptic neuron by secretion of chemical messengers known as neurotransmitters: this is because at synapse the two neurons are not in direct physical contact.

The chemical messenger/neurohumor substances/neurotransmitters are stored in secretory vesicles of presynaptic axonic terminal.

To know more, please click here or read this answer.


Sugar has three major properties that make it ideal for use in topical cosmetics.


First sugar acts as a humectant, that is it draws water from the air and draws it into the skin. This in turn rehydrates and helps your skin better retain moisture.

Second, sugar contains an alpha hyrdroxy acid (AHA), called glycolic acid. AHA's such as glycolic acid help remove the dead (keratinized) cells in your skin's outermost layer (called the stratum corneum) and increases cellular turnover leaving younger cells and a clearer complexion.

Third sugar's physical properties, namely the fact that it's a small, rough crystal make it a great exfoliant which helps remove dead skin cells from the top layer of the skin. Larger crystals such as table salt can actually damage the skin by cutting too deep into the skin (epidermis) resulting in micro-tears in the living, healthy skin below (think large grain sandpaper versus small grain sandpaper).

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