ch6 qs

The body cells of the African clawed frog Xenopus laevis have a ploidy of 2n = 4x = 28. How many different kinds of chromosomes does it have (that is, how many chromosomes make up each set)?

7 (The frog is tetraploid (4𝘹) in the absolute sense, with 28 chromosomes, so it has four sets of chromosomes making up the 28: 28/4=7.)

The body cells of the Lake Oku clawed frog, Xenopus longipes, are diploid relative to the products of meiosis and carry 108 chromosomes, which occur in sets of 9 (i.e., it has 9 different chromosome types). What is the correct chromosome designation for this frog?

2n = 12x = 108 (The frog is diploid = 2n with 108 chromosomes in 12 sets of x = 9: 108/9 = 12 = dodecaploid. Such large ploidies are rare in animals, but occur occassionally among amphibians and fish, and are very common in plants (especially agricultural strains).)

Which of the following statements is correct about the hive insects?

a. Males and females both have a mother and a father

b. Females have both a mother and a father, but males have only a mother

c. Females have only a mother, and males have only a father

d. Females have only a father, and males have only a mother

b (The females are produced from an egg that has been fertilized by a sperm, but the males are produced from an egg that has not.)

Do male ants and bees produce sperm by meiosis or mitosis?

mitosis (Males in the haplodiploid system are already haploid, so they do not need to reduce their chromosome sets during sexual reproduction, but simply copy them all. This means that their sperm are all genetically identical to themselves (clones).)

Imagine a fictional species called ardviks. Among the ardviks, Asel has an allele that promotes selflessness (altruism), whereas Ednok does not. Who is more likely to benefit from interactions between them? (asel or ednok)

enok (the more selfish one, Ednok will benefit from the help of Asel, at Asel’s expense, with nothing given in return. Ednok’s self-centeredness allele will be selected for in this scenario, whereas Asel’s altruism allele will be selected against.)

Asel and Berlof are siblings, and both have inherited the altruism allele from their parents. Are they each likely to be more or less successful in reproduction when they interact and help each other, or when they do not?

when they help each other (Asel and Berlof are more likely to be successful when they help each other. Because they both carry the altruism gene, its passage to the next generation is thus boosted when either helps the other. This is kin selection.)

Suppose that receiving help from others results in much greater reproductive success than does going it alone, such that those who help each other successfully raise on average 2 times more offspring than those who do not, even despite the cost of helping. Consider a situation where the siblings Asel and Berlof both have the altruism allele and help each other, but the siblings Ednok and Ralo do not and are each on their own. Will the altruism allele be selected for in this scenario?

yes, the altruism allele will be passed on more effectively than its counterpart (If Asel and Berlof pass their alleles to twice as many offspring on average, then their shared altruism gene will more successfully flood the market in the next generation.)

What would happen if most of the individuals in the ardvik population never actually reproduce themselves—would kin selection still cause the altruism gene to be selected for?

yes it would (A non-reproducing altruist still helps their siblings successfully pass on their shared alleles. Kin selection works any time the benefits of associating in family units exceed the costs on average among them.)

Do we humans exhibit any secondary sex characteristics?

yes (Body size, hip width, chest development, voice pitch, and degree of facial hair are examples of secondary sex characteristics in humans. (Genitalia are primary sex characteristics, since they directly produce and convey gametes.))

Are we humans best classified as r- or K-strategists?

K-strategists (We typically have only one offspring per reproductive event, which we then invest heavily in rearing. We are actually an extremely K-selected species!)

Which animal mating system achieves the greatest level of genetic recombination?

a. monogamy

b. promiscuity

c. polygamy

b (In promiscuous systems both males and females mate with many others, resulting in the highest level of gene mixing among individuals.)

Which system of polygamy is likely to result in the highest output of offspring?

a. Polyandry

b. Polygyny

b. (Females produce the offspring, so a larger number of females with reliable access to resources typically results in greater total reproductive capacity. This is probably why polygyny is considerably more common than polyandry in animals.)

In which animal group is monogamy most common?

a. Fish

b. Insects

c. Mammals

d. Birds

d (Monogamy tends to be selected for when offspring need rearing, and both parents are equally capable of rearing them. Monogamy is thus most common among nesting birds.)

Fungi are haploid (1n) organisms, meaning their somatic cells carry half the complement of chromosomes that their zygotes do. More specifically, fungi are monoploid (1x) organisms, meaning that in that haploid state their cells carry just one chromosome set. Which two of the following are correct about fungi?

a. Their zygotes are 1n

b. Their zygotes divide by meiosis to produce haploid cells

c. Their zygotes are 2n

d. Their cells divide by meiosis to produce haploid cells

b, c (The cells are already haploid (and monoploid), so they cannot reduce their number of sets any further by meiosis. The zygotes, in contrast, need to cut their chromosome number in half to return to the typical somatic cell ploidy.)

A circle of mushrooms sometimes pops up in a lawn or meadow, often appearing overnight. These circles have been whimsically named fairy rings, as though the mushrooms were put there to be used as stools by fairies during a meeting they held. (Mushrooms are also referred to as toadstools). Why do these mushrooms grow in a ring?

a. Because this improves the chances of spores from different mushrooms mingling after they disperse

b. Because the dikaryotic mycelium grows evenly outward

c. Because the different mating types curve toward each other underground

d. Because spores disperse evenly in all directions

b (The dikaryotic mycelium that forms underground from the fusion of two parents grows outward and eventually upward to form fruiting bodies. In ground with uniform nutrients the growth occurs evenly in all directions, in an expanding circle.)

The sporophytes of a certain species of plant have a ploidy of 8x. What will the ploidy of its gametophytes be?

4x (In plants, the sporophyte is the diploid generation (with paired chromosomes), while the gametophyte is the haploid generation (with half the number of chromosomes). The sporophyte undergoes meiosis to produce haploid gametophytes. In this case, if the sporophyte has a ploidy of 8x, it undergoes meiosis to produce gametophytes with half that ploidy, which would be 4x.)

The sporophytes of a certain species of angiosperm have a ploidy of 8x. What will the ploidy of its spores be?

4x (In angiosperms, the sporophyte produces spores through meiosis. Since meiosis reduces the chromosome number by half, the ploidy of the spores will be half that of the sporophyte.

If the sporophyte has a ploidy of 8x, the spores will have a ploidy of 4x.)

If an angiosperm’s spores are 4x, what will the ploidy of its endosperm be?

12x (In angiosperms, the endosperm is typically triploid (3n), resulting from double fertilization. The two polar nuclei in the central cell (each 4x in this case) fuse with one sperm cell (which would be 4x).

So, the ploidy of the endosperm will be (4x + 4x + 4x), which is 12x.)

Dandelions produce their seeds in little white tufts that float well in air. What does this suggest? 

a. Dandelions do not use animals to disperse their seeds

b. Some animals are not bothered by the white tufts

c. Dandelions are not angiosperms

d. Dandelions do not use animal pollinators

a (Dandelion seeds detach and carry easily to great distances in wind.)

There are four general groups of gymnosperms: conifers, gnetophytes, cycads, and ginkgo. The ginkgo group is represented today by only one surviving representative, the Ginkgo biloba tree, which gets its name from the way its leaves are shaped like a fan split into two lobes. In an example of convergent evolution, the Ginkgo tree produces fruit that is notoriously stinky, usually described as smelling similar to vomit. Given that Ginkgo biloba is not an angiosperm, which of the following is most likely to be true about this fruit?

a. The fruit contains endosperm

b. The fruit is not produced to attract animal pollinators

c. The fruit is derived from gametophyte tissue

d. The fruit is derived from the ovule wall

e. The fruit is derived from ovary tissue

d (The only reason for the Ginkgo tree to produce fruit is to attract animal dispersers, like angiosperms, but without an ovary the fruit is formed from thickening and modification of the ovule wall.)

Capsaicin is a chemical produced by pepper plants—it's the compound that makes peppers seem hot. It is present in the fruit of peppers, and is especially highly concentrated in tissues coating the seeds. What does this suggest?

a. Some animals are not bothered by capsaicin

b. Pepper plants do not use animals to disperse their seeds

c. Pepper plants are not angiosperms

d. Pepper plants do not use animal pollinators

a (Pepper plants produce fruit to attract birds, along with capsaicin to deter mammals from chewing their seeds. Birds are not affected by capsaicin the way mammals are, since they lack the receptor it binds to cause the burning sensation.)

What is the difference between the monoploid number x and the haploid number n in ploidy accounting?

 a. The monoploid number x is the number of different chromosome types present in a cell, whereas the haploid number n is the number of chromosomes that are passed on by a single parent during sexual reproduction.

 b. The monoploid number x is the number of chromosomes that are passed on by a single parent during sexual reproduction, whereas the haploid number n is the number of different chromosome types present in a cell.

c. The monoploid number x is the number of different chromosome types present in a cell, whereas the haploid number n is the total number of chromosomes carried by the cell.

d. The monoploid number x is the total number of chromosomes carried by a cell, whereas the haploid number n is the number of different chromosome types present in the cell.

a

An octoploid (8x) cell undergoes meiosis. How many chromosome sets will its resulting daughter cells have?

a. 1

b. 2

 c. 4

 d. 8

c

Two diploid gametes fuse. The resulting zygote will be what ploidy?

 

Monoploid

 

Diploid

 

Triploid

 

Tetraploid

tetraploid

Which of the following terms is correctly matched with its definition?

 

a. Sperm: a female gamete

 

b. Germ cell: a cell that grows into a new offspring during asexual reproduction

 

c. Gonad: an organ that produces gametes in animals

 

d. Polyploid: carries more than two sets of chromosomes

c

Which of the following is correct about sex determination in animals?

 

a. In the haplodiploid system, fertilized eggs that undergo mitosis develop into one sex, while fertilized eggs that undergo meiosis develop into the other sex.

 

b. The sexes of chickens, honeybees, alligators, and clownfish may change over the course of their lives.

 

c. Sex is genetically determined in all animals.

 

d. The ZW system can be thought of as the reverse of the XY system.

d

What is a secondary sex characteristic?

 

a. A physical feature that indicates male vs. female but is not actually associated with gamete production or conveyance

 

b. A behavior that typically occurs after mating

 

c. A phenotype that is at a reproductive disadvantage compared to the preferred "primary characteristic"

 

d. A physical marker of having already mated, signaling that the individual is no longer sexually receptive

a

Which of these animals is most certain to be oviparous?

 

a. One that lives in an aquatic environment

 

b. One that utilizes external fertilization

 

c. One that always has ready access to mates

 

d. One that cares for its young

b

Which of the following statements is correct?

 

a. Fish eggs have an amnion.

 

b. Kin selection is thought to be particularly strong among animals that use the haplodiploid system of sex determination because it results in siblings sharing an exceptionally high percentage of alleles.

 

c. The amniotic egg has only one membrane.

 

d. Monotremes are mammals that gives birth to relatively undeveloped embryos which then develop the rest of the way in an external pouch.

b

Which statement about animal mating systems is correct?

 

a. Monogamy is more likely to occur in sexually dimorphic species.

 

b. Promiscuity is more common than polygamy.

 

c. r-selected species are more likely than K-selected species to be monogamous.

 

d. Polyandry is more common than polygyny.

b

Which of the following is correct about asexual reproduction in animals?

 

a. Parthenogenesis can only be done by females.

 

b. Parthenogenesis can only produce female offspring.

 

c. Gemmule propagation involves a piece of the parent breaking off, usually due to mechanical stress, and then growing into a new individual.

 

d. Fragmentation occurs only in sponges.

a

Which of the following statements is correct with regard to fungal reproduction?

 

a. Only fungi of the same mating type may reproduce sexually.

 

b. All fungi produce mushrooms to release their spores.

 

c. Fungi do not have male or female sexes.

 

d. Fungi can reproduce asexually only after forming dikaryotic cells.

c

What happens to a zygote in the dikaryotic reproductive scheme of fungi?

 

a. It grows into a haploid mycelium.

 

b. It grows into a dikaryotic mycelium.

 

c. It undergoes meiosis to produce spores.

 

d. It undergoes mitosis to produce spores

c

Which of the following most correctly outlines the sequence of ploidy events that occur to complete a single reproductive cycle (one complete life cycle) of a dikaryotic fungus, from adult to adult?

 

a. 2n --> n+n --> 1n --> 2n

 

b. 1n --> n+n --> 2n --> 1n

 

c. 2n --> 1n --> n+n --> 2n

 

d. 1n --> 2n --> n+n --> 1n

b

What does it mean when we say that a certain fungal species is parasexual?

 

a. It accomplishes sexual reproduction without using gametes anywhere along the way.

 

b. It does not produce a fruiting body during sexual reproduction.

 

c. It reproduces both sexually and asexually interchangeably.

 

d. It reproduces in a way that is effectively sexual but without actually using meiosis anywhere along the way.

d

Which of the following is correct about the reproductive scheme of plants?

 

a. Gametophytes produce spores.

 

b. Sporophytes grow from zygotes.

 c. Spores are multicellular.

 

d. Gametes are produced by meiosis.

b

What happens to haploid plant spores?

 

a. They grow into haploid sporophytes

 

b. They come together to produce a diploid zygote

 

c. They produce gametes

 

d. They grow into haploid gametophytes

d

Which statement is correct about plants?

 

a. The sporophyte of a species has double the chromosomes of a gametophyte of the species.

 

b. Some of the nonvascular plants produce seeds.

 

c. Algae and bryophytes produce ovules but do not have ovaries.

 

d. The flowering plants produce seeds but not spores.

a

Which of the following statements is true?

 

a. Gymnosperms have flowers, ovaries, and double fertilization.

 

b. Sporopollenin is found only in spores.

 

c. A fern gametophyte is larger than a fern sporophyte.

 

d. A pollen grain is a male gametophyte of a seed plant

d

Which of the following statements is correct regarding plants and plant reproduction?

 

a. The main advantage of the double fertilization scheme of angiosperms is that two seeds can be produced for each pollination event.

 

b. Gymnosperms are "covered seed" plants.

 

c. Fruit helps angiosperms be successful by attracting animals to pollinate their flowers.

 

d. During double fertilization in angiosperms, one fertilized cell goes on to form an embryo, while the other develops into its nutrient supply.

d

Angiosperms make up about 90% of plant species known today. Which of the following most accounts for their success compared to the other plant groups?

 

a. They have cellulose in their cell walls

 

b. They get animals to do their pollinating

 

c. They produce seeds

 

d. They have very large sporophytes

b