EVOLUTION From so simple a beginning

BIG QUESTIONS FOR TODAY

1.  What is evolution any way? 2.  If evolution is real, why are there still

chimpanzees? 3.  Is evolution goal-directed? 4.  Are humans “more evolved” than other species?

Fill in the Planck Fill in the blanks in the rap on your worksheet.

Fill in the Planck: Evolution

The Backstory

Is evolution a “theory”? What does that mean? Why did we need a theory like evolution?

Historical Background

§ Common thought – fixity of species, species were created in the form we see them now

§ Erasmus Darwin (18th C) – poem suggesting life originated in the seas, evolved over vast expanses of time, stressed importance of environment

§ Buffon (18th C) – recognized dynamic relationship between the environment and species

§ Jean-Baptiste Lamarck (18-19th C) –

attempted to explain mechanisms of species change through inheritance of acquired characteristics.

§ Thomas Malthus (1798) – An Essay on the Principle of Population

The Voyage of the Beagle §  In 1831, Charles Darwin, having failed out of medical school,

accepted an invitation to explore the world by ship on the HMS Beagle.

What Darwin Noticed

§ The plant and animal life everywhere had similarities, but seemed to be very well suited for that specific environment.

§ Galapagos Islands – different species on each island, but each had slight adaptations that helped them survive on each island.

Darwin’s Theory

§ The voyage on the Beagle – species change slowly over time, leading to new species

§ Adaptation – components of an organism that interact to help the organism survive and reproduce

Darwin’s Theory

§ 3 Points of Evolution § Variation in Fitness § Inheritance of Variation § Struggle for Existence

Darwin’s Theory

§ Natural Selection – traits that give advantages in survival and reproduction are retained in the population, disadvantageous traits disappear.

Darwin’s Finches

NATURAL SELECTION IN ACTION § Peter and Rosemary Grant, 1970’s

Evolution & Species

§ Evolution doesn’t have to lead to change in the same direction over time – evolution causes organisms to change so that they are better adapted to their environment

§ Darwin’s concept of species – “dynamic population of individuals”, species are not fixed

Individual Selection

§ Evolution – population level §  The change in allele frequencies in a population over time.

§ Adaptation & selection – individual level § Adaptation – results from competition among individuals §  Selection – can lead to traits that increase the reproductive success

of individuals but decrease the average reproductive success of the group, population and/or species

Rates of Evolutionary Change

§ Natural selection can cause evolution much more quickly than expected § Humans and chimps ~ 7mya § Galapagos finches ~ .5mya § Dogs and wolves ~ 15kya

Photo Credit: L Densmore

Canis lupus (& subsp) Canis lupus familiaris

Convergent Evolution

§ Convergent Evolution – the evolution of similar adaptations in distantly related groups of organisms

Darwin’s Difficulties

§ Most people accepted Darwin’s views that § New species arise through transformation of existing

species § Natural selection is an important force in species change

§ Most did NOT accept that evolution occurred through an accumulation of small variations § Darwin could not explain how variation is maintained §  “Blending Inheritance” would deplete variation § Selection removes variation from the population § Couldn’t explain how new variations would appear § Darwin didn’t know the answer was already out there!

§ We will answer these questions with GENETICS!

Evolution Branches – not goal oriented