Sharks 101
Transcript
They glide through the water with unmistakable grace, remnants of an ancient past, they dive and they rise from the ocean’s murky depths to it’s sun-kissed shallows, rousing fear and awe like no other creature in the sea.
The world’s biggest living fish is a shark.
Of the estimated 34,000 species of fish, the largest are whale sharks.
These gentle giants usually grow to about 40 feet long and weigh an estimated 15 tons.
Their mouths alone can span four feet wide.
The gigantic whale shark however, pales in comparison to the largest fish that ever existed, the megalodon.
Dating to over 20 million years ago, it’s thought that the prehistoric shark could have reached 80 feet long, weighing up to around 70 tons.
Unlike whale sharks, the megalodon was carnivorous, and consumed any creature that fit into it’s nearly 10 foot wide mouth.
Throughout their lives some species of shark can shed over 30,000 teeth.
Unlike humans who are born with a set number of teeth in their jaws, sharks have a seemingly limitless supply.
They can grow, lose, and replace their teeth as needed.
Furthermore, most sharks have multiple rows of teeth in their jaws.
The jaws of a great white shark, the largest predatory fish in the sea, can contain up to seven rows that hold up to 300 teeth at any one point.
Most sharks, as they hunt their prey, end up losing their teeth individually.
However, the cookiecutter shark loses and replaces the teeth in it’s lower jaw all at once.
Sharks are built for speed.
The fastest known shark, the mako shark, can reach speeds of up to 46 miles per hour.
This speed is largely due to their body’s hydrodynamic design.
Many sharks have torpedo-shaped heads that allow them to cut through the water with little resistance.
Plus, shark skin is covered with flat, v-shaped scales, called dermal denticles.
The denticles help water flow smoothly over the skin, which reduces friction and helps sharks swim quickly and quietly.
Sharks also have skeletons made of cartilage instead of bone.
Cartilage is a much lighter material than bone so sharks have less weight to carry.
Sharks may lay eggs, or bear live young.
Egg-laying sharks only lay a few large eggs.
They may come in various forms, such as sacks called mermaid purses or corkscrews.
These eggs act as external wombs in which shark embryos complete their development.
However, most sharks give birth to live young.
Called pups, the young of most live-bearing species gestate for around one year.
Some even begin practicing their predation skills while in the womb.
Before they are born, the sand tiger shark pups compete with their siblings.
In fact, the strongest pup in each of the two wombs devours its weaker brothers and sister.
Some sharks are at risk of extinction.
Every year an estimated 100 million sharks are killed worldwide, in large part for the shark fin trade.
The sharks are caught and their dorsal fins are removed and sold at a hefty price, primarily in Asia.
In traditional Chinese culture, serving and eating shark fin is a sign of status and wealth.
Because of the high demand and value of shark fins, some shark populations have plummeted by up to 70% causing a ripple effect in ecosystems and endangering at least 74 shark species.
However, measures are being taken to protect sharks with a number of countries and jurisdictions cracking down on unsustainable shark fishing.
In China, shark fin soup is no longer allowed to be served at government banquets, a move hailed by shark conservationists.
Through continued international conservation efforts, the loss of sharks may be curbed, allowing the creatures in all their power and grace to survive for many generations to come.
Vocabulary List
glide
(verb) to move smoothly and effortlessly
unmistakable
(adjective) impossible to mistake for something else
grace
(noun) a simple and beautiful quality
remnant
(noun) a small remaining part of something
murky
(adjective) dark and unclear
sun-kissed
(adjective) having an attractive appearance from exposure to the sun
rouse
(verb) to make somebody feel a particular emotion
awe
(noun) a feeling of great respect and liking for someone or something
span
(verb) to extend over a distance
carnivorous
(adjective) eating meat
shed
(verb) to lose hair, skin, leaves etc. naturally
seemingly
(adverb) appearing to have a particular quality
prey
(noun) an animal hunted or killed for food
largely
(adverb) mostly or mainly
scale
(noun) any of the small flat pieces of skin that cover the bodies of fish, snakes etc.
live-bearing
(adjective) of or relating to animals that give birth to live young, rather than laying eggs
gestate
(verb) to carry a fetus or young in the womb until it is ready to be born
predation
(noun) the act of preying on or killing another animal for food
devour
(verb) to eat something hungrily and greedily
extinction
(noun) the state or process of becoming extinct
trade
(noun) the buying and selling of goods and services
hefty
(adjective) large; larger than usual or expected
plummet
(verb) to decrease in value or amount suddenly and quickly
endanger
(verb) to put in danger or harm
measure
(noun) an action intended to deal with a particular problem
hail
(verb) to describe someone or something as being very good
curb
(verb) to control or restrain
Grammar Lesson
In this lesson, we will:
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observe subject-verb agreement of sentences in the video
Remember:
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We use singular verbs for singular subjects.
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We use plural verbs for plural subjects.
The world’s biggest living fish is a shark.
The world’s biggest living fish = singular subject
is = singular verb
These gentle giants usually grow to about 40 feet long and weigh an estimated 15 tons.
These gentle giants = plural subject
grow = plural verb
The gigantic whale shark however, pales in comparison to the largest fish that ever existed, the megalodon.
The gigantic whale shark = singular subject
pales = singular verb
Unlike whale sharks, the megalodon was carnivorous, and consumed any creature that fit into it’s nearly 10 foot wide mouth.
the megalodon = singular subject
was = singular verb
Unlike humans who are born with a set number of teeth in their jaws, sharks have a seemingly limitless supply.
sharks = plural subject
have = plural verb
Furthermore, most sharks have multiple rows of teeth in their jaws.
Most sharks, as they hunt their prey, end up losing their teeth individually.
most sharks = plural subject
have = plural verb
end up = plural verb
However, band replaces the teeth in it’s lower jaw all at once.
the cookiecutter shark = singular subject
loses = singular verb
Sharks are built for speed.
Sharks = plural subject
are = plural verb
This speed is largely due to their body’s hydrodynamic design.
This speed = uncountable noun (singular subject)
is = singular verb
Plus, shark skin is covered with flat, v-shaped scales, called dermal denticles.
shark skin = uncountable noun (singular subject)
is = singular verb
The denticles help water flow smoothly over the skin, which reduces friction and helps sharks swim quickly and quietly.
The denticles = plural subject
help = plural verb
Cartilage is a much lighter material than bone so sharks have less weight to carry.
Cartilage = uncountable noun (singular subject)
is = singular verb
Egg-laying sharks only lay a few large eggs.
Egg-laying sharks = plural subject
lay = plural verb
These eggs act as external wombs in which shark embryos complete their development.
These eggs = plural subject
act = plural verb
Some even begin practicing their predation skills while in the womb.
some = plural subject (referring to young sharks mentioned in the earlier sentence)
begin = plural verb
Before they are born, the sand tiger shark pups compete with their siblings.
the sand tiger shark pups = plural subject
compete = plural verb
In fact, the strongest pup in each of the two wombs devours its weaker brothers and sister.
the strongest pup in each of the two wombs = singular subject (referring to one pup)
devours = singular verb
Every year an estimated 100 million sharks are killed worldwide, in large part for the shark fin trade.
an estimated 100 million sharks = plural subject
are = plural verb
Because of the high demand and value of shark fins, some shark populations have plummeted by up to 70% causing a ripple effect in ecosystems and endangering at least 74 shark species.
some shark populations = plural subject
have = plural verb
However, measures are being taken to protect sharks with a number of countries and jurisdictions cracking down on unsustainable shark fishing.
measures = plural subject
are = plural verb
In China, shark fin soup is no longer allowed to be served at government banquets, a move hailed by shark conservationists.
shark fin soup = uncountable noun (singular subject)
is = singular verb