Lecture 4

Question 1

What are 3 useful categories of evolution?

Answer 1

1. microevolution
2. speciation
3. macroevolution

Question 2

explain microevolution

Answer 2

changes within a species:
- not controversial, even among most creationist publications
- observed in nature and in laboratory experiments
- includes variation and natural selection!

Question 3

explain speciation

Answer 3

formation of new biological species:
- also shown to occur in nature and laboratory, but still controversial to some

Question 4

explain macroevolution

Answer 4

• changes above species or genus level
• interpretation of fossil record
• the origin of complex adaptations (ex. eyes)

Question 5

How does resistance arise in antibiotic resistant strains in bacteria, and pesticide resistance in insects and weedy plants?

Answer 5

• mycobacterium tuberculosis
• this is natural selection at work, sorting variations that arise spontaneously by mutation

Question 6

What can natural selection act on?

Answer 6

• can act on any heritable trait

ex. a trait with genetic variation

Question 7

What are 3 examples of the presence of different variations a gene (alleles), or whole DNA sequences?

Answer 7

• physical or structural differences: Body or body part size, shape, colours, patterns
• physiological and biochemical differences: proteins, structural and regulatory; enzymes, hormones
• developmental patterns (embryology

Question 8

What are the 2 conditions for natural selection that are met for any trait in a population?

Answer 8

1. there is heritable (genetic) variation
2. the variation results in a fitness differential (=advantage or disadvantage to reproduction in the current environment)
   Then that trait will evolve in that population by natural selection

Question 9

What is evolutionary fitness?

Answer 9

• not survival alone, but an individual’s contribution of genes to the next generation

ex. reproductive success compared to others

Question 10

What are the two fitness concepts and what are they?

Answer 10

• physical fitness: physically fit but not evolutionarily fit if no children produced…
• biological evolutionary: # of surviving offspring determine fitness, genes contributed to next generation (population gene pool) determines fitness

Question 11

What is an example of unplanned selection by humans?

Answer 11

• the average size of Atlantic Cod has declined due to fishing pressure on the largest fish. Smaller female cod also reproduce at a younger age, and produce fewer eggs than earlier populations
• trophy hunting of largest big horn sheep is reducing the mean size of male horns in population

Question 12

What are homologous traits

Answer 12

• similar structures in descendant organisms can be explained as resulting form inheritance from a common ancestor
• homology of forelumb bones, among any others, of tetrapods: vertebrates with 4 limbs
• homology can be obvious or not

Question 13

homology between humans and who are obvious?

Answer 13

• chimpanzees
  -we have similar hands (bones, muscles, ligaments, etc.)
• foot differences greater (grasping big toe in chimps_ but basic bone, muscle, and other structures are similar

Question 14

When we are thinking of feet, what is an example of homology that is not obvious with humans?

Answer 14

• elephant’s foot pads
• elephants walk on high heels, with the heel elevated on a large fat pad.
• this does not imply any direct ancestor-descendant connection between humans and elephants, but it shows a homology of bone structure shared by all mammals with four limbs

Question 15

What indicates transitions between terrestrial amphibious and aquatic forms?

Answer 15

a phylogeny of fossils

Question 16

what does vestigial mean?

Answer 16

• reduced functions

Question 17

What did Cetaceans (whales and relatives) have before that they don’t anymore, and what are some evidences?

Answer 17

• used to have 4 limbs, had 2 hindlimbs
• were “walking” whales
• phylogeny of fossil cetacenas
• vestigial hip and limb bones are found in some living and fossil adult whales and in dolphin embryos
• embryology: hindlimbs in cetaceans begin to form but do not fully develop (dolphin embryos)
  *** the genetic information to make hind limbs is present, but has been stopped at some point (gene regulation!!!!)

Question 18

What are 3 examples of vestigial structures on humans?

Answer 18

• tailbone: monkey’s used their tail for balance and locomotion
• goose bumps: chimps erected their hair for emotional display and insultation
• impacted “wisdom teeth” or third molars

Question 19

What are fossils key evidence for?

Answer 19

• key evidence for the presence, in the geological record (sedimentary rocks), of transitional forms like Archaeopteryx and extinctions of most fossil species

Question 20

What is the Daphne Major?

Answer 20

• dry volcanic island with cactus & sparse plant cover

Question 21

When they measured or observed birds, what was the process? (4 things)

Answer 21

• capture
• measure
• collect data
• release

Question 22

how did the population of finches change from 1976 to 1978?

Answer 22

• 88% died after the drought
• their beak depth increased from 9.4mm to 10.1 mm

Question 23

What does directional selection change?

Answer 23

• changes the average value of a trait (graph could shift to the left or right - the average decreases to increases)

Question 24

What is stabilizing selection?

Answer 24

• any selective force or forces which push a population toward the average, or median trait
• average (mean) individuals are favoured, high fitness = stability
• selection against extreme traits
• a type of natural selection in which the population mean stabilizes on a particular non-extreme trait value
• reduction in variation
• When stabilizing selection acts on normally distributed traits, individuals with extreme phenotypes have poor reproductive success

ex. very small and very large babies are the most likely to die, leaving a narrower distribution of birth weights

Question 25

What are the two things that are required for natural selection? review example with the finches

Answer 25

1. heritable variation exists. - is beak depth a heritable trait? (yes! offspring inherited the larger beaks of surviving parents) 2. a fitness differential exists - is there an advantage or disadvantage for having different beak depths? (yes! survival & reproduction was better for birds with beaks of larger than average size that could crack larger seeds from drought plants)

Question 26

Does natural selection change individuals?

Answer 26

NO! it sorts them - individuals do not change, but the population does ex. during the drought (environment changed), the beaks of individual finches did not change, but the avg. beak depth increased over time because finch individuals with slightly deeper beaks had greater survival and reproductive success (higher fitness) than smaller-beaked variants. The larger beaks of the survivor's offspring resulted in a still variable population, but with bigger beak depths on avg. than before.... SELECTION HAS BEEN DEMONSTRATED

Question 27

How are evolution and development linked? explain using finches as an example

Answer 27

- "evo-devo" - increasing the amount of the protein produced by the Bmp4 gene during development results in a deeper beak. - increased expression of this gene during development would cause the general increase in beak depth in the descendants of surviving finches on Daphne Major

Question 28

What are the 5 misconceptions about natural selection : corrections?

Answer 28

1. individuals can't evolve; only populations of a species can evolve 2. individuals do not select which genes to pass on; reproductive individuals pass on genes that may be advantageous or disadvantageous 3. selection (not random) is adaptive, but mutations and genetic drift occur randomly 4. natural selection is not purposeful or forward-looking (ex. natural selection does not happen for a predetermined objective), but operates in the present environment 5. evolution does not produce perfections, only workable adaptations