Unit 2 Evolution - Manatee School For the Arts / · PDF fileUnit 2 Evolution Evolution: The...

Evolution Unit Mrs. Stahl Biology

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Unit 2 Evolution

Evolution: The process of biological change by which descendants come

to differ from their ancestors.

There are many scientists that were involved:

Developed a classification system for all

types of organisms.

Grouped them according to their

similarities.

Ex- Domain, Kingdom, Phylum, Class,

Order, Family, Genus, Species

Carl Linnaeus

1735

Proposed that species shared ancestors

instead of arising separately.

Suggested that the Earth was older than

6,000 years old.

Georges Buffon

1749


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Charles Darwin’s grandfather. He

proposed that all living things were

descended from a common ancestor, and

that more complex forms of life arose

from less complex forms.

Erasmus Darwin

1794-1796

Proposed that all organisms evolved

toward perfection and complexity.

Species didn’t become extinct, but

rather turned into different forms.

Ex- The environment changed which

caused the organism to change.

Giraffes: giraffes evolved long necks

over many generations due to the trees /

vegetation growing taller. They

essentially “stretched their necks.” This

idea is known as inheritance of acquired

traits.

Jean Baptiste Lamarck

1809


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He thought that animals could become

extinct. He observed that each rock

layer / strata had its own specific fossils.

Fossils in the deep layers were different.

Theory= Catastrophism: sudden

disaster

Natural disasters (floods, volcanoes,

etc.) shaped our landforms and caused

species to become extinct.

Georges Cuvier

Early 1800’s

Changes in landforms resulted from

slow changes over a long period of

time= Gradualism.

Ex- laying down soil or canyons being

created by rivers takes a lot of time.

Today: used to mean the gradual change

of species through evolution.

James Hutton

1785


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Uniformitarianism: Geological

processes that shape Earth are uniform

through time. Things change at a

constant rate and are ongoing.

Charles Lyell

1830’s

1831- He set sail on a five year journey

aboard the HMS Beagle from England to

S. America and the Pacific Islands.

Kept observing variation in species:

differences in the physical traits of an

individual from those of other

individuals in the group.

Interspecific: among members of

different species.

Intraspecific: among individuals of the

same species.

Charles Darwin

1831


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Darwin and the Galapagos

* Galapagos- Islands off Ecuador

* Darwin observed differences in animals that lived on different islands.

* Example 1: Tortoises

a. Saddle back tortoise-> had long necks / legs, lived where plants were tall.

b. Domed tortoise-> shorter necks / legs, lived in wet areas rich in mosses

and short plants.

* Example 2: Finches

a. Strong, thick beaks: lived in areas with large, hard shelled nuts.

b. Delicate beaks: found where insects or fruits were available.

Led Darwin to the idea of adaptation: species genetically change in a population

over time. They adapt to their surroundings.

He found fossil evidence which supported the idea of an ancient Earth.

Argentina: giant armadillos, Glyptodon, thought the Earth was older than 6,000

years.

Andes Mountains: fossils of marine organisms.

Experienced earthquakes: he observed land that was underwater being pushed

above sea level.

His observations supported Lyell’s theory: “geologic processes can add up to great

change over a long period of time.”

Fun Fact: Darwin took three tortoises from the Galapagos back to England and

named them Tom, Dick, and Harry. Relocated them to Australia because they

couldn’t adapt to the climate. They thought they were all males, but later found out

that one of the tortoises was a female and switched her name to Harriet. She died in

2006, she was 176 years old.


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Unit 2- Theory of Natural Selection

Darwin was convinced evolution could occur, but he couldn’t explain how.

He spent more than 20 years researching and eventually turned to farmer and breeders for

help.

The key items that led to the idea:

1. Artificial Selection:

________________________________________________________________________

________________________________________________________________________

a. Darwin noticed a lot of variation in domesticated animals and plants. More so

than in wild populations. He saw that breeders could take certain traits and

produce diversity in an organism.

b. Humans / Breeders:

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c. Example: Breeding pigeons-

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d. Heritability

i. Ability of a trait to be passed down from one generation to the next.

ii. Key factor in making artificial selection possible.

e. Darwin tried to compare adaptation with breeding. Breeders wanted reversed neck

feathers, inflatable crops, tail feathers, etc. Breeders also selected against traits

that they felt were not favorable.

f. In artificial selection ________________________________________________

g. In nature __________________________________________________________

Theory of Natural Selection:

______________________________________________________________________________

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Nature:

______________________________________________________________________________

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2. Struggle to Survive

a. Thomas Malthus: food, water, and shelter were natural limits to population

growth.

i. Example: Human population would grow geometrically if we had

unlimited resources- disease and limited food kept populations smaller.

ii. He stated that the human population has the potential to increase by

doubling or by some other multiple rather than by adding a fixed # of

individuals

iii. Resources can’t keep up, therefore things / factors such as poverty, wars,

plagues, and famines begin to influence populations.

b. If resources are limited and organisms have more offspring than could survive,

why do some organisms survive and others die?

c. Population:

__________________________________________________________________

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Example: a herd of deer

d. Tortoises and finches:

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e. Darwin proposed:

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= DESCENT WITH MODIFICATION.

Natural Selection explains HOW evolution can occur.

Darwin wasn’t alone, Alfred Wallace also proposed similar findings, and the two

collaborated (28 years later, Darwin published Origin of Species).

4 MAIN PRINICPLES:

o 1. Variation:

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Mutation= a permanent change in the nucleotide sequence of the genome

of an organism.

o 2. Overproduction:

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Example: Sea turtles lay a clutch of 100 eggs, only 5% survive. Why?

o 3. Adaptation:

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o 4. Descent with Modification:

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Example see handout diagram: Jaguars- 11,000 years ago they faced

extinction due to a shortage of food and climate change. There were few

mammals to eat so they resorted to reptiles / turtles. They had to make

variations in their jaws and teeth in order to survive.

Natural selection:

1. _____________________________________________________________

a. Phenotypes: physical characteristics such as claws, brown eyes, camouflage color,

etc.

b. Genotype: genetic make-up that determines the phenotype.

2. ______________________________________________________________

a. Alleles: one of two or more versions of a gene. An individual inherits two alleles

for each gene, one from each parent. If the two alleles are the same, the individual

is homozygous for that gene. If the alleles are different, the individual is

heterozygous.

3. ______________________________________________________________

a. Trait: genetically determined condition. They can be physical or behavioral.

Physical such as hair color, behavioral such as nesting in birds.

Peter and Rosemary Grant: Observed Natural Selection in the Galapagos, 1977-1984

1977:

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1984: There was an unusual wet period that decreased the large seeds, which favored the

small seeds, increased the smaller finches, and decreased the population of larger finches.


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Evidence of Evolution

1. Fossils

a. Person who studies fossils= _________________________________

b. Defined as- the remains of plants and animals that lived in the past.

c. Formed in sedimentary rock layers called strata. The oldest are found in the deep

rock layers while the youngest or most recent animals are found closer to the

surface-> fossilized in sand, sediment, or volcanic ash.

d. Most fossils are found near aquatic / semi aquatic regions.

e. Fossils support Darwin’s _____________________________________________

f. Transitional fossils

__________________________________________________________________

__________________________________________________________________

i. Ex- Basilosaurus

g. Age fossils by using Absolute/Radioactive dating.

i. Uses specific radioactive atoms and how fast they break down to date the

rock they are found in.

h. Relative dating

i. Uses the “Law of Superposition” to figure out how old an object is based

on placement in rocks. Oldest rocks on bottom youngest on top.

i. Geologic Time Scale- Picture of when things appeared on Earth.

2. Geography / Biogeography

a. Darwin proposed that species closely resemble the species that reside on the

nearest mainland and that somehow they migrated.

b. Each island had

__________________________________________________________________

__________________________________________________________________

c. Over time, the traits became established on the islands mainly due to the fact that

the mainland population was too far away.

i. Ex- finches

d. Biogeography-

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3. Embryology

a. __________________________________________________________________

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b. Fish, birds, reptiles, and mammals all have gill slits as embryos.

c. In fish the gill slits become gills, mammals they become ears and throats.


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d. __________________________________________________________________

__________________________________________________________________

__________________________________________________________________

4. Comparative Anatomy

a. Defined as the study of the structure of living and fossilized animals and the

similarities (homologies) that indicate evolutionarily close relationships.

i. Homologous structures

ii. Analogous structures

iii. Vestigial structures

b. Homologous Structures:

i. ____________________________________________________________

____________________________________________________________

____________________________________________________________

ii. Appearance across different species offers strong evidence for common

descent.

iii. Ex- ________________________________________________________

iv. In all of the animals the forelimbs have several bones that are similar, but

the same bones vary in function

v. What is the function of a human hand, a bat wing, and a mole foot?

c. Analogous Structures:

i. ____________________________________________________________

____________________________________________________________

____________________________________________________________

ii. Ex- Wings of a bat and the wings of insects.

1. Bats are vertebrates, insects are invertebrates

2. Bats have bones, insects wings have membranes

3. Function evolved separately but their ancestors faced similar

environmental challenges that led to these structures.

d. Vestigial Structures

i. ____________________________________________________________

____________________________________________________________

____________________________________________________________

____________________________________________________________

ii. Ex- snakes have a tiny pelvic bone and stump like limbs. Snakes share a

common ancestor with tetrapods such as lizards and dogs (considered

homologous structures).

iii. Ex- Wings of ostriches. Use their wings for balance but not to fly. Lost the

function of their wings because they learned to run fast and kick their

predators. The gene coding for large wings was not preserved over

generations.


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iv. Ex- Human appendix: remnant of the cecum, part of the large intestine in

plant eating mammals. The appendix breaks down the cellulose in plants.

Evolutionary Biology Today

Molecular and genetic evidence support fossil and anatomical evidence

Basics of DNA and Proteins

DNA- Deoxyribonucleic acid Proteins

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_____________________

Shape looks like a twisted ladder /

double helix

Detailed instructions that build

proteins and are stored in

extremely long carbon based

molecules.

Nucleotides are made up of:

___________________________

___________________________

___________________________

___________________________

___________________________

___________________________

Nitrogen bases always pair up in

the same way!

For DNA: _____________

For RNA: _____________

(thymine in RNA is replaced with

uracil)

Two types= DNA and RNA

ONE FUNCTION!!!!!-> DNA

and RNA work together to make

proteins. DNA passes on genetic

instructions to RNA. RNA

decodes and turns the genetic

information into a protein.

___________________________

___________________________

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We use 20 different amino acids to build

proteins in our bodies.

Your body makes 12 and the others need to

be ingested through meat, beans, and nuts.

Functions: speed up reactions in the body

(enzymes), defensive proteins, storage

proteins, transport proteins, support proteins,

motion proteins, and messenger proteins.


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Scientists use DNA / protein sequence comparisons to show probable

evolutionary relationships between species.

1. DNA Sequence Analysis:

Sequences of nucleotides (sugar, phosphate, and nitrogenous base) in a gene change over

time because of mutations.

-

________________________________________________________________________

________________________________________________________________________

________________________________________________________________________

Example:

2. Pseudogenes: “Fake genes”

Like vestigial structures.

________________________________________________________________________

________________________________________________________________________

They do have the ability to change as they get passed on from generation to generation.

3. Homeobox Genes:

Control the development of specific structures.

Have been found in organisms from fruit flies to humans = common ancestor

Have been found in organisms as far back as 600 million years ago.

4. Protein Comparisons:

Comparing their proteins= “molecular fingerprinting”

________________________________________________________________________

________________________________________________________________________

Example- Proteins found in ancient marine worms were found to closely resemble those

of cells found in the vertebrate eye.


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Why Study Pigeons?

Obtained from: http://learn.genetics.utah.edu/content/pigeons/whypigeons/

Darwin and Pigeons

In his book On the Origin of Species (1859), Charles Darwin wrote about the high degree of

variation among domesticated plants and animals, and their differences from their wild ancestors.

His view, a socially controversial one at the time, was that humans had created such vastly

different breeds by selectively breeding the individuals that had the most-desirable

characteristics—a process he referred to as "artificial selection." Darwin's study of artificial

selection helped him develop his theory of evolution through natural selection. If humans could

create this degree of variation in a few hundred generations, Darwin reasoned, then nature, acting

over much longer timescales, could have given rise to the diverse life forms that populate the

earth.

One of the animals Darwin studied in depth was the domestic rock pigeon. Pigeon breeding was

an ancient pastime even in the 1850s, and through its long history fanciers had published books

filled with practical advice and observations. Darwin decided to keep and breed pigeons himself.

He joined two London pigeon clubs and attended pigeon competitions, where he connected with

fanciers from around the world.

In studying pigeons, Darwin made meticulous measurements of their skeletons and marveled at

the breeds' different behaviors, colors, and proportions. He also noted the patterns of inheritance

of many characteristics, and he showed that birds of very different breeds can in fact produce

fertile offspring, supporting the argument that they all arose from a single species.

Pigeon skulls from Darwin's The Variation of Animals and Plants Under Domestication

(1868). A, Wild Rock Pigeon; B, Short-faced Tumbler; C, English Carrier; D, Bagadotten

Carrier.

“Slow though the process of selection may be, if feeble man can do much by artificial selection, I

can see no limit to the amount of change, to the beauty and complexity of the co-adaptations

between all organic beings, one with another and with their physical conditions of life, which

may have been effected in the long course of time through nature's power of selection, that is by

the survival of the fittest.”

http://learn.genetics.utah.edu/content/pigeons/whypigeons/


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Excerpt from Charles Darwin, On the Origin of Species (1859)

Studying Pigeons Today

Today's evolutionary biologists are looking at variation in pigeons once again. They're using

modern tools like whole-genome sequencing to identify the molecular mechanisms through

which inherited characteristics vary. And like Darwin, they are studying pigeons not for the sake

of understanding pigeons, but to help understand how evolution works in general.

Many of the characteristics that vary among pigeons are similar to characteristics that vary

among wild animal species. Like the Fantail breed of pigeons, the wild turkey has a broad, up-

turned tail. The male cardinal has a crest on the head, much like the ornaments in some pigeon

breeds. Beak size and shape varies dramatically among pigeon breeds, as it does among other

bird species. And the genetic variations that influence feather color are similar to those that

influence pigmentation in many animals, including not only other birds, but also reptiles and

mammals—even people.

If we can understand how artificial selection has acted on genetic variations in pigeons, we will

gain insight into the molecular underpinnings of natural selection as well.

Why Pigeons?

What do we gain by understanding the molecular mechanism of feather color in pigeons, you

might ask?

Inherited characteristics are the products of genes that pass from parent to offspring. Genes code

for proteins (and RNA), and proteins make our cells and bodies function. Some inherited

characteristics involve single genes that follow predictable patterns of inheritance. But most

involve multiple genes, and the inheritance patterns are complex and less predictable.

Model organisms like pigeons, which are easy to breed and study in the lab, show promise for

helping us understand not only simple but also complex characteristics. When scientists work out

the molecular mechanism of feather pigmentation in pigeons, for example, they gain insight into

how genes work together to produce complex and varied phenotypes. They can then apply this

understanding to other complex characteristics, including human diseases.

http://learn.genetics.utah.edu/content/pigeons/crest/

http://learn.genetics.utah.edu/content/pigeons/color/

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