Chapter 14: Evolution: A History and a Process

Evolution: What is Evolution? –change over time. Biological evolution: the development of a species or organism from its original or primitive state to its present or specialized state.

Prior to Darwin In the mid 1700s: –the study of fossils led Georges Buffon to suggest that Earth is older than 6,000 years, and fossils might be early versions of modern forms In the early 1800s: –Jean Lamarck proposed that life evolves, or changes. –His idea was called inheritance of acquired characteristics. –He recognized that species are not permanent and explained evolution as a process of adaptation.

Adaptation An inherited characteristic that improves an organism’s ability to survive and reproduce in a particular environment. –Ex: camouflage

Hey! I’m a walking stick. I look just like a stick you’d find on the ground.

Do you see the cricket in this picture?

The Voyage of the Beagle Their mission was to chart the South American coastline for the British navy. Accompanying the captain was a 22 year old Charles Darwin. His main interest was to study the geology, plants, and animals encountered on the way.

The Galapagos Islands Darwin was intrigued by life on the Galapagos. The Galapagos are a chain of relatively young islands off the western coast of South America. He observed many unique organisms on these islands.

The Galapagos Islands Most of the species on the islands were similar to, but different from the plants and animals of the nearest mainland. From these observations, Darwin inferred that mainland species had changed after they colonized the islands and adapted to their various new environments.

Ideas from Geology The writings of the geologist Charles Lyell had a particularly strong influence on Darwin. Lyell's Principles of Geology led him to realize that still- operating natural forces gradually change Earth.

Origin of Species After his return, Darwin began to document his observations and his new theory of evolution Alfred Wallace conceived a theory almost identical to Darwin's. Darwin's Origin of Species was published in 1859

Darwin’s two main Points: 1.Descent with modification: species of organisms living on Earth today descended from ancestral species. In other words, life has a history of change. 2.Natural selection: the process by which individuals with inherited characteristics well-suited to the environment leave more offspring on average than do other individuals.

Natural Selection: One of the basic mechanisms of evolution. The process by which species adapt to their environment. “struggle of existence” & “survival of the fittest”

Natural selection can alter variation in a population in 3 ways: –Stabilizing selection: favors the intermediate (common) phenotypes –Directional selection: acts against individuals at one of the phenotypic extremes –Disruptive selection: favors individuals at extremes of the phenotypic range

Original population Evolved population Stabilizing selection Phenotypes (fur color) Frequency of individuals Directional selection Disruptive selection

Fossils Fossils are formed from the remains of organisms buried in sediments, dust, or ash.

Where are the younger layers located? Where are the older layers located?

Geologic Time Scale Divided in 4 distinct ages: –Precambrian: earliest era, oldest known fossils- prokaryotes (3.5 billion years ago) –Paleozoic: fish, and insects appear (570 million and 230 million years ago) –Mesozoic: flowering plants appear, age of reptiles, including dinosaurs (230 and 65 million years) –Cenozoic: present era; explosive evolution of mammals and birds (beginning 65 million years ago)

Activity Time: Battle of the Beaks Materials: (for 28 students) –7 scissors –7 plastic spoons –7 tweezers –7 large binder clips –4-5 boxes of large paper clips –200 large rubber bands –4-5 boxes of toothpicks –2 cups of macaroni –28 plastic cups (best if clear)

Battle of the Beaks You will all be birds for today, very hungry birds. Yu will need to select your beak: either a spoon, tweezers, binder clip or pair of scissors. Grab a plastic cup that represents your stomach and then sit quietly in a large circle.

Battle of the Beaks You must hold your beak in one hand and your stomach in the other. You can only place food in your stomachs with your beaks. Certain food items will be placed in the feeding area (middle of the circle). When I say “go” you are to collect as much food and place it in your stomachs as possible until I say “stop.”

Battle of the Beaks At the end of each trial, you will empty your stomachs and count the contents and record them on your Recording Sheet. Paper ClipsMacaroniRubber BandsToothpicks Scissors Spoons Tweezers Binder Clips

Battle of the Beaks: Discussion  What did you notice about your feeding abilities?  Did everyone with your type of beak have the same success rate with the same foods? Why or why not?  What did you notice about your behavior and the behavior of others?  Which bird was most successful? Why?  According to Darwin, was it nature selecting?  What do you think will happen to this population of bird in a few generations? In a million years?