Download Chapter Seven: The Evolution of Living Things Teacher Notes

Chapter Seven: The Evolution of Living Things
Teacher Notes
Lesson One: Change Over Time
-Differences Among Organisms
-Adaptation-a characteristic that improves an individual’s ability to survive and
reproduce in a particular environment.
-examples-physical such as long neck or striped fur or could be behaviors
such as finding food, protecting itself, or reproducing.
-Species-a group of organisms that are closely related and can mate to produce
fertile offspring.
-Members of the same species can reproduce to create fertile offspring
-Do Species Change Over Time?
-scientists think Earth and the living things on it have changed greatly
-many species have died out and new species have appeared
-species have also changed over time; scientists think this is how new
species form
-Evolution-the process in which inherited characteristics within a
population change over generations such that new species sometimes
arise.
-Evidence of Changes Over Time
-History of organisms is found in the layers of the Earth; older layers are
deposited before newer layers and are buried within Earth.
-Fossils-the remains or physical evidence of an organism preserved by geological
processes.
-can be complete organisms, parts of organisms, or footprints
-usually formed when dead organisms are covered with sediment
-The Fossil Record-a historical sequence of life indicated by fossils found in
layers of the Earth’s crust.
-organizes fossils by their estimated ages and physical similarities
-fossils found in newer layers tend to be similar to present day organisms
-fossils found in older layers are less similar to present day organisms;
many of these no longer exist.
-Evidence of Ancestry
-scientists think that all living species are descended from common ancestors.
-Drawing Conclusions
-scientists draw models to illustrate their hypothesis
-scientists e information about species to sketch a “tree of live” that
includes all known organisms.
-this information is incomplete because there are parts of the fossil
record that are incomplete.
-Examining Organisms-gives clues about ancestors
-Case Study: Evolution of the Whale
-think that the ancestors of whales were probably mammals who lived on
land and that could run on four legs.
-more recent ancestors were probably mammals that spent some time on
land and some time in water.
-Walking Whales-some evidence of this is found in related ancestry and some
found inside the bodies of whales.
-Comparing Organisms-can be found by comparing the groups’ DNA
-Comparing Skeletal Structures-scientists look at the similarities in bone structure
and bone order to find similar organisms.
-Comparing DNA
-scientists have learned that traits are inherited through DNA’s genetic
code.
-DNA of a cat is more similar to that of a tiger than a dog
Lesson Two: How Does Evolution Happen?
-Charles Darwin
-graduated from college at age 21 but didn’t know what he wanted to do
-his father wanted him to be a doctor but blood made him sick
-Darwin enjoyed studying plants and animals
- signed on to voyage around the world for 5 years on the HMS
Beagle as a naturalist (a scientist who studies nature)
-Darwin’s Excellent Adventure
-Darwin collected thousands of plant and animal samples
-kept careful notes of his observations
-he found the Galapagos Islands very interesting
-Darwin’s Finches
-Darwin noticed that animals and plants of the Galapagos Islands were a
lot like those in Ecuador.
-The finches were not exactly the same; they each had adaptations
to their environment.
-Darwin’s Thinking
-Ideas About Breeding-farmers and breeders were producing plants and animals
with desired traits.
-Selective Breeding-the human practice of breeding animals or plants that have
certain characteristics.
-examples-horses that are fast or strong, crops with large fruit
-Ideas About Population-Darwin drew the conclusion that offspring of the
survivors inherit traits that help the offspring survive in their environment.
-Ideas About Earth’s History
-Darwin began to think that species could evolve over time; most
geologists didn’t think Earth was old enough to allow for slow changes.
-Darwin’s Theory of Natural Selection
-natural selection-the process by which individuals that are better adapted to their
environment survive and reproduce more successfully than less well adapted
individuals do; a theory to explain the mechanism of evolution.
-Genetics and Evolution
-Darwin lacked evidence for some parts of his theory
-knew organisms inherit traits but not ho
Lesson Three: Natural Selection in Action
-Changes in Populations-not all populations change and adapt at the same rate so some
organisms survive for longer amounts of time.
-Adaptation to Hunting
-changes may occur when a force affects the survival of an individual
-example-most elephants used to have tusks but now most are born
without tusks because less males with tusks survive to reproduce
due to them being killed for the ivory.
-Insecticide Resistance
-some chemicals that used to work well no longer work because the
insects have adapted to survive. They quickly develop resistance because
they often produce many offspring and have short generation times.
-Generation Time-the period between the birth of one generation and the
birth of the next generation.
-Competition for Mates
-individuals find mates that they feel will give their offspring the best
chance of survival
-Forming a New Species
-Speciation-the formation of new species as a result of evolution
-occurs when so many changes have occurred that the different types can
no longer reproduce.
-Separation-when one member (or small group of members) is separated from the
large group.
-may occur because of the formation of a canyon, mountain range, or lake
-Adaptation
-populations constantly undergo natural selection
-after separation occurs to groups continue to evolve with traits for their
environment.
-Division
-over time the two separated groups of the population become very
different.
-even if brought back together they may no longer be able to breed