Natural Selection

Darwin's Observations

• On his journey Darwin studied a fossil of an extinct species of giant sloth. Where did it go? Why did it die out if there are still sloths alive today?

• On the Galapagos he noticed that on each separate island there were different species of finches that were similar but had slight variation in the shape of their beaks, their size, color and diet. Why were they all different?

• He also studied the species of tortoise found there. Some were small with short necks, and some where giant with long necks. Why??

Multiple Choice

Where did Charles Darwin travel to?

• Australia
• Barbados
• Galapagos 
• Trinidad

The Common Ancestor

• Darwin began to theorize that these species shared a common ancestor and through a process called natural selection adapted to the environment they were in.

• A common ancestor of the finches and tortoises must have been trapped on the Islands when sea levels rose and then adapted to the environment they were in.

• These adaptations made them different, even though they all came from a common ancestor.

Open Ended

Why did Darwin theorize that the finches were different on each island?

Natural Selection

• This adaptation Darwin called natural selection.

• Let's use the finches as an example. A species of blue finch that eats fruit inhabits a jungle. There's lots of food and the blue helps it find mates. The jungle is huge, it can easily escape predators.

• But then the sea rises, and the jungle becomes a bunch of islands. Some birds are stuck on big islands, some on small islands. On some islands there's lots of food, on some there is little food. On some there's lots of fruit, others nuts, on the next insects.

Multiple Choice

The process of a species adapting is called...

• overproduction

• mutations

• natural selection

"On the Origin of Species"

• Darwin put all his findings into a book entitled "On the Origin of Species".

• It caused waves in the scientific world and still remains one of the most important scientific books ever published.

• It also shook peoples understanding of how the world was made and where we came from.

• Darwin argued that all species were descended from a common ancestor, and, over time, thanks to changes in the environment, they had adapted and evolved to become the species they are today.

Multiple Choice

A variation that can help a species survive in its environment is called...

• a characteristic

• an adaptation

• its habitat

• competition

Multiple Choice

A mutation could result in a beautiful white tiger. The mutation is beautiful, but how would it affect the tiger's ability to survive?

• It would have no effect on the tiger's ability to survive.

• It would reduce his ability to survive in the wild.

• It would increase his ability to survive in the wild.

Multiple Choice

Based on the bird beaks, what kind of food would "D" most likely eat?

• Insects
• Seeds
• Nectur
• Fish

Multiple Choice

Based on the bird beaks, what kind of food would "E" most likely eat?

• Insects
• Seeds
• Nectur
• Fish

Multiple Choice

Which one of the following is not a reason why species adapt and change?

• too much food available

• producing too many young

• producing too many offspring

• competition for the same resources