biology chapter 11

Which one of the three types of life cycles of sexually reproducing organisms does not have a multicellular haploid stage?

diploid-dominant

How are spores produced in haploid-dominant and alternation of generation life cycles?

meiosis

What part of meiosis is most similar to mitosis?

meiosis II

What is a source of variation in asexual reproduction?

mutation of DNA

What is one thing that is true of haploid-dominant life cycles but not of alternation of generation life cycles?

(+) and (−) mating types

In prophase I, the homologous chromosomes are paired up and linked together. What binds the chromosomes together and maintains their alignment?

synaptonemal complex

What structure is most important in forming the tetrads?

synaptonemal complex

Which three processes lead to variation among offspring that have the same two parents?

fertilization, crossing over, random chromosome assortment

What is a haploid cell produced in a diploid-dominant organism by meiosis called?

gamete

Fungi typically display which type of life cycle?

haploid dominant

During which phase does the second round of genetic variation occur during meiosis?

metaphase 1

One of the ways that sexual reproduction enhances the diversity of offspring from the same parents is through a process called crossing over. What entities does this occur between during prophase I?

nonsister chromatids of homologous chromosomes

1. How many and what type of daughter cells does meiosis produce?

4 haploid

Reproductive cells in most species are different from the cells that make up the rest of the organism. What are the body cells called and how are they different from the reproductive cells?

Body cells are called somatic cells and have double the number of chromosomes found in reproductive cells.

What is a disadvantage of sexual reproduction over asexual forms of reproduction?

Half the population is capable of carrying offspring.

Compare the three main types of life cycles in multicellular organisms and give an example of an organism that employs each.

In a diploid dominant cycle, the multicellular diploid stage is present, as in humans. Haploid-dominant life cycles have a multicellular haploid stage, as in fungi. In alternation of generations, both haploid-dominant and diploid-dominant stages alternate, as in plants.

Though the stages of meiosis have the same names as the stages of mitosis, they exhibit fundamental differences. What are the main differences between the two processes?

Meiosis differs from mitosis in that the number of chromosomes is halved and genetic variation is introduced in meiosis, but not in mitosis.

Which of the following is not true during crossing over? a. Chiasmata are formed. b. Nonsister chromatids exchange genetic material. c. Recombination nodules mediate cross over events. d. Spindle microtubules guide the movement of chromosomal material.

d

Which of the following distinguishes metaphase I from metaphase II?

Prophase I condenses the chromosomes and eliminates the nuclear membrane. The microtubules arrange in a spindle. Prophase II mimics prophase I. Metaphase I occurs when chromosomes appear in homologous pairs on the spindle. Metaphase II has a single line of chromosomes on the spindle. Pairs of chromosomes are pulled apart and migrate towards the poles during anaphase I, while in anaphase II sister chromatids separate. Telophase I reconstitutes the nucleus and condenses the chromosomes, while telophase II mimics telophase I.

What phase(s) of mitotic interphase is missing from meiotic interkinesis?

S

What is a likely evolutionary advantage of sexual reproduction over asexual reproduction?

Sexual reproduction results in variation in the offspring.

Spores are structures produced by some plants and all fungi. Which is true about them?

Spores are haploid cells formed only during asexual reproduction and so are not formed by meiosis.

At metaphase I, homologous chromosomes are connected only at what structures?

chiasmata

Explain how the orientation of homologous chromosomes during metaphase I of meiosis contributes to greater variation in gametes.

The random alignment of homologous chromosomes at the metaphase plate ensures the random destination of the chromosomes in the daughter cells.

Explain how the Red Queen's catchphrase, "It takes all the running you can do to stay in the same place," describes co-evolution between competing species.

When one species gains an advantage with a favorable variation, selection increases on another species with which it competes. This species must also develop an advantage or it will be outcompeted. The two species "run [evolve] to stay in the same place."

Describe what happens to the tetrads after they form. A. Prophase I of meiosis forms the tetrads. They line up at the midway point between the two poles of the cell to form the metaphase plate. There is equal chance of a microtubule fiber to encounter a maternally or a paternally inherited chromosome. Orientation of each tetrad is independent of the orientation of other tetrads. B. Prophase II of meiosis forms the tetrads. They line up at the midway point between the two poles of the cell to form the metaphase plate. There is equal chance of microtubule fiber to encounter maternally or paternally inherited chromosome. Orientation of each tetrad is independent of the orientation of other tetrads. C. Prophase I of mitosis forms the tetrads. They line up at the midway between the two poles of the cell to form the metaphase plate. There is equal chance of a microtubule fiber to encounter a maternally or a paternally inherited chromosome. Orientation of each tetrad is independent of the orientation of other tetrads. D. Prophase I of meiosis forms the tetrads. They line up at the midway between the two poles of the cell to form the metaphase plate. There is a chance of microtubule fiber to encounter maternally inherited chromosome. Orientation of each tetrad is independent of the orientation of other tetrads.

a

There are three sources of genetic variation in sexual reproduction. Which is not considered random? All are random. crossing over egg and sperm fertilization tetrad alignment on the meiotic spindle

a

Which type of life cycle has both a haploid and a diploid multicellular stage?

alternation of generations

At which stage of meiosis are sister chromatids separated from each other?

anaphase 2