G10 Evidence for Evolution

Question 1

The age of fossils can be determined through different methods, and the most commonly used ones are relative dating and absolute dating.

Question 2

refers to the method of determining the age of a rock layer and the fossils within based on sequences of events

Answer 2

Relative dating

Question 3

four major laws in the field of geochronology

Answer 3

law of original horizontality
law of lateral continuity
law of superposition
law of crosscutting

Question 4

which merely states that depositions for the layers are usually in a horizontal manner

Answer 4

law of original horizontality

Question 5

which states that layers spread out laterally until they thin at the edges of the area, or into a different rock layer segment

Answer 5

law of lateral continuity

Question 6

which states that the oldest rock layers are usually found under newer rock layers

Answer 6

law of superposition

Question 7

which states that rocks and other features are younger than the layers that they intrude into

Answer 7

law of crosscutting

Question 8

It gives a numerical estimate of the age of the object being tested

This method relies on the decay of certain elements through their half-life
The half-life of an element is the time it takes for that element to be reduced to half of its original amount

Answer 8

absolute dating

Question 9

Absolute dating will usually involve taking the estimated age of a rock layer, or sometimes, even the fossil itself.
The most commonly used elements for absolute dating are carbon-14 with a half-life of 5,730 years, and potassium-argon dating with a half life of 1.3 billion years

Question 10

fossil classification

Answer 10

mold fossils
trace fossils
true form fossils
cast fossils

Question 11

is formed when an impression of an organism is made over a substrate. Most of the time, this creates a concave image (or a “negative”) of the organism in the substrate

Answer 11

mold fossil

Question 12

is the fossilized remains of the traces of an organism

examples of fossils include remains of footprints, nests, and the like

Answer 12

trace fossil

Question 13

is the fossilized remains of a part or the entire organism. Examples include dinosaur bones and insects trapped in amber

Answer 13

true form fossil

Question 14

can be formed alongside a mold fossil

occur when a substance fills in the mold fossil, which forms a replica of the organism from the cast

Answer 14

cast fossil

Question 15

A fossil record is derived from the discovered fossils all over the world. It shows the history of life as documented by fossils.

Question 16

are fossils of organisms that are used for determining the age of surrounding rocks, and consequently, the age of the fossils within these rocks

Answer 16

index fossils/guide fossils

Question 17

four criteria for classifying a fossil as an index fossil

Answer 17

abundance of the fossil
ease of identification
geographic range
temporal range of the fossil

Question 18

From fossils, scientists were able to construct an evolutionary tree based on the similarities between specific structures of organisms.

Question 19

Amphibians are known to have descended from fish, and the fossils of these fish have been found. Scientists based the evolutionary tree they created on the development of the different structures found, as well as the change from fins to legs.
Another example is the Pakicetus which is considered to be one of the ancestors of modern whales. They are land animals with long skulls and large carnivorous teeth, and their skulls strongly resemble those of the living whales.

Question 20

are body parts of different organisms with similar forms but the functions are not necessarily the same

This implies that these structures may come from the same sources but have possibly evolved as a result of different pressures.

Answer 20

Homologous structures

Question 21

refer to the repeating structures found within one organism

Answer 21

serial homology/homotopy

Question 22

Serial Homology

Also known as homotopy, serial homologies refer to the repeating structures found within one organism.
These structures perform roughly the same function but may have different specializations.
An example of a serial homology is the presence and structure of human vertebrae.

Question 23

The Implications of Homologous Structures in Evolution

Homologous structures suggest descent from a common ancestry.
Taking a look at the different functions of homologous structures also gives a perspective of how these structures came to be.
The specific modifications of these structures may show what environmental pressures these animals have faced which led to the adaptation of these modifications.

Question 24

The limbs of tetrapods (amphibians, reptiles, birds, and mammals) share the same arrangement of bones. They are all composed of the radius, ulna, and humerus. However, these limbs serve different functions.

The upper limbs of bats are for flying, whereas those of humans are used for grasping. In whales, the upper limbs are found in the flippers, which are used for movement in the water.

Question 25

are ones that have the same function but have evolved differently

Answer 25

Analogous structures

Question 26

which are traits shared by a group of species but are not present in their common ancestor.
These structures imply an independent development of these structures within these animal groups.

Answer 26

homoplasies

Question 27

The Value of Analogous Structures in the Study of Evolution

While analogous structures and homoplasies do not give much perspective as to how related lineages have evolved, looking at them can also give a view of the environmental pressures that organisms had to overcome, much like the view the homology gives.

Question 28

Analogous Structures

The wings of insects and birds both have the function of flight but these traits arose independently from each other.

Question 29

Homoplasies

An example would be the development of structures that animals use for sight, which is found in many groups but not all found in their common ancestors.

Question 30

are organs that are present in an organism but do not perform any particular function

Answer 30

Vestigial structures

Question 31

Vestigial structures are organs that are present in an organism but do not perform any particular function.
Some examples of vestigial structures are the tailbone and appendix in humans.

Question 32

The Implications of Vestigial Structures in Evolution

Vestigial structures predict the organism’s evolutionary past, suggesting common ancestry with species that have similar structures but are still functioning.

Question 33

Whales have retained their vestigial hind limb, which is disconnected from the spine.
This vestigial structure is considered to be a remnant of their time on land.
The use of these structures in looking at the evolution of whales, as well as structures observed in the fossil record, have shown a clear picture of the evolutionary history of whales.

The vestigial hind limbs of snakes, much like the vestigial hind limbs of whales, gives a view of how these organisms might have evolved.
Scientists believe that snakes descended from lizards over a hundred million years in the past.
More recent genetic evidence also supports this claim, stating that snakes and lizards are indeed very closely related. In fact, snakes and lizards belong to the same reptilian group known as Squamata

Question 34

Homologous structures are body parts of different organisms with similar forms but the functions are not necessarily the same. Homologous structures suggest descent from a common ancestry.
Analogous structures are ones that have the same function but have evolved differently.
Vestigial structures are organs that are present in an organism but do not perform any particular function. Vestigial structures predict the organism’s evolutionary past, suggesting common ancestry with species that have similar structures but are still functioning.

Question 35

Modern studies regarding the evolutionary history of organisms most often use genetic data to infer the relationship between species and groups of organisms.
This is in contrast with earlier studies that purely used morphological and anatomical features for looking at evolutionary relationships.
Morphology and anatomy, along with genetics, are used side-by-side in order to properly gain an insight on how organisms are related.

Question 36

is a branch of biology that studies genes, heredity, and genetic variation

provides a more complex evidence of evolution

Answer 36

Genetics

Question 37

a universal genetic message

This genetic message is the same in all organisms on earth. Therefore, it supports the idea that there is a common ancestor for all life forms.

Answer 37

triplets of DNA nitrogen base sequences that code for specific amino acids

Question 38

details how genetic information is processed into a usable product.
This concept can be summarized into the flow of information, wherein DNA is transcribed into mRNA, and mRNA is translated in order to form proteins.

Answer 38

The Central Dogma of Molecular Biology

Question 39

The Universal Genetic Code

There is a universal genetic message—the triplets of DNA nitrogen base sequences that code for specific amino acids.
This genetic message is the same in all organisms on earth. Therefore, it supports the idea that there is a common ancestor for all life forms.

The Central Dogma of Molecular Biology details how genetic information is processed into a usable product.
This concept can be summarized into the flow of information, wherein DNA is transcribed into mRNA, and mRNA is translated in order to form proteins.
Since organisms that are closely related share much of their genetic code’s sequences and identity, this means that many of the products of their genes are also shared. This leads to the many physical similarities between closely related species.

Question 40

Genetic Similarity and Evolution

Organisms with similar characteristics mean that there is a chance that they have shared genes. The study of genetics looks at the similarities in the DNA of organisms in order to infer the possible evolutionary relationship between them.
For example, approximately 96% of human genes are similar to those of chimpanzees, and 90% of these genes are similar to those of cats.
These percentages do not prove that humans evolved from chimpanzees or cats. However, they mean that humans, chimpanzees, and cats may have shared a common ancestor in the past.
The differences between the genes correspond to how long ago the genetic lines between the organisms have changed.

Question 41

Mutations and Evolution

Certain changes that arose from mutations can be used to determine the evolutionary relationship between species.
For example, suppose that you are looking at three closely-related species and trying to understand which of the three are more closely related.
Suppose that two of them share the same changes, then the chances of these two being more closely related to each other are higher compared to the other one that does not have the change from the mutation.
Mutations can also give an estimate of when divergences from certain lineages have occurred.
Take the example of the three species above again. There are multiple possible situations that can arise regarding their evolutionary history if the timing is taken into account.
One is that the mutation first occurred in the ancestor, and these were passed on to the two species while the other one diverged.
Another possibility is that the ancestor did not have the change from the mutation, but a divergence occurred which eventually led to the formation of the species with the changes from that mutation.
Mutations must persist for evolution to take place.
One instance that this may happen if the phenotype that is the manifestation of these mutations can bestow an adaptive advantage to the organisms that possess them, thereby increasing their fitness and reproductive success.
A higher reproductive success for these organisms means that they have a chance of successfully passing on these genes, including the newly-mutated ones.

Question 42

Methods in Genetics

Answer 42

DNA Extraction
DNA Amplification
Genetic Sequencing
Analysis

Question 43

involves the isolation and retrieval of a sample of the organism’s DNA.
The sample collected must be pure, meaning the DNA must come from the organism and that organism alone.

Answer 43

DNA extraction

Question 44

is needed in order to increase the amount of material in the sample.

effectively increases the amount of DNA by creating exact copies of the desired sample. As shown in the figure below, just after the 35th cycle, 68 billion copies of DNA are already made.

Answer 44

DNA amplification

Question 45

The amount of DNA extracted is usually small, so a method known as DNA amplification is needed in order to increase the amount of material in the sample.

DNA amplification effectively increases the amount of DNA by creating exact copies of the desired sample. As shown in the figure below, just after the 35th cycle, 68 billion copies of DNA are already made.

In most cases, specific genes are used and analyzed when trying to determine evolutionary relationships.
When amplifying DNA, these genes are usually targeted so that more copies of the desired gene is created. These genes are usually the ones that are sequenced and analyzed.

Question 46

involves the identification of the individual nucleotides that make up the gene

Answer 46

Genetic Sequencing

Question 47

Certain softwares are used in order to check the similarity of the nucleotide sequences from the organism compared to other organisms. The more similar they are, the more likely that they are related to each other.

Answer 47

Analysis

Question 48

Modern studies regarding the evolutionary history of organisms most often use genetic data to infer the relationship between species and groups of organisms.
Genetics is a branch of biology that studies genes, heredity, and genetic variation. Genetics provides a more complex evidence of evolution.
Organisms with similar characteristics mean that there is a chance that they have shared genes. The study of genetics looks at the similarities in the DNA of organisms in order to infer the possible evolutionary relationship between them.
One of the most commonly used methods in looking at evolutionary relationships from a genetic standpoint would be through the use of DNA.
Genetic sequencing involves the identification of the individual nucleotides that make up the gene

Question 49

once contained the vast majority of the world’s landmasses. It formed more than 300 million years ago and broke up around 175 million years ago.

Answer 49

supercontinent of Pangaea

Question 50

The supercontinent of Pangaea had two major regions of land, which were

Answer 50

Gondwana

Laurasia

Question 51

Pangaea was surrounded by the superocean known as

Answer 51

Panthalassa

Question 52

refers to the movement of populations across a geographical location, most usually a barrier

Answer 52

Dispersal

Question 53

occurs when populations are isolated by the appearance of geographical barriers that make it impossible for these populations to continue interbreeding.

Answer 53

Vicariance