Chapter 15 - Evidence For Evolution

Question 1

What is a genome?

Answer 1

The complete set of DNA in each cell of an organism

Question 2

What happens to DNA when speciation occurs?

Answer 2

The DNA of the two species will be very similar

Question 3

What happens to new species as they change due to evolutionary mechanisms?

Answer 3

They accumulate more differences in their DNA

Question 4

How much DNA do humans share with chimps?

Answer 4

98%

Question 5

What is junk DNA?

Answer 5

DNA that has no apparent function and serves no purpose

Question 6

What is an example of junk DNA?

Answer 6

Endogenous retroviruses

Question 7

What is an ERV?

Answer 7

A viral sequence of DNA that has become a part of an organisms genome

Question 8

How does an ERV become inserted into a cell?

Answer 8

• enter cell - copies RNA genome into DNA (reverse transcription)
• DNA becomes inserted into one of the host cells chromosomes

Question 9

When does an ERV become endogenous?

Answer 9

• when it inserted into a sperm or an egg cell

Question 10

How does DNA provide evidence for evolution?

Answer 10

• all species use the same 4 bases that make up DNA
• the sequence of these bases varies from species to species
• the more similarities, the more closely related

Question 11

What is the structure of mitochondrial DNA?

Answer 11

Small circular molecules

Question 12

Where is mtDNA found?

Answer 12

Mitochondria

Question 13

How does mtDNA provide evidence for evolution?

Answer 13

• only inherited through mother’s lineage
• mtDNA mutates faster than DNA
• more similarities more closely related through mother’s lineage

Question 14

How do amino acids provide evidence for evolution?

Answer 14

• all proteins in all species are made up of the same amino acids
• the sequence of these amino acids varies form species to species
• the more similarities between the amino acid sequence of a protein of two species the more closely related

Question 15

What it an ubiquitous protein?

Answer 15

Proteins found in a range of organisms and perform the same function

Question 16

What is an example of an ubiquitous protein?

Answer 16

Cytochrome c

Question 17

How does cytochrome c provide evidence for evolution?

Answer 17

• some sequences of amino acids of cytochrome c are always the same
• differences also exist between species
• the less differences that exist the more closely related two species are

Question 18

How does embryology provide evidence for evolution?

Answer 18

• involves comparing the embryos of different species
• many similarities exist between different species in the embryonic stage eg. Gills - evolved from fish hundreds of millions of years ago
• the later differences arise, the more closely related species are

Question 19

How do homologous organs/structures provide evidence for evolution?

Answer 19

• involves comparing structures that are similar but used in different ways

Question 20

What are vestigial organs?

Answer 20

Organs that may have once been important but have lost or changed their function as a species has evolved

Question 21

How do homologous structures provide evidence for evolution?

Answer 21

• present in ancestors

Question 22

What are some examples of vestigial organs?

Answer 22

• appendix: digesting leaves
• coccyx: part of the tail
• wisdom teeth: help grind down plant matter

Question 23

What is a fossil?

Answer 23

An preserved trace left by an organism that lived long ago

Question 24

What is stratigraphy?

Answer 24

The study of layers, or strata

Question 25

What is an index fossil?

Answer 25

A fossilised organism that was widely distributed and only present on earth for a short period of time

Question 26

What does the correlation of rock strata involve?

Answer 26

Involves matching similar layers of rock from different areas

Question 27

What does the principle of superimposition assume?

Answer 27

Assumes that in layers of sedimentary rock the layers at the top are younger than those beneath them

Question 28

What is a half life?

Answer 28

The time required for half of any amount of radio active material to decay into a stable non radioactive material

Question 29

How can index fossils be used to relatively date?

Answer 29

- using index fossils to date relatively is more precise because of their short span of life on earth - sedimentary rocks that contain the same index fossils are assumed to be the same age

Question 30

What does fluorine dating involve?

Answer 30

- bone absorbs fluorine ion from water in soil | - the older the bone, the more fluorine it contains

Question 31

Why is it not possible to relatively date fossils from different sites using fluorine dating?

Answer 31

- the bones absorb fluorine from the surroundings | - the concentration of fluoride ions varies between locations

Question 32

What is the half life of carbon 14?

Answer 32

5730 years

Question 33

What does carbon 14 decay to?

Answer 33

Nitrogen

Question 34

How does carbon 14 dating work?

Answer 34

- living organisms take in carbon - an organism stops taking in carbon when it dies - the carbon then begins to decay to nitrogen - it's has a half life - by comparing the ratio of carbon to nitrogen in the sample and knowing the half life an approximate age of when the organism died can be determined

Question 35

What is the half like of potassium?

Answer 35

1.26 billion years (1.3)

Question 36

What does potassium-40 decay to?

Answer 36

Argon-40

Question 37

What are limitations of potassium argon dating?

Answer 37

- fossils over 100,000 years old - rock being dated must be the same age as the fossil being dated - the rock sample must be igneous containing potassium

Question 38

What are some limitation of carbon dating?

Answer 38

- can only be used to date up to 70,000 years - sample must be organic and contain carbon - is only reliable if the amount of C-14 in the air has been constant

Question 39

What are some limitations of stratigraphy?

Answer 39

- the law of superposition cannot always be applied, as due to the earths shifting tectonics strata can be flipped upside down - fossils can be buried by animals after the deposition of sediment and the animal may be younger then the layers above it

Question 40

What are some limitations of index fossils?

Answer 40

- the longer the time period a species lived, the less reliable the index fossil - an animal may have lived in different areas at different times - an animal may have become extinct in one area before another