Lesson 4 - Evolution

Question 1

Why does Darwin’s theory of evolution contrast contemporary beliefs?

Answer 1

• People interpreted genesis as a few 1000 years earlier. If organisms had been evolving for thousands of years, then this theory was disproved.
• Contrasted the idea that God created man in his image.

Question 2

Influences of Darwin:
Lyell

Answer 2

Fossils are evidence that creatures lived millions of years ago.
Uniformitarianism (originally published by Hutton)

Question 3

What prompted darwin to think of evolution as a slow process?

Answer 3

Lyell’s reference to uniformitarianism.

Question 4

How did Wallace improve the creditability of the theory of natural selection?

Answer 4

• Both Wallace and Darwin came to the same theory independently.
• Similar ideas
• This means that more evidence was available (collected by both scientists)
• Published / Presented paper together

Question 5

Explain natural selection:

Answer 5

… have evolved to have … through the process of natural selection.
New alleles are the result of a random mutations within their DNA. This creates variation in the gene pool.
Some of these mutations have created …
… have adapted these … to give them a selective advantage.
These individuals are more likely to survive as they can obtain more food (selection pressure), increasing their chances of survival and reproduction.
These adapted … pass on their advantageous allele to their offspring.
Over time, the advantageous allele frequency increases within the population.

Question 6

When did Wallace and Darwin publish their theory on evolution?

Answer 6

1858

Question 7

When did Darwin publish ‘On the Origin of Species’?

Answer 7

1859

Question 8

Evidence for evolution:

Answer 8

• palaeontology
• comparative anatomy
• comparative biochemistry

Question 9

Palaentology

Answer 9

The study of fossils and fossil records

Question 10

Comparative anatomy

Answer 10

The study of similarities and differences between organisms’ anatomy.

Question 11

Comparative biochemistry

Answer 11

The study of similarities and differences between the chemical makeup of organisms.

Question 12

Fossil records:

Answer 12

Different layers of earth correspond to different geological eras. Different organisms are found in each layer.

Question 13

Evidence for evolution in fossil records:

Answer 13

• Simple bacteria and algae fossils are found in the oldest rocks, progressing to more complex vertebrates in newer rocks.
• Plant fossils appear before those of animals that feed on these plants, indicating a natural order of evolution.
• Fossils enable scientists to investigate the links between extinct and extant organisms.
• By studying the similarities between fossils, scientists can work out how organisms evolved from common ancestors.

Question 14

Why are fossil records incomplete?

Answer 14

• Many organisms decompose before they can fossilise.
• Fossilisation is rare and it requires specific conditions for an organisms to be preserved.
• Over time, many fossils have been lost due to geological processes and erosion.
• Many organisms have not yet been discovered.
• Soft-bodied organisms decompose before they can fossilise.

Question 15

Homologous structure

Answer 15

Structure that appears superficially different but has the same underlying structure.

Question 16

Example of a homologous structure:

Answer 16

Pentadactyl limb of vertebrates.

Question 17

Divergent evolution

Answer 17

Species diverge over time into two different species, resulting in the new species becoming less like the original one. This is a result of new habitats and migration.

Question 18

Evidence of divergent evolution:

Answer 18

homologous structures

Question 19

Comparative anatomy proof of evolution:

Answer 19

Homologous structures are physical features in different species that have a similar underlying structure but may serve different functions.
Organisms who share homologous structures likely evolved from a common ancestor, and have adapted these structures for different functions.
Homologous structures are evidence for divergent evolution, where organisms evolve different adaptive traits as they occupy new ecological niches.

Question 20

Comparative anatmoy

Answer 20

Comparative anatomy examines the anatomical structures of different living species to find similarities and differences.

Question 21

Evidence for evolution in comparative biochemistry:

Answer 21

• Cytochrome C
• Ribosomal RNA
• Nuclear, mitochondrial, chloroplast DNA
• Messenger RNA
• Amino acids

Question 22

Evidence for evolution in comparative biochemistry:
Cytochrome C

Answer 22

Highly conserved protein involved in cellular respiration, so slight changes can help identify evolutionary links

Question 23

Evidence for evolution in comparative biochemistry:
Ribosomal RNA

Answer 23

Integral to protein synthesis, so it changes slowly. Useful for showing connections between species that diverged a long time ago.

Question 24

Evidence for evolution in comparative biochemistry:
Nuclear, mitochondrial, chloroplast DNA

Answer 24

Species that are more closely related will have similar DNA sequences.

Question 25

Evidence for evolution in comparative biochemistry: Messenger RNA

Answer 25

Base sequences from mRNA are complementary to DNA so can assess DNA diversity.

Question 26

Evidence for evolution in comparative biochemistry: Amino acids

Answer 26

If they are closely related evolutionarily, two species have more similar amino acid sequences because they are determined by mRNA and DNA

Question 27

Neutral evolution

Answer 27

Most variability in the molecule's structure does not change its function.

Question 28

Why is it important to assess neutral evolution?

Answer 28

'Neutral' changes that don't affect function accumulate at a fairly regular rate as they are not affected by natural selection. Comparing the rates of neutral substitutions in the molecular sequences of different species lets scientists estimate the time since two species diverged from a common ancestor. Generally, a greater number of differences indicates a more ancient divergence.