Summary
This ESL lesson for C1 English students explores Paleontology and evolution. Using a real video as the basis for discussion, students develop reading and listening comprehension, vocabulary, and grammar skills across a 90-minute class.
The grammar focus is Using present participle (-ing) phrases. Key vocabulary includes prospered (verb), encompassing (verb (participle)), spurred (verb) and more, all drawn directly from the source material. The practical English section gives students useful phrases for real-life situations: You are in a university seminar or a museum tour, discussing scientific theories about the past. You need to express how sure you are about your claims..
Activities
- A warm-up discussion to activate prior knowledge and get students thinking about the topic before watching or reading.
- Comprehension exercises based on the video to check understanding of the main ideas and key details.
- A grammar focus on Using present participle (-ing) phrases. At an advanced level, we often use present participle phrases to add information to a sentence concisely. These phrases act like adjectives or adverbs.
- Vocabulary expansion with advanced expressions related to Paleontology and evolution not found in the source material.
- Practical English phrases for You are in a university seminar or a museum tour, discussing scientific theories about the past. You need to express how sure you are about your claims., with exercises to practise using them naturally.
- A speaking task where students role-play a real-world scenario, applying vocabulary and phrases from the lesson.
A procession of segmented creatures moves across the sea floor.
Up ahead, hundreds have begun shedding their exoskeletons
and piling on top of one another in what appears to be... a massive orgy.
But this is not some alien world.
It’s Earth about 500 million years ago,
when these creatures, called trilobites, prospered.
Prevailing for around 270 million years
and encompassing more than 20,000 distinct species,
trilobites are some of the most successful lifeforms in Earth’s history.
When they sprung into existence,
they were among the most diverse and sophisticated organisms
Earth had yet seen.
And, as the earliest known animals with complex eyes,
trilobites had a unique perspective on the ancient world.
For almost all of Earth’s history before the rise of the trilobites,
life had mostly consisted of microscopic marine organisms.
But then, scientists think an increase in oxygen allowed multicellular lifeforms
to extract more energy from their food and perform more complex functions.
This then enabled the rise of carnivores,
which in turn spurred a productive arms race,
resulting in what’s known as the Cambrian explosion.
Within about 20 million years,
life had branched out to include most of the animal groups we know today.
Trilobites were an important part of this surge.
All trilobites had three lengthwise lobes,
but building off the same basic components,
they varied greatly.
Species ranged in length from a few millimeters to almost one meter
and some were equipped with intriguing ornaments.
As a result, they filled many distinct niches over the ages.
Many trilobites plowed or burrowed into the sea floor while others swam freely.
Certain species had spines, horns, and even protruding tridents.
And their social behavior was complex:
they came together to search for food, find safety in numbers, migrate and mate.
In fact, their fossilized conga lines represent
some of the first evidence of animal group behaviour.
Like modern arthropods,
trilobites had compound eyes composed of many tiny lenses.
But theirs were made of the mineral calcite,
which also constituted their exoskeletons.
These lenses allowed trilobites to form sharp images
and quickly sense changes in light.
Some had long eye stalks that helped them peep above the muddy sea floor
as they burrowed beneath.
Others had large dragonfly-like eyes
that they probably used to scour the ocean bottom
as they swam upside-down in dim waters.
And some trilobites had pillar-like eyes that may have offered 360 degree views,
along with structures that provided shade from overhead light.
Yet despite their dominance of the seas,
trilobites were vulnerable to environmental changes and predators.
About 444 million years ago, Earth cooled and sea levels dropped,
radically changing some of their habitats.
This was the beginning of what would prove to be the trilobite’s long demise.
Some 20 million years later, fish with jaws began sweeping the sea.
Trilobites developed spiky ornamentation
and neat ways of locking their joints shut.
Many species could curl themselves into balls,
entirely sealing their soft parts inside their hard exoskeletons.
Then, another extinction event shook the world.
Trilobite diversity dwindled, and come about 360 million years ago,
only one of the 10 former trilobite orders remained.
Finally, rapid climate change spurred
the greatest known mass extinction event in Earth's history.
This catastrophic period finished the trilobites off—
along with approximately 96% of all marine species.
But trilobites left a remarkable record behind.
Their calcite exoskeletons made for hardy fossils
that would remain intact for hundreds of millions of years to come.
We’ve found trilobite fossils on every single continent—
many in unlikely environments that were once part of the ocean floor.
Trilobites have no direct descendants,
but their evolutionary cousins are alive and well.
And since arthropods make up over 80% of current animal species,
we might say that, although Earth may no longer be the planet of the trilobites,
their distant relatives still reign supreme.
Vocabulary focus
The vocabulary section introduces C1-level words and phrases related to Paleontology and evolution. Key terms include prospered (verb), encompassing (verb (participle)), spurred (verb), niches (noun), constituted (verb). Students practise using these terms in context through exercises drawn from the source material.
Grammar focus
This lesson focuses on Using present participle (-ing) phrases. At an advanced level, we often use present participle phrases to add information to a sentence concisely. These phrases act like adjectives or adverbs.
Trilobites & Evolution: C1 Modals of Speculation
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