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TNPSC Free Notes Biology- Types of Animal Eggs

இந்தக் கட்டுரையில், TNPSC குரூப் 1, குரூப் 2, குரூப் 2A, குரூப் 4 மாநிலப் போட்டித் தேர்வுகளான TNUSRB, TRB, TET, TNEB போன்றவற்றுக்கான  முறைகள் இலவசக் குறிப்புகளைப் பெறுவீர்கள்.தேர்வுக்கு தயாராவோர் இங்குள்ள பாடக்குறிப்புகளை படித்து பயன்பெற வாழ்த்துகிறோம்.

Types of Animal Eggs

Amount of Yolk
1. Alecithal: In mammalian egg yolk is absent. If present, it is in a negligible
2. Microlecithal: The eggs containing small amount of yolk are called
microlecithal. Example: Amphioxus.

3. Mesolecithal: Moderate amount of yolk is found in these eggs. Example:
4. Macrolecithal: Enormous amount of yolk is present. Example: birds.
Distribution of yolk:
1. Isolecithal or Homolecithal: Yolk is in small amount and
distributed evenly throughout the cytoplasm (e.g.,Amphioxus).
2. Telolecithal: Distribution of yolk is unequal. Yolk is more in the
lower part. (e.g., frog).
3. Centrolecitha: Yolk is concentrated in the centre of the egg
4. Discoidal: The amount of yolk is enormous (e.g., birds).
Presence or absence of shell:
1. Cleiodoic: These eggs are laid on land and fully surrounded by a
waterproof shell. eg., reptiles,
2. Non-cleiodoic: These eggs are laid in water and not protected by shell.
e.g., amphibian.
Type of development:
1. Determinate or Mosaic eggs: Such eggs are called determinate eggs.
Indeterminate or Regulative eggs: Such eggs are called indeterminate
Binomial Nomenclature:
 Carolus Linnaeus introduced the method of naming the animals with two
names known as binomial nomenclature.
 The first name is called genus and the first letter of genus is denoted in
 The second one is the species name denoted in small letter.
 The binomial names of some common animals are as follows


Binomial name
Amoeba Amoeba proteus
Hydra Hydra vulgaris
Tapeworm Taenia solium
Roundworm Ascaris lumbricoides
Earthworm Lampito mauritii / Perionyx


Leech Hirudinaria granulosa
Cockroach Periplaneta americana

Comparison of chordates and non-chordates
Chordates Non-chordates
1. Notochord is present Notochord is absent
2. Dorsal, hollow and single nerve cord Double ventral solid nerve cord
3. Pharynx perforated by gill slits Gill slits absent
4. Heart is ventrally placed Heart is dorsal or laterally placed or Absent
5. A post anal tail is present A post anal tail is absent
6. Alimentary canal is placed ventral to the nerve cord Alimentary canal is placed



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