How does chemical coordination take place in animals?
Chemical coordination takes place in animals by the chemical messengers called hormones, which are secreted by the endocrine glands or occurs by the nervous system.
Hypothalamus is the important part in intergrating the nervous and endocrine system.
When endocrine glands secrete hormones, neurosecretory cells are present in the brain which secrets the neurotransmitters. And these chemical messengers get converted into electrical signals and goes into muscles or glands for the movement or for the growth and development of an animal.
When a 12 V battery is connected across an unknown resistor, there is a current of 2.5 mA in the circuit. Find the value of the resistance of the resistor.
Outline a project which aims to find the dominant coat colour in dogs.
Draw the structure for the following compounds.
(i) Ethanoic acid (ii) Bromopentane*
(iii) Butanone (iv) Hexanal.
*Are structural isomers possible for bromopentane?
A hot plate of an electric oven connected to a 220 V line has two resistance coils A and B, each of 24 Ω resistance, which may be used separately, in series, or in parallel. What are the currents in the three cases?
How is the sex of the child determined in human beings?
(a) What property do all elements in the same column of the Periodic Table as boron have in common?
(b) What property do all elements in the same column of the Periodic Table as fluorine have in common?
Calculate the number of electrons constituting one coulomb of charge.
What is an homologous series? Explain with an example.
Why is variation beneficial to the species but not necessarily for the individual?
A man with blood group A marries a woman with blood group O and their daughter has blood group O. Is this information enough to tell you which of the traits – blood group A or O – is dominant? Why or why not?
The change in focal length of an eye lens is caused by the action of the
(a) pupil. (b) retina.
(c) ciliary muscles. (d) iris.
The position of three elements A, B and C in the Periodic Table are shown below –
Group 16 Group 17
- -
- A
- -
B C
(a) State whether A is a metal or non-metal.
(b) State whether C is more reactive or less reactive than A.
(c) Will C be larger or smaller in size than B?
(d) Which type of ion, cation or anion, will be formed by element A?
Judge the equivalent resistance when the following are connected in parallel – (a) 1 Ω and 106 Ω, (b) 1 Ω and 103 Ω, and 106 Ω.
List two methods of producing magnetic fields.
Why does the cord of an electric heater not glow while the heating element does?
What are the disadvantages of fossil fuels?
How can you help in reducing the problem of waste disposal? Give any two methods.
What would you observe when zinc is added to a solution of iron(II) sulphate? Write the chemical reaction that takes place.
Suggest some approaches towards the conservation of forests.
Use Mendeléev’s Periodic Table to predict the formulae for the oxides of the following elements:
K, C, AI, Si, Ba.