Question

Biology lab question:

1. Molecular clock data place the evolution of diatoms around the time period following the Permian extinction. One hypothesis is that an adaptive radiation occurred as they colonized new marine niches. Based on what you know about the effects of ocean acidification on the formation of tests made from calcium carbonate and the composition of the tests (cell walls) of diatoms, what is a possible explanation for this diatom “explosion”?

2. what is the distinguishing features of the sexual and asexual phases for Chlamydomonas? What is the term for the type of syngamy (cell fusion) that occurs between gametes of this Genus? Why?

3. Why are the Phaeophytes considered more structurally complex than the other algal group? Why is fucus said to have a very similar life cycle to a human?

4. What is the main growth form of Volvox? Why isn't it considered multicellular?

Answer 1

Answer 1 :- on evolutionary basis we find that diatoms are living from ancient time where there are extreme environmental condition . Due to this one hypothesis said that they becomes one from two algal cells which are engulf by red algae and living symbiotically.

When the acidification of ocean going on the calcium from the corals leaches out and diatoms use this calcium and deposited into cell wall as calcium carbonate with silicon molecule. Due to silicon the test of diatoms becomes so rigid and protect the cell in living condition. Even after the death of diatom cell the wall [silicated and calcilated] is present for ever and form diatomaceous earth.

Answer 2 :- when we observe the life cycle of Chlamydomonas, it reproduce sexually and asexually .

1.Asexual reproduction :- takes place during favourable conditions by The zoospore formation. The zoospores are identical to the parent cell in structure but smaller in size. The zoospores simply enlarge to become mature Chlamydomonas. Under favourable conditions the formation of zoospores can take place every 25 hours.

2.The sexual reproduction :- in Chlamydomonas it can be isogamous [These gametes are morphologically similar but physiologically dissimilar.], anisogamous [The male gametes or microgametes are smaller, the female gametes or macrogainetes are larger ] or oogamous [non motile female gamete and motile male gamete].

3.The gamete are also look like zoospore but they are different in physiology contaent and behave as male or female. By swimming with flagella they fuse together [called fertilization], the process of fusion of two gametes call symgamy, which produce a hybrid diploid zygote.

Answer 3 Phaeophytes are multicellular complex brown algae . The plant body is divided into frond, stipe and hold fast . It is attached to the substratum by hold fast and living vertical posture. The chromosome set in parental focus plant is two in number [diploid]. It means the dominantphase of life cycle is diploid [2n] , Also you can called that the plant body is sporophytic in nature. During sexual reproduction , the gametes are formed by meiosis , and gametes are haploid in nature [1n] . After fertilization of gamete again there diploid sporophytic condition is come back and a new plant come from that zygote is diploid. When we observe the llife cycle of human , it is in same manner, that means diploid sporophytic phase [our body] is dominant . And gametic haploid phase [sperms and ova] is short lived.