Structural Organisation In Animals

Chloragogen cells of Pheretima posthuma are analogous to liver of vertebrates. They are said to be excretory. They may also store the reserve food material and manufacture glycogen from fatty acids.

Parasphenoid bone is a flattened and inverted T-shaped bone which lies in the median line along the floor of cranium.

Simple reflex action is a nerve mediated spontaneous automatic and involuntary response to a stimulus acting on a specific receptor without consulting the will of the animal.

Conditioned reflexes are those reflex actions that are not present at birth but develop later in life through learning, habit, experience or regular association of an indifferent stimulus with unconditioned stimulus.

Striped (striated or skeletal or voluntary) muscles are syncytial. Nuclei are spindle shaped, peripheral in position and lie near the sarcolemma. They are multi nucleate because each fibre is formed by the fusion of a number of embryonic stem cells (myoblasts), hence, regarded multicellular syncytial body.

Tadpoles can be made to grow in size and become adult by injecting thyroxine hormone. By metamorphosis, tadpole grows in size and becomes adult. It is under neuroendocrine control.

Thyroxine Releasing Factor or TRF is secreted by Hypothalamus.

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Anterior Pituitary gets stimulated and produces TSH.

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Thyroid produces T₄ and T₃ hormones.

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Metamorphosis of the tadpole starts.

The basement membrane is a thin, fibrous, extracellular matrix of tissue that seperates the lining of an internal or external body surface from underlying connective tissue.

Pheromones are the secretion of small amount of chemical substances leading to specific physiological or behavioural responses in other members of the same species. They are mainly used to induce mating. 

In frog, all nerve cells connecting to central nervous system (brain and spinal cord) with receptor and effectors constitute the peripheral nervous system. Some small masses of nerve cell bodies are called ganglia. They develop from neural crest cells in frog.

In cockroach, excretion is mainly performed by one or two pairs of malpighian tubules. One of this pair opens into the middle region of intestine and other pair of coxal glands are located in prosoma and opens at bases of fifth walking legs.

Mimicry is a process by which two or more organisms independently derive protection from predation. This may be done by acquiring body colour blending with the surrounding or sometimes they bring resemblance to a distasteful, poisonous or harmful organisms. Leaf butterfly and stick insect show the colour of leaf, stem etc by which they can dodge their enemies and predator.