Chapter 10

Question 1

Fossil Record

Answer 1

Information derived from fossils that help map out the history of life on Earth - Geologic time frame.

Question 2

Fossil

Answer 2

Preserved body, impressions or traces of a dead organism.

Question 3

Process of fossilisation

Answer 3

1. Remanents of organisms covered by sediment, therefore not exposed to oxygen, microorganisms + other disturbances.
2. Over sediment layers build + compact until pressure cements together to form sediments.
3. Fossilised remains can take many forms including permineralised, mould or cast fossil.

Question 4

Conditions that increase the chance of fossilisation

Answer 4

• Physical protection from scavengers + decomposers.
• Areas of rapid sediment accumulation.
• Constant cool temperatures.
• Low oxygen.
• Low light exposure.

Question 5

Using the fossil record - relative dating

Answer 5

Uses the law of fossil succession to assign a relative age in relation to other fossils and rock strata.
- Use transitional fossils.

Question 6

Transitional fossils

Answer 6

Assist in relative dating.
- Shows traits common to both ancestral and descendant groups. - Shows the evolutionary changes.
Is useful when the descendant group is physically distant from the ancestral species.

Question 7

Using the fossil record - absolute dating

Answer 7

Known half-lives or different radioisotopes can be used to measure the absolute (estimated) age of a fossil.

Question 8

Radioactive isotopes

Answer 8

Radioactive atom of a specific element that breaks down into a predictable + stable product.

Question 9

Absolute dating is based on:

Answer 9

1. Radioisotopes.
2. Breakdown of these atoms is constant + can be modelled.
3. Half-life; amount of time before half of the mass of the radioisotope is broken down into predictable + stable products. 14C –> 14N.

Question 10

Radiocarbon dating

Answer 10

Form of absolute dating that determines the age of a fossil by measuring properties or radiocarbon (a radioactive isotope of carbon).

Question 11

General principles of radiocarbon dating.

Answer 11

1. Living things exist as a ratio between 12C (isotope; stable) and 14C (radioactive isotope).
2. Death of an organism –> 14C decays and breaks down into 14N(stable). 12C remains the same.
3. 14C is used to measure how long ago a fossil died. Comparing the ratio to the ratio in the atmosphere.

Question 12

Homologous structures

Answer 12

Features found in different species that may look and function very differently from one another but derived from the same ancestor.

Question 13

Analogous structures

Answer 13

Features present in 2 or more species with the same function, but don’t originate from a common ancestor.

Question 14

Vestigial structures

Answer 14

Features that have lost all or most of their usefulness as a result of revolution.
eg. Human coccyx (tail bone) was used to balance in trees –> modern humans now use inner ears to help balance on the ground.

Question 15

Aminoacid sequence similarity

Answer 15

Compare amino acid sequences to determine how related different organisms are.
- Haemoglobin
- Cytochrome c.

Question 16

Molecular homology

Answer 16

Study of the similarities between organisms at DNA + amino acid level.

Question 17

Haemoglobin

Answer 17

4 polypeptide chains; 146 amino acids.
Assesses the number of amino acid differences between chains of different organisms regarding the degree of relatedness.

Question 18

Cytochrome C

Answer 18

Enzyme in mitochondria - 104 amino acids in mitochondrial DNA.

Question 19

DNA sequence similarity

Answer 19

Determines relatedness.
High similarity = closer relatedness.

Question 20

Mitochondrial DNA

Answer 20

Maternally inherited.
ADVANTAGES:
- The mutation rate of mtDNA is much higher.
- No recombination during mitosis.

Question 21

Limitation of analysing amino acid sequences

Answer 21

Closely related species share similar sequences for certain proteins.

Question 22

Phylogenetic trees

Answer 22

Shows the evolutionary relationships between different species.
- timeline of lineages.
- relatedness between taxa.
- shared characteristics of different taxa.

Question 23

Phylogenetic tree construction

Answer 23

1. Figure out the largest shared trait.
2. Trait shared by the second largest number of animals.
3. Branch animals that share traits - directly.

Question 24

Structure of phylogenetic trees

Answer 24

Root –> the line at the origin.
Branch –> Each line of the tree.
Node –> Point where branches split.
Leaf –> End of the branch; the animal.