What is Biological Evolution?and

Who first proposed that “life changes over time”?

Not Darwin….

Charles Darwin

1809-1882

It was Greek philosophers such as Anaximander, 2600 years ago!

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Before going into details, let’s cover some basics first and clarify some confusion that frequently exists.

Do you believe in God

or some type of Supreme Being or Force?

Do you believe in cells…that they are the fundament units of life?

Are these the same sort of beliefs?

In your head:

As a scientist, I do NOT believe that cells are the fundamental units of life (part of Cell Theory).

I also DO NOT believe that the planets orbit about our sun (part of Heliocentric Theory).

I simply CONCLUDE (or think) that Cell Theory and Heliocentric Theory are

powerful and very well supported explanations of how our world works.

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I also do not BELIEVE in evolution.

I simply find it to be one of the most powerful theories in all of science…

If someone in the future proposes a theory that explains all that evolution explains and more, science must be

willing to consider that theory instead.

Such is the TENTATIVE nature of science.

….supported by many independent lines of evidence…which we will review briefly.

Heliocentric Theory:That the planets orbit the sun…

is just a theory too.

Cell TheoryCell Theory::All life is made of All life is made of cells...cells...……is is just a theoryjust a theory too too..

Theory of Inheritance:How DNA codes for life……is just a theory too.

Theory of Inheritance:How DNA codes for life……is just a theory too.

Germ Theory:Many diseases result from viral and bacterial infections……is just a theory too.COLD VIRUSES

HIV - the cause of AIDS

Atomic Theory:…the structure of the atom…is just a theory too.

Theories are the strongest,

most well supported explanations

in all of science.

There is NO term that we use in science with greater confidence.

Science is VERY CONFIDENT that evolution occurs.

https://www.youtube.com/watch?v=85diEXbJBIk&list=PL5270149AB732F0FB

So you have to wonder…

In many textbooks, there is confusion about some terminology.

Many elementary and high school textbooks use the word “Development”

instead of “Evolution”.

These two terms mean completely different things.

Development addresses the changes that occur within an individual’s lifetime.

Evolution addresses the changes that occur in species over time.

And… “What is a Species?”

For organisms that reproduce sexually…which is by far most animals…

Dr. Ernst Mayr proposed the Biological Species Concept:

A species is:

“a group of interbreeding natural populations that are reproductively isolated from other such groups.”

What are we speaking about, when we talk about “Evolution”?

Fact - That evolution occurs…

•That life has changed over time,

•That life continues to change over time, and

•That all life has a common ancestry.

Course / Ancestry - Who gave rise to whom and who is most closely related to who…are matters of ancestry and are still greatly explored & debated. “the family tree”

Mechanism - Darwin & Wallace proposed Natural Selection as the mechanism. Although Natural Selection clearly occurs, it is still debated in science whether or not there are other mechanisms of evolution working too.

Chapter 15

Jean-Baptiste Lamark-180915-2 pg 3761. Organisms strive to improve themselves

2. Most used body structures develop “Use it or lose it”

3. Used modification is inherited by offspring

Ex: giraffe necks & muscle builders

August Weisman- 1883

Uses mice to disprove Lamark Cuts tails off of mice, didn’t lead to tailless

mice

“cut off the tails of 901 young white mice in 19 successive generations, yet each new generation was born with a full-length tail. The final generation, he reported, had tails as long as those originally measured on the first”

Now on with the story of Charles Darwin

and his contributions to science.

-Entered & left medical school-Entered & left ministry-Cambridge-meets John Henslow

Studies geology & biology

15-1At the age of 22, Darwin began a 5 year voyage around the world on HMS Beagle

-5 year, global voyage -Goal was to make maps of S. America

Galapagos Islands- Darwin notices that many groups of animals represent variations on a theme.

Similar by DESIGN….

Similar because of shared ancestry.

Similar because of shared ancestry.

Similar because of shared ancestry

Was all of life related…and thus similarbecause of shared ancestry?

Into this world Darwin offered

5 theories, in his major work,

On the Origin of Species…

1) Evolution occurs:

The world is not constant. - Instead, it is changing, and organisms change over time.

2) Common Descent:Every group of organisms is descended from a common ancestor.

3. Natural Selection: Evolution occurs through 1) the production of genetic variety and 2) the subsequent advantages that result from certain combinations.

4. Gradualism: Evolution occurs through gradual change instead of the sudden appearance of new forms.

Gradualism as proposed by Charles Darwin

Punctuated Equilibrium - proposed by scientists

working after Darwin

5) Multiplication of species: a) Species multiply by splitting into daughter species or b) by geographic isolation of a founder population.

Darwin titled his book “On the Origin of Species…” because he saw this part of his idea as one of the most important contributions of his ideas.

HOW SPECIES FORM.

Summarizing Darwin’s main ideas: Natural Selection

1. There is variation within populations2. Some variations are favorable3. More offspring are produced than can

survive4. Favorable variations = survival5. Change over time leads to population

change

Lamark vs Darwin

Both theorized that: Life changed gradually over time and

was still changing that living things change to be better

suited and adapted to their environments

all organisms are related

15-3 Publication

Alfred Russel Wallace-makes similar voyage, but his notes were destroyed Wants to publish findings

So…..Darwin publishes 1858 “On the Origin of Species”

Darwin referred to evolution as“Descent with Modification”

The phrase “survival of the fittest” originated with another scientist, Herbert Spencer, after reading Darwin’s

book Origin of Species.

In the 6th Edition of Orgin of Species, Darwin Retitled Chapter IV,“Natural Selection; or the Survival of the Fittest.”

Today we know that this phrase is circular.

Thus the phrase means “survival of the survivors!”.So the phrase “survival of the fittest” is not commonly

used by scientists.

To be fit includes the ability to survive.

A note about the phrase “survival of the fittest”

EVIDENCE FOR EVOLUTION

Multiple Lines of Evidence Increases Confidence

http://learn.genetics.utah.edu/content/variation/related/

Anatomical Studies1. Homologous- modified structure

seen among different groups Similar in structure & function

Ex: forelimbs-reptiles, mammals, birds

2. Analogous- similar in function, different structure

ex: insect vs bird wing

3. Vestigial- structure once used but not now ex: appendix in humans eyes of sightless species

16.1 Populations

All individuals of the same species that live in the same environment & interbreed

Features of populations: 1. Population size- # of individuals

Small is bad- interbreeding, natural disasters

2. Population density- # of individuals in an area Spaced widely apart= no mating

3. Dispersion- random, even, or clumped

Growth Rate

Exponential or J-shaped curve

*not true because of diseases, predators, & resources

Carrying Capacity (K)

Population size that an environment can actually hold

Gives us a Logistic Model

Gene pools- total genetic info in a population

Allele frequency- look at inside (genes) # of A / # of all individuals

Phenotypic frequency- look at outside appearance # of curved mouth / # of

all individuals

Population studies

Look at 1 specific population and determine frequencies

16-2 Hardy-Weinberg Principle P2 + 2pq + q2 = 1 Genetic Equilibrium- frequencies of alleles in

a population don’t change unless there is evolutionary force acting

What are the 5 things that have to be in place to stay in Genetic Equilibrium? Pg 401-402

If genetic equilibrium is in place or occurring, then there is NO EVOLUTION! (this does not happen in the real world)

What cancels Hardy-Weinberg?(What causes Evolution?) 1. Mutations- from environment

(chemicals, UV) or spontaneous (cells)

2. Gene Flow/Migration- changes which genes are part of the frequencies used

3. Non-random Mating- inbreeding, self-fertilizing (plants), choosing specific mates

4. Genetic Drift- random change in alleles Usually because of small populations

5. Natural Selection- “Survival of the Fittest” Affects phenotypes

3 types of Natural Selection A. Stabilizing- favors

average Ex: large spiders get

eaten, small spiders can’t get enough food

B. Directional- favors 1 extreme Ex: Woodpeckers with

longer beaks can reach more insects

C. Disruptive- favors both extremes, eliminates middle Ex: limpets: white blend in with

sand, dark brown hide on rocks, tan are seen and eaten

Peppered Moths

16-3 Speciation- forming new species (Microevolution) What is a Species?

The morphological species-species are determined by looking alike

The biological species concept- Ernst Mayer says, "Species are groups of interbreeding natural populations that are reproductively isolated from other such groups."

How does it happen?

Isolation

-when the two species can no longer interbreed.

A. Prezygotic Isolation (mechanisms take effect before or during fertilization)

1. Geographic/ Habitat Isolation: when a barrier or living in different habitats prevents breeding ex: different species of manzanita shrubs live at

different altitudes and habitats Ex: earthquake that results in separation of species,

Glaciers, continents

Archipelagos- island chain some distance away from a continent

The division of a population, may form two new species.

Sympatric speciation - new species evolve from a single ancestral species while inhabiting the same geographic regionAllopatric speciation - evolution of geographically isolated populations into distinct species

2.Reproductive Isolation any heritable features of body form,

functioning, or behavior that prevent interbreeding between populations.

Temporal (Seasonal) Isolation: different groups may not be reproductively mature at the same season, or month, or year

ex: mating seasons of frogs in north vs south

3. Behavioral Isolation: patterns of courtship may be altered

ex: albatross courtship rituals- dancing birds, separates dogs from wolfs(aggressive)

http://www.youtube.com/watch?v=7dx2CUMtZ-0

4. Mechanical Isolation: reproductive organs prevent successful interbreeding

ex: floral arrangements in sage plants discriminate between different bee pollinators

*Note: (2,3,4 can be overcome in the lab) = Hybrids

5. Gametic Isolation: incompatibilities between egg and sperm prevent fertilization or the sperm is killed outright by the female reproductive tract.

B. Postzygotic Isolation (mechanisms take effect after fertilization) 1. Developmental Isolation: Fertilization may occur, but development of the embryo is irregular and development is not completed.

2. Hybrid Inviability: Fertilization does occur between different species, but the hybrid embryo is weak and dies.

3. Hybrid Sterility: In some instances the hybrids are vigorous but sterile

ex: mule produced by a male donkey and a female horse

Models for Other Speciation Routes1. Polyploidy- inheritance of three or more of each type of chromosome due to improper separation of chromosomes during meiosis or mitosis example:

2. Parapatric Speciation- reduced gene flow within the population, interbreed with local individuals only

Artificial Selection/ Selective Breeding Breeding animals with desired

characteristics to produce the next generation

Different breeds of dogs

Super Cow http://www.youtube.com/watch?

v=IDN-QeVhQTc

17.4 Patterns of Speciation

Branching and Unbranched Evolution Cladogenesis applies to populations

that become isolated from one another and subsequently diverge in different directions.

Anagenesis is a pattern of descent in which species form within a single, unbranched line.

Divergent Evolutionpattern in which species that once were all similar become more distinct, species adapt to different environments

1. Adaptive Radiation- many related species evolved from a single ancestral speciesex: finch beaks based on niche are all from 1 ancestral bird

Convergent Evolution- unrelated species become more similar in appearance as they adapt to the same type of environment

Ex: fish and dolphins same body shape and fins

Coevolution- two organisms adapting together

Ex: plants and animals that pollinate them

Evolutionary Trees and Rates of Change

1. The gradual model of speciation is represented by tree diagrams with branches at slight angles to each other to show slow change over time. Ex: support from fossil record

2. The punctuation model of speciation is drawn with short, horizontal branches that represent abrupt periods of speciation followed by stable periods.Ex: introduction of a new predator

Macroevolution

the processes outlined above, but is evolution at taxonomic levels above the species level.

occurs when evolution creates entirely new adaptations previously non-existent

Adaptations

1. Structural- changes in the structure of body parts

ex: thorns, spines of sea urchins, mole rat (larger teeth & claws)

Mimicry- copy appearance of another species Ex: moth wings look like

eagle eyes Camouflage- blend in with

surroundings Ex: sand snakes, walking

stick

2. Physiological- changes in an organisms metabolic processes Ex: bacteria resistance, weeds

resistant to pesticides

Hox Genes

Master control genes- control growth as an embryo develops

http://www.hhmi.org/bulletin/fall-2014/keeping-tabs-development