*SCIENCE REVISION*
Q1) What are isomers? Draw all possible isomer of hexane.
Q2) How is sex of the child determined in human beings?
Q3) What is ovulation?
Q4) What changes occur during the time of birth?
Q5) What are magnetic field lines?
Q6) How is the direction of magnetic field at a point determined?
Q7) How is it beneficial for the foetus to have a circulatory system that is not directly attached to the circulatory system of mother?
Q8) List two unisexual and bisexual flowers.
Q9) What are amphoteric oxides? Give examples.
Q10) Define variation.
Q11) Give the characteristics of food chain.
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Answers
Answer:
1)C6H14 is hexane. It has 5 structural isomers viz. n-hexane, 2-methylpentane, 3-methylpentane, 2,2-dimethylbutane, 2,3-dimethylbutane.
2)Men determine the sex of a baby depending on whether their sperm is carrying an X or Y chromosome. An X chromosome combines with the mother's X chromosome to make a baby girl (XX) and a Y chromosome will combine with the mother's to make a boy (XY).
3)Facts about timing. Ovulation is when a mature egg is released from the ovary. The egg then moves down the fallopian tube where it can be fertilised.
4)A cycle of uterine contractions followed by labour pains, dilation of cervix and the vagina slowly pushes the foetus out of the uterus. The uterine contractions are initiated by decreased progesterone secretion and the secretion of oxytocin hormone by the pituitary gland.
5)A magnetic field is a vector field that describes the magnetic influence on moving electric charges, electric currents, and magnetized materials. A charge that is moving in a magnetic field experiences a force perpendicular to its own velocity and to the magnetic field.
6)The direction of a magnetic field at a point is determined by placing a small compass needle. The N - pole of compass indicates the direction of magnetic field at that point.
7)Placenta. The circulatory system of the mother is not directly connected to that of the fetus, so the placenta functions as the respiratory center for the fetus as well as a site of filtration for plasma nutrients and wastes.
8)Unisexual flowers :- A flower having either male or female reproductive system is known as Unisexual flowers. Example :- Coconut flowers, Papaya, Watermelon, Cucumber, Maize, White mulberry . Bisexual flowers :- A flower having both male and female reproductive systems are called Bi sexual flowers .
9)In chemistry, an amphoteric compound is a molecule or ion that can react both as an acid and as a base. Many metals (such as copper, zinc, tin, lead, aluminium, and beryllium) form amphoteric oxides or hydroxides. Amphoterism depends on the oxidation states of the oxide. Al2O3 is an example of an amphoteric oxide.
10)change or slight difference in condition, amount, or level, typically within certain limits.
11)Four characteristics of food web are: 1) It consists of number of interconnected food chains through which energy travels in an ecosystem. 2)Usually members of higher trophic level feed upon many organism of lower trophic level. 3)Presence of complex food webs increases the stability of the ecosystem.
Explanation: