Protists

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Conjugation is separate from reproduction, which generally occurs by binary fission.

Slide 19

Paramecium

Contractile vacuole

Oral groove

Cell mouth

Cilia

Micronucleus

Macronucleus

Food vacuoles

(a) Feeding, waste removal, and water balance

50 µm

MEIOSIS

Compatible mates

Diploid micronucleus

Haploid micronucleus

The original macronucleus disintegrates.

Diploid micronucleus

MICRONUCLEAR FUSION

(b) Conjugation and reproduction

Key

ConjugationReproduction

Slide 20

Diatoms

Diatoms are unicellular algae with a unique two-part, glass-like wall of hydrated silica.

Diatoms usually reproduce asexually, and occasionally sexually.

Diatoms are a major component of phytoplankton and are highly diverse.

Fossilized diatom walls compose much of the sediments known as diatomaceous earth.

Slide 21

Freshwater Diatom with glass-like wall of silica

3 µm

Slide 22

Golden Algae

Golden algae are named for their color, which results from yellow and brown carotenoids.

The cells of golden algae are typically biflagellated, with both flagella near one end.

All golden algae are photosynthetic, and some are also heterotrophic.

Most are unicellular, but some are colonial.

Slide 23

Colonial Golden Algae

25 µm

Outer container

Flagellum

Living cell

Slide 24

Brown Algae

Brown algae are the largest and most complex algae. All are multicellular, and most are marine.

Brown algae include many species commonly called “seaweeds.” Giant seaweeds called kelps live in deep parts of the ocean.

Brown algae have the most complex multicellular anatomy of all algae.

The algal body is plantlike but lacks true roots, stems, and leaves and is called a thallus.

The rootlike holdfast anchors the stemlike stipe, which in turn supports the leaflike blades.

Slide 25

Brown Algae

Blade

Stipe

Holdfast

Slide 26

Alternation of Generations

A variety of life cycles have evolved among the multicellular algae.

The most complex life cycles include an alternation of generations, the alternation of multicellular haploid (gametophyte) and diploid forms (sporophyte).

Heteromorphic generations are structurally different.