Worksheet 5:
Protists Part 3 Answers
Supplemental Instruction
Iowa State University / Leader: / Courtney
Course: / Bio 211 (4)
Instructor: / Boury
Date: / 9/10/12

1)In the Burkholder experiment ___dinoflagalletes_____ were used to test for toxicity under different food-type growth conditions. The two food types were __fish__ and ___algae____.

2. Define the following:

Mitosis- the process in which nuclear division results in 2 nuclei each of which receives the same complement of chromosomes

Meiosis – the process by which haploid cells are produced from a cell that was originally diploid

Haploid-(1N) containing one set of chromosomes

Diploid- (2N) containing two sets of chromosomes

Chromosome – A discrete unit of genetic material composed of DNA and associated p roteins.

3. Describe and draw the Zygotic life cycle

Populations of haploid cells grow by mitotic divisions

Environmental change stimulates cells to develop into gametes (+ -). Gametes are then released.

Mating of opposite gametes

Fertilization

Diploid (2n) dormant zygote forms

Zygote divides by meiosis yielding 4 haploid cells.

Answer the following questions about the sporic life cycle and briefly describe each step.

The gametophyte is ___haploid___ and it produces gametes (egg or sperm)

The sporophyte is _____diploid____ and it produces spores.

  • When mature, the diploid seaweed produces haploid spores by meiosis
  • A haploid spore(1N) swims away and eventually attaches to a surface and grows into a sperm-producing or egg-producing gametophyte (1N)
  • Eggs secrete chemicals that attract sperm and fertilization occurs
  • Fertilization
  • Zygotes grows into diploid sporophytes by mitosis

Egg + Sperm  fertilization zygote

5. In the gametic life cycle all cells except the ___gametes___ are diploid. And gametes are produced by ___meiosis___.

When diatoms reproduce one daughter cell arising from mitosis is smaller than the other. It is also smaller than the parent cell. This happens because diatom cell walls are composed of two overlapping halves (much like the 2part round glass laboratory dishes having lids that overlap bottoms). Needs sexual reproduction to prevent becoming too small.

  • Diatom cells mate within a blanket of mucilage each partner undergoing meiotic divisions to produce haploid gametes.
  • The gametes fuse to form a diploid zygote that is larger
  • The 2n zygote undergoes mitotic divisions to produce diploid cells that have the normal shape and maximum size for that species.

Reproduction in Ciliates:

a) In the Asexual phase the organisms go through ______mitotic division____

b) The sexual phase is known as __conjugation_____, in which the organisms exchange ___micronuclei___ .

Conjugation:

  • 2 cells line up side by side and partially fuse together
  • in each cell the micronucleus undergoes meiosis producing 4 haploid products (3 degenerate)
  • in each cell the remaining haploid micronucleus undergoes mitosis
  • the cells exchange a haploid micronucleus and each cells macronucleus degenerates
  • the paired cells separate. In each cell the genetically different micronuclei fuse to form a diploid nucleus
  • the diploid nucleus undergoes 3 rounds of mitosis
  • the cell then has 4 mature cells that have 1 micronucleus and 1 macronucleus