Name: 學習英語 - 第1系列，第14集：垃圾DNA。 (Study English - Series 1, Episode 14: Junk DNA)
Uploaded: 2021-01-14T07:45:28.000Z
Duration: 10 min 1 s
Description: 【看影片學英語】數萬部 YouTube 影片，搭配英漢字典即點即查，輕鬆掌握單字發音與用法，長久累積看電影不必再看字幕。

Hello. I'm Margot Politis. Welcome to Study English, IELTS preparation.

Today we're going to look at conditional sentences. They're sentences that use 'if'.

情態副詞

If you listen carefully, you'll be able to hear Dr Malcolm Simons talking about junk

DNA, the parts of DNA that people used to think were just rubbish. Listen to the different

Under Darwinistic notions, you would think that junk would drop off under the theory

of natural selection, just like species drop off if they hit ecological niches, which is

incompatible with survival. If they can adapt to those niches, then those that can, survive,

and those that can't, die, is the notion. If you apply that to the DNA sequence, then

the coding region genes, which survive, have a function, and by the way the non-coding

sequences have survived as well. So the proposition would have to be that if they're there, they've

In listening to Dr Simons, you can hear that he uses a variety of sentences. This makes

for much more interesting language. You should practice using sentences of different lengths

Today we're going to look at one of the ways you can create complex sentences using an

An 'if clause' is a phrase that gives a condition that's necessary for something else to happen.

They're often called conditional clauses.

If means when, provided that, or on condition that.

There are a few basic patterns for the 'if clause'.

If they can adapt to those niches, then those that can, survive, and those that can't, die.

So the proposition would have to be that if they're there, they've got a function.

If they can adapt, then those that can survive.

The pattern here is: if + simple present tense verb, then &hellip;.

Then introduces a clause describing the consequences.

Look at the second example in the extract.

If they are there, they have got a function.

Notice that the then is left out in this example. Then is optional.

He could have said if they are there, then they have a function.

If you have a university education, then you have more opportunities.

But the then is optional - you can leave it out.

If you have a university education, you have more opportunities.

Notice that this pattern can be reversed.

You have more opportunities if you have a university education.

We never include then when the pattern is reversed like this.

Let's try with the example from the story.

They have got a function, if they're there.

OK, now here's the second pattern for 'if' sentences.

This is for when the suggestion is less definite, or less likely.

If you had a university education, then you would have more opportunities.

The pattern here is: if + past tense, then + would + verb.

We use this pattern when we are talking about the future, and about something that may not

If you study hard, then you will pass your test.

If you studied hard, then you would pass your test.

In the first example, it's a bit like making a useful suggestion.

The second sentence is less definite, and less polite. It suggests that the person doesn't

So that's 2 ways of making the conditional tense - how to say that one thing will happen,

or might happen, if something else happens. There are other forms of the conditional tense

If you learn them, then your English will improve!

OK, now we're going to look at ways of making opposites by using prefixes.

and those that can't, die, is the notion.

If you apply that to the DNA sequence, then the coding region genes, which survive, have

a function and by the way the non-coding sequences have survived as well.

In the passage we heard the words survive and die. They have opposite meanings.

'To survive' means to keep on living and 'to die' means to stop living. We call words with

Sometimes opposites are formed from the same word stem using prefixes. Two of the prefixes

And by the way the non-coding sequences have survived as well.

He calls the junk DNA the non-coding sequences.

Non-coding means not coding. Notice that we use a hyphen with the non- prefix.

It means 'not in the group of', so we have non-European, non-Aboriginal or non-government.

Non- can also just means not, giving a negative sense to a word - non-fiction, non-smoking

The prefix 'in' is used with adjectives as well. It also makes opposites, and means 'not'.

It forms words like: insignificant, not significant; inexpensive, not expensive; intolerant, not

We can have unfair, unattractive, unusual, unnatural.

But un- can also be used with verbs. It means that an action is reversed.

There aren't many rules about what sorts of words take these prefixes. You'll have to

A good way to do this is to try to find out the opposite every time you come across a

Finally for today, let's have a look at how you can form adjectives from people's names.

Darwinistic here is an adjective, but it's got a capital letter - do you know why?

Well, that's because It comes from the name 'Darwin' - referring to Charles Darwin, who

developed the theory of natural selection.

The -ic suffix forms adjectives that mean belonging to, or like. So 'Darwinistic' means