Evolution. Life’s Adaptations Over Time. Can a Species Change Over Time?. All breeds of dog are descended from the wolf. (they are domesticated wolves!) Genus: Canis Species: lupus All of the different breeds of dog have been produced by controlling how they reproduce. .
Life’s Adaptations Over Time
The “Heike Crab”
What is meant by the term evolution?
Theories of Evolution
Why is evolution important in the study of life (biology)?
muscles built by exercise
giraffes stretching their necks
In the selective breeding of dogs, we select individuals with certain features we like and allow them to reproduce and pass on their traits.
Darwin called this “natural selection.”
All organisms produce more offspring than can survive.
Differences, or variations, occur among individuals of a
Variations are passed on to offspring: they are inherited.
Some variations are helpful. Individuals with helpful
variations survive and reproduce better than those without
Over time, the offspring of individuals with helpful
variations make up more of a population and eventually
become a separate species.
The evolution of the horse shows gradual changes
over the last 60 million years.
Archaeopteryx – a primitive bird, Jurassic Period (150 million years ago)
Tyrannosaurus and Triceratops:
Dinosaur Predator and Prey
Western U.S., 70 million years ago
180 million years old
Dinosaur State Park
Laetoli hominid footprints
3.2 million years old
Tanzania, East Africa
Insects trapped in tree sap (fossilized into amber)
5 million years ago, Baltic region, Europe
Extinct mammoth trapped in natural tar 40,000 years ago
La Brea Tar Pits, Los Angeles, California
Besides fossils and modern studies of changes in species,
there are many examples of indirectevidence for evolution:
Similarities in the developing embryos of these organisms
provide indirect evidence that they shared ancestors.
Homologous structures in these organisms (limb bones) are indirect evidence that they evolved from a common ancestor.
had different adaptations:
(East Africa, 4 to 2 million years ago)
Homo habilis fossils:
(East Africa, about 2.5 to 1.5 million years ago)
Homo erectus fossils:
(Europe, Asia, Africa, about 1.5 MYA to 400,000 years ago)
Homo sapiens fossils:
Neanderthals in Europe (adapted to ice-age climate)
(became extinct about 30,000 years ago)
Cro-Magnon in Europe, Asia, Africa
thought to be direct ancestors of modern humans
(10,000 to 40,000 years ago)
Evolution and Biodiversity
10. Give examples of ways in which genetic variation and environmental factors are causes of evolution and the diversity of organisms.
11. Recognize that evidence drawn from geology, fossils, and comparative anatomy provide the basis of the theory of evolution.
12. Relate the extinction of a species to a mismatch of adaptation and the environment.
Changes in Ecosystems Over Time
17. Identify ways in which ecosystems have changed throughout geologic time in response to physical conditions, interactions among organisms, and the actions of humans. Describe how changes may be catastrophes such as volcanic eruptions or ice storms.
18. Recognize that biological evolution accounts for the diversity of species through gradual processes over many generations.
From “Life Science (Biology), Grades 6-8,” Massachusetts Science and Technology/Engineering Curriculum Framework, Massachusetts Department of Education, May 2001.