Genes Evo & Dev L1

Question 1

What is Evolution?

Answer 1

The gradual change in allele frequency of a population over time.

Question 2

Conditions for evolution by natural selection?

Answer 2

1. Range of characteristics
2. Characteristic heredity
3. Advantageous characteristics enable survival & reproduction.

Question 3

What does it mean if offspring is “naturally selected” for?

Answer 3

Advantageous phenotypes passed to offspring from parental genotypes enable survival & reproduction.

Question 4

In what other situations does natural selection occur besides ecosystems of plants & animals?

Answer 4

Also applies to medical conditions eg. Antibiotic resistance & cancer.

Question 5

Evidence for Evolution?

Answer 5

1. Fossils
2. Vestigial Traits
3. Imperfection

Question 6

Types of Fossil Evidence -> evolution?

Answer 6

• Trilobites
• Whales
• Tiktaalik Roseae

Question 7

Fossil evidence -> evolution -> whales?

Answer 7

Basilosaurus;
Hind limbs inherited from ancestors no longer advantageous as aquatic lifestyle adapted.

> Closest relative = Hippo.
(Give birth & nurse underwater ; multi-chambered stomach ; internal testicles.)

Question 8

Vesitgilal evidence -> evolution?

Answer 8

• Vestigial muscle of forearm
• > grip in arboreal species.

Darwin’s tubercle -> calibration of ears for sound detection

Question 9

What are vestigial traits?

Answer 9

Characteristics which were useful in common ancestors that are no longer needed, but are still present.

Question 10

Imperfection Evidence -> Evolution?

Answer 10

Laryngeal Nerve

Question 11

Why is the Laryngeal nerve imperfect?

Answer 11

• 1m long
• Distance from brain to larynx is <30cm.
• Loops around aorta

Question 12

How did the laryngeal nerve become imperfect?

Answer 12

1. Originated from 4th branch Vagus nerve.
2. Initially: Fishes – Brain -> gills
3. Evolution:
   - Gills become irrelevant
   - Larynx develops from branchial arch
   - Nerve ending displaced over time as neck evolves

4.Later: Mammals – Brain -> larynx

Question 13

Why did the laryngeal nerve remain & grow rather than design of a new nerve?

Answer 13

• Evolution cannot predict.
• Easier to build on existing structures than spend energy starting new design.
• Gradual lengthening & looping back of laryngeal nerve over time.

Question 14

How did Charles Darwin think of theory of evolution by natural selection?

Answer 14

• Trip to Galapagos islands in 1835.
• Shape of Finches bills:
  i) Specially adapted to environment
  ii) All derived from common ancestor

Question 15

Describe the distribution of species on the Galapagos islands.

Answer 15

• Little gene flow (movement of genes) between islands & mainland.
• > Species endemic to the Galapagos eg. Finches, penguin, marine iguana.
• > Close relatives on each island
• > Differentiated over time to form new species (speciation

Question 16

Evidence Evolution by natural selection can be observed within a short period of time &/Or occur on small scales in the Galapagos?

Answer 16

3 year study -> Decreased rainfall levels during one year’s rainy season :

• Plants did not produce new seeds
• Less food for ground finches
• No mating & reproduction.
• Population decreases.
• Only fiches with long & deep enough beaks to access certain seeds survive.

This causes evolution by natural selection > Beaks 0.54mm deeper & 0.39mm longer after 1 season.
> Change in sex ratio.