A brief look back Over the past few weeks, we have acquired a significant amount of evidence for evolution Natural selection (the common ancestry of brown bears and polar bears; dinosaurs and chickens) Artificial selection (humans selecting for desired traits, such as dog breeding) 13 different finch species now inhabiting the Galapagos Islands all evolving from a common Mainland finch ancestor Icefish evolving an antifreeze gene to live in sub-freezing water Humans evolving the sickle cell allele to combat malaria Stickleback fish adapting to freshwater because of pelvic spine gene mutation

Co-evolution As we continue learning about evolution, we must expand our view to consider the concept of co-evolution. Co-evolution is the idea that organisms do not evolve in a vacuum. The term co-evolution is used to describe cases where two (or more) species reciprocally affect each other's evolution. Plants and insects represent a classic case of coevolution — one that is often, but not always, mutualistic. Many plants and their pollinators are so reliant on one another and their relationships are so exclusive that biologists have good reason to think that the "match" between the two is the result of a co- evolutionary process. For more, visit the evolution.Berkeley.edu website!

Important vocabulary for the road ahead Host: an organism that harbors a parasite, or a mutual or commensal symbiont, typically providing nourishment and shelter. Bacteria: microscopic living organisms, usually one-celled, that can be found everywhere. They can be dangerous, such as when they cause infection, or beneficial, as in the process of fermentation (such as in wine) and that of decomposition.

Important vocabulary for the road ahead Virus: Any of various simple submicroscopic parasites of plants, animals, and bacteria that often cause disease and that consist essentially of a core of RNA or DNA surrounded by a protein coat. Unable to replicate without a host cell, viruses are typically not considered living organisms. Infection: Invasion and multiplication of an infectious agent in body tissues of the host and may lead to clinical symptoms or local cellular injury as a result of competition in metabolism, production of toxins, intracellular replication, or antigen antibody response.

Important vocabulary for the road ahead Symbiosis: the interaction between two different organisms living in close physical association. Symbiotic Relationships: Mutualism: symbiosis that is beneficial to both organisms involved. Commensalism: an association between two organisms in which one benefits and the other derives neither benefit nor harm. Parasitism: a non-mutual symbiotic relationship between species, where one species, the parasite, benefits at the expense of the other, the host.

Mutualism (win-win) Mastigias papua and zooxanthellae Soybean plant roots with bacteria-filled nodules Crocodile and plover Remoras and shark

Commensalism (win-meh) Clown fish and sea anemone Whale and barnacles

Parasitism (win-lose) Ticks and dogs Exigua replacing fish tongue Intestinal tapeworm Lice and humans