Protist #2•Life cycles•Algae•Dichotomous key

Human life Cycle

Gametes (unicellular) are only haploid cells

Alternation of generations: BOTH diploid and haploid multicellular stages

•Individual haploid spores divide by mitosis (rather than fusing together).•Gametes produced by mitosis fuse to make zygote

(inc. some algae)

Zygote (1 cell) is only diploid cell

Generalized alternation of generation life cycle

2 copies of each chromosome

1 copy of each chromosome

Algae is not a taxon• Algae (informal term) = photosynthetic protist

– 1.5 b.y.o.– Previously organized by color (photosynthetic pigment)

• Red, green, brown, golden– Description based on ecological role as a producer

• Form base of fresh water and marine food chains

If humans had alternation of generations

2n

n

n

n

n

n

2n

n

n

n

n

n

Figure 28.2aDiplomonads

Parabasalids

EuglenozoansE

xcavata

Diatoms

Golden algae

Brown algae

Dinoflagellates

Apicomplexans

Ciliates

Forams

Cercozoans

Radiolarians

“SA

R” clad

e

Stram

eno

piles

Alveo

latesR

hizarian

s

Green

algae

Red algae

Chlorophytes

Charophytes

Land plants

Arch

aeplastid

a

Slime molds

Tubulinids

Entamoebas

Nucleariids

Fungi

Un

ikon

ta

Choanoflagellates

Animals

Am

oeb

ozo

ans

Op

istho

kon

ts

Primary endocytosis of cyanobacteria

Secondary endocytosis of red algae

Figure 28.3

Cyanobacterium

Nucleus

Membranesare representedas dark linesin the cell.

1 2 3

Heterotrophiceukaryote One of these

membraneswas lost inred andgreen algaldescendants.

Red alga

Green alga

Primaryendosymbiosis

Secondaryendosymbiosis

Dinoflagellates

Plastid

Stramenopiles

Plastid

Euglenids

Chlorarachniophytes

Secondaryendosymbiosis

Secondaryendosymbiosis

Figure 28.3a

Cyanobacterium

Nucleus

Membranesare representedas dark linesin the cell.

1 (from euk) 2 (outer cell wall lipid layer—lost)

3 (plasma membrane of bacteria)

Heterotrophiceukaryote One of these

membraneswas lost inred andgreen algaldescendants.

Primary endosymbiosis

Red alga

Green alga

mitochondria

divergence

Figure 28.3b

Red alga

Secondary endosymbiosis

Dinoflagellates

Plastid

Stramenopiles

4 membranes & neucleomorph

Figure 28.2aDiplomonads

Parabasalids

EuglenozoansE

xcavata

Diatoms

Golden algae

Brown algae

Dinoflagellates

Apicomplexans

Ciliates

Forams

Cercozoans

Radiolarians

“SA

R” clad

e

Stram

eno

piles

Alveo

latesR

hizarian

s

Green

algae

Red algae

Chlorophytes

Charophytes

Land plants

Arch

aeplastid

a

Slime molds

Tubulinids

Entamoebas

Nucleariids

Fungi

Un

ikon

ta

Choanoflagellates

Animals

Am

oeb

ozo

ans

Op

istho

kon

ts

Primary endocytosis of cyanobacteria

Secondary endocytosis of red algae

Archaeplastida• Red Algae (rhodophyta)• Green algae (chlorophyta and charophyta)• Land plants• Share a common eukaryotic ancestor that obtained plastid

through endosymbiosis of cyanobacteria• Primary endosymbiosis

Green

algae

Red algae

Chlorophytes

Charophytes

Land plants

Arch

aeplastid

a

Red Algae (rhodophytes)• Mostly marine, mostly multicellular, concentrated in warm tropical

waters• Pigments:

– Chlorophyll– Phycoerythrin (erythr = red)

• Absorbs blue and green light (most penetrating wavelengths)• Shallower water = less phycoerythrin greenish red• Deeper water = more phycoerythrin very dark (almost black) red

• Genus Porphyra = nori• Reproduce asexually and sexually (w/ alt. of generations). • Gametes not flagellated

• agar, carrageenan

Color of pigment = color NOT absorbedAbsorbed = energy to make organic molecules

Green Algae• Mostly freshwater (but some marine and terrestrial)• Range of complexity

– Unicellular, colonial/filamentous, & multicellular

• Chloroplasts to land plants– Chlorophyll

• Most have both sexual and asexual stages.• Mostly by biflagellated gametes• Alternation of generation in some

ChlamydomonasIsogamous = same shape

Poor env.syngamy

Resistant zygospore

spirogyra Conjugation•Sexual reproduction•Different strains•- Strain nucleus moves to + strain and nuclei (isogametes) fuse zygote zygospore

Volvox

• Differentiated cells• Haploid “adult”• Asexual reproduction daughter colonies• Sexual reproduction w/ oogamy• Oogamy

– Small, motile sperm fertilize large non-motile egg

Ulvamulticellular green alga w/ alternation of isomophic generation

SAR AlgaeDiatoms

Golden algae

Brown algae

Dinoflagellates

Apicomplexans

Ciliates

Forams

Cercozoans

Radiolarians

“SA

R” clad

e

Stram

eno

piles

Alveo

latesR

hizarian

s

Brown Algae (phaeophytes)

• All multicellular• Mostly marine

– Common in temperate and cold water

• Can have specialized structures (e..g. holdfast, blades, stipes, etc)

• Important habitat—kelp forests• Food (kombu)• Algin in cell walls• Some alternation of generations

A brown alga life cycle

Golden Algae• Mostly unicellular• Freshwater and marine phytoplankton

– Some mixotrophic• yellow-brown carotenoid pigments• Biflagellated• Can form protective cysts that can survive for decades under poor

conditions

Diatoms• Unicellular• Cell wall (frustule) of silica (silicon dioxide, glass like)

– Protects– two overlapping halves

• Important phytoplankton• Large deposits on the ocean floor and form

sedimentary deposits known as diatomaceous earth• Blooms uptake & sequester large amounts of CO2• Only limited number of species have flagella, most are

planktonic (drifters)

Dinoflagelates• Unicellular, mostly marine• A number have cell walls of cellulose, • two flagella at right angles • Important phytoplankton

– but many species are heterotrophic and many are mixotrophic• Dinoflagellate blooms produce red-tides

– (carotenoid pigments create colors)– toxins

• Symbionts in cnidarians (e.g., corals, jellies, and anemones)• Bioluminesence

1a. Organism is square…………………go to 31b. Organism is not square……………. Go to 2

2a. Organism has stripes……………….. go to 42b. Organism has no stripes……………. Go to 5

3a. Organism has legs ………………… Right walky3b. Organism has no legs……………... Right sitty

4a. Organism has antennae…………….. Roundy feely4b. Organism has no antennae………….go to 6

5a. Organism is happy …………………. Go to 75b. Organism is not happy……………… Plain grumpy

6a. Organism has arms………………….Touchy feely6b. Organism has no arm ………………. Roundy touchy

7a. Organism has 2 or less toes per foot…………. Plain footys7b. Organism has 3 or more toes per foot ………..Plain toesies

Dichotomous Key