1. Change Over Time

2. Who was Charles Darwin?
1831
HMS Beagle set sail from England on a 5 year trip of discovery…..
Darwin’s job was to learn as much as possible about the living things he saw on the voyage.
He saw many plants and animals he had never seen before
His discoveries led him to develop a scientific theory of evolution by natural selection.

3. Species:
Scientists estimate that there are 1.7 million species of organisms on Earth.
Species – a group of similar organisms that can mate with each other and produce fertile offspring.

4. Galapagos Island Here Darwin observed many unusual life forms
Giant Tortoise
Lizards
Seals

5. Similarities and Differences
Darwin noticed that some animals found on the Galapagos Island were similar to the animals found on the mainland (South America)

6. How did these creatures get here?
Darwin inferred that a small number of different plant and animal species had come to the Galapagos from the mainland.
Blown out to sea during a storm
Floated on a drifting log
Over time (millions of years), their offspring changed into what they are today….

7. Adaptations: Birds – Finches
Differences depending on which island they came from
Size and shape of beaks
Eat insects: beaks were sharp, needlelike
Eat seeds: beaks had strong, wide beaks
Adaptation – a genetic trait that helps an organisms survive and reproduce

8. Theory of Evolution Darwin spent 20 years studying his findings
Darwin reasoned that plants and animals that arrived on one of the Galapagos Islands faced conditions that were different from those on the mainland.
Perhaps species gradually changed over many generations and became better adapted to the new environment……
Evolution – the change in species over time

9. Selective Breeding:
Evidence to support his theory of evolution

10. Natural Selection
Natural selection – the process by which individuals that are better adapted to their environment are more likely to survive and reproduce than other members of the same species.
Affecting factors:
Overproduction
Competition
Variation

11. Overproduction:
Most species often produce more offspring than can possibly survive
Why? What is passed on to the next generation?

12. Competition: Food and other resources are limited
Members of species must compete with each other to survive.
Can lead to starvation and being prey for predators
Will the weak be able to pass on their DNA?

13. Variation:
Members of a species differ from one another in many of their traits
Any difference between individuals of the same species is called a variation.
Example: baby turtles swimming faster than their siblings…..WHY?
Some variations can make an individual better adapted for survival.

14. Natural Selection:
Surviving offspring will live to pass on their helpful traits to their offspring.
This cycle of passing on the helpful traits keeps on going
The environment has “selected” individuals with the necessary traits for survival
Over long periods of time – this can lead to change

15. Example of Natural Selection:
New predator is introduced into an environment
Those that can outrun the predator will survive
They will be able to pass on their “fast-running” genes on to their offspring.
The slow runners will slowly disappear…..why?
Over LONG periods of time, the entire species will have the “fast-running” gene.

17. How does a new species form?
Variations can lead to a new species
Geographic isolation – complete separation from the original species
River, volcano, mountain range, storm washing animals into sea and eventually landing on an island, earthquake
Once isolated, the members of a species can no longer mate with the original group
Accumulation of different traits

18. Continental Drift…. Pangaea – supercontinent
Over millions of years, Pangaea gradually drifted apart due to continental drift (convection currents)
Climates changed
Species became isolated from one another
Natural selection occurred
Example: Australia  Marsupials

19. Fossil Record

20. What is a fossil?
In order to understand what occurred long ago, scientists act like detectives to solve clues….using fossils!
Fossil – preserved remains or traces of an organism that lived in the past.
Bone, tooth, shell, footprints, worm burrows, etc…..
Formed when organisms become buried under sediments after they die.

21. Determining a Fossils age…..
The age of a fossil can be used to reconstruct the history of life on earth.
Relative Dating: Looking at the layers of rock top layer is the newest, bottom layer is the oldest.
Absolute Dating: Using the actual radioactive elements found in the fossils

22. Fossil Record:
The millions of fossils that scientists have collected are called the fossil record.
Almost all of the species preserved as fossils are now extinct.
Extinct – NO members of a species are still alive
Scientists use the fossils and foot prints to rebuild and understand the creature
Provides evidence about WHEN different kinds of organisms may have lived on earth.
Estimate ages of fossils – created a “calendar” of events that date back 4.6 billion years!!
Geological Time Scale

23. Incomplete Fossil Record
The fossil record is incomplete because most organisms that died did not leave behind fossils.
These gaps have left many unanswered questions.
Scientists do not know how rapidly species change.

24. Causes of extinction:
Changes in environmental conditions can affect the survival of species.

25. Causes of extinction: Natural events Major changes in climate
An asteroid threw huge clouds of dust and gas into the atmosphere
The dust clouds blocked the sunlight, making the climate cooler and killing plants.
Herbivores died
Carnivores died
Massive volcanic eruptions

26. Causes of extinction: Human activities Habitat destruction
Loss of environment
Pollution
Hunting and killing too many of a species

27. Other Evidence of Change

28. Similarities in body structure:
Scientists compare body structures of living organisms
Body structures: basic body plan
How the bones are arranged
Organ systems
Fish, amphibians, reptiles, birds and mammals all have similar body plans.
Internal skeleton with a backbone

29. Homologous structures:
Scientists use the similar structures of forelimbs as evidence that these three organisms share a common ancestor.

30. Similarities in early devolvement
Scientists also make inferences about evolutionary relationships by comparing the early development of different organisms.
Compare a bird, frog and rat…..very different right?
HOWEVER, during early development, these organisms have some similarities.

31. Similarities in DNA:
Scientists compare genes of different species to determine possible relationships among species.
Compare DNA
More similar two species DNA is, the more closely related they are
Horse and zebra
Lion and tiger
Cat and dog?

32. Combining the Evidence:
Scientists have combined evidence from fossils, body structures, early development, and DNA …
Example: Scientists have inferred that dogs were more closely related to wolves than to coyotes based on similarities in body structure, DNA and early development.
Branching Tree – a diagram that shows how scientists think different groups of organisms are related.
Common Ancestor 