Differences between Chondrichthyes and Osteichthyes

 

Feature	Chondrichthyes	Osteichthyes
Common Name	Cartilaginous fishes	Bony fishes
Habitat	Exclusively marine animals	Marine and freshwater fishes
Endoskeleton	Cartilaginous	Bony
Body Shape	Streamlined body	Streamlined body
Mouth Position	Ventrally located	Mostly terminal
Gills	Gill slits are separate and naked	Four pairs of gills covered by operculum
Scales	Skin is tough, containing minute placoid scales	Skin is covered with cycloid/ctenoid scales
Teeth	Modified placoid scales, backwardly directed	Derived from bones
Jaws	Very powerful	Well-developed jaws
Mode of feeding	Predaceous	Vary from filter feeders to predators
Notochord	Persistent throughout life	Replaced by bony vertebral column in adult
Air Bladder	Absent, requiring constant swimming to avoid sinking	Present, regulates buoyancy
Heart	Two-chambered (venous heart), single circulation.	Two-chambered (venous heart), single circulation.
Body Temperature	Cold-blooded (poikilothermous) animals	Cold-blooded (poikilothermous) animals
Sexes	Separate	Separate
Fertilization	Internal	Usually, external
Development	Many of them are viviparous	Mostly oviparous and development is direct
Special Features	Some have electric organs (e.g., Torpedo); some possess poison sting (e.g., Trygon). In males, pelvic fins bear claspers.	Males bear brood pouch in Hippocampus
Examples	Scoliodon (Dog fish), Pristis (Saw fish), Carcharodon (Great white shark), Trygon (Sting ray)	Marine: Exocoetus (Flying fish), Hippocampus (Sea horse); Freshwater: Labeo (Rohu), Catla (Katla), Clarias (Magur); Aquarium: Betta (Fighting fish), Pterophyllum (Angel fish)

Characteristic features of Amphibians:

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Habitat: As their name suggests (from Greek, Amphi meaning dual and bios meaning life), amphibians can live in both aquatic and terrestrial habitats.

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Limbs: Most amphibians possess two pairs of limbs.

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Body Division: Their body is typically divisible into a head and a trunk. Some species may also have a tail.

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Skin: Amphibian skin is moist and lacks scales.

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Eyes: Their eyes are equipped with eyelids.

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Ear: A tympanum serves as their ear.

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Cloaca: The alimentary canal, urinary, and reproductive tracts all open into a common chamber called the cloaca, which then opens to the exterior.

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Respiration: Respiration in amphibians occurs through gills, lungs, and through their skin.

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Heart: They have a three-chambered heart, composed of two auricles and one ventricle.

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Body Temperature: Amphibians are cold-blooded animals.

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Sexes: Sexes are separate in amphibians.

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Fertilization: Fertilization is external

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Development: They are oviparous (egg-laying), and their development is indirect.

Examples of amphibians include Bufo (Toad), Rana (Frog), Hyla (Tree frog), Salamandra (Salamander), and Ichthyophis (Limbless amphibia)

Good morning, all, 

Day 3 summary

Porifera are parazoans (handicapped animals) as they lack neurons. The animal nature was established by Robert Grant.

Poriferans are mostly marine, exhibit cellular level of organization, and they are asymmetrical.

The characteristic feature of Porifera is Water Canal System which helps in gathering food, exchange of gases and removal of wastes.

Body of sponges is supported by Spicules made of either calcium carbonate or silica. it also has softer spongin fibers.

Sexes are not separate, and reproduction is asexual or sexual. Fertilization internal and development indirect with larval forms.

Spongilla is fresh water porifera, Euspongia is bath sponge.

Euplectella is Venus flower basket.

Good morning, all.

Day 2 Summary

Coelom plays a crucial role in the organization and functionality of animal bodies, especially in more advanced organisms such as Organ Development & Compartmentalization, Movement & Flexibility, Circulatory System Efficiency, Shock Absorption & Protection, and Space for Complex Structures. Based on type of Coelom, animals are categorized as 

Acoelomates - Body cavity is entirely filled with tissue as in Platyhelminthes (flat worms)

Pseudocoelomates - Mesoderm occurs as scattered pouches as in Aschelminthes (round worms)

True Coelomates - Body cavity lined by mesoderm as in Annelida and higher phyla

Again, true coelomates can be Schizocoelomates - coelom formed by splitting of mesoderm (Annelida, Arthropoda and Mollusca) or Enterocoelomates - coelom formed from out pouches of enteron. (Echinodermata, Hemichordata and Chordata). 

** All body cavities are not coeloms as they are all not lined by mesoderm. Coelom is a body cavity lined by mesoderm.

** In Porifera, body cavity is called Spongocoel and in Coelenterata, it is called Gastrovascular cavity.

** In organisms with open kind of circulatory system, body cavity is filled with blood and is called Haemocoel. 

In metameric segmentation (metamerism or true segmentation), body id divided into segments with serial repetition of at least some organs.

Complete segmentation (both internal and external) is found in Annelida whereas we can find external segmentation in Arthropoda and internal segmentation in Chordata.

** Pseudo segmentation is found in Tapeworms, the members belonging to phylum Platyhelminthes.

All Chordates shows presence of Notochord - a rod like skeletal element derived from mesoderm, during their embryonic development. In some members of Chordates, it is replaced by bony Vertebral column, and they are called Vertebrates.

"All Vertebrates are Chordates, but all Chordates are not Vertebrates"

Good morning students.

So, Day 1 concluded. We entered Animal Kingdom and trying to explore their amazing world. To summarize day 1 contents, we had a discussion on need for classification and the basis for classification.

1. Levels of structural organization: - Cellular (Porifera) - Tissue (Coelenterata and Ctenophora) - Organ (Platyhelminthes) - Organ System (all other phyla)

2. Body Symmetry: Radial Symmetry (Coelenterata, Ctenophora and adult Starfish) and Bilaterial Symmetry (all triploblasts and larval forms of snail and starfish)

*** adult Snail is asymmetrical while adult Star fish exhibits pentamerous radial symmetry.

3. No. of germinal layers: - Diploblasts (Coelenterata and Ctenophora) and Triploblasts (Platyhelminthes to Chordata).

you can find below the link to the chapter 'ANIMAL KINGDOM' from NCERT I PU Biology Textbook.

ANIMAL KINGDOM

Hi Dear Students. 

Welcome to my zoology blog! As your dedicated zoology teacher, I aim to stay connected with you beyond the classroom, offering insights, discussions, and valuable resources to deepen your understanding of the fascinating world of animals. Let's continue exploring and learning together!