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.