EVOLUTION 1809 Lamarcks Theory 2 Major Principles Use

EVOLUTION

1809 - Lamarck’s Theory 2 Major Principles: • Use and Disuse • • The more an animal uses a body part, the more developed it becomes (and vice-versa) Inheritance of Acquired Characteristics • Characteristics an organism develops or acquires in its lifetime can be passed on to its offspring

I. What is Evolution? • The slow, gradual change in a species over time. • ‘Slow’ means thousands to millions of years (in most cases). . . • Species with short reproductive rates; like bacteria, evolve quickly. Bacteria reproduce about every 20 minutes. • Just in the last few millions of years, hundreds of species have become extinct- while hundreds of others have developed. • How do we know evolution is happening? Let’s look at the evidence…

I. Evidence for Evolution

II. Fossil Evidence • Definition: Any trace or remains of an organism that has been preserved by natural processes. • Studying fossils allows scientists to compare the remains of ancient organisms with present day species to determine evolutionary relationships. • Fossils form from amber, ice, tar, petrification, bones buried under sedimentary rock. • The older the fossil, the deeper it will be buried.

Fossil Evidence

III. How do we KNOW? ? evolutionary relationships Evidence can be: Structural Molecular/ Biochemical

Structural Evidence Homologous Structures: Similar internal structure, but different form and function.

Structural Evidence Analogous structures: Similar external form and function, but different internal structure. BOTH FLY- BUILT DIFFERENTLY

Structural Evidence Vestigial structures: Structures that are remnants of structures that were functional in ancestral forms, but are now reduced in size and serve little or no purpose. • DO THE TOP “ 10”

Structural Evidence Embryological evidence: Comparing embryos at various stages of development may show similarities not present after birth. WHO DOES THIS GUY LOOK LIKE? ? ?

IV. Molecular Evidence Gel electrophoresis: Technique used to separate DNA fragments according to their size. - +

Molecular Evidence DNA sequencing: A A-G-C-T-A-G-G-C-C-A-T-G-T-A-A-T-G-G-C-C-T-C-A-T-A-G-G-C-C-G-C-T-A-T-C B A-G-C-T-A-G-G-C-C-A-T-G-T-A-A-C-G-G-C-C-T-C-A-T-A-G-G-C-A-G-C-C-A-T-C C A-G-C-T-A-G-G-C-C-A-T-G-T-A-A-T-G-G-C-C-T-T-A-G-G-C-T-A-T-C How many differences are there between sequence A and B?

Molecular Evidence DNA sequencing A A-G-C-T-A-G-G-C-C-A-T-G-T-A-A-T-G-G-C-C-T-C-A-T-A-G-G-C-C-G-C-T-A-T-C B A-G-C-T-A-G-G-C-C-A-T-G-T-A-A-C-G-G-C-C-T-C-A-T-A-G-G-C-A-G-C-C-A-T-C C A-G-C-T-A-G-G-C-C-A-T-G-T-A-A-T-G-G-C-C-T-T-A-G-G-C-T-A-T-C How many differences are there between sequence A and B?

Molecular Evidence DNA sequencing A A-G-C-T-A-G-G-C-C-A-T-G-T-A-A-T-G-G-C-C-T-C-A-T-A-G-G-C-C-G-C-T-A-T-C B A-G-C-T-A-G-G-C-C-A-T-G-T-A-A-C-G-G-C-C-T-C-A-T-A-G-G-C-A-G-C-C-A-T-C C A-G-C-T-A-G-G-C-C-A-T-G-T-A-A-T-G-G-C-C-T-T-A-G-G-C-T-A-T-C Between B and C?

Molecular Evidence Protein analysis or Amino Acid Sequencing Carp Bullfrog Alligator Mouse Human 24 19 14 9 Mouse 19 10 9 0 Alligator 18 11 0 Bullfrog 19 0 Carp 0 The numbers represent the number of differences between protein samples. Human 0

What next?

V. Charles Darwin The Father of Evolution • Born February 12, 1809 • 1831 - 1836 Served as naturalist aboard the HMS Beagle • 1835 Arrived in the Galapagos Islands • 1859 Published On the Origin of Species… • 1882 Died and buried in Westminster Abbey

Charles Darwin • Darwin’s thoughts on Natural Selection explained a lot about evolution, but he didn’t explain the mechanism by which traits change over time. • The field of Genetics explains this… MUTATIONS. (they are not always bad!).

Darwin’s and His Theory of Evolution (summarized in 5 major points) 1. OVERPRODUCTION: Most species produce far more offspring than can survive. Those that die are considered ‘weak. ’ These weak organisms do not live long enough to reproduce. Therefore, weak traits are weeded out of the species.

Darwin’s Points… 2. COMPETITION: Since living space and food are limited (limited resources), offspring must compete for resources. Those who are good at competition survive long enough to reproduce.

Darwin’s Points… 3. VARIATIONS & ADAPTATIONS: The characteristics of the individuals in any species are not exactly alike. Those individuals that have favorable variations (adaptations), will have a greater chance of living long enough to reproduce.

Darwin’s Points… 4. NATURAL SELECTION: Organisms with variations that make them better adapted to their environment survive and reproduce; passing on these favorable traits to their offspring.

Types of Natural Selection DIRECTIONAL- an extreme phenotype becomes favorable ex… long neck giraffes

Types of Natural Selection STABILIZING- the average phenotype becomes favorable and the extremes are unfavorable Ex. Widow tail bird

Types of Natural Selection DISRUPTIVE- two opposite phenotypes become favorable and the average is unfavorable Ex. Bird beaks- small seeds and large seeds on an island. . What beaks work? Medium beaked birds would have to compete with both large and small beaks.

Darwin’s Points… 5. SPECIATION: Over many generations, favorable adaptations gradually accumulate in the species and bad traits disappear. Eventually, the accumulated changes become so big that the result is a new species.

Now, who wants to play a game? I wanna play! Click on the guy to play

VI. The Rate of Evolution How Fast is Evolution Occurring? • There are TWO theories… scientists cannot seem to agree on which one is correct. • THEORY #1: • GRADUALISM (based on Darwin’s ideas)…species arise through gradual accumulation of small variations… evolution is slow and continuous over millions of years.

The Rate of Evolution How Fast is Evolution Occurring? • THEORY #2 (Steven Gould)… • PUNCTUATED EQUILIBRIUM species remain the same (in equilibrium) for extended periods of time- evolution occurs quickly for short periods of time.

VII. Sources of Genetic Variation • MUTATIONS: Random changes in the genetic makeup of an organism. (Actually a rare event, but causes new traits to arise). • GENETIC RECOMBINATION: Gametes uniting during fertilization. (Included within this is concept are meiosis and crossing over). • MIGRATION: New traits being brought into a population or taking traits out of a population. Has the greatest effect on small populations. • GENETIC DRIFT: Affects small populations; changes in the gene pool due to storms, a catastrophe, etc. Harmful because it tends to decrease the gene pool. Not significant in large populations.

Peppered Moth CLICK ON THE PICTURE TO SEE AN ANIMATION

VIII. The Modern Theory of Evolution • Focuses on the population rather than the individual. • Population Genetics: The study of changes in the genetic makeup of populations. • Frequencies: how often a particular allele (trait) is found within a population. • Gene Pool: the total of all the alleles present in a population. • Mathematically explained by Hardy- Weinberg. See Packet.

IX. ADAPTATIONS • STRUCTURAL ADAPTATIONS: Involves parts of the body ( wings for flying, fins for swimming). • PHYSIOLOGICAL ADAPTATIONS: Involves metabolism of the organism (poison venom). • Other adaptations are mating, behavioral, hibernation, etc. • Bald eagle adaptations to the right…

X. ADAPTIVE RADIATION • DEFINITION: The emergence of many species from a common ancestor that was introduced to a new environment. • Example: Darwins Finches… 14 finch species diverge from one common ancestor on the South American Mainland. Each species became specialized feeders for their particular environment.

ADAPTIVE RADIATION

Imagine these are beaks…

Some are great for big seeds…

While others are best for little ones

Without the best beak for the available food source… Some finches will not survive to pass their unfavorable traits on to offspring.

XI. Two more concepts… 1. Convergent Evolution: Natural selection that causes non- related species to resemble one another. 2. Coevolution: Two or more species evolve in response to each other through competitive or cooperative adaptations. Example are flowers and their pollinators.

GENE POOL- the total of all the alleles present in a population