a measure of improbability or 'surprise value'"?

Failed to understand "Darwinian is challenged to explain the source of all the information in living matter, in the technical sense of information content as a measure of improbability or 'surprise value'" clearly.

Grammatically, the sentence says:
...to explain the source as a measure (a scalable indicator) of improbalility?
And the language of the explanation should be in the technical sense (of information content/of what the information contains)?
Yes, Darwinian is challenged to answer this?

Context:


The creationist misappropriation of the argument from im-
probability always takes the same general form, and it doesn't make
any difference if the creationist chooses to masquerade in the
politically expedient fancy dress of 'intelligent design' (ID).* Some
observed phenomenon - often a living creature or one of its more
complex organs, but it could be anything from a molecule up to the
universe itself - is correctly extolled as statistically improbable.
Sometimes the language of information theory is used: the
Darwinian is challenged to explain the source of all the information
in living matter, in the technical sense of information content as a
measure of improbability or 'surprise value'. Or the argument may
invoke the economist's hackneyed motto: there's no such thing as a
free lunch - and Darwinism is accused of trying to get something
for nothing. In fact, as I shall show in this chapter, Darwinian
natural selection is the only known solution to the otherwise un-
answerable riddle of where the information comes from. It turns
out to be the God Hypothesis that tries to get something for
nothing. God tries to have his free lunch and be it too. However
statistically improbable the entity you seek to explain by invoking
a designer, the designer himself has got to be at least as improbable.
God is the Ultimate Boeing 747.