1. Give characteristics of cephalochordates 2 What is parthenogenesis? Give one

Question

1. Give characteristics of cephalochordates 2 What is parthenogenesis? Give one example. 3. Ovarian follicles develop first time in females A) Before birth B) 3 months after birth C) puberty D) menopause 4 Distinguish between fission and fragmentation in animals 5. Distinguish between menstrual and estrous cycles and give 1 example for each 6. Distinguish between fission and fragmentation in animals 7. Embryonic structure with trophoblast and inner cell mass )Blastula 8) Morula C) gastrula D) blastocyst Development of new individual from old individual by folding out A) parthenogenesis Match the terms: 8. B) budding C) fission D) all of these 9 Body covered with a tunic, notochord in tail of larva 10 Circular mouth, slime glands, 4 tentacles around mouth 11 Notochord and nerve tube in adult, headless fish like animal C. Tunicate A. Hag fish B. Lancelet

Explanation / Answer

1. Cephalochordata includes two genera, 1. Asymmetron and 2. Branchiostoma(Amphioxus). Cephalochordates are small fish like animals which show Chordate characters. The notochord extends the entire length of the body. They show a dorsal, tubular neural tube without a definite brain.

General Characters:

1. Body is fish -like and is useful for burrowing and swimming.

2. It has a head.

3. It shows a tail.

4. Appendages are absent.

5. Dorsal, caudal and ventral fins are present.

6. Body- wall shows one- cell thick, non-ciliated epidermis, dermis, connective tissue, striated muscle and parietal peritoneum.

7. It has no exoskeleton.

8. Notochord extends from the anterior end to posterior end.

9. Enterocoelic coelom is present. However, reduced in the pharyngeal region by atrium.

10. The alimentary canal is long. It includes a large pharynx with many gill-slits ciliary modes of feeding is developed.

1 1. Gills will perform respiration.

12. The circulatory system is closed.

13. Heart and respiratory pigments are absent.

14. A hepatic portal system is present.

15. The excretory system shows paired protonephridia with solenocytes.

16. A brain is not present

17. Two pairs of cerebral and several pairs of spinal nerves are present.

18. Sexes are separate. Gonads are metamerically arranged and without gonoducts.

19. Asexual reproduction will not take place.

20. Fertilization is external.

2. parthenogenesis is a type of asexual reproduction in which the offspring develops from unfertilized eggs. It is particularly common amongst arthropods and rotifers, can also be found in some species of fish, amphibians, birds, and reptiles, but not in mammals.

It is also found in bees.

3. They develop before birth.

4. Binary fission occurs when a parent cell splits into two identical daughter cells of the same size. Fragmentation occurs when a parent organism breaks into fragments, or pieces, and each fragment develops into a new organism.

5. Binary Fission and Fragmentation, both are known as forms of 'asexual reproduction'. Binary fission is the splitting of one cell into two, and while conjunction is the same, it also involves exchanging DNA between two organisms. Fragmentation is the process of breaking off a piece of organism followed by mitosis cell division.

Binary Fission, fission is the subdivision of a cell or a multi-cellular body into one or more parts and the regeneration of each of the parts into a complete individual. It is a simple mitotic division in which each new cell receives half of the cytoplasm of the original cell. The line of cytoplasmic may be either miscellaneous or longitudinal. Examples include Protista, Monera, etc. Binary fission produces two split cells, populations, species, etc., whereas, multiple fission produces more than two cells, populations, species, etc. Prokaryotic fission, which is binary fission, is a form of asexual reproduction and cell division used by all prokaryotes.

Fragmentation is the process of the division of a piece of organism, after which each part differentiates into a full-sized organism. Some helminths, annelids experience fragmentation. Fragmentation is basically a form of asexual reproduction, where an organism is split into fragments. The splitting might or might not be deliberate. Each of these fragments develops into mature, grown-up individuals that are a replica of the original organism. If the organism is split any further, the process is continual. Fragmentation is caused by mitosis. Meiosis is not involved in fragmentation.

5.

Menstrual Cycle:

1. It occurs in primates (monkeys, apes and human beings) only.

2. This cycle consists of menstrual phase, proliferative phase and the secretory phase.

3. Blood flows in the last few days of this cycle.

4. The broken endometrium is passed out during menstruation.

5. Sex urge is not increased during menstruation.

6. Female does not permit copulation during menstrual phase of the cycle.

Oestrous Cycle:

1. It occurs in non-primates such as cows, dogs, etc.

2. It consists of a short period of oestrous or heat (e.g., 12-24 hours in cow) followed by anoestrous or passive period.

3. Blood does into flow in this cycle.

4. The broken endometrium is reabsorbed.

5. Sex urge is increased during oestrous period.

6. Female permits copulation only during oestrous period.

8. b) budding

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