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By the end of this section, you will be able to:
  • Describe the difference between jawless and jawed fishes
  • Explain the main characteristics of amphibians, reptiles, and birds
  • Describe the derived characteristics in birds that facilitate flight
  • Name and describe the distinguishing features of the three main groups of mammals
  • Describe the derived features that distinguish primates from other animals

Vertebrates are among the most recognizable organisms of the animal kingdom ( [link] ). More than 62,000 vertebrate species have been identified. The vertebrate species now living represent only a small portion of the vertebrates that have existed. The best-known extinct vertebrates are the dinosaurs, a unique group of reptiles, reaching sizes not seen before or since in terrestrial animals. They were the dominant terrestrial animals for 150 million years, until they died out near the end of the Cretaceous period in a mass extinction. A great deal is known about the anatomy of the dinosaurs, given the preservation of their skeletal elements in the fossil record.

Photo a shows a tiger and cub in the snow. Photo b shows a yellow frog with black spots sitting on a leaf. Photo c shows an eagle with a white breast, brown wings, and grey face.
Examples of critically endangered vertebrate species include (a) the Siberian tiger (Panthera tigris altaica ), (b) the Panamanian golden frog ( Atelopus zeteki ), and (c) the Philippine eagle ( Pithecophaga jefferyi ). (credit a: modification of work by Dave Pape; credit b: modification of work by Brian Gratwicke; credit c: modification of work by "cuatrok77"/Flickr)

Fishes

Modern fishes include an estimated 31,000 species. Fishes were the earliest vertebrates, and jawless fishes were the earliest of these. Jawless fishes—the present day hagfishes and lampreys—have a distinct cranium and complex sense organs including eyes, distinguishing them from the invertebrate chordates. The jawed fishes evolved later and are extraordinarily diverse today. Fishes are active feeders, rather than sessile, suspension feeders.

Jawless fishes

Jawless fishes are craniates (which includes all the chordate groups except the tunicates and lancelets) that represent an ancient vertebrate lineage that arose over one half-billion years ago. Some of the earliest jawless fishes were the ostracoderms (which translates as “shell-skin”). Ostracoderms, now extinct, were vertebrate fishes encased in bony armor, unlike present-day jawless fishes, which lack bone in their scales.

The clade Myxini    includes 67 species of hagfishes. Hagfishes are eel-like scavengers that live on the ocean floor and feed on dead invertebrates, other fishes, and marine mammals ( [link] a ). Hagfishes are entirely marine and are found in oceans around the world except for the polar regions. A unique feature of these animals is the slime glands beneath the skin that are able to release an extraordinary amount of mucus through surface pores. This mucus may allow the hagfish to escape from the grip of predators. Hagfish are known to enter the bodies of dead or dying organisms to devour them from the inside.

Photo a shows wormlike hagfish clustered in a muddy hole. Photo b shows leech-like sea lampreys latched onto a large fish.
(a) Pacific hagfishes are scavengers that live on the ocean floor. (b) These parasitic sea lampreys attach to their lake trout host by suction and use their rough tongues to rasp away flesh in order to feed on the trout’s blood. (credit a: modification of work by Linda Snook, NOAA/CBNMS; credit b: modification of work by USGS)

Questions & Answers

what are the factors effecting demand sedule
Kalimu Reply
we should talk about more important topics, you can search it on Google n u will find your answer we should try to focus on how we can improve our society using economics
shubham
so good night
hon
ways of improving human capital
kelly Reply
what is human capital
kelly
Capital can be defined as man made assets use in production .
Abdulai
What is the differences between central Bank And Commercial Bank ?. 2 for each
Abdulai
Two types of bank clearing house.
Abdulai
what are the most durable assets of a bank
Ngongang
What is Opportunity Cost?
Cephas Reply
may be defined as expression of cost in terms of forgone alternative.
Abdulai
Helloo, im new, can i get to know more?
Saniya Reply
You ask questions on any topics you find difficult.
Favour
What is opportunity cost?
Cephas
is price elasticity of demand the same as elasticity of demand
Favour Reply
not really
Victoria
hi
Gh
hello
Bhartendu
i hope everyone be ok
Gh
No
Hassan
please explain
Favour
No
William
explanations please
cleophas
price elasticity of demand is the reaction of customers /demand to price changes(increase or decrease) elasticity of demand is the reaction of prices brought about by the change in demand
Victoria
thank you
Favour
state the laws of demand and supply
William
dd: when price rises demand decreases whereas when price reduces dd rises ss: when ss rises the price rises and when ss decreases price also reduces. There is a positive relationship
Dhoonah
nice
Victoria
Draw a demand curve graph
William
though price elasticity and elasticity are used interchangeably, the demand can respond to income changes and prices of related goods as well.
Gurpalak
explain the difference between merit goods and public goods and show why it is possible for profit to be made in the supply of one of these types of good but not the other
Kavishek
Public goods are defined as products where, for any given output, consumption by additional consumers does not reduce the quantity consumed by existing consumers. Merit goods are, for example, education and to some extent the health-care. They are provided by state as "good for you".
ahmed
The ladies are doing much better than the men
Blacks
what happens when there is a shift in demand curve?
Favour
What is Specialization ? Explain in detail
Muhammad
any one ?
Muhammad
specialisation is a method of production whereby an entity focuses on the production of a limited scope of goods to gain a greater degree of efficiency.
Favour
It's ok
Muhammad
hello
Onome
yah
Abdulai
No. price elasticity of demand refers to the manna in which price of good demanded fluctuate mean while elasticity of demand explains the way consumer change in their willingness as they plan or purchase a good
Ngongang
diffirence between demand and supply
Bonny
what is economic
Seray Reply
It is a social science which studies human behavior as a relationship between ends and scarce which have alternative uses
Obeng
what is norminal wage
Demba Reply
is the wages measured in money as distinct from actual purchasing power
Favour
what is demand curve
Azeez Reply
this is a curve that slop downward from left to rich
Obeng
yes
Basanta
different between capital and wealth
Samuel Reply
Wealth refers to the amount of asset you have, while, capital is the amount of cash money you have with you now and willing to invest in any business.
Favour
What is scale of reference?
Finda Reply
What is monopoly?
Finda
It is the control of market by single seller or producer
Mayen
the exclusive possession or control of the supply or trade in a commodity or services
Brains
what is scarcity
Bonny Reply
scarcity means that the resources which we can produce goods and services relatives to wants for them.
Bonny
what is demand
Sophia Reply
demand means that's good demand according to your needs is called demand
Bonny
needs of people ar called demand
Francis
what's the difference between opportunity cost and production possibility curve?
Francis
apportunity cost means a goods which can be replace by other goods without any ease of saticfaction
Bonny
different between capital and wealth
Samuel
apportunity cost means the profit lose when one alternative is selected over other
Bonny
what is economocs
Bonny Reply
Economics is a science which studies human behaviour as a relationship between ends and scarce means which have alternative uses.
Abubakari
It deals with making choices in the face of scarcity
Abu
what is perfect complements?
Bilal Reply
explain the return to scale with the help of mathematical expression
Bilal
what is scarcity
Bonny
difference between fixed policy and monetary policies
Doris Reply
Difference between extinct and extici spicies
Amanpreet Reply
While the American heart association suggests that meditation might be used in conjunction with more traditional treatments as a way to manage hypertension
Beverly Reply
in a comparison of the stages of meiosis to the stage of mitosis, which stages are unique to meiosis and which stages have the same event in botg meiosis and mitosis
Leah Reply

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Source:  OpenStax, Concepts in biology (biology 1060 tri-c). OpenStax CNX. Jan 15, 2014 Download for free at https://legacy.cnx.org/content/col11617/1.1
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