Topic 4: Evolution

Question 1

What evidence suggests the first cells were RNA and not DNA?

Answer 1

• RNA can self-replicate
• RNA can form a double helix
• RNA can store genetic info
  *RNA enzymes (ribozymes) can catalyse simple chemical reactions

Question 2

What evidence suggests the first cells were Prokaryotic?

Answer 2

Stromatolites (Fossil Records)

Question 3

What is the Endosymbiotic Theory?

Answer 3

Eukaryotic Cells evolved from Prokaryotes that were engulfed via endocytosis.
Aerobic Bacterium - Respiration
Cyanobacterium - Photosynthesis

Question 4

What evidence supports the Endosymbiotic Theory?

Answer 4

• Have own circular DNA (like prokaryotes)
• Have their own ribosomes similar to prokaryotes
• Can Self-replicate
• Double-membrane - Inner: Prokaryotes, Outer: Eukaryotes

Question 5

What is Comparative Genomics? What are Examples?

Answer 5

Provides evidence for evolution & helps establish evolutionary relationships between different species.
- DNA & RNA Sequences
- Protein (amino-acid) Sequences
- DNA-DNA Hybridisation

Question 6

How is DNA used to show evolutionary relationships and the most recent common ancestor of species?

Answer 6

The more closely related two species are - more DNA in common - More Recent Common Ancestor.
The less closely related two species are - Less DNA in common - More Distant Common Ancestor.

Question 7

What is DNA-DNA Hybridisation?

Answer 7

• DNA from Different species is separated into single strands using heat
• If two strands from different species share similar sequences, they will Anneal
• Amount of Heat required to separate hybrid indicates Similarity

Question 8

What does high Temperature suggest for DNA-DNA Hybridisation?

Answer 8

↑ Temp - ↑ Hydrogen bonding between strands - ↑ DNA in Common
∴ More Recent Common Ancestor

Question 9

What does Low Temperature suggest for DNA-DNA Hybridisation?

Answer 9

↓Temp - ↓ Hydrogen bonding between strands - ↓ DNA in Common
∴ More Distant Common Ancestor

Question 10

What is the definition of a Species?

Answer 10

Group of organisms that can actually or potentially interbreed to produce fertile offspring.

Question 11

How can species that reproduce asexually be defined?

Answer 11

Similarities in:
Morphology - Shape & Anatomy
Biochemistry - Chemical composition of cells & tissues, some metabolic processes
Genetic Composition - DNA nucleotide sequences in genomes

Question 12

What is Reproductive Isolation?

Answer 12

Mechanisms that prevent members of two different species from mating & producing fertile offspring

Question 13

What are the Pre-Zygotic Isolation Mechanisms?

Answer 13

1. Ecological - Species occupy different habitats/niches
2. Temporal - Species are sexually mature at different times
3. Mechanical - Species have different sized shaped genitalia
4. Behavioural - Different Courtship Patterns
5. Gametic - Incompatible gametes (unsuccessful fertilisation)

Question 13

What are the Post-Zygotic Isolation Mechanisms?

Answer 13

Hybrid Unviability - Offspring is unhealthy & unlikely to produce its own offspring
Hybrid Sterility - Offspring reaches sexual maturity but is sterile (Meiosis fails to produce gametes due to diff. in chromosomes)

Question 14

What is a Gene Pool?

Answer 14

Set of all genes in a population at a given time

Question 15

What does a Large Gene Pool Suggest?

Answer 15

• Extensive genetic diversity
• More likely to survive selection pressures

Question 16

What does a Small Gene Pool Suggest?

Answer 16

• Low genetic diversity
• Greater risk of Extinction

Question 17

What is Natural Selection?

Answer 17

Selection Pressures lead to advantageous alleles increasing in frequency in the population

Question 18

When Does Natural Selection Occur?

Answer 18

1. Population contains genetic variation
2. Due to selection pressures - not all individuals survive to reproduce
3. Individuals that survive & reproduce pass on their alleles to the next generation
4. Frequency of favourable alleles/traits increase in population

Question 19

What are Selection Pressures?

Answer 19

Abiotic/Biotic Factors that affect the chances of an individual’s survival & reproduction (Drives evolution of certain traits)
Examples:
- Predation
- Competition for Resources
- Food/water Availability

Question 20

What are sources of Genetic Variation?

Answer 20

• Mutations
• Independent Assortment & Crossing Over
• Random Fertilisation

Question 21

What is Genetic Drift?

Answer 21

Changes in frequency of alleles in the gene pool of a population due to CHANCE.
*Occurs in all populations
* Can lead to loss of advantageous alleles (↓ genetic diversity)

Question 22

What is Genetic Bottleneck?

Answer 22

Size of Population is dramatically reduced by natural disasters

Question 23

What is Allopatric Speciation?

Answer 23

Separated by Geographical Barrier
* Prevents interbreeding & gene flow

Question 24

What is Sympatric Speciation?

Answer 24

Results of reproductive isolation - Ecological, Behavioural, Temporal *No Physical Barrier

Question 25

What is Convergent Evolution?

Answer 25

Unrelated Species evolve similar structural, biochemical or behavioural characteristics due to similar selection pressures * Convergent structures = Analogous Structures

Question 26

What is Adaptive Radiation?

Answer 26

Organisms diverse rapidly from their ancestral species into a variety of new forms. * More Frequent * Homologous structures - look different on the exterior but have the same bones in different forms

Question 27

What is Ecological Succession?

Answer 27

Changes that take place in an ecosystem over time

Question 28

What is Primary Succession? What are the steps involved in forming a Climax Community?

Answer 28

Occurs in nutrient-poor soil that is incapable of sustaining life. Pioneer Species --- Intermediate Species --- Climax Community

Question 29

What is a Climax Community?

Answer 29

When all species in an ecosystem possess necessary adaptions to survive

Question 30

What is Secondary Succession?

Answer 30

Takes place after natural disasters such as landslides, bushfires, etc..

Question 31

How do Humans Negatively impact species?

Answer 31

- Increased Predation - Introduced Species - Compete for resources (↓ pop. of native species) - Habitat Destruction

Question 32

How do Humans Contribute to Climate Change?

Answer 32

- Combustion of Fossil Fuels: Releases large quantities of greenhouse gases (CO2) into the atmosphere - Deforestation: Fewer Trees available to remove CO2 from atmosphere - Agriculture: Releases Methane & CO2, ↑ conc. of both gases in the atmosphere

Question 33

What are the principles of conservation?

Answer 33

Protecting Habitats - Maintain Ecosystem Diversity Minimising Pollution - Prevent Introduction of new selection pressures that lead to extinction Protecting Species - Different Species are monitored & protected to prevent extinction (↓ species diversity)