Evolution Notes

Evolution: Change Over Time

Learning Target: What is Evolution and How Is It Studied?

  • Extensive evidence suggests that life on Earth began 3 billion years ago.

  • Fossils in ancient rocks provide clues about past life forms.

  • The first living organisms were simple, single-celled organisms.

  • Over time, more complex single-celled organisms evolved.

  • About a billion years ago, increasingly complex multicellular organisms appeared.

  • Evolution explains how species change over time.

The Theory of Evolution

  • The Theory of Evolution is a central theme in modern biology.

  • It explains how variations among individuals can lead to changes in an entire species.

  • Charles Darwin first suggested the concept of evolution.

  • The theory has been refined by substantial evidence from numerous scientists.

  • Evolution is a well-supported theory, tested and confirmed in various ways.

  • Scientists use the theory to make predictions about the natural world.

Example of Evolution: The Horse

  • Eohippus is an ancient ancestor of the modern horse.

  • Eohippus was fox-sized with 4 toes on its front feet and 3 toes on its hind feet.

  • As the Eohippus evolved, it grew larger, and its feet elongated.

  • The surrounding toes shrank until the modern horse retained one large middle toe (the hoof) and two tiny splints.

  • The modern horse (Equus) is a one-toed animal.

Fossil Evidence: The Horse

  • Fossils of species between Eohippus and the modern horse show a gradual loss of toes.

  • This loss resulted in a more efficient hoof.

  • The skull grew longer, and the teeth became flat-topped.

Studying Evolution

  • The Theory of Evolution helps biologists understand similarities among different organisms (e.g., bone structure, biochemistry).

  • It explains the history of life revealed by the fossil record.

  • The fossil record is a collection of fossils providing clues to the history of Earth's organisms.

  • The fossil record spans much of geologic time, revealing changes in environment and species.

Geologic Time

  • Earth is estimated to be 4.5 billion years old.

  • Life began with simple, single-celled organisms.

  • Increasingly complex, multicellular organisms evolved over time.

  • Geologic time divides EONS into smaller units called ERAS.

  • ERAs are further divided into PERIODS to facilitate the study of evolutionary time.

Geologic Timeline

  • Hadean Eon: Formation of the Earth (3,800-4,600 million years ago).

  • Archean Eon: Formation of the continents, early life (bacteria, archaeans) (2,500 million years ago).

  • Proterozoic Eon: First sponges, colonial algae, and soft-bodied invertebrates (570 million years ago).

  • Paleozoic Era:

    • Cambrian Period: Rise of all major animal groups (543 million years ago).

    • Ordovician Period: Echinoderms and bryozoans dominant in oceans (505 million years ago).

    • Silurian Period: First land plants, primitive fungi, and seaweed (440 million years ago).

    • Devonian Period: First spiders, scorpions, centipedes, early insects, vascular plants, jawed fish, and large reefs (410 million years ago).

    • Carboniferous Period:

      • Mississippian: First amphibians (360 million years ago).

      • Pennsylvanian: First reptiles, cockroaches, and mayflies (325 million years ago).

    • Permian Period: Major extinction of 95% of marine species and 50% of all animal families (286 million years ago).

  • Mesozoic Era:

    • Triassic Period: Origin of mammals, dinosaurs, and true flies (245 million years ago).

    • Jurassic Period: Dinosaurs and gymnosperms dominate the land (208 million years ago).

    • Cretaceous Period: Marsupials, ants, bees, butterflies, flowering plants appear. Mass extinction of most large animals and many plants (146 million years ago).

  • Cenozoic Era:

    • Tertiary Period: Apparition of all mammals (50 million years ago).

    • Quaternary Period: Modern humans appear. Four major glaciations cause rapid shifts in ecological communities (1.8 million years ago).

Definition of Evolution

  • Evolution is the process of change in species over a long period of time.

Best Description of Evolution

  • Evolution is best described as a process of change in species over a period of time.

Yes, you can add another PowerPoint. To do so, provide me with the new content, and I will format it to match the existing note.

Yes, you can add another PowerPoint. To do so, provide me with the new content, and I will format it to match the existing note.

Yes, you can add another PowerPoint. To do so, provide me with the new content, and I will format it to match the existing note.

Yes, you can add another PowerPoint. To do so, provide me with the new content, and I will format it to match the existing note.