Biology Test 321

Coelenterates have radial symmetry. Aschelminth are pseudocoelomates. Molluscs do not show metamerit Sponges are diploblastic.

The animals in which the coelom is absent are called acoelomates, for example flatworms (Planaria). In them the space between ectoderm and endodorm is filled with parenchyma derived from mesoderm.

(i) Diploblastic - Poriferans, Coelenterates

(ii) Triploblastic - Platyhelminthes to Chordates

(iii) Acoelomate - Poriferans, Coelenterates, Platyhelminthes

(iv) Pseudocoelomate - Aschelminthes/Roundworms

(v) Eucoelomate - Annelids to Chordates

So, the correct answer is '(i), (ii), (iii), (iv) and (v)'.

Plasmodium completes their life cycle in two hosts, female anopheles and human beings. The motile zygote of plasmodium occurs in gut of female anopheles, which get transferred to human being during mosquito bite.

• Typhoid fever in the human being is caused by Salmonella typhi.
• The pathogen enters the small intestine through food and contaminated water and migrates to other organs through blood

This illustration depicts a photomicrograph of Salmonella typhi bacteria:

Alzheimer disease is a neurological disorder in which the death of brain cells causes memory loss and cognitive decline. It is caused in human due to deficiency of acetylcholine.

The gut microbiota can influence the central nervous system through the synthesis of ACh and other neuroactive molecules:

Please note that there are 2 sets of information given in the question. The first set (options a-e) mentions the names of compounds. The second set (options 1-4) mentions the combinations of the first set of options.

• Auxin refers to a group of plant hormones that regulate plant growth.
• Based on their origin, auxins can be divided into:
  • Natural Auxins - They occur naturally in the plant and affect physiological functions. E.g. - IAA, IBA.
  • Artificial Auxins - These are synthetically-derived chemical compounds that resemble IAA in biological activity. E.g. - NAA.
• Artificial auxins are widely used in horticultural practices, as weedicides, rooting agents, and defoliating agents.

• IPA
  • Indole-3-pyruvic acid (IPA) is an intermediate in the IAA biosynthesis pathway.
  • Hence, it is not an artificial auxin.
• PAA
  • Phenylacetic acid (PAA) is a natural auxin.
• NAA
  • Naphthalene acetic acid (NAA) is an artificial auxin that is used as a rooting agent.
• 2,4,5-T
  • 2,4,5 - Trochlorophenoxyacetic acid is an artificial auxin that is used as a herbicide.
• 2,4-D
  • 2,4 - Dichlorophenoxy acetic acid (2,4-D) is an artificial auxin that is widely used as a herbicide.

Thus the answer will be (c), (d), and (e).

I.A.A. is auxin. The precursor of auxin is tryptophan and Zn.

Presumptive pathways of IAA biosynthesis from tryptophan:

• Gibberellic acid is a Terpene.
• All known gibberellins are diterpenoid acids that are synthesized by the terpenoid pathway in plastids and then modified in the endoplasmic reticulum and cytosol until they reach their biologically-active form.
• All gibberellins are derived via the ent-gibberellane skeleton, but are synthesized via ent-kaurene.

The following are plant growth regulators or phytohormones that control various developmental as well as physiological functions of a plant:

Auxin:

• It helps in cell elongation, growth, and differentiation.
• It is present mainly at the root and shoots apices.
• It is responsible for the phenomenon of apical dominance, where the apical buds inhibit the growth of lateral buds.
• It results in increasing the height of a plant due to apical dominance.
• It can also initiate root growth in stem cuttings.
• It may also promote flowering and prevent early fruit drop.

Cytokinin:

• It is mainly associated with cell division and is present in regions of rapid cell division.
• It helps to overcome apical dominance and promotes lateral shoot growth.

Ethylene:

• It is a gaseous phytohormone produced in the tissues undergoing senescence.
• It helps in fruit ripening and other senescence-related activities.
• It breaks seed and bud dormancy to initiate germination in some species.
• It also induces leaf epinasty under stress conditions.
• The triple response of ethylene includes reducing the rate of elongation, increasing lateral expansion, and swelling of the region below the hook in seedlings.

Abscisic acid:

• As the name suggests, it helps in abscission and dormancy.
• It inhibits plant growth, metabolism, and seed germination.
• It also plays an important role in the closure of stomata under stress conditions.