CH 12 Eukaryotes

Why eukaryotic reproduction more complex?

• Reproduce by mitosis (growth and repair) or meiosis (sexual reproduction)

• Have Multiple linear chromosomes in nucleus

• DNA replication, chromosome separation, and cell division involve many regulated steps.

• The nucleus and organelles must also be duplicated and distributed.

• Uses a mitotic spindle to accurately separate chromosomes.

Mitosis

1. Prophase

2. Metaphase

3. Anaphase

4. Telophase

3 stages of cell cycle

1. Interphase (where the cell grows and copies its DNA)

2. mitosis (where the nucleus divides)

3. cytokinesis (where the cytoplasm splits to form two new cells)

Prophase

1. DNA condensed into 2 identical chromatids

2. Chromatids are joined at the centromere to form a chromosome

3. Microtubules form a spindle

4. Nuclear envelope disappears

Metaphase

Chromosomes line up on a plane in the middle of the cell and attach near their centromeres to microtubules of the spindle.

Anaphase

Chromatids separate to opposite sides of spindle. Now called chromosomes

Telophase

Nuclear membrane formation, chromosome decondensation, and spindle breakdown

• cytokinesis is ready to begin (cell division)

Cytokinesis

• The cytoplasm is divided between the two new cells.

• The cell membrane pinches inward (or a new cell wall forms in plants).

• Organelles are distributed to each daughter cell.

• The result is two separate cells, each with its own nucleus and complete set of chromosomes

Mitosis vs Meiosis

Mitosis

• DNA Rep. = During interphase, before nuclear division

• Phases = Prophase, metaphase, anaphase, telophas

• Tetrad formation = NONE

• Crossing over = NONE

• Cytoplasmic divisions = 1

• Nuclei = 2 diploid

Meiosis vs Mitosis

Meiosis

• DNA Rep = During interphase, before meiosis I begins

• Phases = Meiosis I—prophase I, metaphase I, anaphase I,telophase I; Meiosis II—prophase II, metaphase II,anaphase II, telophase II

• Tetrad formation = Early in prophase I

• Crossing Over = Following formation of tetrads during prophase I

• Cytoplasmic Divisions = 2

• Nuceli = 4 haploid

Schizogony

Multiple mitosis without intervening cytokineses produce a multinucleate schizont, which later undergoes cytokinesis to produce many daughter cells.

• asexual Plasmodium (protozoa) reproduction

Protozoa Characteristics

1. Eukaryotic

2. Unicellular

3. Lack cell walls

• Move by cilia, flagella, pseudopods (except apicomplexans/malaria)

• Free living chemoheterotrophs (except dinoflagellates and euglenoids)

• Very few are pathogenic

Parabasalids

Parabasal body; single nucleus; lack mitochondria; Flagellated protists

• Trichomonas vaginalis (STD)

Diplomonads

lack mitochondria, Golgi bodies, and peroxisomes

• Flagellated with 2 nuclei

• Giardia (GI disease)

Euglenoza

Flagella with internal crystalline rod; disk-shaped mitochondrialcristae

• Euglena (flagellated with chloroplasts)

• Trypansoma (African Sleeping Disease)

• Leishmania (parasite from sand flies causing skin ulcers or mucosa damage)

Alveolates

Alveoli (membrane-bound cavities underlying the cytoplasmic membrane); tubular cristae in mitochondria

• Ciliates (paramecium)

• Apicomplexans (Malaria Plasmodium, cyclospora, toxoplasma)

• Dinoflagellates (Red tide)

Rhizaria

Threadlike pseudopods.

• Zooplankton with calcium carbonate or silica shells

Amoebozoa

Includes amoeba, parasitic amoebas (Acanthamoeba = cause blindness), and slime molds

Fungi

Includes molds, mushrooms, and yeast

• Chemoheterotrophic

• Cell walls contain nitrogenous polysaccharide Chitin

Mycology

Study of fungi

Beneficial Fungi

Decompose dead organisms and recycle their nutrients

• Food source

• Form antibiotics (like penicilin and cephalosporins)

Harmful Fungi

• Produce mycoses

• Spoilage of many foods

Mycoses

Fungal diseases of plants, animals, and humans

Mycelium

Body of mold composed of tangled hyphae

Saprobes

Fungi that absorb nutrients from dead organisms

• main form of nutrition in fungi

Lichens

Organisms composed of a fungus living in partnership with photosynthetic microbes, either green algae or cyanobacteria

• The fungus receives carbohydrates (glucose) produced through photosynthesis.

• The alga or cyanobacterium receives protection, moisture, minerals, and a stable place to live.