Algal structure, habit, habitat, size, reproduction of algae, sexual and asexual methods, cellularity

1. ALAGE
R. Nithya, M. Sc., M. Phil., Ph. D,
Assistant Professor in Biotechnology,
Sri Adi Chunchanagiri Women’s College, Cumbum
Theni Dt.

2. INTRODUCTION
 Algae are simple, chlorophyll bearing plants. Autotrophic organisms.
 Mostly unicellular, others are aggregation of many similar cells
 Study of Algae – Algology or Phycology
 (Phykos - alga in Greek)
 Algae varies in
Size
Habit
Habitat
Reproduction processes

3. Size
Size ranges from microscopic to several metres in length (e.g. Sea
weeds)

4. Habitat
Abundantly present in sea water, fresh water, on damp soil, plants and animals,
rocks, stones, barks trees.
Algae are aquatic or terrestrial
Most of them are aquatic. Terrestrial forms are live in moist place
Aquatic algae may be marine of fresh water forms
They are either free living or attached forms

5. Free living - Plankton

6. Algae attached to rocks - Lithophytes

7. Algae attached to plants - Epiphytes

8. Algae attached to animals – epizoophytes

9. Few algae are - Parasites

10. Some live as symbionts with fungi to form- Lichens

11. Cellularity
Exist in unicellular forms
Multicellular forms
Filamentous
Membranous
Blade like or tubular
Unicellular
They are single celled algae
They may be motile flagellated. Ex. Chlamydomonas
They may be non-motile coccoid. Ex. Chlorella
Chlorella

12. Multicellular forms
May be in the forms of colonies Ex. Volvox
in the form of filaments Ex. Spirogyra
Volvox

13. Filamentous
 Simple or branched filamentous
algae
 Simple filamentous Algae
 It consist single row of cells Ex.
Ulothrix
 May be free floating or attached
 Simple filament of blue green algae
is called trichomes
Ulothrix

14. In some algae
The plant body (thallus) is
differentiated into root, stem and leaf
Eg. Sargassum
Fucus
Laminaria
Sargassum
Fucus
Laminaria

15. Structure of algae
 The plant body is called thallus
 It does not differentaiated into
root, stem, leaf and true tissues
 May be prokaryotes or Eukaryotes
Prokaryotes
 All blue green algae are prokaryotes

16. Eukaryotes
Cell consist cell wall
plasma membrane
cytoplasm
Nucleus
Cytoplasm consists mitochondria
Plastids
Ribosomes
Golgi complex
Endoplasmic reticulum

17. Cell wall
Cell wall is surrounded by a thin, rigid cell wall
Have an outermatrix lying outside the cellwall
Outer matrix is flexible & gelatinous like bacterial capsule
Nucleus
True nucleus is present
It has nuclear envelope with pores
With in the nucleus Nucleolus, Chromatin, Karyolymph is present.

18. Mitochondria
Structure of mitochondria varies greatly
Euglenoids have – discoid cristae
Green and red algae – lamellar cristae
Golden brown, Yellow green, Brown algae, diatoms – tubular cristae

19. Chloroplast
In algae chloroplast exist in different shapes
Chlamydomonas - cup shaped
Ulothrix - gridle shaped
Zygnemia - star shaped
Spirogyra - spiral shaped

20. CHLOROPLAST
It has membrane bound sac called
thylakoids
Thylakoids carry out the light reaction of
photosynthesis
These organelles are embedded in the
stroma where dark reactions is takes place
Also contains one or more spherical bodies
called pyrenoids
Pyrenoids synthesis and store the starch
material

21. Plastids (Chromatophores)
Contain pigments
There are 3 types
Chlorophylls
Carotenoids
Biliproteins or phycobilins
Chlorophyll
Green pigment
Five types of chlorophylls are present
Chlorophyll a – found in all classes of algae
Chlorophyll b
Chlorophyll c
Chlorophyll d
Chlorophyll e
Other types (b, c, d, e) are found in some algae

22. Carotenoids
Yellow, orange or red pigment
2 types – carotenes and xanthophylls
Carotene – 3 types
Carotene a, b and g
Xanthophylls – yellow in colour
Bili proteins
Protein pigments
Two types
Phycocyanin – blue in colour
Phycoerythrin – red in colour
These pigmetns are present in chloroplast
Flagella
Some algae possess flagella
Algae are motile

23. Reproduction
Occur in three ways
Vegetative
Asexual
Sexual
Vegetative
Fragmentation
Plant body thallus breaks up and each
fragmented part grows to form a new thallus

24. Asexual Reproduction
Occur by spore formation and binary
fission
Spore are formed in ordinary vegetative
cells or in specialized structure termed
sporangia
Sporangia produce two types of spores
Flagellated motile spore – zoospores
Non motile spores – aplanospores

26. Binary fission
In some unicellular algae reproduction occur by binary fission

27. Sexual reproduction
Occur by egg formation
Eggs are formed in unmodified vegetative cells called oogonia
Oogonia function as female structure
Sperms are produced in male reproductive structure called antheridia
In sexual reproduction these gametes fused together to produce diploid zygote