"What Darwin Never Knew" Video Worksheet

The gene in humans was radically different from that found in chimps. There had been a large series of (mutation).

mutation

The (answer) molecule is one of the real secrets of life. It's a perfect system for storing the vast amounts of information that's necessary for building all kinds of creatures.

DNA

But one port of call on Darwin's voyage proved more important than all the others: the (answer). This cluster of 13 isolated islands lies 600 miles off the coast of Ecuador, in the Pacific Ocean.

Galapagos islands

The pattern that Darwin saw was that the creatures that survived were those best (answer) to the specific environments they lived in.

adapted

Charles was offered a place on the British Navy ship, The H.M.S. (answer), whose mission was to survey the waters around South America.

beagle

The (answer) genes determine where the head goes; where the limbs go, and what form they take: whether they are arms, legs or wings.

body plan

Ultimately one type of (answer) could be transformed into something utterly different. It's a process Darwin called "descent with modification.

creature

It's not the genes you have but how you use them that creates (answer) in the animal kingdom.

diversity

Originally, there must have been just one type of (answer) on the Galapagos, but over time it had diversified into many kinds, with different beak shapes; the same for the tortoises. One type of (tortoise) must have turned into many kinds, with different shells depending on which island they lived on.

finch; tortosie

If Darwin were right, somewhere out there, there had to be a transitional form, a fossil that was part (answer), but had the beginning of (answer).

fish; legs

These genes determine where the (answer) and the (answer) of the animal's going to be; the top, the bottom; the left, the right; the inside, the outside; where the eyes are going to be; where the legs are going to be; where the gut's going to be; how many fingers they're going to have.

front; back

Amazingly, in all four limbed animals, even us, exactly the same (answer) create the long, upper arm bone.

genes

Oftentimes, the origin of whole new structures in evolution don't involve the origin of new (genes) or whole new genetic recipes. Old genes can be reconfigured to make marvelously wonderful new things.

genes

Switches are not (answer). They don't make stuff like hair, cartilage or muscle, but they turn on and off the genes that do.

genes

Basically, you can make (answer) changes, just changing those switches. So a (answer) change, a couple of D.N.A. letters, could have a profound effect.

massive; small

But eventually, hunting through the vast stretch of D.N.A. that does not code for proteins, he found it, a section of D.N.A. that had (answer) in the lake stickleback. These mutations meant that the switch was broken. It didn't turn on the gene that makes spikes.

mutated

(answer) is a critical ingredient in the recipe for evolution. Without mutation, everything would stay constant, generation after generation. Mutation generate (answer) differences between individuals.

mutation; variation

These variations accumulate and eventually new species branch off. This is evolution by (answer). It is one of the keys to how new species are formed.

natural selection

It all goes back to Darwin's idea of the tree of life, that all life-forms are ultimately (answer), and from the earliest common ancestor, over billions of years, they have (answer) and diversified, so that creatures that started out looking the same, evolved to become completely different.

related; changed

In total, he has found some 21 different mutations responsible for microscopically. Sometimes, one of the D.N.A.'s chemical letters is (answer) with another letter, sometimes letters are (answer) entirely, but whatever the defect is, they all stop the brain cells from dividing at a very early stage of development.

replaced; missing

Darwin had this amazingly bold idea: the tree of life—that all (answer) were connected.

species

Scientists now realize that not all genes are created equal. Some make the stuff of our bodies, and (answer) are needed to turn many of these stuff genes on and off. The (answer) genes are what throw these switches, which tell the stuff genes what to do and when.

switches; body plan

This was a revelation. The same genes were responsible for the beaks in all types of finch. Any differences were in (answer) and (answer).

timing; intensity

Tiktaalik is a perfect (answer) form. Much of its body is that of a fish. It's covered in scales. But it also had something very un-fishlike, an arm-like fin, or, perhaps, a fin-like arm. Tiktaalik had the bone structure that is seen in the arms and legs of every (answer) limbed animal: one big bone at the top; two bones underneath, leading to a cluster of bones in the wrist and ankle.

transitional; four-limbed

When she looked at that D.N.A. in chimps and compared it to the same D.N.A. in a chicken, it was different in just (answer) letters. But in humans it was different by (answer) letters. A massive mutation.

two; eighteen

Hox genes have been found in all complex animals, from the velvet worm that dates back some 600 million years, to the modern human. And in all that time, the letters of their D.N.A. have remained virtually (answer).

unchanged

Darwin realized that (answer) must be the starting point for change in nature. In any generation, the animals in a litter are never quite the same. And in the wild, such a tiny (answer) might make all the difference between life and death.

variation

People were freaked out by the relatively small number of genes. It's down to something like (answer) protein-coding genes in a human genome

22000-23000

One percent may not sound like much, but it's still some (answer) of D.N.A.'s chemical letters: As, Ts, Cs and Gs.

30 million

Given all the obvious differences between humans and chimps, you might expect our D.N.A. to be really different. But, in fact, it's more like (answer) percent identical

99%