* Evolution (Ch 29-30)

Question 1

*Fossils

Answer 1

• Fossils are the preserved remains of organisms which may be infiltrated by minerals to become petrified. Various types of fossils include entire organisms in ice/ amber, hard skeletal materials, imprints

Question 2

Formation of fossils

Answer 2

1. When organism died, their soft body parts decayed while their hard body parts buried in the sand and mud
2. These hard body parts are infiltrated by mineral salts and became hardened
3. Under the great pressure of the earth layers, the hardened body parts became petrified

Question 3

• Fossil as evidence for evolution

Answer 3

1. Most fossils found demonstrated a close resemblance between fossils and living species, indicating present life forms arose from pre-existing life forms
2. A greater diversity of fossils is found in the younger rock -> existing organisms stemmed from a common ancestry
3. Fossils in younger rocks are more complex than those in older rocks -> organisms evolved from simple to complex form

Question 4

• Limitations of fossil records

Answer 4

1. There are missing links in fossil records
2. Some fossils are incomplete or damaged
3. Some fossils are found inaccessible areas
4. Some organisms having a soft body may not be fossilized

Question 5

Comparing DNA base / amino acid sequences of similar proteins to establish phylogenetic relationship between organisms

Answer 5

• The genetic code is universal, all organisms use the same DNA triplet code to code for the same amino acid in polypeptide synthesis
• Mutation in a codon would result in a different amino acid sequence of similar proteins of the organisms, the closer is the phylogenetic relationship
• The greater the similarities between the amino acid sequence of similar proteins of the organisms, the closer is the phylogenetic relationship between them

Question 6

Criteria for identification of homologous structures

Answer 6

• Similar anatomical pattern of bones and joints
• Similar body position
• Same embryonic origin
• Strong resemblance in nerves, blood vessels and muscles

Question 7

Mixing DNA of two species -> the more closely related the species, the higher the separation temperature

Answer 7

• More closely related -> more similarities in DNA -> more hydrogen bonds formed by complementary base pairing -> need higher temperature to separate

Question 8

Darwinism vs Lamarckism

Answer 8

Both: organisms become more adaptive to the environment over generations

Darwinism:
- Variations exist naturally among individuals
- Individuals with favourable variations have a higher chance to survive and reproduce while those with unfavourable variations will be eliminated
- Favourable variations have a higher chance to be passed to the next generation

Lamarckism
- Changes in environment create needs that cause the organisms to modify the existing organs
- Repeated use of the organs will make them become more efficient while the disused organs will be degenerated
- Acquired character can be inherited to the next generation

Question 9

Struggle for existence, survival of the fittest

Question 10

• Evolution (by natural selection)

Answer 10

1. Genetic variation existed in the X populations, some are A and some are B
2. Individuals with A has greater ability to…
3. They have greater chance to survive and reproduce
4. The population of the subsequent generations would have a greater proportion of X with A

Question 11

• Speciation

Answer 11

1. Separation due to geographical change resulted in isolation of two groups of X, stopping gene flow between the two groups of ancestors
2. Each isolated group was subjected to a different set of environmental conditions
3. They evolved differently from each other due to natural selection
4. Until their genetic compositions were different that they cannot interbreed to give fertile offspring