Bio 1010 Dr. Bonnie A. Bain

Chapter 13: Evolution

Evolution: Change over time Mechanism: Natural Selection

Selection Event: Any occurrence that kills large numbers of the population The survivors of the selection event are the ones which go on to reproduce and form the next generation

Natural Selection: Hurricanes, floods, fires, disease, etc. Artificial Selection: Breeding of crops, farm animals, pets, etc. The selection event is a human deciding which ones to breed

Figure 1.15a Artificial Selection

Figure 1.15b Artificial Selection

Figure 13.1 Evolution of pesticide resistance in insects Selection event: Application of lots of pesticide

1 Evolution of Pesticide Resistance Pesticides often have encouraging early results First application can kill up to 99% of all insects The resistant survivors produce the next generation In each subsequent generation, there are more and more resistant survivors Evolution at work!

Evolution: change over time Mechanism: Natural Selection As a result of natural selection, a population will change over time Individuals don't evolve, but populations do

Natural Selection leads to evolutionary adaptation: Defined as, “ a population's increase in the frequency of traits suited to the environment” Adaptation can also refer to the trait itself Example: camouflage is an adaptation that helps the organism avoid predators

Figure 1.14a

Figure 1.14b

Figure 1.14c

Figure 1.14d

Figure 13.2 Camouflage

Figure 1.2g

Extra Photo 01.02gx2

Sea spider, Pallenoides sp.

Aposematic Coloration The opposite of camouflage The individual is brightly colored and really stands out from the background The brightly colored individual is poisonous or venomous and can sting or bite Examples: bumblebee, wasp, coral snake

Aposematic Coloration in a Monarch Butterfly

Aposematic coloration in a sea spider

This species of sea spider, Stylopallene longicauda, lives on a poisonous bryozoan, Amathia It eats this bryozoan and stores the poison in its own tissues When a fish tries to eat it, it spits the sea spider right back out

Natural selection events, like hurricanes, floods, fires, etc. can cause a change in food supply for a population This situation can also lead to the evolution of a population Classic example of this: Darwin's Finches

Figure Darwin's Finches

Galapagos Finches (Darwin's Finches)‏ Galapagos Islands Lots of fairly isolated small islands – No island-hopping—birds are too small Each island has several finch species Main differences among all the species: Beak size and shape

Figure 13.4

Fig c Galápagos Islands PACIFIC OCEAN Pinta 40 miles 40 km 0 Florenza 0 Fernandina Marchena Genovesa Equator Santiago Daphne Islands Pinzón Española Isabela Santa Cruz Santa Fe San Cristobal

Fig a

Figure 13.5a

Fig a Green sea turtle in the Galápagos Islands

Figure 1.13

Galapagos Finches (Darwin's Finches) Within a population of these finches, ‏beaks come in small, medium, large (population variation): Small beaks: feed on small seeds Medium beaks: feed on medium-sized seeds Large beaks: feed on large seeds

Mixed population of small, medium, and large individuals Smaller members of the population eat small seeds Medium-sized ones eat small to medium- sized seeds, etc.

A selection event occurs: A really severe storm wipes out finch food supply Only plants with big hard seeds left on the island

Only the biggest survivors (with the biggest beaks) can eat the remaining seeds This leads to the formation of a new species (with a large tough beak)‏ Evolution in action!

Darwin observed and wrote about this when he visited these islands and this has actually been observed in modern times (1980's) by Dr. Peter Grant and his students from Yale University Peter Grant wrote a book on this: “The Beak of the Finch”

Figure 1.13 Darwin's finches, An example of Adaptive Radiation: The rapid formation of lots of species from one common ancestor

During Darwin's voyage around the world (as ship's naturalist on the HMS Beagle), his ship stopped in the Galapagos for a while and Darwin spent a long time observing the finches He later wrote in his journal that these finches were one of the most important aspects of his trip around the world since they got him started on working out the mechanism for evolution