Protists

Unit 6

Chapter 19

Protist characteristics

Eukaryotic: having organelles and nucleus Unicellular or multicellular Heterotrophic, autotrophic, or saprobic Microscopic or large Divided into three major groups: protozoans,

algae, and fungus-like protists

Protozoans: animal-like protists

Heterotroph: consume organic matter Unicellular

Algae: plant-like protists

Autotroph: uses light to make sugars through photosynthesis

Lack roots, stems, and leaves

Fungus-like protists

Decompose dead matter Motility during some stage of life cycle No chitin in cell walls

Protist-borne diseases

Malaria Sleeping sickness

Helpful protists

Algae through photosynthesis produce oxygen, that makes up the ozone layer.

Algae and protozoans can also be part of the plankton that feeds marine animals.

Fungus-like protists decompose matter and returns nutrients back to the soil.

plankton

Protist reproduction

Mostly asexual: requiring one source of DNA for offspring

Sometimes sexual: requiring two sources of DNA for offspring

Freshwater algae asexually reproducing

Protozoans

Animal-like protists

Major groups of protozoans

Amoeba Flagellate Ciliate Sporozoan

Movement with pseudopods

Pseudopod: “false foot”

Amoeba, shapeless cells

Feeding with pseudopods

The extensions of the cellular body surround food particles, which the amoeba then draws into itself for digestion.

Other amoeboid protozoans

foraminiferans radiolarians

Movement with flagella

This disease causing Giardia protozoan has flagella to move around.

Flagellates whip their tails back and forth to propel the cell.

Movement with cilia

Note the fine cilia that surround the paramecium, making a “halo glow.”

Notice the starburst shaped organelle, the contractile vacuole that helps to pump out excess water.

Sporozoans: parasitic protozoans

Disease causing Produces spores within

host cell Spore: reproductive cell

that forms without fertilization and produces a new organism

Plasmodium, cause of malaria

The protist is transmitted through a mosquito bite to a human host.

The protist reproduces inside the human red blood cells, making them puckered and unable to carry oxygen to the body.

Malaria life cycle

Algae

Plant-like protists

Algae pigmentation

All have chlorophyll Some have other

pigments: purple, rusty-red, olive-brown, yellow, and golden-brown.

Algae are grouped according to their pigmentation.

Ex: green algae

Major groups of algae

Euglenoid Diatom Dinoflagellate Green algae Red algae Brown algae

Euglenoids

Unicellular Aquatic Animal-like Plant-like:

photosynthetic No cell wall,

just tough cell membrane

Flagella

Euglenoid

Diatoms: golden algae

Shells made of silica (major component of glass)

Carotenoid pigment Unicellular Photosynthetic Various shapes Oily inside

Diatoms

Uses of diatoms, dredged from ocean floors abrasives in tooth and metal polishes added to paint to give the sparkle that makes

pavement lines more visible at night

Dinoflagellates

Many pigments Two flagella at

grooves Bioluminescent: emit

light Symbiotic relationship

with jellyfish Produce toxins

Red tide

Concentration of nerve toxins from certain dinoflagellates cause water bodies to appear red.

This water and contaminated shellfish can make humans sick.

Red algae

Multicellular Commonly called seaweed Thallus: Seaweed body that attaches to a

surface Found deep in the ocean because they can

use the light that filters to the bottom for photosynthesis

Red algae

Brown algae

Mostly multicellularMostly in cool, marine watersAir bladders in thallus keeps the

algae floating

Kelp forests

Dense growth of brown algae

Habitat for many marine animals

Green algae

Most diverse Chlorophyll-rich Can grow anywhere,

even in fur of sloth (below)

Colonial algae called Volvox

Unicellular green algae

Multicellular green algae

Fungus-like protists

slime molds, water molds, and downy mildews

Slime molds: most like true fungus

Cool, moist environments Able to move around to feed during most of

the life cycle Two major types

Water molds and downy mildews

Fuzzy white growth on decaying matter

How water molds and downy mildews feed They grow long extensions over the organic

material and absorb nutrients through their cell membranes.

A particular species infected the Irish potato crop and caused a large famine.