Do Now 1.Come in quietly 2.Copy the objective (To learn about Evolution) 3.Relax and wait until class starts 4.And please dont put the textbooks that are.

Do NowDo Now

1.1. Come in quietlyCome in quietly

2.2. Copy the objective (To learn about Copy the objective (To learn about Evolution)Evolution)

3.3. Relax and wait until class startsRelax and wait until class starts

4.4. And please don’t put the textbooks that And please don’t put the textbooks that are on your desks on the floor.are on your desks on the floor.

Evolution Evolution

Darwin in a nutshellDarwin in a nutshell

Individual organisms in nature differ from one Individual organisms in nature differ from one another.another.

Organisms in nature produce more offspring Organisms in nature produce more offspring than can survive. than can survive.

Because more organisms are produced than Because more organisms are produced than can survive, competition for limited resources can survive, competition for limited resources takes place.takes place.

Since each organism is unique, each has Since each organism is unique, each has distinct advantages and disadvantages in the distinct advantages and disadvantages in the struggle for existence.struggle for existence.

Darwin (con’t)Darwin (con’t)

Individuals best suited to their environment Individuals best suited to their environment survive and reproduce most successfully. The survive and reproduce most successfully. The characteristics that make them survive are characteristics that make them survive are passed on to their offspring.passed on to their offspring.

Species change over time.Species change over time. Species alive today have descended with Species alive today have descended with

modifications from species that used to live in modifications from species that used to live in the past.the past.

All organisms on Earth are united into a single All organisms on Earth are united into a single tree of life by common ancestors. tree of life by common ancestors.

Gene PoolsGene Pools

A gene pool is the A gene pool is the combined genetic combined genetic information of all the information of all the members of a members of a particular population.particular population.

Sources of Genetic Sources of Genetic VariationVariation

MutationsMutations – – A change in sequence of A change in sequence of

DNA. Things that can DNA. Things that can cause mutations:cause mutations:

Mistakes in DNA Mistakes in DNA RadiationRadiationChemicalsChemicals

They can affect a single They can affect a single base, a length of DNA or base, a length of DNA or an entire chromosomean entire chromosome

Genetic ShufflingGenetic Shuffling – –

This is basically the This is basically the genetic variation that genetic variation that occurs with the occurs with the process of sexual process of sexual reproduction reproduction (crossing over, 4(crossing over, 4nn, , etc.) etc.)

Genetic DriftGenetic Drift

Occurs when one Occurs when one portion of the portion of the population finds a population finds a new habitat. new habitat.

Now, there are Now, there are different types of different types of genes present in the genes present in the new gene pool new gene pool

This creates a new This creates a new population.population.

Genetic EquilibriumGenetic Equilibrium

This is a situation where allele This is a situation where allele frequencies (the amount of times a trait frequencies (the amount of times a trait occurs) stay the same.occurs) stay the same.

In order for this to happen, the following In order for this to happen, the following must occur:must occur:

A.A. There must be random There must be random matingmating

Random mating Random mating ensures that each ensures that each organism has an organism has an equal chance to pass equal chance to pass on its genetic on its genetic informationinformation

Random Mating Allowed

No Random Mating Allowed

B. Large PopulationB. Large Population

A large population A large population would limit the effect would limit the effect of Genetic Driftof Genetic Drift

C. No movement into or C. No movement into or out of the populationout of the population

Genetically, this Genetically, this would keep the gene would keep the gene pool of a certain pool of a certain population in tact and population in tact and totally different from totally different from nearby gene poolsnearby gene pools

D. No MutationsD. No Mutations

A mutation would A mutation would alter the types and alter the types and numbers of alleles numbers of alleles present in the gene present in the gene pool.pool.

E. No natural selectionE. No natural selection

No phenotype can No phenotype can have a selective have a selective advantage over advantage over another.another.

SpeciationSpeciation

This is the formation This is the formation of a new species of a new species from pre-existing from pre-existing ones.ones.

Isolating MechanismsIsolating Mechanisms

In order for speciation to occur, there must be an In order for speciation to occur, there must be an isolation in gene pools between the ‘old’ species and isolation in gene pools between the ‘old’ species and the newer forming species.the newer forming species.

Reproductive IsolationReproductive Isolation

Once the new Once the new species has changed species has changed enough where it no enough where it no longer can share a longer can share a gene pool with the gene pool with the ‘original species’, ‘original species’, both species are said both species are said to be reproductively to be reproductively isolated. isolated.

How does reproductive How does reproductive isolation occurisolation occur??

One way is called One way is called BEHAVORIAL BEHAVORIAL ISOLATION.ISOLATION.

This is when there is This is when there is a difference in a difference in behavior (duh) behavior (duh) namely in courtship namely in courtship rituals.rituals.

Bufo alvarius

Bufo

cognatus

A second way that isolation can occur is called A second way that isolation can occur is called GEOGRAPHIC ISOLATIONGEOGRAPHIC ISOLATION..

This is where two populations are separated by This is where two populations are separated by a geographic barrier. a geographic barrier.

A third way that isolation can occur is A third way that isolation can occur is TemporalTemporal..

Temporal isolationTemporal isolation is when the two species is when the two species have a different mating season, duration, etc. have a different mating season, duration, etc.

Speciation In Darwin’s Finches:

1. Founders Arrive

2. Separation of Populations

3. Changes in the gene pool

4. Reproductive isolation

5. Ecological Competition

6. Continued evolution

Final Important TermsFinal Important Terms

Adaptive RadiationAdaptive Radiation – –

When a single species When a single species has evolved into has evolved into several different several different forms that live forms that live successfully in successfully in different waysdifferent ways

Convergent EvolutionConvergent Evolution – –

When two or more unrelated organisms evolve to When two or more unrelated organisms evolve to look like each other.look like each other.

Ex. Aquatic animals (sharks, dolphins, etc.)Ex. Aquatic animals (sharks, dolphins, etc.)

Coevolution – Coevolution – Two species evolve in response to changes in each Two species evolve in response to changes in each

other over time.other over time.