yam懂你英语 Level4 Unit2 Part1

2021年1月9日发(作者：裘海正)
L4-U2-P1 英语流利说 4-2-1 懂你英语 Level4 Unit2 Part1
L4-U2-P1-1 Listening : Extinction Events 1
The Earth was formed about 4.6 billion years ago.
The first life appeared about a billion years later.
The first plants didn't appear until around 2 billion years ago.
Until about 580 million years ago, life forms were small
and microscopic.
Since that time, life has evolved into many different types,
or species.
However, scientists estimate that more than 99% of them are
now extinct.
When did the first plants first appear on Earth
? -The first plants
didn't appear until around 2 billion years ago.
Since that time, life
has evolved
into many different
types
, or
species.
There have been several extinction events in the history of the Earth.
In an extinction event many life forms, or species of life, die out.
The causes of mass extinction events are unsolved mysteries.
These events are not predictable and can happen at any time.
Scientists think that some of them were started by asteroid
impacts or volcanic eruptions.
Events like these can change the global conditions that life depends
on.
What is an asteroid impact?
- It's when an asteroid collides with
something.
There have
been
several extinction
events
in the
history
of
the Earth.
One major extinction event happened about 66 million years ago.
That event may have been started by a large asteroid that hit the
Earth.
As a result, the dinosaurs and about half of all species on the planet
died out.
When the asteroid hit the earth, it started a chain of events.
A chain of events is a series of events linked together, like a chain.
What may have caused the extinction of the dinosaurs? -
An asteroid
hit the Earth and started a chain of events.
A
chain
of events is a
series
of events
linked
together, like
a chain.
This particular chain of events happened over a period of months and
years.
When the asteroid hit the Earth, it caused a huge cloud of dust to
enter the atmosphere.
This cloud of the dust blocked the sun and darkened the Earth for
many months.
Without enough sunlight, plants and plant-eating animals quickly
died.
With the deaths of so many plants and animals, the food chain
collapsed.
This led to the deaths of many more species.
What may have darkened the Earth for many months? -
This cloud of
the dust blocked the sun and darkened the Earth for many months.
(1) When the asteroid hit the Earth, it caused a huge cloud of dust
to enter the atmosphere.
(2) This cloud of the dust blocked the sun and darkened the Earth
for many months.
(3) Without enough sunlight, plants and plant-eating animals quickly
died.
(4) With the deaths of so many plants and animals, the food chain
collapsed.
This particular chain of events happened over a period of months
and years.
Mass extinction events have played an important part in the evolution
of life.
In fact, some extinction events have helped to accelerate evolution.
For example, some mammals lived through the age of the dinosaurs,
but they couldn't compete.
When the dinosaurs were removed, the mammals were able to compete
more successfully.
Once they could compete, mammals evolved to a higher state.
Without extinction events, perhaps we wouldn't be here today.
What may have blocked the evolution of mammals? -
Mammals couldn't
compete successfully with the dinosaurs, so their evolution was
blocked.
When the dinosaurs
were removed
, the mammals
were
able
to
compete
more successfully.
There have been several extinction events in the history of the
Earth.
These events are not predictable and can happen at any time.
With the deaths of so many plants and animals, the food chain
collapsed.
That event may have been started by a large asteroid that hit the
Earth.

Once they could compete, mammals evolved to a higher state.


L4-U2-P1-2 Listening : Extinction Events 2
Scientists estimate that there have been at least 5 mass extinctions
in the last 540 million years.
They also believe that we have entered a new extinction event.
Species are becoming extinct at a much faster rate than before.
Instead of asteroids or volcanic eruptions, the current event is the
result of human activities.
Human activities, for example, have led to global warming.
What is causing the current mass extinction event?
-This new
extinction event is caused by humans.
Global warming is the result of an increase in carbon gases in our
atmosphere.
These gases
trap heat
from the sun, so the Earth is getting warmer.
As a result, sea levels are rising and weather patterns are changing.
In addition, we humans are destroying the
habitats
of many plants
and animals.
Cutting down forests and polluting rivers destroys the habitats of
many forms of life.
What traps heat from the sun?
- Carbon gases in the atmosphere
trap heat from the sun.
Cutting down
forests
and polluting
rivers
destroys
the
habitats
of many
forms
of life.
There is no longer any doubt that this is happening.
Species of life are disappearing at an increasing rate.
Global temperatures are rising and weather patterns are changing.
Scientists are warning us that fast action is necessary to save our
future.
If we don't act, we may go the way of the dinosaurs.
There is no longer any
doubt
that this is happening.
If we don't act, we may go the way of the dinosaurs.
Species of life are disappearing at an increasing rate.
Scientists are warning us that fast action is necessary to save our
future.

Global warming is the result of an increase in carbon gases in our
atmosphere.


L4-U2-P1-3 Vocabulary : Body Systems
The body's circulatory system includes the heart and blood
vessels.
The heart pumps blood to all parts of the body through a network
of arteries and veins.
The digestive system breaks down and absorbs food into the
body.
It supplies the energy that the body needs for growth and repair.
After digestion, excess food is turned into waste and eliminated
from the body.
The nervous system includes the brain, spinal cord and nerves.
This is your body's control system.
It controls your muscles and organs, including your circulatory and
digestive system.
The respiratory system includes the nose and lungs.
It brings air and oxygen into the body and removes carbon dioxide.
The lungs are where oxygen enters the bloodstream, and carbon
dioxide is removed.
The immune system protects the body
against infections and diseases.
Sneezing and fever are examples of how the immune system works.
If an infection invades the body, the immune system attacks it.