Introduction to algae

What are algae?

• A diverse assemblage of organisms

• Range in size from very small microalgae (you need a microscope to see them) to very large macroalgae (some seaweeds are over 3 stories high)

• Come in a variety of body types, ranging from unicellular to simple colonies to forms with different tissue types and organs

• Belong to different evolutionary lineages

• Mostly aquatic, oxygen-producing photosynthetic autotrophs

What is Nostoc sphaericum?

A cyanobacterium

What is the diameter of a Chlamydomonas cell?

About 10 µm

What is Pediastrum?

A green alga that forms colonies that are ≈70 µm across

What are Acetabularia?

Very large single cells that range in size from 4-10 cm tall

What is Noctiluca scintillans?

• A bioluminscent dinoflagellate

• Each cell is about 0.5 mm

What is Stepanodiscus sp.?

• A centric diatom

• Cells range in size from 20-100 µm in diameter

What is Cymbella sp.?

• A pennate diatom

• Length: 13-360 µm

• Width: 35-68 µm

What are Giant Kelp and Bull Kelp?

• Seaweeds that form underwater “forests”

• Individuals can grow to lengths of 60 m (200 ft)

• Some are over 3 stories high

List 4 types of microalgae.

• Unicellular coccoid (spherical)

• Colony of coccoid cells held together by mucilage

• Coenobial colonies

• Filamentous forms

What are coenobial colonies?

Distinctly shaped colonies, each with a fixed number of cells

List 2 types of filamentous forms.

• Unbranched

• Branched

List 2 types of macroalgae.

• Coenocytic/siphonous

• Parenchymatous body

What does coenocytic/siphonous mean?

Body is one large, multinucleate cell

What is a parenchymatous body?

Composed of 3-D arrays of cells that are often connected to each other by intercellular connections

List the 3 domains.

• Eubacteria

• Eukaryota

• Archaea

Which domains are algae found in?

Eubacteria and Eukaryota

List the 4 supergroups in the Eukaryotic domain.

• Unikonts

• Excavata

• Archaeplastida/Plantae

• SAR/Chromalveolata

Which eukaryotic supergroups are algae found in?

• SAR

• Archaeplastida

• Excavata

What are the Unikonts?

Animals and fungi

What are the Excavata?

Euglena

What are the Archaeplastida/Plantae?

• Red algae

• Green algae

• Glaucophytes

• Land plants

What are the SAR/Chromalveolata?

• Stramenopiles

• Alveolates

• Rhizaria

Where do algae live?

• Many algae are aquatic

  • Several types of algae live in the ocean, including microscopic (planktonic) forms

  • Macroalgae (seaweeds) are found in both the subtidal and intertidal zones

  • There are also freshwater algae

• Some algae occupy extreme habitats

  • Microbial mats in hot springs contain organisms, including many algae, that thrive in hot environments

  • Snow algae found on the coast mountains of BC

List 5 examples of algae that live in freshwater.

• Chroococcus sp. (cyanobacterium)

• Micrasterias sp. (green alga)

• Bangia sp. (red alga)

• Euglena sp. (euglenoid alga)

• Tabellaria sp. (pennate diatom)

Why are snow algae not green?

The orange and red colour is from accessory pigments that are photoprotective

List 3 examples of snow algae.

• Chloromonas spp.

• Sanguina nivaloides

• Chlainomonas rubra

Where does photosynthesis occur in eukaryotic algae?

In chloroplasts located inside the cells

Where does photosynthesis occur in Cyanobacteria?

On membranes distributed throughout the cytoplasm

What is an example of algae that can survive dry environments?

• Algae were found in the desert near Albuquerque, New Mexico

• After completely drying out, they revive and start photosynthesizing within seconds of being immersed in a drop of water

• Scientists are studying these algae to find out how they are so resilient to drying out

Describe the 3-way mutualistic relationship between the sloth, the green algae that live in its fur, and a moth.

• The sloth climbs down the tree and poos on the ground, providing a place for the female moths that live in the sloth fur to lay their eggs

• Larval moths live in and consume the sloth poo

• Adult moths make their way onto another sloth host where they die and decompose, providing nutrients that fertilize the algae living in the fur

• The sloth consumes the algae living in its fur, presumably as a supplement to the diet of leaves that it also eats

Describe an example of an epizoic alga

• An algal mat was found on the head of a lizard that lives in a Mexican rainforest

• The algal mat consisted of several species of eukaryotic green algae, a type of cyanobacteria, and a type of bryophyte

• The lizard’s head provides a suitable habitat for the algae to live and grow

• It is thought that the green mat might help to camouflage the lizard amongst the vegetation in the rainforest

What does epiphytic mean?

Living on plants

What does epizoic mean?

Living on animals

List 2 examples of epiphytic algae.

Melobesia mediocris and Smithora sp. grow on Surf Grass (Phyllospadix scouleri) and derive physical support from the host

Describe an example of algae that are unable to photosynthesize.

• Green algae belonging to the genus Prototheca are heterotrophs that live in the soil

• On culture plates, they form white colonies that do not have photosynthetic pigments

• Prototheca are pathogenic and can infect humans, cats, dogs, and dairy cattle

• In dairy cows, they can cause mastitis and a degradation of milk quality