Which of the following statements related to the pituitary gland are correct?
(a) It is divided anatomically into adenohypophysis and neurohypophysis. (b) It secretes follicle stimulating hormone. (c) It secretes melanocyte stimulating hormone. (d) It does not secrete prolactin.
Choose the correct answer from the options given below:
The pituitary gland consists of adenohypophysis and neurohypophysis. It secretes FSH, MSH and prolactin. Therefore statement (d) is incorrect.
Assertion (A): The logistic growth model of populations is considered more realistic than the exponential growth model.
Reason (R): Resources are finite.
In the light of the above statements, choose the most appropriate answer from the options given below:
The logistic growth model is more realistic because environmental resources are limited. As resources become limiting, population growth slows and approaches the carrying capacity (K).
Which of the following statements are true with reference to the sex determination in honeybees?
(A) An offspring formed from the union of a sperm and an egg develops as a female (queen or worker).
(B) An unfertilized egg develops as a male by parthenogenesis.
(C) A male has half the number of chromosomes than that of a female.
(D) Males produce sperms by meiosis.
(E) Honeybees have a haplodiploid sex-determination system.
Choose the correct answer from the options given below:
Male honeybees are haploid and produce sperms by mitosis, not meiosis. Therefore statement D is incorrect.
Since the origin and diversification of life on Earth, there have been five episodes of mass extinction of species.
How is the sixth, which is in progress, different from the previous episodes?
According to NCERT, the ongoing sixth mass extinction is primarily driven by human activities, with extinction rates estimated to be 100 to 1000 times higher than the natural background rate.
I. Accumulation of dark coloured amorphous colloidal substance
B. Detritus
II. Release of inorganic nutrients by the activity of microbes in soil
C. Mineralisation
III. Breaking down of complex organic matter into simpler substances
D. Humification
IV. Dead remains of plants and animals including faecal matter
Decomposition breaks down detritus. Detritus consists of dead organic matter. Mineralisation releases inorganic nutrients. Humification forms dark-coloured humus.
I. Gross primary productivity minus respiration losses
B. Net primary productivity
II. Rate of formation of new organic matter by consumers
C. Gross primary productivity
III. Rate of biomass production
D. Secondary productivity
IV. Rate of production of organic matter during photosynthesis
Productivity is the rate of biomass production. Net primary productivity equals GPP minus respiration losses. Gross primary productivity is the rate of photosynthesis, while secondary productivity is the rate of biomass formation by consumers.
(A) The Amazon rainforest being cut and cleared for cultivation of soyabeans is an example of habitat loss. (B) Steller's sea cow and passenger pigeon became extinct due to over-exploitation by humans. (C) The Nile perch introduced into Lake Victoria in East Africa helped in population growth of cichlid fish in the lake. (D) Water hyacinth is an invasive species. (E) When a species becomes extinct, the plant and animal species associated with it are not affected.
Choose the correct answer from the options given below:
Amazon deforestation is habitat loss. Steller's sea cow and passenger pigeon became extinct due to over-exploitation. Nile perch caused decline of cichlid fishes. Water hyacinth is an invasive alien species. Extinction may lead to co-extinctions.
