Algae

Algae discription

Algae are chlorophyll-bearing, simple, thalloid, autotrophic and largely aquatic (both fresh water and marine) organisms

Algae habitat

moist stones, soils and wood. Some of them also occur in association with fungi (lichen) and animals (e.g., on sloth bear).

algae form and size

size of algae is highly variable, ranging from colonial forms like Volvox and the filamentous forms like Ulothrix and Spirogyra . marine forms such as kelps, form massive plant bodies.

Algae:vegetative repro

Vegetative reproduction is by fragmentation. Each fragment develops into a thallus

Algae repro:asexual

Asexual reproduction is by the production of different types of spores, the most common being the flagellated zoospores (motile) and on germination give rise to new plants.

Algae repro:sexual

Sexual reproduction takes place through fusion of two gametes.

These gametes can be flagellated and similar in size (as in Ulothrix) non-flagellated (non-motile) but similar in size (as in Spirogyra). Such reproduction is called isogamous.

Fusion of two gametes dissimilar in size, as in species of Eudorina is termed as anisogamous.

Fusion between one large, nonmotile (static) female gamete and a smaller, motile male gamete is termed oogamous, e.g., Volvox, Fucus.

Major role of algae in carbon dioxide fixation

about 50% of the total CO₂ fixation on Earth through photosynthesis

How do algae affect oxygen levels?

Being photosynthetic, they increase dissolved oxygen in their surroundings.

Why are algae important in aquatic food chains?

they are primary producers, forming the base of aquatic food cycles.

Examples of edible marine algae

porphyra, Laminaria, Sargassum — some of the ~70 species used as food.

What are hydrocolloids from algae?

Water-holding substances; brown algae produce algin, and red algae produce carrageenan.

Uses of algin and carrageenan

Used commercially in food, cosmetics, and industrial products due to their thickening properties.

Source and uses of agar

Obtained from Gelidium & Gracilaria; used to grow microbes, and in ice creams & jellies.

Why is Chlorella special?

Protein-rich unicellular alga; used as a food supplement, even by space travelers.

What are the classes of algae

Chlorophyceae (Green)

Phaeophyceae (brown)

Rhodophyceae (red)

Why are chlorophyceae called green algae?

Because they contain chlorophyll a & b, giving a grass-green colour.

Types of plant body in green algae

Unicellular, colonial, filamentous

Where are pigments located in green algae?

In distinct chloroplasts.

Different shapes of chloroplasts in green algae

Discoid, plate-like, reticulate, cup-shaped, spiral, ribbon-shaped

What are pyrenoids?

torage bodies in chloroplasts containing protein + starch.

Other form of food storage in some green algae

Oil droplets

Composition of green algae cell wall

inner: cellulose
Outer: pectose

Vegetative reproduction in green algae

Fragmentation

Asexual reproduction in green algae

Flagellated zoospores formed in zoosporangia

Sexual reproduction types in green algae

Isogamous, anisogamous, oogamous

Examples of green algae

Chlamydomonas, Chara,Volvox, Ulothrix, Spirogyra, Chara

pneumonic-chal chal ke vo udhar sogaya

Habitat of brown algae (Phaeophyceae)

Primarily marine

Range of size and form in brown algae

from simple filamentous forms (Ectocarpus) to profusely branched forms represented by 100 tall kelps.

Pigments in brown algae

Chlorophyll a, chlorophyll c, carotenoids, xanthophylls.

What range of colours of brown algae are seen and the reason for the same

Olive green to various shades of brown

Due to amt of fucoxanthin (a xanthophyll pigment).

Food storage products in brown algae

complex carbs in the form of Laminarin and mannitol.

Cell wall structure in brown algae

Inner cellulose, outer gelatinous algin layer.

Major parts of brown algae thallus

Holdfast (attached to ground),

stipe(stalk),

frond (leaf like, photosynthetic).

Protoplasm of vegetative cell of brown alga contains

plastids

centrally located vacuole

nucleus

Vegetative reproduction in brown algae

fragmentation

Asexual reproduction in brown algae

Biflagellate, pear-shaped zoospores with two unequal lateral flagella.

Sexual reproduction in brown algae

maybe iso, aniso ,oogamous

Where does fertilization occur in oogamous brown algae?

Inside the oogonium.

Describe the gametes in sexual reproduction of brown algae

Pyriform (pear shaped)

2 laterally attached flagella

examples of brown algae

Ectocarpus, Dictyota, Laminaria, Sargassum, Fucus

Every Dude Loses Sanity For girls