1

Red tide—population explosion of certain types of dinoflagellates.

Kills large amounts of fish. Depletes water of oxygen and releases toxins into the water.

Apicomplexans

• Apicomplexans– Are parasites of animals and some cause

serious human diseases– Are so named because one end, the apex,

contains a complex of organelles specialized for penetrating host cells and tissues

– Have a nonphotosynthetic plastid, the apicoplast

Flagellated Alveolates• Apicomplexans

merozoites about to rupture a red blood cell

Plasmodium spp.

Malaria

Life cycle

2

sporozoitesporozoites

merozoite

male gametocyte in red blood cell

Fig. 22-11, p.359

Plasmodium sp. life cycle

It takes two hoststo complete

Stramenopiles

• Stramenopiles have “hairy” and smooth flagella

• The clade Stramenopila– Includes several groups of heterotrophs as

well as certain groups of algae

• Most stramenopiles– Have a “hairy” flagellum paired with a

“smooth” flagellum during some part of their life cycle

Smoothflagellum

Hairyflagellum

5 µm

3

Photosynthetic Stramenopiles

• Chrysophytes

Chrysophytes

Golden algae Yellow-green algaecoccolithophores

diatoms

p.351b

4

• Diatoms are unicellular algae – With a unique two-part, glass-like wall of

hydrated silica

3 µm

• Diatoms are a major component of phytoplankton– And are highly diverse

50 µm

Brown Algae

• Brown algae, or phaeophytes– Are the largest and most complex algae– Are all multicellular, and most are marine

Photosynthetic Stramenopiles

5

Photosynthetic Stramenopiles• Brown Algae

holdfast

bladder

blade

stipe

Kelp -- Macrocystis

Phylum Phaeophyta: brown algae

Underwater forests—habitats

Kelp—food, habitats for aquatic organisms

Pectin—used to make gelatin

Diversity of Kingdom Protista

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 and

diploid forms

6

Colorless Stramenopiles• Oomycotes (egg

fungi)

Oogonium

Colorless Stramenopiles•Oomycotes (egg fungi)

water molds

Saprolegnia Phytophtora

Alternation of generations in Saprolegnia

7

Algae

Red algae and green algae are the closest relatives of land plants

• Over a billion years ago, a heterotrophic protist acquired a cyanobacterialendosymbiont– And the photosynthetic descendants of this

ancient protist evolved into red algae and green algae

Red Algae

• Red algae – Are usually multicellular; the largest are

seaweeds– Are the most abundant large algae in coastal

waters of the tropics

(a) Bonnemaisonia hamifera. This red alga has a filamentous form.

Dulse (Palmaria palmata). This edible species has a “leafy” form.

(b)

A coralline alga. The cell walls ofcoralline algae are hardened by calcium carbonate. Some coralline algae aremembers of the biological communities around coral reefs.

(c)

8

Red Algae

• Red algae are reddish in color– Due to an accessory pigment call

phycoerythrin, which masks the green of chlorophyll

Green Algae

• Two groups – Chlorophytes & Charophytes

• All have chlorophylls a & b

• Some are symbionts

Green Algae

• Chlorophytes

9

• Most chlorophytes– Live in fresh water, although many are

marine• Other chlorophytes

– Live in damp soil, as symbionts in lichens, or in snow

Ulva – sea lettuce

Fig. 22-19a1, p.364

Fig. 22-19c, p.364

Volvox colony

10

Fig. 22-20b, p.365

Chlamydomonas

Environment-resistant zygote

Green Algae

• Life Cycle Model

zygote (cross-section)

meiosis and germination

Diploid Stage

Haploid Stage

Mainly when nitrogen levels are low and light is of a certain quality and intensity, the cells develop into gametes.

d

g

ef

bc

a

nuclear fusion

cytoplasmicfusion

Gametesof different mating types meet.

_ +

More spores are produced.

More spores are produced.

ASEXUALREPRODUCTION:

ASEXUALREPRODUCTION:

SEXUALREPRODUCTION:

Mitosis occurs. Whether the resulting cells develop into spores or gametes will depend on environmental conditions.

_

+

haploid cell(+ strain) haploid cell

(– strain)

A thin-walled resistant zygote develops.

Fig. 22-20a, p.365

Alteration of generations in Chlamydomonas

11

Amoebozoa

• Amoebozoans have lobe-shaped pseudopodia

• Amoebozoans– Are amoeba that have lobe-shaped, rather

than threadlike, pseudopodia– Include gymnamoebas, entamoebas, and

slime molds

Fig. 22-21, p.366

A. proteus

Heterotroph

pseudopod

12

Entamoeba histolytica Amoebic dysentary

Amoebozoa

• Slime Molds• plasmodial (Myxomycetes)

Fig. 22-22a, p.366

Plasmodia --- multinucleated cytoplasmic mass

13

Fig. 22-22b, p.366

Hard times produce fruiting bodies

Fruiting bodies produce haploid sporesGood times, spores germinateProduce ‘gametes’ – fusion of two= new plasmodium

• At one point in the life cycle– They form a mass called a plasmodium

Feedingplasmodium

Matureplasmodium(preparing to fruit)

Youngsporangium

Maturesporangium

Spores(n)

Germinatingspore

Amoeboid cells(n)

Zygote(2n)

1 mm

Key

Haploid (n)Diploid (2n)

MEIOSIS

SYNGAMY

StalkFlagellated cells(n)

The feeding stageis a multinucleateplasmodium that liveson organic refuse.

1 The plasmodiumtakes a weblike form.2 The plasmodium erects

stalked fruiting bodies (sporangia)when conditions become harsh.

3

Within the bulboustips of the sporangia,meiosis produces haploidspores.

4These cells are

either amoeboid orflagellated; the twoforms readily convertfrom one to the other.

6The cells unite

in pairs (flagellatedwith flagellatedand amoeboid withamoeboid), formingdiploid zygotes.

7The resistant spores disperse

through the air to new locationsand germinate, becoming activehaploid cells when conditionsare favorable.

5

Amoebozoa

• Slime Molds• cellular slime molds (Amoeba-like)

14

Fig. 22-23f, p.367

clip

• The life cycle of Dictyostelium, a cellular slime mold

Spores(n)

Emergingamoeba

Solitary amoebas(feeding stage)

ASEXUALREPRODUCTIONFruiting

bodiesAggregatedamoebas

Migratingaggregate

SYNGAMY

MEIOSIS

SEXUALREPRODUCTION

Zygote(2n)

Amoebas

600 µm

200 µm

Key

Haploid (n)Diploid (2n)Figure 28.27

In the feedingstage of the lifecycle, solitary haploidamoebas engulf bacteria.

1 During sexual repro-duction, two haploidamoebas fuse andform a zygote.

2

The zygotebecomes a giantcell (not shown)by consuminghaploid amoebas.After developing aresistant wall, thegiant cell undergoesmeiosis followed byseveral mitoticdivisions.

3

The resistantwall ruptures,releasing newhaploid amoebas.

4

When food is depleted,hundreds of amoebascongregate in response to achemical attractant and forma sluglike aggregate (photobelow left). Aggregateformation is the beginningof asexual reproduction.

5

The aggregate migrates for awhile and then stops. Some of the

cells dry up after forming a stalk thatsupports an asexual fruiting body.

6

Othercells crawl

up the stalkand developinto spores.

7

Sporesare released.

8

In a favorableenvironment, amoebasemerge from the sporecoats and begin feeding.

9

15

1 Stalked, spore-producing structure releases spores.

MITOTICCELLDIVISION

2 Spores give rise to free-living amoeboid cells that feed, grow, and reproduce by mitotic cell division.

3 When food gets scarce, the cells will stream together to form an aggregate that crawls like a slug.

AGGREGATION

4 The slug may start developing at once into a spore-bearing structure, or it may migrate elsewhere first.

MATUREFRUITINGBODY

CULMINATION

eitheror

MIGRATINGSLUG STAGE

a Life cycle of Dictyostelium discoideum. Fig. 22-23a, p.367

p.367

midwife amoeba attracted to two stuck-together daughter cells

LE 16-25

Unicellular protist Colony

Locomotorcells

Gamete

Somaticcells

Later organism thatproduces gametes

Early multicellular organismwith specialized, interdepen-dent cells

Food-synthesizingcells

The evolution of multicellular organisms