BIOL 215 Lecture Notes - Lecture 17: Macroevolution, Stabilizing Selection, Heritability

Recently I have found myself in a discussion with a guy thatisn't a creationist, but denies evolution. He cites several studiesthat show problems like this one, but I do not have the knowledgeto refute it properly. Whats the problem with the following:

One problem is that population genetics shows us evolutiondestroys functional sequences much faster than it creates them inany large-genome animal with low reproductive rates, becausedeleterious mutations arrive faster than selection can remove them.This would include just about all mammals, reptiles, and birds--anyof our would-be ancestors over the last 300m years.

Specifically, humans get 60 to 160 mutations per generation,10-20+% of our genome is sensitive to substitution, and this givesus 6-32 deleterious mutations per offspring (most slight). Evenwith the low estimate of 6, every child is less fit than theirparents and natural (or even artificial) selection can only choosethe least degenerate each generation. For every generation where amutation can be selected, random mutations destroy 5-32+ previouslyselected. Beneficial mutations like lactose tolerance (a jammedswitch) take 1000s of years to appear and fixate.

If you know the genome size, mutation rate, and reproductiverate, you can calculate at what rate deleterious mutations arrivefaster than they can be removed:

"It has been estimated that there are as many as 100 newmutations in the genome of each individual human. If even a smallfraction of these mutations are deleterious and removed byselection, it is difficult to explain how human populations couldhave survived. If the effects of mutations act in a multiplicativemanner, the proportion of individuals that become selectivelyeliminated from the population (proportion of `genetic deaths') is1-e^-U, where U is the deleterious mutation rate per diploid, so ahigh rate of deleterious mutation (U>>1) is paradoxical in aspecies with a low reproductive rate." High genomic deleteriousmutation rates in hominids, (Nature, 1999)

They worry about a deleterious rate of U much greater than 1 asbeing prohibitively high and we're talking about it being 6-32+,since we now know the functional genome is much larger than wethought it was in 1999. Taking their Poisson probabilitydistribution and using U=6, that means 1-e^-6 = 99.752% of thepopulation will have to be selected away each generation for onelucky enough to have no deleterious mutations. For two to surviveand maintain constant population size that would require on average806 offspring per female--impossible for most mammals, birds, andreptiles. Actually much more since natural selection is notomnisciently efficient.

1. Humans have the scientific name Homo sapiens. We are members of the family Pongidae, in the order Primates, in the class Mammalia, in the phylum Chordata. Based only on this information, which of the following is not a correct statement?

a. The speciation event (lineage-splitting) that generated the genus Homo occurred earlier than the speciation event that generated the species H. sapiens.

b. The most inclusive of these taxonomic groups is Chordata.

c. The genus Homo might have as many species as are in the entire family Pongidae.

d. There can be no other species in the genus Homo.

e. All mammals must be Chordates.

2. Endotherms differ from ectotherms in that:

a. Environmental temperature has little effect on the energy budget of endotherms but a strong effect on the energy budget of ectotherms.

b. An endotherm's metabolic rate is not affected by temperature whereas the metabolism of an ectotherm has a Q10 of 2-3.

c. Endotherms are vertebrates and ectotherms are invertebrates.

d. On average, endotherms are much better sprinters (i.e., can run faster for short distances) than ectotherms.

e. Endotherms are much better able to support endurance exercise than ectotherms.

3. You measure oxygen consumption of a lizard at three temperatures, as follows: 18 °C: 0.090 ml O2/min 23 °C: 0.135 ml O2/min 28 °C: 0.200 ml O2/min From these data you calculate the Q10 to be:

a. 1.8

b. 2.0

c. 2.2

d. 2.5

e. none of these are correct.

4. What is the best description of how evolution by selection (natural or artificial) works?

a. mutation generates variation randomly, sex makes new combinations of genes randomly, and selection picks the best ones for reproduction.

b. selection leads to non-random mutation to make useful new alleles, which are then combined by sex.

c. exposure to environmental factors leads to non-random mutations that improve fitness.

d. through selection, mutations occur in those genes that will improve fitness.

e. mutation generates random new alleles, and sex combines them in ways that select the best for future generations.

5. Which of the following is a correct match between a major lineage and its characteristics?

a. Archaea: extremophiles, ribosomes, RNA as genetic material, no nuclear membrane

b. Eukarya: mitochondria, DNA as genetic material, photosynthetic or chemohetrotrophic

c. Bacteria: mitochondria, DNA as genetic material, no nuclear membrane

d. Eumetazoa: extremophiles, ribosomes, DNA as genetic material, nuclear membrane, chemoheterotrophic

e. Protostomes: triploblastic, eucoelomate, blastopore becomes anus, indeterminate cleavage

6. Which of the following statements about animal life history events is correct?

a. Being multicellular requires a larval stage in the life cycle.

b. Mutation is sufficient to produce considerable genetic variation between different tissues in an individual.

c. Senescence is defined by slow, constant decline in survival as individuals get older.

d. Different cell types are formed when different but specific portions of the zygote’s DNA are lost from the different germ layers during development.

e. In an individual, the only cells that differ genetically from other cells are gametes.

7. Which of the following statements about terrestrial vertebrates is correct?

a. Jaws evolved from paired appendages, which in turn evolved because they improved swimming ability.

b. Legs evolved from fins after early fishlike vertebrates invaded the land.

c. Jaws and inner ear bones evolved from gill arches, and leglike appendages evolved under selection for aquatic locomotion.

d. Viviparity (giving birth to well-developed young instead of laying eggs) was vital to the ability to reproduce on land without returning to the water.

e. Lungs for breathing air evolved after early fishlike vertebrates invaded the land (the first land vertebrates had to depend on gills for breathing air)

8. The essential features of a hydrostatic skeleton include:

a. antagonistic muscles.

b. a non-deformable fluid-filled space

c. flexible joints.

d. compressible material capable of changing volume

e. all of the above (a) – (d) are correct.

9. You are a Peace Corps volunteer physician in a developing country. You notice that some of the villages you visit have a high incidence of a parasitic disease, but other nearby villages are unaffected. Investigating you find the villages with disease are in wet areas with lots of snails and frogs, while the disease-free villages are in drier places but have lots of insects and mice. From this information, what might you reasonably conclude about the type of parasite responsible for the disease?

a. It’s a trematode (these need mollusks as intermediate hosts).

b. It’s a nematode (these are vectored mainly by frogs).

c. It’s an apicomplexan parasite (these require wet areas and enter the skin through standing water).

d. It’s a trypanosome (these are transmitted by mammal bites).

e. The information doesn’t provide useful clues about the type of parasite.

10. Which of the following pairs of primary diagnostic characters is correctly matched with taxonomic groups?

a. circulatory system vs. water vascular system: Nematoda vs. Echinodermata

b. schizocoely vs. enterocoely: Radiata vs. Bilateria

c. pharyngeal slits vs. polyp and medusa: Chordata vs. Cnidaria

d. gastrovascular cavity vs. complete gut: Cnidaria vs. Cestoda

e. hemocoel vs. contractile vacuole: apicomplexans vs. rhizopoda

Please provide explanation too.