Plant Kingdom Test - 84

Fucus (rockweed), a brown alga, displays a diploid life history. The zygote (2n) becomes an embryo (very young sporophyte) and developes into the mature Fucus with receptacles at the tip of the algae. The receptacles are reproductive branches and contain many cavities with external pores, which contain antheridia (male) and oogonia (female), then through meiosis, sperm (1n) and egg (1n) are produced. Syngamy occurs when the two fuse and become a zygote (2n).

Volvox are one-celled algae that live together in a colony. The  colony is a hollow ball with 500 to 20,000 individual cells. Each volvox cell has two flagella. The flagella beat together to roll the ball through the water. Volvox cells have chlorophyll and make their own food by photosynthesis. Daughter colonies are small, dark green balls inside the volvox colony. When the daughter colonies mature, the parent ball bursts open and releases the daughter colonies.

External fertilization occurs mostly in wet environments and requires both the male and the female to release their gametes into their surroundings (usually water). An advantage of external fertilization is that it results in the production of a large number of offspring. One disadvantage is that environmental hazards such as predators greatly reduce the chance of surviving into adulthood. Amphibians and fish, aquatic algae are examples of animals that reproduce this way.

Green algae have chlorophylls a and b and store starch as a food reserve inside their plastids. The colours of brown algae cover a spectrum from pale beige to yellow-brown to almost black and contain such as chlorophyll c and fucoxanthin. They also lack the plasmodesmata and starch production. Rhodophytes contain chlorophyll a,  which is masked by phycobilin pigments bound to proteins. The chloroplasts in red algae resemble cyanobacteria both biochemically and structurally. Food reserves are stored outside of the chloroplasts as Floridean starch. 

Rhodophyta (red algae) has predominance of the red pigment, phycoerythrin along with chlorophyll a and chlorophyll d The red algae usually reproduce vegetatively by fragmentation, asexually by non-motile spores and sexually by non-motile gametes. The common members are Polysiphonia, Porphyra, Gracilaria and Gelidium.

So, the correct answer is 'Phycoerythrin'

Polysiphonia (branching form) is a small marine alga. The filament is complex. Apical cells cut off proximal segments which elongate to become axial cells. These cut off pericentral cells of the same length. The central axial cell is now surrounded by pericentral cells of the same length, forming one tier or segment. Polysiphonia can have four to 24 pericentral cells present per tier. Porphyra is multicellular membranous. Laminaria and Dictyota have a root-like holdfast, a stem like stipe and leaflike blades. Fucus Rockweed, found at the beach, tips of the thallus have bladders that you can pop.

Seaweeds can be classified into three broad groups based on pigmentation: brown, red and green. Botanists refer to these broad groups as Phaeophyceae, Rhodophyceae and Chlorophyceae, respectively. 

Brown seaweeds are usually large, and range from the giant kelp i.e., often 20 m long, to thick, leather-like seaweeds from 2-4 m long, to smaller species 30-60 cm long. 

Red seaweeds are usually smaller, generally ranging from a few centimeters to about a meter in length; however, red seaweeds are not always red: they are sometimes purple, even brownish red, but they are still classified by botanists as Rhodophyceae, because of other characteristics. 

Green seaweeds are also small, with a similar size range to the red seaweeds. Seaweeds are also called as macro-algae. This distinguishes them from micro-algae (Cyanophyceae), which are microscopic in size, often unicellular, and are best known by the blue-green algae, that sometimes bloom and contaminate rivers and streams.

The Ordovician is best known for the presence of its diverse marine invertebrates, including graptolites, trilobites, brachiopods and the conodonts (early vertebrates). A typical marine community consisted of these animals, plus red and green algae, primitive fish, cephalopods, corals, crinoids, and gastropods. A burst of evolution went on to triple the diversity of marine animal life in the space of 50 million years.

Pyrenoids are commonly present in the chloroplasts of many algae and also in the bryophyte are associated with the operation of a carbon-concentrating mechanism (CCM). Pyrenoids are composed of a granular, homogeneous matrix around which are found starch deposits. A filamentous and fibrillar nature of the pyrenoid matrix are present in certain green algae.