AP Biology Chapter 28 Protists

8/8/2019 AP Biology Chapter 28 Protists

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Copyright 2005 Pearson Education, Inc. publishing as Benjamin Cummings

Protists

Overview: A World in a Drop of Water

Even a low-power microscope

Can reveal an astonishing array of organisms

in a drop of pond water

50 Qm


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These amazing organisms

Belong to the diverse kingdom of mostly

single-celled eukaryotes

Protists are more diverse than all other

eukaryotes

Most protists are unicellular

And some are colonial or multicellular


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Protists, the most nutritionally diverse of all

eukaryotes, include

Photoautotrophs, which contain chloroplasts

Heterotrophs, which absorb organic molecules

or ingest larger food particles

Mixotrophs, which combine photosynthesis

and heterotrophic nutrition

There is now considerable evidence

That much of protist diversity has its origins in

endosymbiosis


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Protist habitats are also diverse in habitat

And including freshwater and marine

species

Figure 28.2ad

100Qm

100Qm

4 cm

500Qm

The freshwaterciliateStentor,

a unicellular protozoan (LM)

Ceratium tripos, a unicellularmarine dinoflagellate (LM)

Delesseria sanguinea, a multicellularmarine red alga

Spirogyra, a filamentous freshwatergreen alga ( inset LM)

(a)

(b)

(c)

(d)


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Reproduction and life cycles

Are also highly varied among protists, with

both sexual and asexual species

We will cover a few examples but please

understand there is A LOT more detail out

there


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A sample of protist diversity

T

able 28.1


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Figure 28.12

50 mThousands of cil ia cover

the surface ofParamecium.

The undigested contents of foodvacuoles are released when the

vacuoles fuse with a specialized

region of the plasma membrane

that functions as an anal pore.

Paramecium, like other freshwaterprotists, constantly takes in water

by osmosis from the hypotonic environment.

Bladderlike contractile vacuoles accumulate

excess water from radial canals and periodicallyexpel it through the plasma membrane.

Food vacuoles combine with

lysosomes. As the food is digested,

the vacuoles follow a looping paththrough the cell.

Paramecium feeds mainly on bacteria.Rows of cilia along a funnel-shaped oral

groove move food into the cell mouth,where the food is engulfed into food

vacuoles by phagocytosis.

Oral groove

Cell mouth

Micronucleus

Macronucleus

FEEDING, WASTE REMOVAL, AND WATER BALANCE

Example ofa typical Pond WaterProtist.

Exploring structure and function in a ciliate

Contractile Vacuole


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CONJUGATION AND REPRODUCTION

8 7

2

MICRONUCLEAR

FUSION

Diploid

micronucleus

Diploidmicronucleus

Haploid

micronucleus

MEIOSIS

Compatiblemates

Key

Conjugation

Reproduction

Macronucleus

Two cells of compatiblemating strains align side

by side and partially fuse.

1 Meiosis of micronucleiproduces four haploid

micronuclei in each cell.

2 3 Three micronuclei in each cell

disintegrate. The remaining micro-

nucleus in each cell divides by mitosis.

The cells swap

one micronucleus.

4

The cells

separate.

5

Micronuclei fuse,

forming a diploid

micronucleus.

6Three rounds of

mitosis without

cytokinesis

produce eight

micronuclei.

7The original macro-

nucleus disintegrates.

Four micronuclei

become macronuclei,

while the other four

remain micronuclei.

8Two rounds of cytokinesis

partition one macronucleus

and one micronucleus

into each of four daughter cells.

9


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Example ofcolonial Protists

Most golden algae are unicellular

But some are colonial

Figure 28.17

25 m


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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

Before we get to that lets look at some typical

life cycles.


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Diploid LifeCycle

Adult individuals

consist of ________

cells

A diploid cell

goes through

_______________

to produce gametes

Diploid Life

Cycles contain

organisms who

spend most of life

as diploids.

Haploid state is

short lived and

mediatesmechanism for

genetic diversity


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Haploid Life Cycle

Many Protistshave haploid lifecycles.

Spend most oftheir life ashaploid, onlyunder diploid statefor DNA repair to

generate geneticdiversity inrepsonse to stress


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LOOK OUT!!!

And Now the Dreaded Alternation of

Generations.A life cycle so evil it is

normally reserved for plants..


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The life cycle of the brown algae Laminaria

Figure 28.21

Sporophyte(2n)

Zoospores

Female

Gametophytes(n)

MEIOSIS

FERTILIZATION

Developingsporophyte

Zygote(2n)

Mature femalegametophyte

(n)

Egg

Sperm

Male

Sporangia

Key

Haploid (n)Diploid (2n)

The sporophytes of this seaweedare usually found in water just below

the line of the lowest tides, attachedto rocks by branching holdfasts.

1

In early spring, at the end ofthe main growing season, cells on

the surface of the blade developinto sporangia.

2

Sporangia producezoospores by meiosis.3

The zoospores are allstructurally alike, but

about half of them developinto male gametophytes

and half into femalegametophytes. The

gametophytes looknothing like the sporo-

phytes, being short,

branched filaments thatgrow on the surface ofsubtidal rocks.

4

Male gametophytes releasesperm, and female gametophytes

produce eggs, which remainattached to the female gameto-

phyte. Eggs secrete a chemicalsignal that attracts sperm of the

same species, thereby increasingthe probability of fertilization in

the ocean.

5

Sperm fertilizethe eggs.

6

The zygotesgrow into new

sporophytes,starting life

attached tothe remains of

the femalegametophyte.

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AP Biology Chapter 28 Protists