natural selection define the term evolution. what comes to mind when you hear the term evolution?

Natural Selection

Define the term evolution.What comes to mind when you hear the

term evolution?

Pre-discussion Questions:

1. What is genetic recombination? 2. What is variation? 3. Name the 3 levels of mutations:

Population

A group of organisms of one species that interbreed and live in the same place at the same time (e.g. deer population).

Gene Pool

The total number of genes of every individual in an interbreeding population.A large gene pool indicates high genetic diversity, increased chances of biological fitness, and survival. A small gene pool indicates low genetic diversity, reduced chances of acquiring biological fitness, and increased possibility of extinction.

Gene Pool

Gene pool increases when mutation occurs and survives. Gene pool decreases when the population size is significantly reduced (e.g. famine, genetic disease, etc.). Some of the consequences when gene pool is small are low fertility, and increased probability of acquiring genetic diseases and deformities.

Discussion:

The 4 Ways that DNA can Change Genetic Recombination:

Crossing Over Independent Assortment of Homologous

Chromosomes (2n) Fertilization Mutations (Genes, Nucleotides, Non-disjunction)

EvolutionA genetic change (within the gene pool) in

a population over time. Must be a change to the DNA

Individual must reproduce to change the gene pool.Therefore those who reproduce the most will “direct” Evolution.

The change is caused by natural selection

Important Scientists

1798 - Malthus – Essay on Population Control.1809 – Lamarck – Use and Disuse

(Has been DISPROVED!!!!!!)Gene changes are random and not thought out

Organisms cannot thoughtfully change their DNA

If you work out really hard,Will you pass that on to yourOffspring?

Important Scientists

1858- Wallace – coined Natural Selection1858 – Darwin – Published Origin of Species.

Charles Darwin

NaturalistSailed on the Beagle

Studied variationOn Galapagos Islands

Continued his study & wrote Origin of SpeciesBook describing the principles of Natural Selection.

Trip of a Life Time

1831-183622 years old!

(a) Cactus eater. The long,sharp beak of the cactusground finch (Geospizascandens) helps it tearand eat cactus flowersand pulp.

(c) Seed eater. The large groundfinch (Geospiza magnirostris)has a large beak adapted forcracking seeds that fall fromplants to the ground.

(b) Insect eater. The green warbler finch (Certhidea olivacea) uses itsnarrow, pointed beak to grasp insects.

Beak variation in Galapagos finches

Darwin had studied Selective Breeding of animals & crops

Breed parents with traits you wantLike Long hair dogs

for living in coldor good milk cows

This is called Artificial Selection

Around 650 AD, startedCross breeding varietiesTo get the seedlessOnes we eat today !

Natural SelectionA genetic change in a population that occurs when organisms with favorable variations for a particular environment survive and pass on the trait to the next generation.

*** Survival of the fittest

Which of these is the fittest?

What does fittest mean?Fitness refers to an organisms ability to reproduce and pass its genetic code to offspring in their environment.

• The more offspring the more fit the organism

• Combination of physical traits & behaviors.

4 Natural Selection Principles:1. There is a variation within the

population.2. Some of the variations are favorable

Allows organisms to survive better than others in THAT environment

3. There is a struggle for existenceMore individuals are produced than live to reproduce

4. Those that survive have the favorable variation and REPRODUCE.

The next generation has the favorable trait Traits are GENETIC = In DNA

Variation and allele frequencies

Biological sciences definition of evolution:

The sum total of the genetically inherited changes of a population’s gene pool

Variation and allele frequencies

The effects of evolution are felt by individuals but it is the population as a whole that actually evolves

Variation and allele frequencies

Evolution is simply a change in the allele frequency of the gene pool in a population over time

Hardy Weinberg Equilibrium

Godfrey Hardy and Wilhelm Weinberg concluded that gene pool frequencies are inherently stable but that evolution should be expected in all populations all the time

Hardy Weinberg Equilibrium The hardy Weinberg equilibrium model suggests that evolution will NOT occur if the following 5 conditions are met

1. No Mutations (no changes in alleles)

2. No Natural selection (all alleles/traits are favored)

3. The population is infinitely large

4. All mating is totally random

6. No migration into or out of the population

Hardy Weinberg Equilibrium If no mechanisms of evolution are acting on a population, evolution will not occur and the gene pool (allele) frequencies will not change – it will remain constant

. This is called genetic equilibrium

Hardy Weinberg EquilibriumIt is highly unlikely that any of these seven

conditions will happen in the real world and evolution (DNA change) is inevitable.

Evolution is the result of a disruption in genetic equilibrium

Variations

The differences between individual members of a population.

Peppered Moths – Allele changes in population

Dark vs. light variants

Year % dark % light1848 5 951895 98 21995 19 81

VariationsFavorable variations are often caused by genetic recombination.

1.Crossing Over

2.Random Assortment of Homologous Chromosomes

3.Fertilization

4.Mutation

Changes caused by mutations in DNA that allows the organism to better survive are called:

Advantageous Mutations

VariationsWhen these variations occur there

will be more offspring from these organism because of the survival rate.

This slowly changes the species over time.

Based upon generational time.

AdaptationsAn inherited trait that increases a population’s chances of survival and reproduction in a particular environment

AdaptationsTypes of adaptations

1. Structural: Used for defense against predators

Structural AdaptationsExamples:Defense - Horn, Thorn, Armor, PoisonMimicry and Camouflage to hide

Adaptations

2. Physiological: Changes in metabolic processes for survival.

Physiological Adaptation

Examples:Resistance to chemicals such

as antibiotics.Pest resistance

to pesticides

Patterns/Types of Natural Selection

Based on the favorable adaptations and variations within a population,

There are patterns of change that populations will follow based upon the genetic variation present in the

population.

Normal DistributionGet a bell shaped curve of variation

But Environmental Stress can favor certain phenotypes

Patterns of Evolution (changes in allele frequency)

Natural Selection (3 patterns) 1. Stabilizing Selection 2. Disruptive Selection 3. Directional Selection

Artificial Selection Example: Dog Breeding

1. Stabilizing Selection: this type of natural selection favors the average individuals within the population. The extreme phenotypes in the population are selected against.

Natural Selection

1. Stabilizing Selection: this type of natural selection favors the average individuals within the population. The extreme phenotypes in the population are selected against.

Natural Selection

Natural Selection 2. Disruptive Selection: This type of natural selection selects for the extreme phenotypes in a population. The trait selected against is the average phenotype.

3. Directional Selection: This type of natural selection is where one extreme phenotype of the population is favored. The other extreme is selected against within the population

Natural Selection

Disruptive

Artificial Selection

Human interference to breed organisms (cats, dogs, plants etc.) with desirable traits.

Controlling the population through selective breeding

Evidence for EvolutionThe Keys to the Past & the Future are often what we know in the Present ! How is the earth changing RIGHT now?

…. New islands by volcanos, deserts growing

How do we know animals have not always been the same?

….. Fossils,

Banana fossils in Oregon,

fish fossils in Idaho desert

Evidence for EvolutionThe Keys to the Past & the Future are often what we know in the Present !

Evidence for EvolutionThe Keys to the Past & the Future are often what we know in the Present !

4 main pieces of evidence for evolution 1. Fossils

2. Embryological Comparisons

3. Anatomical Comparisons

4. Genetic Comparisons

Fossils 2 ways to date fossils

1. Relative dating

Comparing fossils to different rock layers in the sediment.

The deeper the fossil, the older the specimen

2. Radioactive dating Testing the half life of chemicals (mainly carbon) to date the materials

Embryological Comparisons

A comparison of vertebrate embryos to support the theory of evolution

Early embryos

look similar

Humans have

Gill pouches

Anatomical Comparisons

A. Vestigial Structures– structures that have no use to the organism any more

Example: Tail bone, whale pelvis, snake legs

Anatomical Comparisons

B. Homologous structures– similar structures seen in organisms with similar ancestors

Example: Fore arms of various mammals including whales, horses and humans

Anatomical Comparisons

C. Analogous structures – structures that are similar in function but not in form

Example: A bat wing and an insect wing…. …both exist in an airborne environment

Genetic Comparisons

The strongest piece of evolution that scientists have today

Uses the genetic code of various organisms to show the relationships genetically

Genetic Comparison

More base sequences the same, closer you are related !

Oldest: ATCCGTAATC

Order the closest related to furthest:

A. ACCCTTACGC

B. ATCGGTACTC

C. ACCCTTACGT

21 most alike3 most different

Time of Evolution

Two general theories about how fast evolution happens

Remember it occurs in generational time

1. Punctuated Equilibrium

2. Gradualism

Punctuated Equilibrium

A model of evolution in which short periods of drastic change in species, including mass extinctions and rapid speciation are separated by long periods of little or no change

Gradualism

A model of evolution in which gradual change over a long period of time leads to biological diversity

Rate of SpeciationDoes speciation happen gradually or rapidly

Charles DarwinCharles Lyell

Stephen Jay GouldNiles Eldredge

Gradualism Punctuated Equilibrium

rapid bursts of change mixed with long periods

of little or no change

gradual accumulation of small changes over long time

Causing a new species: Speciation

Speciation occurs when the DNA changes enough to create a new species

Species: a group of organisms that live in the same place and can freely interbreed AND produce fertile offspring

2 general causes of speciation

1. Population Isolation a. Reproductive

b. Geological

2. Genetic Drifta. Bottle Neck

b. Founders Effect --Happens to small populations

Population Isolation

a. Reproductive Isolation The inability of members of a population to successfully interbreed with members of another population or related species because of :

Mating TimeMating Rituals Sexual Selection (ex. Why birds are brightly colored)

Population Isolation

b. Geographic Isolation Caused by geographical barriers or any physical barrier that would isolate a population of individuals from its parent population

Ex. Mountains, rivers, canyons, etc.

Genetic Drift

A. Bottle Neck Effect Where a population is affected dramatically by a disaster or reproduction failure.

Only a few organisms survive to reproduce

Genetic Drift

B. Founders Effect When a small group of organisms move from one area to another, leaving the parent population and create a change in a new genome.

Patterns of Evolution

A. Divergent EvolutionAdaptative Radiation

B. Co-Evolution

C. Convergent

Evolution

Patterns of Evolution

A. Divergent Evolution When a population becomes separated by a geographical barrier and evolve separately.

Evolve from a common ancestorAdaptive Radiation:

• Many species evolve from a common ancestor and have a lot of room to occupy.

• Example: Finches

Phylogenetic trees

Like a tree

Adaptive Radiation & Darwin’s Finches

Adaptive Radiation & Darwin’s Finches

Patterns of Evolution

Co-Evolution When two species interact they evolve traits

together to continue that relationship.Symbiotic Relationships

Example: Predation, Mutualism, Parasitism

Coevolution

Patterns of Evolution

Convergent Evolution Two species who are not

related evolve similarities

in appearance OR

behavior

Example: bats + birds + insectAll have evolved in an airtime

environment

Have Analogous Structures, convergent evolution.

Similar function, but different structures

Convergent EvolutionOrganisms evolve into similar body forms

due to similar ecosystemsNot Related – No common ancestors

Summary

Natural Selection is what causes evolution and changes in organisms over time.

That natural selection tends to act on Phenotypes of individuals and affect the resulting genotypes!