Chondrichthyes and Osteichthyes | Animal kingdom | Biology | Khan Academy

Summary

In this Khan Academy video, the differences and similarities between two classes of fish, Chondrichthyes and Osteichthyes, are explored. Both classes fall under the umbrella of fish, yet exhibit distinct characteristics. Chondrichthyes, comprising species like the great white shark, have cartilaginous skeletons and a ventral mouth, while Osteichthyes, like goldfish, possess bony skeletons and terminal mouths. The video explains the contrasting gill structures, scales, buoyancy mechanisms, and modes of reproduction in these aquatic classes. Both fish have two-chambered hearts and are cold-blooded. While Chondrichthyes practice internal fertilization and are viviparous, Osteichthyes reproduce through external fertilization and are oviparous.

Highlights

• Chondrichthyes, such as sharks, have skeletons made of cartilage. 🎣
• Osteichthyes, including goldfish, have skeletons composed of bone. 🐟
• Gill slits vs. operculum: a unique structural difference between Chondrichthyes and Osteichthyes. 🌬️
• Unique scales: placoid scales for Chondrichthyes and cycloid/ctenoid scales for Osteichthyes. 🔍
• Swimming strategies: no swim bladders in Chondrichthyes vs. air bladders in Osteichthyes for maintaining depth. 🌊
• Chondrichthyes require constant movement to stay afloat. 🏊
• A shared feature is their two-chambered hearts, distinct from the four-chambered human heart. ❤️
• Both classes cannot regulate body temperature, being cold-blooded like many other fish. ❄️
• Reproductive strategies differ, with internal fertilization in Chondrichthyes versus external in Osteichthyes. 🐣

Key Takeaways

• Chondrichthyes have cartilaginous skeletons, while Osteichthyes have bony ones. 🦴
• Great white sharks (Chondrichthyes) have ventral mouths, unlike goldfish (Osteichthyes) with terminal mouths. 🦈🐠
• Both fish classes have gills but vary in structure: Chondrichthyes feature gill slits, while Osteichthyes have an operculum covering the gills. 🌊
• Different scale types: Chondrichthyes have placoid scales (tooth-like), while Osteichthyes may have cycloid or ctenoid scales. 🐟
• Chondrichthyes lack swim bladders and must swim to maintain buoyancy, whereas Osteichthyes use swim bladders for buoyancy. 🏊‍♂️
• Both classes possess a two-chambered heart and are cold-blooded (poikilothermic). ❤️❄️
• Reproductive differences: Chondrichthyes are viviparous with internal fertilization, whereas Osteichthyes are oviparous with external fertilization. 🥚

Overview

Fish are fascinating, and in this video, we delve into two classes: Chondrichthyes and Osteichthyes, like comparing sharks to goldfish. Both are undeniably fish but differ in many intriguing ways. Chondrichthyes sport cartilaginous skeletons and awkwardly positioned ventral mouths, while Osteichthyes exhibit bony skeletons and terminal mouths. Learning about fish anatomy has never been so entertaining with these underwater marvels!

A curious part of our exploration is how these fish breathe and remain buoyant in water. While both classes utilize gills, the structures differ uniquely. Chondrichthyes have open gill slits, whereas Osteichthyes enjoy the operculum's protection. Not to forget their scales! From tooth-like placoid scales in Chondrichthyes to the varied cycloid and ctenoid scales in Osteichthyes, skin armor comes in many forms. Plus, sustaining buoyancy is quite an art—Chondrichthyes swim non-stop, whereas Osteichthyes adjust their swim bladders.

When it comes to matters of the heart and reproduction, both classes have two-chambered hearts but diverge significantly in reproduction. Chondrichthyes engage in internal fertilization, bringing forth live young, while Osteichthyes depend on external fertilization and egg-laying. Poikilothermic as they are, these fish can't regulate their body temperature and conform to their aquatic environments. Clearly, fish biology blends complexity with marvel.

Chapters

• 00:00 - 00:30: Introduction to Chondrichthyes and Osteichthyes The chapter explores the similarities and differences between two classes of fish: Chondrichthyes and Osteichthyes.
• 00:30 - 01:00: Body Structure and Streamlined Shape The chapter titled "Body Structure and Streamlined Shape" focuses on the concept of streamlined body shapes found in both marine and freshwater fish. It explains how having a streamlined shape reduces resistance when moving through water and air, similar to designs used in airplanes and cars.
• 01:00 - 02:00: Differences in Skeletons and Mouth Positions The chapter discusses the differences between two types of fish based on their skeletal structure and mouth position. The 'Condric Thies' have skeletons made of cartilage, as indicated by the term 'control,' meaning cartilage. In contrast, the 'Ostic Tease' have skeletons made of bone, as suggested by 'osto,' meaning bone. Additionally, the chapter notes the position of the mouth, stating that fish in the 'Contrac Tees' group have their mouth positioned at the bottom of the body.
• 02:00 - 03:00: Gill Structures This chapter discusses the anatomical structures of gills, specifically focusing on the position of the mouth and gill slits in certain organisms. It explains the distinction between the ventral and dorsal sides of these organisms, noting that while some have a ventral mouth, others may have their mouth positioned at the tip of the head.
• 03:00 - 04:00: Types of Scales This chapter discusses the types of scales and anatomical features found in fish, focusing on gills and their differences among species. It mentions the presence of gill slits, which are openings in the skin through which gills can be accessed. The chapter appears to compare these features between different types of fish, possibly osteichthyes (bony fish) and another group, although the comparison isn't fully specified in the provided transcript.
• 04:00 - 05:00: Buoyancy Mechanisms The chapter 'Buoyancy Mechanisms' discusses the anatomical features of fish that play a role in buoyancy and survival. It mentions the gills and the operculum, which covers the gills. It also contrasts the types of scales found in different fish, specifically noting that chondrichthyans (cartilaginous fish) have scales with projections similar to teeth.
• 05:00 - 06:00: Heart Chambers and Thermoregulation The chapter discusses different types of scales found in ostriches, focusing on their structures and characteristics. The primary focus is on cycloid scales, which are circular in shape. Another type of scale is mentioned, which resembles the cycloid scale but differs by having teeth-like structures similar to a comb.
• 06:00 - 08:00: Reproductive Differences The chapter 'Reproductive Differences' introduces the concept of tenoid scales, explaining their name origin from a comb-like structure. It contrasts these scales with black oil scales that form teeth, like the tiny scales in a shark's mouth which are modified plaque scales. The narrative progresses to discuss the buoyancy mechanisms of ostic thies.

Chondrichthyes and Osteichthyes | Animal kingdom | Biology | Khan Academy Transcription

• 00:00 - 00:30 this big scary animal and this tiny little thing both of them are fish so how are they similar and how are they different that's what we are going to explore in this video the great white shark belongs to the class convictis and the Goldfish belongs to the class or stick these both of which are fish all the members of convictis including the great white shark they are Marine that means they live in the seas
• 00:30 - 01:00 and in the ocean whereas in austik these you find both Marine and fresh water varieties both the types of fish have a streamlined body a streamlined body has this type of a shape which provides minimum resistance when something is moving through water and in air and it's a similar shape that can be found in airplanes and in cars as well if you
• 01:00 - 01:30 look at their skeletons the condric thies have a cartilaginous skeleton so their skeleton is made of cartilage control means cartilage and osto means bone so the skeleton in ostic tease is made of bone the fish in contractes have a mouth at the bottom if you consider this as a top of the body and this bottom the underside of the body the mouth is
• 01:30 - 02:00 present on the underside and that's the ventral side so contract these have a ventral mouth this is a ventral side while that is the dorsal side so the mouth is on the ventral side and the austrates their mouth is neither dorsal nor ventral it is at the end at the very tip of their head so they are set to have
• 02:00 - 02:30 a terminal mouth [Music] as far as gills are concerned both are fish and hence both have gills but in contract these they have these things these are slits In Their Skin and they are called Gill slits [Music] and if you go inside the slits that's where the gills are present whereas in austick these these right here are the
• 02:30 - 03:00 gills so these are the gills whereas on top of the gills there is discovering which is the operculum so gill slits and operculum next we come to the scales so the two fish have different types of scales which look different the condrict these they have these scales which have a projection kind of like a tooth these scales are
• 03:00 - 03:30 called [Music] placoid scales ostriches have several different types of scales the commonest forms are the one on the left here is a cycloid scale so it's circular hence the name is cycloid and the this other scale kind of looks like the cyclot scale but they have these teeth like a comb and are
• 03:30 - 04:00 called tenoid scales 18 stands for a comb hence they are called tenoid scales in contract these the black oil scales also form teeth so the scarity that you see in the mouths of sharks those are actually nothing but modified plaque scales now we come to the question of how they stay afloat ostic thies have a
• 04:00 - 04:30 swim bladder or an air bladder so you see how the size of the swim bladder is decreasing so the fish can control that it can control the amount of air that is contained inside the bladder if the amount of air is less the fish goes towards the bottom and if there's more air the fish floats towards the top so how about the convictis the convictes don't have any swim bladders or air
• 04:30 - 05:00 bladders so if they want to stay afloat or if they want to maintain their depth then they have to keep swimming so they have to keep swimming in order to maintain their depth that doesn't mean that if they stop swimming they'll die it's just that if they don't swim they tend to go towards the bottom of the sea a big similarity between these two classes of fish is the presence of a two-chambered heart so this chamber here
• 05:00 - 05:30 is an atrium and this is a ventricle so we have Atria and ventricles too but in us there are two atria and two ventricles whereas in fish there is only one of each type both the types of fish are [Music] boy kilo thermic
• 05:30 - 06:00 that means cold-blooded so neither chondrictis nor ostriches can regulate their body temperature so we human beings we can keep our body temperature at around 37 degrees Celsius no matter what season or what part of the earth we are in but the fish they cannot do that depending on what environment they are in their body temperature fluctuates hence they are called poiculothermic or cold-blooded
• 06:00 - 06:30 coming to reproduction their sexes are separate that means male and female individuals are separate and that's true for both chondrictes and ostriches in contract these fertilization is internal that means the egg is there in the female body and the sperm comes in and fertilizes the Egg and these fish the contractes they give birth to young ones [Music]
• 06:30 - 07:00 so these are young ones since they give birth to young ones they are called Vivi Paris and the fertilization is internal [Music] what about ostick these in ostic teas
• 07:00 - 07:30 before fertilization itself they lay eggs [Music] so they lay eggs in the water hence they are called oviparous oviparous is animals which lay eggs whereas rivers or animals which give birth to young ones so since the eggs are laid outside the fertilization has to happen outside the sperms come in and fuse with the
• 07:30 - 08:00 eggs in the water itself and hence the fertilization is external [Music]