Changes Over TimeChapter 5 Section 1: Darwin’s Voyage

Charles DarwinCharles Darwin was an English naturalist on the British naval ship HMS Beagle

A naturalist is a person who studies the natural world

On Darwin’s journey, he made many observations that led him to develop the theory of Natural Selection

Charles DarwinDarwin’s first stop was South AmericaIn Brazil, Darwin saw amazing creatures, like giant insects and armadillos

Charles DarwinThere is a huge amount of diversity in South America

There are many different species of animals and plants

A species is a group of similar organisms that can mate with each other and produce fertile offspring

If the offspring is not fertile, the parents are not the same species Horse + Donkey = Mule (not fertile)

There are 2.5 million species of organisms on Earth!!

The Galapagos Islands

Darwin’s next stop was the Galapagos Islands, off of the west coast of South AmericaHere Darwin encountered the giant tortoise

The Galapagos Islands

Darwin observed that many of the plants and animals on the Galapagos were similar to the ones on the mainland.BUT…there were some key differences

Eg The comorants on the mainland could fly, but those on the Galapagos couldn’t

The Galapagos Islands

The iguanas of the Galapagos have large claws so they can grip slippery rocksThe iguanas on the mainland had smaller claws so they can climb trees

The Galapagos Islands

Darwin realized that some how, these animals came from the mainland and eventually started to become different from their “distant cousins”These organisms began to adapt…

AdaptationsAn adaptation is a trait that helps an organism survive and reproduceDarwin observed birds called finches.There were different types of finches that Darwin studied, each with a different shape beak

AdaptationsFinches have different beaks to help them eat their food.Large wide beaks to crack hard seedsLong sharp beaks to hunt and eat insects

Evolution“Survival of the fittest”Darwin believed that species gradually change over time…this is EvolutionSpecies change and adapt so that they can survive when their environments change

Natural Selection

In 1859, Darwin wrote the book The Origin of Species

In this book, Darwin explained that evolution happens because of natural selection

Natural Selection is the process by which individuals that are better adapted to their environment are more likely to survive.

What Affects Natural

Selection?Overproduction

Some species have many babies at one time

Example: Sea turtles lay 100s of eggs

With so many offspring produced, there won’t be enough resources for all of the baby sea turtles**Remember** All organisms need food, water and living space

What Affects Natural

Selection?Competition

If there are not enough resources, organisms will have to compete for food, water, and a place to liveSome times there are fights for territorySome times it’s a competition of “who can run the fastest” from predators

**Remember** The masked booby chicks that fight to see who will be the one to survive

What Affects Natural

Selection?Variations

A variation is a difference in traits that members of the same species may have.

Examples of variations:Parrots with different colorsTurtles that swim faster than others

What Affects Natural

Selection?Selection

Some individuals are better adapted to their environment than others because of their traits

They are the ones that are “selected” to survive and reproduce

The individuals that don’t have these adaptations won’t survive

Geographic Isolation

Isolation is the complete separation.Isolation happens when one group of a species is “cut off” from the rest of the speciesGeographic Isolation is when a group is isolated because of a river, volcano, mountain range, etc.

Geographic Isolation

The two separated groups begin to adapt to their specific environment and develop different traits.When this happens a new species forms.The Northern and Mexican Spotted Owl is an example of this.

Continental Drift

Many millions of years ago, all of the continents wereOver time, the continents drifted away from each otherThis was caused by Continental DriftWhat do you think happened to many species after the continents separated???