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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 America
In 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 America
Here 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
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 rocks
The 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 reproduce
Darwin 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 seeds
Long sharp beaks to hunt and eat insects
Evolution“Survival of the fittest”
Darwin believed that species gradually change over time…this is Evolution
Species 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 colors
Turtles 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 species
Geographic 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 were
Over time, the continents drifted away from each other
This was caused by Continental Drift
What do you think happened to many species after the continents separated???
