# data[].attributes.body
These species are all related up to their class, chondrichthyes.   When it reaches the Order they all split off to different branches of the class chondrichthyes which is why all the exemplary species are different in some way.

# data[].attributes.body
live in shallow coastal waters

prefer estuaries and bays

long, narrow flattened head

snout lined with teeth that resemble a saw

feed on small fish, crabs, and shrimp

15 feet long

# data[].attributes.body
largest living ray

18 feet from wing tip to wing tip

live in warm salt water

prefer oceanic habitat over reef

travel vast distances

visit shallow reef seasonally

have pectoral 'wings', small dorsal fin, and a thin tail

mainly solitary

peaceful and graceful

diet consists of plankton

# data[].attributes.body
Live at tropical shorelines in highly populated areas

shallow, warm waters

can survive in fresh or salt water

7-11 feet long

thick, stout body

very aggressive

mainly eat bony fish

# data[].attributes.body
Over a long period of time, chondrichthyes have shown that they have descended with modifications.  For example, when sharks were still developing, they were many different shapes.  However, through natural selection more sharks developed the streamlined body that is seen today.  This demonstrates descent with modification because sharks with the streamlined body were faster and could catch prey better so they could survive and produce offspring.  This resulted in all sharks having a streamlined body.

# data[].attributes.body
When it comes to chondrichthyes, a small number of offspring, around one to two per birth, is favorable.  This is because when an organism only has few offspring, these offspring are more likely to have a higher fitness and will be able to survive longer. This shows directional selection because one extreme, very few offspring, is better for the survival of the species.

# data[].attributes.body
Chondrichthyes, especially sharks, experience non-random mating.  This means that they choose their mate for a specific reason.  In most cases the female will choose the male based on whichever one is the most dominant.  Male sharks will follow a female when she produces certain hormonal chemicals.  These chemicals signal to the males that she is ready to mate which will attract a few.  These sharks will then fight each other and whoever wins, wins the female.  Non-random mating affects evolution because it leads to stronger offspring.  If only the stronger, more desirable males are mating, their genes are passed down leading to the offspring having similar traits and the species becoming

# data[].attributes.body
65 million years ago

# data[].attributes.body
375 million years ago

# data[].attributes.body
145 million years ago

# data[].attributes.body
409 million years ago

# data[].attributes.body
Squalene
Squalene is a lipid found in the spleen of chondrichthyes  that reduces their body density.  Without this lipid is would require a lot of energy to stay at a certain water depth without sinking or floating up towards the surface.

Dentin sialophosphoprotein

This is a protein that makes up the teeth and placoid scales of chondrichthyes.  This protein is what makes the scales of these organisms completely different than those of bony fish.

# data[].attributes.body
380 million years ago

# data[].attributes.body
2.6 million years ago

# data[].attributes.body
The Class Chondrichthyes is an example of divergent evolution.  This is because this class diverged from another class, Osteichthyes, or bony fish, around 400 million years ago.  They split off before these fish had developed scales so they have completely different scales than bony fish do.

# data[].attributes.body
Speciation: Gradual
Chondrichthyes show gradualism because of how slowly they evolve.  They evolve so slowly in fact that it is hard to tell where one species stops and another begins.

# data[].attributes.body
Different types of sharks have different mating seasons and migrate to different regions to mate.  This prevents any two different species from mating with each other.

# data[].attributes.body
Bull Shark

Kingdom - Animalia

Phylum - Chordata

Class - Chondrichthyes

Order - Carcharhiniformes

Family - Carcharhinidae
Genus - Charcharhinus

Species - leucas

Giant Manta Ray
Kingdom - Animalia
Phylum - Chordata
Class - Chondrichthyes
Order - Rajiformes
Family - Mobulidae
Genus - Manta
Species - bitrosis

Knifetooth Sawfish
Kingdom - Animalia
Phylum - Chordata
Class - Chondrichthyes
Order - Pristiformes
Family - Pristidae
Genus - Anoxypristis
Species - cuspidata

# data[].attributes.body
Physical:
Cartilaginous Skeleton
Jaws
Placoid Scales
Pectoral Fins
Ampullae of Lorenzini

Chambered Hearts

Behavioral:

Most migrate seasonally

Social - form groups or schools with the same organisms

Some are very aggressive while others are very peaceful

Complex mating behaviors

Internal fertilization

Produce relatively few offspring

Habitat

Live in very diverse habitat

salt or freshwater

warm or cold water

shallow or deep water