Unit 6 – Natural Selection and Evolution Study Guide

Vocab: define the following terms

Adaptations o any alteration in the structure or function of an organism or any of its parts that results from

natural selection and by which the organism becomes better fitted to survive and multiply in its environment

Mutations o A Mutation occurs when a DNA gene is damaged or changed in such a way as to alter the

genetic message carried by that gene. A Mutagen is an agent of substance that can bring about a permanent alteration to the physical composition of a DNA gene such that the genetic message is changed

Structural adaptations o Structural adaptations are physical features of an organism like the bill on a bird or the fur on a

bear

Behavioral adaptations o Behavioral adaptations are the things organisms do to survive. For example, bird calls and

migration are behavioral adaptations.

Physiological adaptations o Physiological Adaptations are internal systematic responses to external stimuli in order to help

an organism maintain homeostasis

Camouflage o Many animals have evolved to exhibit some form of camouflage, which is an adaptation that

allows animals to blend in with certain aspects of their environment. Camouflage increases an organism's chance of survival by hiding it from predators.

Warning coloration o a bold, distinctive pattern of color characteristic of a poisonous or unpalatable organism, as the

skunk or the monarch butterfly, that functions as a warning to and defense against predators

Mimicry o mimicry is a similarity of one organism, usually an animal, to another that has evolved because

the resemblance is selectively favored by the behavior of a shared signal receiver that can respond to both

Natural selection o Two major mechanisms that drive evolution are natural selection and genetic drift. Natural

selection is the process by which heritable traits increase an organism's chances of survival and reproduction. Originally proposed by Charles Darwin, natural selection is the process that results in the evolution of organism

Evolution o Biological evolution, simply put, is descent with modification. This definition encompasses small-

scale evolution (changes in gene frequency in a population from one generation to the next) and large-scale evolution (the descent of different species from a common ancestor over many generations).

Population o A group of organisms of one species that interbreed and live in the same place at the same time

(e.g. deer population)

Species o A group of closely related organisms that are very similar to each other and are usually capable

of interbreeding and producing fertile offspring.

Adaptive radiation o In evolutionary biology, adaptive radiation is a process in which organisms diversify rapidly from an

ancestral species into a multitude of new forms, particularly when a change in the environment makes new resources available, creates new challenges, or opens new environmental niches

Geographic isolation o Geographic isolation is a term that refers to a population of animals, plants, or other organisms

that are separated from exchanging genetic material with other organisms of the same species. Typically geographic isolation is the result of an accident or coincidence.

Convergent evolution o In evolutionary biology, convergent evolution is the process whereby organisms not closely

related (not monophyletic), independently evolve similar traits as a result of having to adapt to similar environments or ecological niches.

Co-evolution o In biology, coevolution occurs when two or more species reciprocally affect each

other's evolution

Variation o Variation, in biology, any difference between cells, individual organisms, or groups of organisms

of any species caused either by genetic differences (genotypic variation) or by the effect of environmental factors on the expression of the genetic potentials (phenotypic variation).

Mutation o A Mutation occurs when a DNA gene is damaged or changed in such a way as to alter the

genetic message carried by that gene. A Mutagen is an agent of substance that can bring about a permanent alteration to the physical composition of a DNA gene such that the genetic message is changed

Genetic Recombination o The process of forming new allelic combination in offspring by exchanges

between genetic materials (as exchange of DNA sequences between DNA molecules).

Migration o Animal migration is the relatively long-distance movement of individuals, usually on a seasonal

basis. It is found in all major animal groups, including birds, mammals, fish, reptiles, amphibians, insects, and crustaceans

Immigration o Immigration is when new organisms join a population, changing allele frequencies

Emigration o Emigration is when members of a population leave, taking with them their genes

Genetic Drift o Genetic drift is a mechanism of evolution in which allele frequencies of a population change

over generations due to chance (sampling error). Genetic drift occurs in all populations of non-infinite size, but its effects are strongest in small populations

Biodiversity o Biological diversity' means the variability among living organisms from all sources including,

inter alia, terrestrial, marine and other aquatic ecosystems and the ecological complexes of which they are a part; this includes diversity within species, between species and of ecosystems

Inheritance o the inheritance of genetic information is necessary for the natural selection process to occur.

o Without an inheritance component and being able to pass information from generation to generation,

genetic information (genes and traits) would be randomly assigned.

Over-production o Overproduction within a population is necessary for the natural selection process to occur.

o Without overproduction, there is less competition allowing less adapted organism to survive better than

they normally should.

Competition o Competition is an essential component of the natural selection process.

o Competition allows for the environment to select the better adapted individuals within a population.

Homologous structures o Structures with the same embryonic origin and similar appearance found in different species

o Ex: forelimbs in mammals

Comparative anatomy o Comparative anatomy is the study of similarities and differences in the anatomy of different

species. It is closely related to evolutionary biology and phylogeny (the evolution of species).

Analogous structures o In evolutionary biology, the term analogous structures pertain to the various structures in

different species having the same function but have evolved separately, thus do not share common ancestor. Examples of analogous structures are as follows: wings of insects and birds used for flying

Vestigial structures o Vestigial structures are often homologous to structures that are functioning normally in other

species. Therefore, vestigial structures can be considered evidence for evolution, the process by which beneficial heritable traits arise in populations over an extended period of time.

Artificial selection o The breeding of plants and animals to produce desirable traits. Organisms with the desired

traits, such as size or taste, are artificially mated or cross-pollinated with organisms with similar desired traits.

Selectively breeding o The intentional breeding of organisms with desirable trait in an attempt to produce offspring with

similar desirable characteristics or with improved traits.

Questions: Answer the following questions about the unit

1. What is an adaptation? Provide an example. How are mutations related to adaptations? How do they

relate to evolution? When do adaptations occur for an organism?

Adaptations: an inherited trait which enables an organism to survive and reproduce. i. An inherited characteristic that increases an organism’s ability to survive and reproduce in its

specific environment

ii. An inherited characteristic that makes an organism more well suited to its environment.

An inherited trait that increases the population’s chances of survival and

reproduction in a particular environment.

Allows organisms to fit best into a particular niche (habitat and role)

An adaptation is a change in an animal’s physical structure, behavior, or physiology that helps an

animal to survive in their habitat.

i. Examples: The shape of a bird’s beak, number of fingers and toes, or the color of an

animal’s fur.

Adaptations result from mutations! If the mutation gives the organism a way to compete with

others in the same species, then it is an adaptation.

i. Adaptations are controlled by alleles (genes) which are inherited.

ii. New traits can enter a gene pool through random genetic mutations (remember that not

all mutations are bad).

Physical adaptations in an entire species do not develop during one lifetime, but over many

generations.

ALL adaptations occur by CHANCE and not by choice!

All species have experienced adaptation and will continue to slowly adapt as the next generations

are born.

Organisms well suited to their environment survive and reproduce more successfully than those less

suited to their environment.

In summary:

a. Inherited characteristics

b. Increases organism’s chance of survival

c. Helps meet needs & WANTS

d. NOT by choice! By CHANCE.

2. List the 3 types of adaptations. What is a structural adaptation? What is a physiological adaptation?

What is a behavioral adaptation? Provide an example of each type.

3 Types:

i. Structural

adaptations involving the body

Structural adaptations (sometimes called morphological) are based on the

morphology of an organism and how it is “built”

a. EX: A stick insect (body is shaped like a stick)

b. Ex: Elk have antlers to fight one another

c. Ex: The shape of an animal’s teeth is related to its diet.

i. Herbivores, such as deer, have many molars for chewing tough

grass and plants.

ii. Carnivores, such as lions, have sharp canines to kill and tear meat.

d. Ex: Penguins have wings shaped like flippers that help them swim through the

water

ii. Physiological

Adaptations which are associated with particular functions in organisms

Physiological adaptations are chemical based and have to do with bodily

functions.

a. Examples:

i. Enzymes needed for blood clotting

ii. Proteins used for spider silk

iii. Chemical defenses of plants

iv. The ability of certain bacteria to withstand extreme heat or cold

v. Hibernating bears vi. A penguin’s heart rate can slow down greatly during a dive so that it can

conserve oxygen and spend more time underwater hunting for food

iii. Behavioral

adaptations involving the actions of an organism

behavioral adaptations have to do with the way an organism acts (behaves)

a. Ex: Cockroach runs when lights are turned on

b. Ex: Zebras stand in large herds huddled together to confuse predators

c. Ex: penguins live in extremely cold environments and often huddle together to

conserve body heat

3. What are the different types of coloration adaptations? Provide an example of each type.

Coloration:

i. adaptations involving color or patterns

Ex: Black widow spider has red hour-glass shape on stomach to warn predators

Camouflage:

i. Definition: A protective adaptation that enables an organism to blend into its environment

Example: The cuttlefish (related to the octopus) can change colors to blend into

the environment

Warning Coloration

i. Definition: The colors of the animal make it easier to see

This is a warning that says to predators: “Don’t eat me, I’m poisonous!”

a. Example: The inedible monarch butterfly warns away potential predators

with its bright colors

b. Example: The poisonous coral snake warns away potential predators with

its bright bands of colors

Mimicry

i. Definition: One organism is protected from its enemies by its resemblance to another

(sometimes dangerous) species

Example: The edible viceroy butterfly is avoided by predators because it so

closely resembles the monarch butterfly in color and markings

Example: the scarlet king snake is avoided by predators because it so closely

resembles the coral snake in color and markings

4. What are the three options that a species has if their environment changes?

Move (Migrate)

Adapt

Die

5. Define life functions. List the 7 life functions.

Life Functions: required actions for survival

i. Obtain food and water

ii. Provide for shelter and protection

iii. Respiration

iv. Excretion

v. Respond to stimuli

vi. Grow

vii. Reproduce

6. Who was Darwin? Where did Darwin travel to? What animal is Darwin famous for?

Charles Robert Darwin, FRS FRGS FLS FZS (/ˈdɑːrwɪn/; 12 February 1809 – 19 April 1882) was an English naturalist, geologist and biologist, best known for his contributions to the science of evolution.

Darwin travels on the HMS Beagle along coastal South America.

i. Rich diversity of tropical life, mainland and island species, makes deep impression on

young Darwin.

He collected samples of many species from the different islands and notices that

the finches had different shaped beaks due to the different food sources.

One of the stops were the Galapagos Islands off west coast of Ecuador

i. He noticed the birds (finches) were the same species on the different islands, but they

looked totally different

ii. Darwin noticed the same for other animals on the islands as well

According to Darwin, the reason for the variations in the beaks of the finches he studied was because they

lived on different island that had different food sources.

7. What is the core principle that Darwin came up with about evolution?

Core principles of evolution:

i. All life is linked through a common ancestor;

ii. Populations of living things change with time (evolve), the environment influences this

change (natural selection) so that helpful traits are selected over less-helpful traits and the

former become more common in the population (descent through modification).

Darwin proposed a mechanism for evolution that he called natural selection i. Organisms well suited to their environment survive and reproduce more successfully than those

less suited to their environment.

8. What theory of evolution did Darwin come up with? What did Darwin believe with natural selection?

Darwin defined evolution as "descent with modification," the idea that species change over time, give

rise to new species, and share a common ancestor.

i. Darwin concluded that species alive today descended with modification from ancestral species

that lived in the distant past.

The mechanism that Darwin proposed for evolution is natural selection. Because resources are limited in

nature, organisms with heritable traits that favor survival and reproduction will tend to leave more

offspring than their peers, causing the traits to increase in frequency over generations.

i. Natural selection causes populations to become adapted, or increasingly well-suited, to their

environments over time. Natural selection depends on the environment and requires existing

heritable variation in a group.

Darwin believed in natural selection:

i. those with best traits survive and pass their traits to offspring

Natural selection can best be described as the survival and reproduction of the organisms

with traits that make them well suited to their environment

9. What are the three major aspects to Darwin’s theory of natural selection?

1. There is variation within a population

i. All species have variations which keep them alive long enough to reproduce

ii. Those traits are then passed down to their offspring

iii. After a long enough period of time (sometimes millions of years), you get new traits or

new species

iv. Darwin called this “Descent With Modification”

2. Some variations are beneficial

3. Not all young produced in a generation can survive

i. This leads to a struggle for existence.

ii. Survival of the fittest.

iii. Those that survive and reproduce are those with the good variations.

10. List Darwin’s 5 steps of natural selection. Explain what happens in each step and provide an example

for each step.

often referred to as the five

fingers of evolution\

i. 1.Organisms

overproduce In nature, organisms

have more offspring

than will survive to

reproductive age

Ex: sea turtles lay

150-200 eggs

2. Not all

organisms

survive Some eggs never hatch

Many babies are eaten before

making it to the ocean

Only 0.001% survive from

hatching to sea

3. Organisms are born with variations i. In any population, individuals vary in color, size, speed, etc.

4. Those with the best variations survive (“survival

of the fittest”) o Individuals with certain useful variations (such as speed) survive in their environment

5. Those that survive pass their traits to their

offspring

Over time, offspring with certain variations make up most of the population &

may look entirely different from their ancestors

Natural selection ultimately depends upon successful reproduction, adaptations being passed from

parent to offspring.

11. Using the steps of natural selection, describe how frogs that once had short tongues developed long

tongues.

A frog with a short tongue compared to a frog with a long tongue. The long-tongued frogs would

be the fittest out of the species because they can catch their food from a farther distance which

means their meal (a fly) wouldn't be scared off. The frogs with shorter tongues would scare off

their meal and starve. The death of the shorter tongued frogs would eliminate the "short tongue

genes" from the frog population. i. Step 1: frog populations overproduce and lay millions of eggs at once

ii. Step 2: not all of the eggs become tadpoles and not all of the tadpoles become adult frogs

iii. Step 3: there is variation between the frogs due to tongue length. Some tongues are short

while others are long.

iv. Step 4: the frogs with long tongues are able to catch food while the short tongue frogs are

not. The shorter tongue frogs die off.

v. Step 5: the population shifts to having longer tongues due to be better adapted to catching

food.

In summary: i. In a certain species of aquatic frog, variation existed in tongue length. Some individuals had

shorter tongues and some had longer tongues. These frogs captured insects that landed on

vegetation along the shoreline. Persistent drought caused the water level to drop making the

vegetation along the shoreline further from the water. Over time, frogs with short tongues became

less common while frogs with long tongues became more common.

12. The big idea for natural selection is NOT to just survive, but instead to….

Survive and reproduce and pass on your traits to your offspring and future generations

13. What is a species? Why is a mule and liger not considered a separate species?

A species is: i. A group of organisms that can naturally interbreed and produce fertile, viable offspring

ii. Group of similar organisms

Structurally

biochemically

iii. Can interbreed successfully in nature

Offspring are healthy

Offspring are fertile (can reproduce)

iv. Species is a group of organisms that can naturally interbreed and produce fertile, viable

offspring.

If either/both of these points are not met, then the groups are said to be

reproductively isolated from each other and are not part of the same species.

v. Mule and liger are not new species because:

A mule is the hybrid offspring of a female horse and male donkey.

Because mules are sterile, they are not classified as a distinct species.

The liger is a hybrid cross between a male lion (Panthera leo) and a female tiger

(Panthera tigris). Cannot product viable offspring.

14. What are the four origins of a species? What is speciation?

Speciation – evolution of one or more species from a single ancestor species.

Speciation / reproductive isolation can be from:

i. Origin of a species:

Divergent (adaptive radiation)

Geographic Isolation

Convergent

Co-evolution

Ultimately, a new species evolves from an existing species when reproductive isolation occurs

15. What is divergent (adaptive radiation)? Geographic Isolation? Convergent evolution? Co-evolution?

Provide an example of each.

Divergent Evolution (aka adaptive radiation)

i. Many different species evolve from one ancestral species – each new species has a

different niche

ii. Occurs when members of the initial population migrate into different niche where they,

eventually, become reproductively isolated

iii. Isolation – usually because of a geographic barrier such as a canyon, mountain, or island

iv. Isolated populations of a species evolve independently of each other from a common

ancestor

Ex – polar bears and brown bears

Ex - The various species of finches that Darwin observed on the Galapagos Islands

descended from a common ancestor on the South American mainland. Individuals from

the mainland flew to the various Galapagos Islands. On those islands they experienced

differing environments which resulted in the evolution of different beak types. Eventually

the various populations of finches became reproductively isolated and became different

species.

Geographic Isolation

i. Geographic isolation occurs when the members of a group become separated from each

other by some sort of barrier and, over time, become reproductively isolated from each

other.

Ex: squirrels at the grand canyon a. When the Grand Canyon formed, squirrels that had once been members of the

same population became isolated from each other. And evolved into two

different species

Convergent

i. Through convergent evolution, organisms of different species can have similar/same

adaptations based on the same common need from the environment they occupy.

ii. Natural Selection produces analogous (similar) adaptations in different organisms (not a

close common ancestor) in response to similar environments:

Ex: African Serval cat & south American maned wolf

a. These animals have similar ears, legs, acute hearing, habitat, and Occupy

similar niches

Ex: Darwin found entirely different species of animals on the continents of South

America and Australia that had similar anatomies and behaviors. Through

convergent evolution, the animals evolved similar adaptations because of similar

environments and selectional pressures.

Co-evolution

i. Through coevolution, organism of different species (that have some sort of symbiotic

relationship) will adapt in response to each other species adaptations. Because of their

relationship, when one species changes, the other will change in response.

ii. Co-evolution- Species that interact closely often adapt to one another due to a mutualistic

relationship

Ex: humming bird and flowers

Ex: A certain species of ant protects the tropical Acacia tree by attacking any other

herbivore that approaches the tree. The Acacia tree has developed special structures that

produce food for the ant. This long term change that occurs in species due to their

symbiotic relationship is an example of co-evolution

16. Define evolution.

evolution - change in the gene pool of a population over time

i. (population – a group of organisms of the same species that live in the same place at the

same time.)

In genetic terms, any changes in the relative frequency of alleles in a population is called

evolution

17. What is variation? How does variation relate to evolution? What are the causes of variation in a

species?

Variation – differences between individual members of a population

i. Members of a species are very similar, but differences can be observed, making each

individual unique.

ii. May be caused by mutations

iii. Variation is a key component for a population’s ability to change and adapt to its

environment. Is re key to a population’s ability to change and adapt to environmental changes.

That, without variation, populations have a harder time adjusting to environmental

changes and have a lower survivability.

Causes of variation in a species:

i. Mutation

ii. Genetic Recombination (Independent assortment during Meiosis, Crossing over, Sexual

Reproduction)

iii. Migration (Immigration, emigration)

iv. Genetic Drift

Variations within a species leads to genetic diversity.

Changes in organism’s environment cause it to adapt or become extinct.

Without variation & genetic diversity within & among species, organisms could become extinct

easily.

If the environment does not change, neither will the organism.

18. What is a Mutation? Genetic Recombination (Meiosis, Crossing over, Sexual Reproduction)? Migration

(Immigration, emigration)? Genetic Drift? Explain how each of these cause variations for a species.

Provide an example of each.

Mutation:

i. Mutations (changes to the genetic code/DNA on an organism) can occur.

ii. Changes in DNA base sequences

iii. These mutations are random in nature and can be affected by heritable and environmental

factors.

iv. Most are either neutral or harmful

v. Those that allow the organism to survive better in a particular environment are good and

are more likely to be passed on to future generations.

Genetic Recombination (Meiosis, Crossing over, Sexual Reproduction)

i. The sexual reproduction process (and its related processes) can create a lot of variation

for a population.

ii. Sexual reproduction combines genes from different parents

iii. Crossing over during meiosis can produce variations

Migration (Immigration, emigration)

i. Genetic flow, also called gene migration, is the transfer of genes between different

populations through migration

Ex: when people from another country come to the united states and start families

in the new country with the people already living in the united states

a. This is considered gene flow or migration

ii. Gene flow (the movement of genetic information) between populations can change the

normal allelic diversity of a population and increase variation.

iii. Immigration is when new organisms join a population, changing allele frequencies

iv. Emigration is when members of a population leave, taking with them their genes

Genetic Drift:

i. Definition:

A change in allele frequency in a population due to random chance

ii. Through random chance, certain alleles can be increased/decrease causing a change in the

allelic frequency.

iii. Thus, creating variation in normal pool of genes.

Ex: A population of rabbits lives in a forest. The rabbits have many different fur colors:

black, grey, white, tan, and brown. The alleles that cause fur color are equally distributed.

A forest fire kills 90% of the rabbit population. By chance, the only rabbits remaining are

black and grey.

19. How are inheritance, competition, and overproduction related to evolution?

Inheritance:

i. the inheritance of genetic information is necessary for the natural selection process to

occur.

ii. Without an inheritance component and being able to pass information from generation to

generation, genetic information (genes and traits) would be randomly assigned.

Competition:

i. Competition is an essential component of the natural selection process.

ii. Competition allows for the environment to select the better adapted individuals within a

population.

allows for the environment to select for survival the better adapted within a population

and is an essential component of the natural selection process

Overproduction:

i. Overproduction within a population is necessary for the natural selection process to

occur.

ii. Without overproduction, there is less competition allowing less adapted organism to

survive better than they normally should.

20. Who was Lamarck? What did Lamarck believe? What are the three ideas of Lamarck’s ideas of

evolution? Give an example of Lamarckism.

Lamark i. Proposed first theory of evolution in 1809

ii. Present species evolved from preexisting species

iii. Caused by their need to adapt to changes in their environment

iv. The more an animal uses a particular part, the stronger & better developed it becomes

v. These characteristics could be passed to offspring

vi. He said that change is made by what the organisms want or need.

For example, Lamarck believed that elephants all used to have short trunks. When

there was no food or water that they could reach with their short trunks, they

stretched their trunks to reach the water and branches, and their offspring

inherited long trunks.

vii. Lamarck also said that body parts that are not being used, such as the human appendix

and little toes are gradually disappearing. Eventually, people will be born without these

parts.

viii. Lamarck also believed that evolution happens according to a predetermined plan and that

the results have already been decided. ix. Lamarck believed that individuals acquire characteristics during their lifetime that help them live

more successfully in their environment. These acquired characteristics are then passed on to their

offspring.

We now know that genes are not affected by an individual’s life experiences!

Ex: frogs changing from short to long tongues Over time, frogs stretched their tongues in order to catch insects that were further away. The frog’s offspring were

then born with longer tongues

Ex:

21. Using Lamarck’s ideas, explain how a giraffe evolved to have long necks.

ex: said giraffes got long necks because they strained to reach food, thereby stretching their

necks. This got passed on to offspring – he thought that particles from giraffe’s neck are sent to

its gametes and therefore are passed on!

22. Explain the other scientists and ideas that helped Darwin to refine his idea of natural selection and

evolution.

Rapid advances in new field of geology set the stage for Darwin’s ideas. Darwin struggled with

his theory because he thought that Earth wasn’t old enough for species to evolve. But geologists

proved that the age of Earth WAS old enough for changes to occur.

i. 1. On voyage, reads Lyell’s Principles of Geology; stressed that land was constantly

changing. Therefore, Darwin said that if Earth is changing, LIFE on Earth would be

changing as well.

Lamarck’s ideas about inheritance of acquired characteristics were wrong, but notion of change

in organism over time was sound. He got everyone else thinking about evolution.

i. Use and Disuse

ii. Inheritance of Acquired Characteristics

If an organism changes during life in order to adapt to its environment, those

changes are passed on to its offspring.

Tour of Galapagos Islands impresses Darwin with its tremendous diversity; striking correlation

between form of finch species and the environment they inhabit. Maybe the island species are

derived from mainland species and have become different over time because of a change in the

environment (food source) on the islands.

Back in England, Malthus’ book on limits to human population growth has strong impact

(struggle for existence, preservation of good traits, loss of bad traits).

Wallace’s letter outlining basic principles of natural selection spurs Darwin into taking his ideas

public.

After much fierce debate, Darwin’s thesis that living beings evolve over time in response to

natural forces is accepted among most scientists by about 15 years after publication of On the

Origin of Species by Means of Natural Selection. “Means” of natural selection are debated into

modern times.

i. Advances in genetics in the twentieth century yield the mechanism through which natural

selection operates, vindicating Darwin’s ideas.

23. Compare and contrast Darwin and Lamarck’s ideas of evolution.

Darwin:

i. Darwin believed that the desires of animals have nothing to do with how they evolve, and

that changes in an organism during its life do not affect the evolution of the species.

ii. He said that organisms, even of the same species, are all different and that those which

happen to have variations that help them to survive in their environments survive and

have more offspring.

iii. The offspring are born with their parents' helpful traits, and as they reproduce, individuals

with that trait make up more of the population.

iv. Other individuals, that are not so well adapted, die off.

v. Ex: Most elephants used to have short trunks, but some had longer trunks. When there

was no food or water that they could reach with their short trunks, the ones with short

trunks died off, and the ones with long trunks survived and reproduced. Eventually, all

the elephants had long trunks.

vi. Darwin also believed that evolution does not happen according to any sort of plan.

vii. Middle 1800’s

viii. Invented “Theory of Natural Selection”

ix. Wrote book Origin of Species

x. Went on 5 year trip to study nature

xi. Based some of his theory on Lamarck’s theory of evolution

Lamark

i. Early 1800’s

ii. Invented “Theory of Evolution”

iii. Believed your life experiences were passed down to your kids

iv. Example: giraffe’s stretch their necks to reach and babies are born with longer necks

How they agreed:

i. Unlike most other people at that time, Darwin and Lamarck both thought that life had

changed gradually over time and was still changing, that living things change to be better

suited and adapted to their environments, and that all organisms are related. Darwin and

Lamarck also agreed that life evolved from fewer, simpler organisms to many, more

complex organisms.

24. List the 5 main categories of evidence for evolution.

Evidence of common ancestry among species comes from many sources.

i. #1 Fossil evidence

Fossils

a. Earth is billions of years old!

Fossils in older layers are more primitive than those in the upper layers.

Extinct Fossils resemble modern animals.

This shows a common ancestry.

Fossil record

a. In rock layers, more complex organisms were found the higher up you

were (more primitive forms were buried further down)

Fossil records demonstrates that earth’s climates and environments have changed,

populations have changes and evolution has increased the overall complexity of

organisms (over time).

a. This is supported by the complexity of organisms decreasing as you get

deeper/older in the fossil record.

Sharks and alligators are considered living fossils because they have changed so little

over millions of years. This indicates that their environments have changed very little

over time.

ii. #2 Geographical Distribution

Geography & environment gives evidence for evolution

Island species most closely resemble nearest mainland species

Populations can show variation from one island to another

Biogeography: study of the distribution of organisms on the planet

a. the distribution of organisms have changed dramatically over the history

of earth, based on the changes in the environment and populations.

i. Shows how organisms have changed and migrated over time

iii. #3 Embryology

Embryo (early developmental stage) gives evidence of evolution

Identical larvae, different adult body forms

Similar embryos, related but diverse organisms

Shows common ancestry

There are developmental similarities between different groups of organisms that

can be used to demonstrate evolutionary relatedness.

a. Ex: In their early stages of development, chickens, turtles, and rats look similar,

providing evidence that they shared a common ancestry b. Ex: Vertebrates all share gill slits and a tail in their early embryo stage;

Share a common ancestor i. The human embryo and embryos of all other animals with backbones

have gill slits. This information best supports the idea that all animals

with backbones are related

Comparative embryology: closely related species develop similarly

iv. #4 Comparative Anatomy

The study of anatomy provides evidence of evolution

a. Different species have either

i. Homologous structures

ii. Analogous structures

b. When compared

Homologous structures:

a. Structures with the same embryonic origin and similar appearance found

in different species

b. Internal structures that different organisms share, but serve a different

function, are said to be homologous structures.

c. These homologous structure show common ancestry and can be used to

show evolutionary relatedness.

d. Homologous structures are similar in structure but different in function.

e. Homologous structures ARE EVIDENCE of a common ancestor.

i. Ex: forelimbs in mammals

Analogous structures:

a. structures with similar external forms & functions, but different internal

structures

b. Analogous structures look similar, but do not have common internal

structures.

c. Therefore, they are not the result of common ancestry and cannot be used

to demonstrate evolutionary relatedness

d. Analogous structures are similar in function but differ in structure

e. Analogous structures DO NOT show common ancestry

f. Analogous structures: similar functions but diff structure/development

i. ex: wing of a bat and insect

ii. Ex: wings of a bird and fly

Vestigial structures: a. are remnants of organs or structures that had a function in an early

ancestor. i. Organs that are so reduced in size that they are just traces of homologous

organs in other species

b. Vestigial traits are used to show evolutionary relatedness based on their

presence as a non-adaptive trait

c. organs useless to present owners but serve important functions in other

species – remnants of once used structures that are now smaller and serve

little or no function.

i. Examples include ostrich wings, human appendix, and wisdom

teeth, whale and snake pelvis/hind legs

1. Extinct elephant bird and present African ostrich have

extremely reduced forelimbs (wings) and over time lost the

ability to fly

2. All are skinks – a type of lizard. In some, the legs have

become vestigial-they are so reduced they no longer

function

v. #5 Molecular and Genetic Evidence

AKA Biochemical Evidence

AKA Comparative Biochemistry

a. Two closely-related organisms will have similar DNA, RNA, and protein

(amino acid) sequences.

This also gives evidence of a common ancestor.

Biochemical similarities that exist between different groups of organisms can be

used to determine evolutionary relatedness.

Closely related species have similar genes/proteins

25. How are fossils formed? What evidence do fossils provide? What methods do scientists use to find the

age of a fossil? What is the oldest fossil found & how old is it? What does a fossil record show

scientists?

How fossils are formed/types of fossils

i. Permineralization occurs when minerals carried by water are deposited around a hard

structure

ii. A natural cast forms when flowing water removes all of the original tissue, leaving an

impression.

iii. Amber-preserved fossils are organisms that become trapped in tree resin that hardens

after the tree is buried.

Fossilized insects

iv. Impressions are imprints left in rock

v. Preserved remains form when an entire organism becomes encased in material such as

ice, ash, tar …

What do fossils show us?

i. Fossils in older layers are more primitive than those in the upper layers.

ii. Extinct Fossils resemble modern animals.

iii. This shows a common ancestry.

Dating of fossils

i. Estimates the time during which an organism lived

ii. It compares the placement of fossils in layers of rock

iii. Scientists infer the order in which species existed

Radiometric Dating of Fossils a. Measures the half-life of the isotope – the time it takes for ½ of the isotope

to break down

b. Carbon-12 stable; Carbon-14 radioactive (carbon in ALL organisms)

c. Example:

d. Carbon-14 has a half-life of 5730 years; decays into Carbon-12

i. Compare ratio of C-14 to C-12 to age fossil

ii. Uses Radioactive Isotopes: atoms of the same element with

differing neutrons

e. The oldest fossil is a fossil of bacteria that lived 4.2 billion years ago

Fossil records demonstrates that earth’s climates and environments have changed, populations

have changes and evolution has increased the overall complexity of organisms (over time).

i. Fossil records show that life on earth has changed and has become more complex

Older fossils in older rock layers tend to be less complex than the newer fossils

a. This illustrates evolution / changes in species and organisms ii. If we were to assume that species do not change, we would expect to find the same types of

fossils in old and new rock layers

26. Define biogeography. Explain how this is an evidence for evolution.

Biogeography: study of the distribution of organisms on the planet

i. the distribution of organisms have changed dramatically over the history of earth, based

on the changes in the environment and populations.

Shows how organisms have changed and migrated over time

27. Define comparative embryology. How is it an evidence for evolution? Give an example of comparative

embryology.

#3 Embryology i. Embryo (early developmental stage) gives evidence of evolution

ii. Identical larvae, different adult body forms

iii. Similar embryos, related but diverse organisms

iv. Shows common ancestry

v. There are developmental similarities between different groups of organisms that can be

used to demonstrate evolutionary relatedness.

Ex: Vertebrates all share gill slits and a tail in their early embryo stage; Share a

common ancestor

vi. Comparative embryology: closely related species develop similarly

28. Define comparative anatomy. How is it an evidence for evolution? Define homologous structures.

Give an example of homologous structures. Define analogous structures. Give an example of

analogous structures. Define vestigial structures. Give an example of vestigial structures.

#4 Comparative Anatomy i. The study of anatomy provides evidence of evolution

Different species have either

a. Homologous structures

b. Analogous structures

When compared

ii. Homologous structures:

Structures with the same embryonic origin and similar appearance found in

different species a. Structures that have different mature forms but develop from the same embryonic

tissues

Internal structures that different organisms share, but serve a different function,

are said to be homologous structures.

These homologous structure show common ancestry and can be used to show

evolutionary relatedness.

Homologous structures are similar in structure but different in function.

Homologous structures ARE EVIDENCE of a common ancestor.

a. Ex: forelimbs in mammals

iii. Analogous structures:

structures with similar external forms & functions, but different internal structures

Analogous structures look similar, but do not have common internal structures.

Therefore, they are not the result of common ancestry and cannot be used to

demonstrate evolutionary relatedness

Analogous structures are similar in function but differ in structure

Analogous structures DO NOT show common ancestry

Analogous structures: similar functions but diff structure/development

a. ex: wing of a bat and insect

b. Ex: wings of a bird and fly

c. Ex: The wings of a penguin and the pectoral fins of fish are both fin-like

structures that help each species swim. These structures do not have common

internal structures and are not the result of common ancestry

iv. Vestigial structures:

are remnants of organs or structures that had a function in an early ancestor.

Vestigial traits are used to show evolutionary relatedness based on their presence

as a non-adaptive trait

organs useless to present owners but serve important functions in other species –

remnants of once used structures that are now smaller and serve little or no

function.

a. Examples include ostrich wings, human appendix, and wisdom teeth,

whale and snake pelvis/hind legs

i. Extinct elephant bird and present African ostrich have extremely

reduced forelimbs (wings) and over time lost the ability to fly

ii. All are skinks – a type of lizard. In some, the legs have become

vestigial-they are so reduced they no longer function

29. Define comparative biochemistry. How is it an evidence for evolution? Give an example of comparative

biochemistry.

#5 Molecular and Genetic Evidence i. AKA Biochemical Evidence

ii. AKA Comparative Biochemistry

Two closely-related organisms will have similar DNA, RNA, and protein (amino

acid) sequences.

iii. This also gives evidence of a common ancestor.

iv. Biochemical similarities that exist between different groups of organisms can be used to

determine evolutionary relatedness.

v. Closely related species have similar genes/proteins

Humans, apes and chimpanzees have identical or very similar amino acid sequences for

certain proteins. This is an example of comparative biochemistry

30. List and describe the 5 factors that can allow for evolution. Give an example for each factor that allows

for evolution.

Genetic drift: i. is a mechanism of evolution in which allele frequencies of a population change over

generations due to chance (sampling error).

ii. Genetic drift occurs in all populations of non-infinite size, but its effects are strongest in

small populations.

Gene Flow:

i. In population genetics, gene flow (also known as gene migration) is the transfer of alleles

or genes from one population to another. Migration into or out of a population may be

responsible for a marked change in allele frequencies (the proportion of members

carrying a particular variant of a gene).

Mutation:

i. In biology, a mutation is the permanent alteration of the nucleotide sequence of the

genome of an organism, virus, or extrachromosomal DNA or other genetic elements.

Sexual selection:

i. natural selection arising through preference by one sex for certain characteristics in

individuals of the other sex.

In 1859, Charles Darwin set out his theory of evolution by natural selection as an

explanation for adaptation and speciation. He defined natural selection as the "principle by

which each slight variation [of a trait], if useful, is preserved".

31. What are the 3 examples of natural selection that are used to support the theory and the evolutionary

theory?

Examples of natural selection that are used to support the theory and the evolutionary theory

i. 1. Peppered Moth

ii. 2. DDT Resistance

iii. 3. Antibiotic Resistance

Natural selection:

i. Natural selection is the process by which favorable heritable traits become more common

in successive generations of a population of reproducing organisms, and unfavorable

heritable traits become less common.

ii. Natural selection acts on the phenotype, or the observable characteristics of an

organism, such that individuals with favorable phenotypes are more likely to survive and

reproduce than those with less favorable phenotypes.

iii. Charles Darwin accumulated a tremendous collection of facts to support the theory of

evolution by natural selection.

iv. One of his difficulties in demonstrating the theory, however, was the lack of an example

of evolution over a short period of time, which could be observed as it was taking place

in nature.

v. Although Darwin was unaware of it, remarkable examples of evolution, which might

have helped to persuade people of his theory, were in the countryside of his native

England.

Peppered moth:

a. One such example is the evolution of the peppered moth Biston betularia.

i. British ecologist H. B. D. Kettlewell.

b. The economic changes known as the industrial revolution began in the

middle of the eighteenth century.

c. Since then, tons of soot have been deposited on the country side around

industrial areas.

d. The soot discolored and generally darkened the surfaces of trees and

rocks.

e. In 1848, a dark-colored moth was first recorded.

f. In 1950 man interceded again with the passage of smoke control laws in

England and the land once again began to be green once again.

g. During 1966- 1969, a survey of the town showed that of the 972

specimens collected, 25 were of the light speckled variety.

h. This is a clear indication that the peppered moth is again in the process of

changing its color once again.

o DDT Resistance – observed natural selection

Important modern-day examples of evolution include the emergence of

drug-resistant bacteria and pesticide-resistant insects.

In the 1950s, there was a worldwide effort to eradicate malaria by

eliminating its carriers (certain types of mosquitos).

The pesticide DDT was sprayed broadly in areas where the mosquitoes

lived, and at first, the DDT was highly effective at killing the

mosquitos.

However, over time, the DDT became less and less effective, and more

and more mosquitoes survived.

This was because the mosquito population evolved resistance to the

pesticide.

The appearance of DDT resistance in various forms of Anopheles

mosquitoes, and the appearance of myxomatosis resistance in breeding

rabbit populations in Australia, are all evidence of the existence of

evolution in situations of evolutionary selection pressure in species in

which generations occur rapidly.

Antibiotic resistance – observed natural selection

o The development and spread of antibiotic resistant bacteria,

like the spread of pesticide resistant forms of plants and insects

is evidence for evolution of species, and of change within

species.

o Thus the appearance of vancomycin resistant Staphylococcus

aureus, and the danger it poses to hospital patients is a direct

result of evolution through natural selection.

o The rise of Shigella strains resistant to the synthetic antibiotic

class of sulfonamides also demonstrates the generation of new

information as an evolutionary process.

32. What is a cladogram? What do cladograms show? Explain how to create a cladogram. Show an

example.

One of Darwin’s revolutionary ideas was that all living organisms are related. They are

connected like branches on a “tree of life.”

At the root of that tree is a 3.8 billion year old single-celled organism that gave rise to all

subsequent life forms – all living things are descendants of that ancestor

Closely related organisms don’t always look alike

Use derived characters to show evolutionary trends - a characteristic that appears in recent parts

of a lineage, but not in its older members

Cladogram:

i. Diagrams that show the evolutionary relationships among a group of organisms

shows probable relationships

shows probable sequence of origins

shows derived characters

ii. Use derived characters/characteristics to show evolutionary trends

A characteristic that appears in recent parts of a lineage, but not in its older

members

iii. Use derived characters to show evolutionary trends

a characteristic that appears in recent parts of a lineage, but not in its older

members

iv. Primitive traits will appear at the bottom of the tree

v. More derived characteristics will appear at the top

vi. More distant relatives are on lower branches that split off a long time ago

vii. The closest relatives that grew apart very recently are on branch tips

Characteristics that appear in recent parts of a lineage but not in its older members are called derived

characteristics

To create a cladogram:

o 1. Make a data table listing various characteristics and fill it in

o 2. The organism with the fewest checks is the most primitive and is first in the cladogram

Looking at the cladogram above:

o The organisms above each derived character/characteristics have that one and all of the ones

that they are above

The lamprey has no of the derived characters

The shark only has jaws

The salamander has jaws and lungs

The lizard has jaws, lungs, and dry skin

The tiger has jaws, lungs, dry skin, and hair

The gorilla has jaws, lungs, dry skin, hair and no tail

o Species close together share a recent common ancestor compared to those far apart

o Species close together are more similar to each other than species far apart

33. What 3 things does a cladogram show? Where will derived characters appear on a cladogram? Where

will more primitive traits appear on a cladogram? Where will closely related species appear on a

cladogram? Where will distantly related species appear on a cladogram?

Diagrams that show the evolutionary relationships among a group of organisms

i. shows probable relationships

ii. shows probable sequence of origins

iii. shows derived characters

Use derived characters to show evolutionary trends

i. A characteristic that appears in recent parts of a lineage, but not in its older members

ii. Use derived characters to show evolutionary trends

iii. a characteristic that appears in recent parts of a lineage, but not in its older members

Primitive traits will appear at the bottom of the tree

i. More derived characteristics will appear at the top

ii. More distant relatives are on lower branches that split off a long time ago

iii. The closest relatives that grew apart very recently are on branch tips

34. Define artificial reproduction/selection. What are the benefits of artificial selection? What are the

disadvantages?

So far, we have been discussing Natural Selection

i. the process whereby organisms better adapted to their environment tend to survive and

produce more offspring.

ii. The theory of its action was first fully expounded by Charles Darwin and is now believed

to be the main process that brings about evolution.

Artificial selection:

i. The breeding of plants and animals to produce desirable traits by humans.

ii. Organisms with the desired traits, such as size or taste, are selectively mated or cross-

pollinated with organisms with similar desired traits.

iii. Does not occur naturally

GMO

o Long before Darwin and Wallace, farmers and breeders were using the idea of

selection to cause major changes in the features of their plants and animals over the

course of decades.

o Farmers and breeders allowed only the plants and animals with desirable

characteristics to reproduce, causing the evolution of farm stock.

o This process is called artificial selection because people (instead of nature) select

which organisms get to reproduce.

o As shown below, farmers have cultivated numerous popular crops from the wild

mustard, by artificially selecting for certain attributes.

o These common vegetables were cultivated from forms of wild mustard. This is

evolution through artificial selection. In the process of artificial selection, nature provides the variation, and humans select

the variations that they find useful.

Selective breeding

o Selective breeding (also called artificial selection) is the process by which humans

use animal breeding and plant breeding to selectively develop particular phenotypic

traits (characteristics) by choosing which animal or plant males and females will

sexually reproduce and have offspring together.

Ex: this is the technique an animal breeder uses to produce hens that lay more eggs

Benefits of artificial selection/selective breeding

1. It can create unique varieties of crops.

2. It helps eliminate disease.

3. It can provide a sustainable food chain.

4. It can produce fitter and stronger animals.

Problems with artificial selection/selective breeding

1. It decreases Variety of Animal and Plant Populations

2. There Is limited Control Over Genetic Mutations

3. Organisms Are At risk

4. It brings about discomfort to animals.

5. It could create a genetic depression.

6. It poses some environmental risks.

7. It can change the evolution of species.

35. Compare and contrast natural and artificial selection.

Natural selection and selective breeding can both cause changes in animals and plants.

The difference between the two is that natural selection happens naturally, but selective

breeding only occurs when humans intervene.

o For this reason selective breeding is sometimes called artificial selection.