Which of the following is a correct statement about sponges (phylum Porifera)?
A. They are exclusively terrestrial.
B. They have tissues and organs.
C. They are multicellular with a cellular level of organization.
D. They have a well-developed nervous system.
Answer: Option C
Solution (By JKSSB Mock Tests)
Sponges are the simplest multicellular animals with a cellular level of organization (no true tissues or organs). They are mostly marine, sessile, filter feeders. Water enters through numerous pores (ostia) into a spongocoel and exits through the osculum. They lack a nervous system. They possess specialized cells like choanocytes and amoebocytes but no coordination.
Explanation:
Plastics are synthetic polymers that resist microbial decomposition and persist in the environment for hundreds of years, causing pollution. Paper, cotton, and vegetable waste are biodegradable and broken down by decomposers.
Explanation:
Prolactin, from the anterior pituitary, promotes mammary gland development and milk synthesis. Oxytocin triggers milk ejection. Estrogen and progesterone prepare breasts during pregnancy but inhibit milk secretion.
Explanation:
Phenylketonuria (PKU) is an autosomal recessive disorder due to deficiency of phenylalanine hydroxylase, leading to accumulation of phenylalanine, causing mental retardation if untreated. Albinism is tyrosinase deficiency, sickle cell HbS mutation, cystic fibrosis CFTR defect.
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