Bell Ringer for 5/23 ► I need 2 volunteers to pass back papers… ► Everyone else, take out paper/notebook for notes and your Ch vocab ► Answer the following in your notes for today:  What are three types of evidence we have for the evolution of living organisms?

Today’s agenda ► Discuss 15.1 and review worksheets ► Lecture on 15.2

Fossil Evidence ► Though the fossil record is incomplete, it gives paleontologists a look into the structure of ancient organisms. ► By comparing the anatomical (and in rare cases biochemical) evidence to modern day organisms, they can fill in the gaps of how life has evolved over time.

Anatomical Evidence  What type of structures is this picture showing? Homologous structures These structures are formed in similar ways during embryonic development and share similar ____________; however, they have somewhat different forms and __________________. origin s function s

Anatomical Evidence cont.  What type of structures is this picture showing? Analogous structures Some unrelated animals have organs with similar _____________, yet are very different in form and _____________. These organs are analogous. function origin

Anatomical Evidence cont.  What type of structures is this picture showing? Vestigial structures Organs or structures that have lost their ________ in modern organisms and have become reduced in size are called vestigial structures. function

Analysis and interpretation 1. The homologous structures in Part 1 are evidence of evo. relationships due to each organism having the same bones present in structures that carry out similar functions. 2. The is no recent evolutionary relationship between a fish fin and the flipper of a whale. While both have a similar function, there is no evidence of internal structures being related. 3. Hip bones on a whale – as whales live their entire lives in the water, they no longer need hip bones to support legs to walk on land. Eyes in cave fish – as it is always dark, there is no light for their eyes to use to help guide them/find food/etc, so they are unnecessary. Eyes in cave fish – as it is always dark, there is no light for their eyes to use to help guide them/find food/etc, so they are unnecessary.

Biochemical (DNA) Evidence for Evolution ► What you should have noticed:  In looking at the 2 different proteins (hemoglobin on the front, cytochrome c on the back), humans have the least # of differences with chimps and Rhesus monkeys.  Shows a close evolutionary relationship. ► If the amino acid of an organism are similar, the DNA must also be similar because…  Amino acids are made up of __________.  Codons are made up of __________.  mRna is made from ___________. codons 3 mRNA bases DNA

Can I evolve? Write these down! ► Only populations, NOT individuals, can evolve. Date: 5/23 Topic: Chapter 15.2 – Mechanisms of Evolution How does a population evolve? ► The allelic frequency of a stable, non-evolving pop. is unchanging. (it is in genetic equilibrium) ► If there is a change in the allelic freq., the pop is evolving

► Hanging around the gene pool…

What causes changes in the freq of alleles? Write these down! ► Mutations in individuals that can be passed down to offspring. ► Genetic drift can greatly affect small pops.  either brings, or takes away, genes from a pop ’ s gene pool Topic: Chapter 15.2 – Mechanisms of Evolution

Where does natural selection fit in? Write these down! ► It tests ‘ new ’ genes or alleles to see how well they will survive. ► Allelic freq. ’ s of a pop. change over generations due to the natural selection of those variations. VIDEO ► 3 patterns/types of natural selection Topic: Chapter 15.2 – Mechanisms of Evolution

Stabilizing Write these down! Topic: Chapter 15.2 – Mechanisms of Evolution ► Favors average individuals ► Reduces variation in pop. DirectionalDisruptive ► Favors 1 of the extreme variations ► Leads to rapid evolution of a pop. ► Favors both of the extreme individuals ► Leads to the formation of 2 new species in a pop.

Which type of natural selection? Average skin color over time for the human species Shell colors Video on peppered moths. Initially peppered moths were light, over time they became dark.

How do new species come to be? Write these down! ► Members of similar pops can no longer mate to produce fertile offspring = new species ► Physical barriers  Geographic isolation VIDEO ► Reproductive isolation  Genetic material is too different  Different mating behaviors/seasons ► Change in chromosome #s  polyploidy Topic: Chapter 15.2 – Mechanisms of Evolution What can cause the pops to be so diff?

But ligers and tigons exist, they must be a species…right?!?! ► Nope!! ► In order for an animal to be considered a separate species, it needs to be able to produce offspring that can give birth. ► Ligers, tigons…and mules, zorses, and beefalos…are all unable to make babies!

ConvergentvsDivergent Write these down! ► Convergent evolution  2 distantly related organisms evolve similar traits  Like meeting someone fr. ½ way around the world and finding out you are exactly alike. ► Divergent evolution  Species that were similar, evolve apart  Like you and your best childhood friend becoming 2 very diff. people. VIDEO Topic: Chapter 15.2 – Mechanisms of Evolution