Evolution Part I:

Evolution Part I:

Charles Darwin is known as the Father of Evolution.

What we know now seems like common sense but in Darwin’s day,

it wasn’t. So…..How did Darwin come up

with his new and radical ideas that eventually led to the (controversial)

Theory of Evolution?

After studying at Cambridge, Charles was recommended for a surveying trip on the HMS

Beagle.

He sailed around the world on the Beagle for 5 years, working as a naturalist.

On the voyage, Darwin noticed that everywhere he went,

the animals and plants differed vastly.

Yet, there were similarities

Patterns in the species suggested that the species had changed over time and had given rise to new and

different species.

The Galapagos Islands lie 500 miles west of Ecuador in the Pacific Ocean,

directly on the equator.

Many of Darwin’s conclusions were

based on observations of

wildlife in the Galapagos Islands.

“Galapagos” means turtle.

Were the animals and plants created to match their environment?

Then, why didn’t the Galapagos finches look like the birds of the African continent, since the environments of both the Galapagos and

Africa were similar.

Darwin guessed that some of the birds

from South America migrated to the

Galapagos.

Once on the islands, the birds must have

changed over the years because each island was different

from the others….landscape

and flora.

Darwin called this…

or

(change in species over time)

Darwin concluded:Each species had descended, with changes,

from other species over time.

Descent With Modifications

…or Survival of the Fittest.

The mechanism by which evolution takes place.

Five basic components:

1. All species have genetic variation.

Nature has to have some variety in order to choose.

Look around you…are you all the same?

2. Organisms produce more offspring than can survive. Many that survive do not produce offspring.

The female green sea turtle lays a clutch of about 110 eggs. She may lay several clutches.

It is likely that less than 1% of the hatchlings will ever reach sexual maturity.

3. Since more organisms are produced than can survive, there is competition (struggle for existence).

Competition exists WITHIN and AMONG species.

foodWithin and Among Species for

And Within a Species for

water

mates

shelter space

Short-term natural disasters can have large impacts on competion. (drought, fires, floods, snowstorms, hurricanes, and tornadoes)

Long-term changes in the environment also affect survival. (ice ages, biome shifts, global warming etc)

4. Survival of the fittest Some organisms are more suited to their environment as a result of variations in the species.

Fitness: the ability of an individual to survive and reproduce in its specific environment. Fitness is a result of adaptations.

He who spreads the most genes wins!1st

Individuals that are fit to their environment survive and leave more offspring than those who aren’t.

5. Descent with modification: Living species today are descended with modifications from common ancestral species that lived in the past.

Over time, genes for less favored characteristics will be eliminated from the gene pool.

Example: giraffes and their increasingly longer necks.

Characteristics of fit individuals increase in a population over time.

Natural Selection: Survival of the Fittest

the variation has to already exist.

An adaptation is any inherited characteristic (a genetic variation) that can increase an organism’s chance of survival.

If the environment changes.

the variation may give an advantage to survive environmental change.

An organism does not change because of the need or desire to survive. The organism is either

born with the variation that enables it to survive or it dies.

Darwin published his theory in the book

November 24, 1859

And that is why Darwin is the father of Evolution

NATURAL SELECTION IN ACTION• Camouflage

(Cryptic coloration)

NATURAL SELECTION IN ACTION

• Mullerian Mimicry –untasty imitates untasty ….both benefit by making sure their predators gets the point.

• Monarch and Viceroy Butterfly


• Batesian Mimicry – palatable (tasty) mimics unpalatable (untasty)

• Coral vs. King Snakes: Red on yellow, kill a fellow, red on black friend of Jack

Natural Selection in Action• Warning Coloration (Aposematic

coloration)


• Disruptive Coloration

Natural Selection in Action

• Counter Shading

Natural Selection in Action

• Eye spots

Evolution Things to remember:

a. Populations evolve, not individuals.

b. Natural selection is the mechanism of evolution.

c. Evolution occurs by chance (NOT GOAL ORIENTED).

d. Organisms are born with adaptations, they can’t adapt because they need or want to

Part II

• Speciation • Causes of evolution• Rates of evolution

Species

– An organism that has the potential to interbreed in nature and produce viable, fertile offspring that looks like their parents.

Speciation is the creation of a new species

results from

which include

produced by produced byproduced by

which result in

which result in

Reproductive Isolation

Isolating mechanisms

Behavioral isolation Temporal isolationGeographic isolation

Behavioral differences Different mating timesPhysical separation

Independentlyevolving populations

Formation ofnew species

Occurs when 2 pop. are capable of interbreeding but have different courtship rituals or other reproductive strategies that involve behavior

Two or more species reproduce at different times

Two pop. Are separated by geographic barriers such as rivers, mountains, or bodies of water

Speciation

results from

Reproductive Barriers

A reproductive barrier is any factor that prevents two species from producing fertile hybrids, thus contributing to reproductive isolation.

• Habitat/Geographical Isolation• Temporal Isolation• Behavioral Isolation• Mechanical Isolation• Gametic Isolation

Causes of Evolution1. Mutations - random changes in genetic material at

the level of the DNA nucleotides or entire chromosomes

2. Natural Selection - most important cause of evolution; measured in terms of an organism's fitness– The contribution an individual makes to the gene

pool of the next generation, relative to the contributions of other individuals…the more fit, the more they contribute.

Modes of Selection (types of natural selection)

a. Stabilizing Selection - average phenotypes have a higher fitness over the extreme phenotypes

b. Directional Selection - phenotype at one extreme has a higher fitness over the average and the other extreme

c. Disruptive Selection - both extreme phenotypes have a higher fitness than the intermediate phenotypes

In this case, darker mice are favored because they live among darkrocks and a darker fur color conceals Them from predators.

These mice have colonized a patchy habitat made up of light and dark rocks, with the result that mice of an intermediate color are at a disadvantage.

If the environment consists of rocks of an intermediate color, both light and dark mice will be selected against.

Phenotypes (fur color)

Original population

Originalpopulation

Evolvedpopulation

Freq

uenc

y of

indi

vidu

als

Modes of Selection

Directional DisruptiveStabilizing

Causes of Evolution3. Mating Preferences - Organisms usually do not choose their mates at random, thus the selection process can cause evolution

4. Gene Flow - Transfer of genes between different populations of organisms. This situation leads to increased similarity between the two populations (Tends to reduce differences between populations over time)

5. Genetic Drift (Founder Effect & Bottleneck) - Situation that results in changes to a population's gene pool caused by random events, not natural selection. This situation can have drastic effects on small populations of individuals. Common on islands.

Gene Flow

Genetic Drift

Founder Effect

Bottleneck Effect

RATE OF EVOLUTION

Part III:Types of EvolutionExtinction

TYPES OF EVOLUTION• 1. Divergent Evolution - Multiple

species of organisms descended from the same common ancestor at some point in the past. – Method of evolution accounting for the

presence of homologous structures.– Adaptive Radiation.

• Ex. Darwin’s finches

• 2. Convergent Evolution - Because certain adaptations are more advantageous in different environments, unrelated organisms that live in similar environments will have similar features that perform similar functions.– Method of evolution accounting for the

presence of analogous structures.– Ex. Dolphins and shark

• 3. Coevolution –Organisms that are closely connected evolve together. – Method of evolution accounting for

specialists. • Ex. Monarch butterfly and milkweed plants• Insects and flowers

As the environment changes, organisms must have variations (adaptations) that will determine whether they can survive with the changes or they can’t and they die.

If an entire species cannot adapt, that species will then become extinct.No More, Finished, Bye-Bye!

There have been at least 5 MASS extinctions during Earth’s history where a huge % of the living species were destroyed

At least one of these mass extinctions has been attributed to meteor impact and it’s

consequences.

It is estimated that 1/5 or more of the world’s species will become extinct if the rainforests are destroyed.

Many scientists say that the

earth is currently

experiencing a mass extinction

crisis.

Part IV:Evidence of Evolution

Evidence for Evolution• 1. Fossil Evidence:

– Paleontology - Study of Fossils Fossil - preserved evidence of past life

– Fossil record: shows organisms that are no longer living and how they changed over time. a. Relative dating

– Which rock layer is the fossil found…If you know the age of one, the rest of them are about the same age.

– Index fossils: wide range, short time period b. Radioactive dating

– Measuring radioactive isotope vs. stable atom content

» Carbon 14

FOSSIL FORMATION

MORPHOLOGICAL HOMOLOGY (similarities)

• 2. HOMOLOGOUS STRUCTURES

– Structures that are similar because they are derived from a common ancestral structure

• A structure that serves the same function in two taxa, but is NOT derived from a common ancestral structure is said to be an

ANALOGOUS STRUCTURE

3. Embryology (ontogenic) Homology

• As organisms develop, they go through many stages that are similar to other organisms.– The longer two organisms share developmental

stages, the more closely related they are to each other.

Evidence for Evolution

• 4. Molecular Homology-The comparison of different proteins (amino acids) can show how closely related species are to each other.

-The fewer differences in the genetic make-up, the closer related they are.



Hybridization of DNA can also show evolutionary relationships.

5. Vestigial Structures

• Structures that have marginal, if any, use to the organisms in which they occur. – Reduced in size. – Derived from an earlier ancestor that did

use/need this structure.


6. Biogeography

• The study of the geographical distribution of organisms. – Species that are related to each other tend to live

near each other. (fossils of ancestors are present too)

– As geography changes, populations are separated or combined with new populations.• Continent movement (collide and separate), rivers,

mountains, lakes, etc. separate populations

Phylogeny

Phylogeny: Studying the evolutionary histories and relationships of organisms

• Cladistics: a phylogenic study that assumes when probable groups of organisms diverged and evolved

Theropods

Allosaurus

Sinornis

Velociraptor

Archaeopteryx

Light bones3-toed foot;

wishboneDown

feathers

Feathers withshaft, veins,and barbs

Flight feathers;arms as long

as legs

Cladograms• “Family tree” that represents evolutionary

relationships (and not just physical appearances)

CLADOGRAM

Fur & MammaryGlands

Jaws

Lungs

Claws or Nails

Feathers

Hagfish Fish FrogLizard

Pigeon

Mouse

Chimp

Documents

Evolution Part I: