G10 The Occurrence of Evolution

Question 1

the transformation of species through time. It includes the changes that happen within a species, as well as the origin of new species.

Answer 1

Evolution

Question 2

emergence of new species is known as

Answer 2

speciation

Question 3

Evolution Comes from Changes to Populations

It is the genetic change in population that are passed on to successive generations over time. These changes in the population may be small or large and may be evident or not.
This means that if the changes only happen to an individual member of a certain species, it cannot be considered evolution. A single individual cannot evolve.

Question 4

a set of genes in DNA that determines a particular phenotype or specific physical characteristic

Answer 4

genotype

Question 5

In evolution, the ratio of the alleles in the entire population changes, and it does not just deal with the changes in one organism.

Question 6

An example of a change in the allele ratio can be seen in the peppered moth Biston betularia.
The peppered moth can either be dark with a pattern of light-colored specks or light-colored with a pattern of dark specks.

Before the industrial revolution, the number of light-colored moths was greater because these were the ones that had the most chances of survival through camouflage.
During the industrial revolution, large amounts of soot were deposited into the surroundings, and the darker-colored moths now had a greater chance of survival because of camouflage. Therefore, there was an increase in the frequency of the dark-colored moths. The ratio then shifted.

Note that the moths did not change from light to dark. The increase in the frequency of dark moths was caused by the alteration in the gene pool of the moth population.

Question 7

the concept that the changes that happen to species are small, accumulated changes

Answer 7

Gradualism

Question 8

the concept that species’ characteristics are relatively stable, but when changes do appear, these changes are rapid and large and will lead to the development of new species

Answer 8

Punctuated equilibrium

Question 9

two mechanisms related to speciation

Answer 9

anagesis

cladogenesis

Question 10

evolution of a species into a new lineage

Answer 10

Anagenesis

Question 11

splitting into multiple lineages or gene pools

Answer 11

Cladogenesis

Question 12

Evolution Does not Equate to Speciation

Just because a new species did not emerge as a result of changes in a population of old species, this does not mean that the population did not evolve.
A Species Does not Need to Die Out for Evolution to Occur

The evolution of a new species does not necessarily mean that the ancestral species becomes extinct.
There are two mechanisms related to speciation: cladogenesis and anagenesis.
Anagenesis is the evolution of a species into a new lineage.
Cladogenesis is the splitting into multiple lineages or gene pools.

Question 13

Anagenesis

For example, if all the members of Species A in a geographic area acquire enough changes and become a new species, this change can be considered anagenesis.
Cladogenesis

For example, if half the members of Species A in a geographic area somehow evolve to have the same characteristics and the other half of the members remain the same. This can be considered cladogenesis. Note that cladogenesis may give rise to more than one new lineage.

Question 14

is a process by which organisms cope up with changing conditions, such as habitat, diet, or even competition

Answer 14

Adaptation

Question 15

Environmental Changes

Along with the process of evolution, the environment also continues to change. Varying environmental conditions serve as pressures for organisms to continually adapt in order to not die out.
Adaptation is a process by which organisms cope up with changing conditions, such as habitat, diet, or even competition.
Failure to adapt may lead to failure to evolve. Such failures may lead to extinction.

Question 16

a process in which individual organisms that possess favorable traits have greater survival rate and higher reproductive success rate compared to organisms that do not have the trait

Answer 16

Natural selection

Question 17

refers to the capacity of an organism to live for a longer period of time

Answer 17

high survival rate

Question 18

refers to an increased chance of the organism being able to pass on its genes through reproduction

Answer 18

higher reproductive success rate

Question 19

The Traits Involved in Natural Selection

There are many types of traits involved in natural selection, but some of the most common are the ones that deal with changes in the environment, ones that help in food capture, or those that involve better chances of predator evasion.

Question 20

A classic example of traits that arose from natural selection are the finches that Charles Darwin observed in the Galapagos islands.
These finches had different beak shapes and sizes, and these were based on the type of food that was available in the individual islands that they were found in.
These beaks were highly specialized in order to obtain the food types that these finches were accustomed to.

Question 21

Natural Selection is not the Survival of the Fittest

A common misconception is that natural selection is synonymous with survival of the fittest. This is inaccurate because the survival of the fittest implies a superlative, that only the fittest species will survive.
A more accurate term would be “survival of the fit” as an organism needs only be fit enough to be able to survive and pass on its genes.

Question 22

Natural Selection and Evolution

If natural selection causes no genetic variations in a population, then there is no evolution.

Evolution may only occur if certain traits have been passed on from parents to their offspring. In natural selection, the traits that are passed on confer some sort of advantage to the organisms.

The favorable traits that are passed on (or “good” genes) will eventually result in a higher survival or reproductive rate for the organisms that possess them. This may further result in a change of the genotype ratios in the population, as the individuals with the favorable genes can outnumber those with the unfavorable ones.

Question 23

Mammoths were enormous wooly mammals that inhabited North America and the northern part of Eurasia.
They were adapted to cold conditions by having thick coats of hair.
Through mutation, some individual mammoths developed more hair than others. When the climate became colder or when they migrated to colder regions, the individuals bearing more hair were able to tolerate the more frigid conditions.
The survival of mammoths with thicker hair meant that they were able to produce more offspring than those with thinner hair. They were able to pass on the genes for thicker hair to their offspring.
Therefore, the population with genes for hairiness was favored, and over the next generations, a greater number of hairy mammoths existed as compared to before.

Question 24

refers to the change of allele frequencies as a result of chance

Answer 24

Genetic drift

Question 25

Imagine genetic drift to be like natural selection, except that the cause for the change in allele frequencies in the populations is not because of the advantage given by adaptation, but by pure chance.

Question 26

This may lead to the decrease of the frequency of some alleles and can lead to the complete loss of alleles.
Since the losses are not adaptation-related, even beneficial alleles can completely disappear from the population in question.

Question 27

Examples of Genetic Drift

Suppose that you have a population of 100 fish of the same species. 50 of them have red scales, and the other 50 have blue scales.
Let’s say that a drought kills off the red-scaled fish, while only 3 of the blue-scaled fish die.
The scales have nothing to do with the survival of the fish, and the red-scaled fish being wiped out was a result of chance.
Suppose you have the same setup of fish again. This time, only 45 red fish are killed and 3 blue fish are killed, but still as a result of chance. This brings the ratio to 5 red fish:47 blue fish.
Eventually, after generations, the change in allele frequency could result in the loss of the allele for red scales as the sexual reproduction between the blue and red fish could result in the loss of the allele for red.
This is made more likely by the fact that the number of red fish is already very low.

Question 28

happen when there is a change in the genetic code or in the nucleotides of DNA

Answer 28

Mutations

Question 29

Mutations happen when there is a change in the genetic code or in the nucleotides of DNA. These mutations can either be a change in what nucleotides are found in the gene, or how the nucleotides are arranged.
It leads to genetic variation by affecting a single nucleotide pair or a segment of a chromosome.

Question 30

It is through mutations that genetic changes occur, be they beneficial or detrimental to the survival of the organism.
The organisms that have beneficial traits arising from these mutations have a high chance of surviving and passing on these genes. This may then lead to an increased number of organisms with said traits, which changes the ratio of the organisms with those traits as opposed to those that do not.
If the traits give the organisms certain characteristics that are detrimental to their survival, then the chances of them passing these traits on to their offspring are low since they may not survive long enough to reproduce in the first place.

Question 31

refers to the movement of genes from one population to another. It is the exchange of traits between populations as a result of these populations interbreeding with each other

Answer 31

Gene flow

Question 32

Gene flow refers to the movement of genes from one population to another. It is the exchange of traits between populations as a result of these populations interbreeding with each other.
This can be due to the migration of individuals, or other situations like changes in the environment.

Question 33

The Situations that Affect Gene Flow

Answer 33

migration
environmental changes
isolation

Question 34

The Situations that Affect Gene Flow

The most common example of a change in gene flow is because of migration.
For instance, an offspring from population A of birds immigrate to a place where population B resides. Through mating, there is a mixing of traits between populations A and B, leading to genetic variation.

Gene flow in a population may also be altered because of environmental changes.
One portion of a population may have its gene flow to another portion of the population cut off as a result of natural occurrences.
For example, an earthquake creates a natural geographic barrier. This barrier prevents the organisms on either side from meeting each other. This is effectively cutting off gene flow since they cannot reproduce with each other.

Question 35

Another way is by means of isolation.
If the members of one population are isolated from the other members of the same population for an extended period of time, they may eventually be exposed to different environmental conditions.
These conditions may have different pressures on the separate populations and can eventually result in very different adaptations for both.

Cutting off gene flow is not the only effect that natural incidents can have. Some situations can also facilitate gene flow between populations.
An example would be natural processes that create connections between two bodies of water, which will allow the movement of genes between the populations in each of these bodies of water.

Question 36

Gene Flow Leads to Genetic Variation and Evolution

Changes in gene flow may introduce genes that are not present in a certain gene pool. This is especially notable in the cases of migration or the facilitation of gene flow between populations.
The range of genes may also change for the new population.
For example, if a population of small to medium horses meets a population of horses of the same species that range from a medium height to tall, interbreeding has a chance of increasing the range of heights available to the resulting offspring.

Question 37

the process of combining genetic information from two individuals in order to produce offspring

Answer 37

Sexual reproduction

Question 38

Sexual reproduction is the process of combining genetic information from two individuals in order to produce offspring.
It can create a variety of different gene combinations for the offspring, and some of these can be shared with the parents or completely unique.
The different combinations of genes found in the offspring may translate into different phenotypes.
If there are different phenotypes for the offspring, there is a higher chance of these having different characteristics, and some of these characteristics may confer advantages for these organisms. This means that there may be a higher chance of survival for the population in certain situations.

Question 39

is the principle of selecting plants and animals for breeding

Answer 39

Artificial selection

Question 40

Artificial selection operates on the fact that some traits are heritable. It, therefore, makes sense that selecting parents with these traits and making them produce offspring will yield a good chance of these traits being passed on.

Question 41

Selective Breeding

Artificial selection is also known as selective breeding when new varieties of plants and animals are developed by choosing individuals with desirable traits and allowing them to breed.
This results in an increase in the chances of these desirable traits occurring in the offspring, as well as the number of offspring bearing the desired characteristics. Those that do not have favorable qualities are not selected for further breeding.
Domesticated organisms are a result of selective breeding.
Over many generations, people have chosen characteristics in animals and plants that are desirable in order to gain the benefit out of them.
In the case of animals, certain behavioral and physical characteristics such as being docile or flightlessness are also chosen to help in the ease of taking care of them.