1. Lecture 11: Algae, Bryophytes and Ferns
Kingdom Protista: Algae
Red algae, diatoms, kelps, dinoflagellates, green algae
Significance of algae to humans
Kingdom Plantae: moving onto land
Features and challenges for living on land
Bryophytes
Ferns

2. ALGAE Algae belong to the Kingdom Protista
Algae are eukaryotes (cells have organelles)
Algae are mostly photosynthetic, like plants:
Have 4 kinds of photosynthetic pigments
Many accessory pigments – blue, red, brown, gold
Require moist environments because they lack a waxy cuticle (remember: cuticle prevents water loss in terrestrial plants)

3. General features of Algae
Can be microscopic or macroscopic: size ranges from bacteria size to 50 meters long!
Lack vascular (conducting) tissues – No xylem or phloem
No true roots, stems or leaves
Modes of sexual reproduction:
Both sexual and asexual
Algae illustrate the importance of photosynthesis to the Earth’s ecology!

4. Diversity of Algae
There are millions of algal species, but we’ll focus in these five groups:
Diatoms
Dinoflagellates
Red Algae
Kelps or Brown Algae
Green algae

5. 1. Diatoms Diatoms: Division Bacillariophyta
Large group of algae (many unidentified). Relatively recently evolved group
Habitat: Diatoms live in cool oceans
Structure: mostly unicellular, have silica in their cell walls

6. Diatoms
Very important for aquatic food chains: they provide phytoplankton
sun
Phytoplankton  Zooplankton  small fish  larger fish mollusks whales
Can reproduce asexually for many generations, then sexually

8. 3. Red Algae Red algae: Division Rhodophyta (4000 species)
Are some of the oldest eukaryotic organisms on earth (2 billion year old fossils)
Abound in tropical, warm waters
Act as food and habitat for many marine species
Structure: from thin films to complex filamentous membranes

9. Why are Red algae red?
Accessory pigments! Phycobilins mask the Chlorophyll a – thus they look red.
Due to these accessory pigments, red algae can photosynthesize in deeper waters (at different light wavelengths).

10. Red algae
Commercial uses: Carrageenan used for making ice cream, jellies, syrups, breads.
Also for lotions, toothpaste, pharmaceutical jellies.
Agar for growing bacteria and fungi for research purposes.
As food.

11. 4. Kelps or Brown Algae Kelps: Division Phaeophyta
Closely related to diatoms, also a recent group… but look very different from diatoms!
Habitat: rocky coasts in temperate zones or open seas (cold waters)
Structure: multicellular only
Holdfast, stipe, blade, air bladder
Up to 50 meters long

12. 5. Green Algae Division: Chlorophyta
Largest and most diverse group of algae
Habitat: found mostly in fresh waters and on land.
Float in rivers, lakes, reservoirs, creeks.
Can also live on rocks, trees, soil

13. Green algae Sea lettuce (Ulva) lives in salt waters along the coast.
Structure of green algae: from
Single cells (Micrasterias)
Filaments
Colonies (Volvox)
Thalli (leaf-like shape)

14. Green algae Terrestrial plants arose from a green algal ancestor
Both have the same photosynthetic pigments (Chlorophyll a and b).
Some green algae have a cell wall made of cellulose
Cells divide similarly

15. Benefits of Algae Beneficial algae:
They are the base of the aquatic food chain – photosynthetic organisms
Lichens: algae and fungi symbiosis
Also serve as shelters: Kelps form underwater forests; red alga form reefs

16. Harmful algae Excessive growth of algae causes:
Clogging of water ways, streams, filters… makes the water taste bad.
Can be toxic to animals
“Red tides” caused by dinoflagellates

17. Commercial uses of algae
Algin – a thickening agent for food processing (brown algae)
Carrageenan – foods, puddings, ice cream, toothpaste (red algae)
Iodine (brown algae)
Agar – for growth media used in research (red algae)
As food – red and brown algae
As plant fertilizers
Diatomaceous earth: used for filtering water, insulating, soundproofing

18. Kingdom Plantae
When moving from water to land, both plants and animals faced the same challenges, but evolved different ways to deal with them

19. Plants evolved from algae
Algae cannot survive on land (only in moist environments)
Plants had to adapt (evolve) characteristics that would allow them to survive and live on dry land
Cooksonia is the earliest known land plant (fossil)
It’s non-vascular and similar to today’s bryophytes

20. Ancestor of plants: Green Algae
The ancestor of land plants was probably a green alga: something like modern Coleochaete
1. They both have same photosynthetic pigments (Chlorophyll a & b, carotenes, etc.)
2. Both use starch to store photosynthetic products
3. Both have cellulose in their wall
4. Both have ‘alternation of generations’…
5. Both form a cell plate during cell division

21. Kingdom Plantae Evolutionary tree of plants
From primitive advanced traits
Angiosperms
Gymnosperms
Ferns
Bryophytes
Flowers
Seeds 
Green alga
ancestor
Vascular 
Terrestrial 

22. Living on land
Several environmental challenges had to be met by early plants in order to live on land…
A. OBTAINING ENOUGH WATER
Plants evolved roots to anchor the plant
Roots to absorb water and dissolved minerals

23. B. PREVENTING WATER LOSS
Plants evolved a cuticle – waxy layer
Evolution of multicellular gametangia (sex organs) – helped protect gametes from drying out.
Evolution of a resistant coat on spores that prevents drying out

24. C. GETTING ENOUGH ENERGY
In land, plants obtained enough sunlight for photosynthesis
Different strategies for obtaining light:
Growing taller and above other plants – plants began to evolve support cells
Others had to adapt to lower light intensities

25. D. Photosynthesis/water dilemma
Problems – plants need pores for gas exchange for photosynthesis, but open pores (stomata) allow water to leave (95% water taken is lost)
Solution – stomata open during the day (for photosynthesis gas exchange) and close during the night (to allow plant to recover from water loss)

26. E. MULTICELLULARITY Evolved in algae
Advantages: root better, protect gametes, grow tall to obtain sunshine
Disadvantage: getting water to all cells
Plants evolved vascular tissues, xylem and phloem

27. F. SEXUAL REPRODUCTION Algae have motile gametes and single sex organs
Land plants developed air-borne dissemination of desiccation-resistant stage
Land plants developed multicellular sex organs
Sexual reproduction gives plants genetic variability – enable them to adapt better to their environments

28. G. LIFE CYCLE
Algae, water dependent life cycle  water independent life cycle in land plants
Plants developed dryness-resistant gametophytes (spores) or zygotes (seeds)
Smaller size primitive  larger size plants
Dominant gametophyte stage (n)  dominant sporophyte stage (2n)

29. Life cycles: animals vs. plants
Animals like humans, live in the 2n stage. Dominant 2n stage
Single celled gametes are 1n
2 n = 46
(meiosis)
1 n = 23

30. Plant life cycle: alternation of generations
Plants spend part of their life cycle in the haploid (1 n) stage, and part in the diploid (2 n) stage – both stages are multicellular
Sporophyte generation (2n)
Gametophyte generation (1n)

31. Plants display an alternation of haploid and diploid phases in their life cycle.
(see text and image on page 139 in the textbook “Plants and Society”)

32. BRYOPHYTES Bryophytes include mosses, liverworts
Non-vascular plants, i.e. they don’t have xylem or phloem
Advancements over algae: cuticle, multicellular gametangia, stomata
Habitat: they require moist environment for active growth and sexual reproduction

33. Bryophyte life cycle
Exhibit alternation of generations: they have a gametophyte and sporophyte generation
(See text image on pg. 140 please)

34. Bryophytes Gametophyte generation (1n) is dominant
Has green “leafy stems” and root-like structures called rhizoids, for anchoring (not true roots!)
Have stomata and cuticle
Bryophytes lack vascular tissue – do not have xylem or phloem.
This absence of vascular tissue prevents bryophytes from having true roots, stems or leaves.
Also, lack of conducting tissue limits their size.

35. Bryophyte reproduction
Gametophyte plant produces multicellular sex organs:
Archegonia – produces eggs (female)
Antheridia – produces motile sperm (male)
Outer layers protects and prevents drying
Motile sperm must swim to archegonia.

36. Bryophyte reproduction
Sporophyte occurs after egg is fertilized by sperm (2 n)
Sporophyte grows in the archegonium of the gametophyte plant – it’s dependent on it
Mature sporophyte consists of:
Foot (point of attachment)
Seta (stalk)
Capsule (spore case)

37. Bryophytes
Sporocytes within the Sporophyte undergo meiosis to produce a single kind of haploid spore
If spore lands on suitable place, it will germinate into a protonema, the initial stage of the gametophyte plant.

38. Bryophyte significance
Bryophytes are small and inconspicuous, but important part of the biosphere
Food for mammals, birds
Important to prevent soil erosion along streams
Commercially – peat moss (Sphagnum) is used as fuel, soil conditioner, by florists

39. FERNS An important group of plants – 10,000 species exist
Ferns have developed vascular tissue
Habitat: Moist tropics, woodlands, streambanks
Also exhibit Alternation of Generations, but…
The diploid Sporophyte generation is dominant (larger and more visible)
The haploid Gametophyte is small & short lived.

40. Fern life cycle: dominant sporophyte
Sporophyte generation (diploid) is dominant, larger
Sporophyte has well developed vascular system (xylem, phloem)
(See image on page 141 of the textbook please)

41. Fern sporophyte morphology
Fern sporophyte has fronds (leaves)
Young fronds are called fiddleheads
They also have an underground horizontal stem called the rhizome
True roots arise from the rhizome

42. Fronds
Ferns have complex leaves called fronds, for photosynthesis and reproduction
Under the fronds, spores are produced in sporangia in clusters called sori (sorus = singular)
In sporangia, meiosis occurs producing haploid spores

43. Fern Gametophyte generation (1n)
Single spore grows into the gametophyte plant
Heart-shaped called prothallus, very small.
Archegonia and antheridia produced in prothallus
Female gametophytes produce a chemical that induces spores to produce male gametophytes around it

44. Fern gametophyte
Antheridium produces motile sperm that swim to the archegonia’s egg – fusion occurs and the diploid sporophyte generation begins
Zygote develops into a new embryo – that eventually grows into mature sporophyte

45. Significance of ferns
Ecologically important: Hold and form soil to prevent erosion
As food – fern fiddleheads eaten in Hawaii, Japan, Philippines – very nutritious and delicious!
As ornamental plants
Coal formation from ancient ferns