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Chapter 7 Changes Over Time
Section 1:Darwin’s Theory
What important observations did Darwin make on his voyage?
How did Darwin account for the diversity of species and the differences between similar species?
How does natural selection lead to evolution?
Chapter 7 Changes Over Time
Darwin’s Voyage
Charles Darwin sailed on the HMS Beagle, from England to the Galápagos Islands and back, for 5 years starting in 1831.
Chapter 7 Changes Over Time
Galápagos Islands
Located 525 miles west of Ecuador.
Was visited by Darwin in 1835.
Chapter 7 Changes Over Time
Galápagos Finches
Darwin noticed that on each island, the finches had adapted to the local environment.
Adaptation: a trait that helps an organism survive and reproduce in its environment
Chapter 7 Changes Over Time
Galápagos Finches
Chapter 7 Changes Over Time
Overproduction and Variation
Natural selection is the process by which individuals who are better adapted to their environment are more likely to survive and reproduce than other members of the same species.
Chapter 7 Changes Over Time
Competition and Selection
Variations among turtles make some of them better able to survive. Turtles that survive to become adults will be able to reproduce.
Chapter 7 Changes Over Time
Competition and Selection
Variations among turtles make some of them better able to survive. Turtles that survive to become adults will be able to reproduce.
Chapter 7 Changes Over Time
Factors that Affect Natural Selection
Overproduction
Animals (including humans), plants, and other organisms tend to produce too many offspring, and there may not be enough food, water, or shelter to protect them all.
Chapter 7 Changes Over Time
Factors that Affect Natural Selection
Variation
Members of the same species differ from one another in many of their traits
Example: You may be faster than your sibling, but your sibling may be taller, or have a better immune system, or have better reflexes.
Chapter 7 Changes Over Time
Factors that Affect Natural Selection
Competition
All living things struggle to survive. Sometimes they compete for more food, or running away from a predator, or fighting off a disease.
Chapter 7 Changes Over Time
Factors that Affect Natural Selection
Overproduction + Variation + Competition =
Natural Selection
The environment “selects” which members of a species lives long enough to have offspring. Some members have lots of offspring, others have few, and some have no offspring.
Over time, helpful traits (like speed, camouflage, and disease-resistance) will show up more often in a species. Eventually, most members will have this trait.
Chapter 7 Changes Over Time
Things to Remember
• Species: a group of similar organisms that can mate with each other and produce offspring
• Overproduction: species creating more offspring than can possibly survive
• Adaptation: a trait that can help an organism survive
Chapter 7 Changes Over Time
Section 2:Evidence of Evolution
What evidence supports the theory of evolution?
How do fossils form?
What do scientists learn from fossils?
Chapter 7 Changes Over Time
Homologous Structures
The structure of the bones in a dolphin’s flipper, a bird’s wing, and a dog’s leg is similar. Homologous bones are shown in the same color.
Chapter 7 Changes Over Time
Similarities in Early Development
Chapter 7 Changes Over Time
Similarities in DNA and Protein
Chapter 7 Changes Over Time
How Do Fossils Form?
Most fossils form when organisms that die become buried in sediments.
Chapter 7 Changes Over Time
Types of Fossils
Molds and Casts: Most common fossil; organism dies and gets buried in sediment, creating a mold; more sediment later fills in this mold to create a cast
Chapter 7 Changes Over Time
Types of Fossils
Petrified: rock minerals replace parts of the organism, turning the fossil into a hard, rock-like state
Chapter 7 Changes Over Time
Types of Fossils
Trace: evidence of activity, such as footprints or cave paintings
Chapter 7 Changes Over Time
Types of Fossils
Preserved Remains: organism trapped in amber, tar or ice; produces the best fossils
Chapter 7 Changes Over Time
Section 3:Evolution of Species
What factors have contributed to the diversity of species?
How do new species form?
How do scientists infer evolutionary relationships among species?
What causes the extinction of species?
Chapter 7 Changes Over Time
Evolution in Progress
There are over 150 major breeds of dogs and hundreds of other cross-breeds. All of these dog breeds (and wolves) came from the same ancestral animal
Chapter 7 Changes Over Time
Kaibab and Abert’s Squirrels
These two kinds of squirrels have been isolated from one another for a long time. Eventually this isolation may result in two different species.
Kaibab Squirrel Abert’s Squirrel
Chapter 7 Changes Over Time
A Branching Tree
This branching tree shows how scientists now think that raccoons, lesser pandas, giant pandas, and bears are related.
Chapter 7 Changes Over Time
Extinction of SpeciesExtinction is caused by a change in species' environment. The members of a species may not have adaptations that allow them to survive and reproduce in the changed environment.
Baiji River Dolphin Woolly MammothThylacine
Chapter 7 Changes Over Time
Things to Remember
• Extinct: no more members of a particular species exist; occurs when a species does not have the right adaptations to survive and reproduce
Chapter 7 Changes Over Time
End of Section:Evolution of Species
Chapter 7 Changes Over Time
Section 4:Classifying Organisms
Why do biologists organize living things into groups?
What do the levels of classification indicate about the relationship between organisms?
What characteristics are used to classify organisms into domains and kingdoms?
Chapter 7 Changes Over Time
Classification through Names
Kingdom: Animalia Animalia Phylum: Chordata ChordataClass: Mammalia MammaliaOrder: Primates CarnivoraFamily: Hominidae Felidae Genus: Homo FelisSpecies: H. sapiens F. domesticus
Chapter 7 Changes Over Time
Classification through Names
Kingdom: Animalia Animalia Phylum: Chordata ChordataClass: Mammalia MammaliaOrder: Carnivora CarnivoraFamily: Felidae Felidae Genus: Felis Felis Species: F. domesticus F. chaus
Chapter 7 Changes Over Time
Three Domains of Life
In the three-domain system of classifications, all known organisms belong to one of three domains–Bacteria, Archaea, or Eukarya.
Protists Fungi Plants Animals
Bacteria Archaea Eukarya
Chapter 7 Changes Over Time
Levels of Classification
As you move down the levels of classification, the number of organisms decreases. The organisms at lower levels share more characteristics with each other.
Chapter 7 Changes Over Time
End of Section:Classifying Organisms
Chapter 7 Changes Over Time
Section 5:Branching Trees
How does a branching tree diagram show evolutionary relationships?
Chapter 7 Changes Over Time
A Branching Tree
Branching trees such as this show relationships between groups of organisms. It also shows the order in which specific characteristics may have evolved.
Chapter 7 Changes Over Time
Shared Derived Characteristics
A branching tree diagram shows evolutionary relationships by grouping organisms according to shared derived characteristics.
ReptilesAmphibians
Egg with shellFishes
Four limbs
Backbone
Invertebrates
Ancestor of animals
Chapter 7 Changes Over Time
End of Section:Branching Trees
