How is the equal genetic contribution of male and female parents ensured in the progeny?
Equal genetic contribution of male and female parents is ensured by the equal number of inheritance of chromosomes. Human beings possess a normal diploid (2N) chromosome number in human beings is 46. Each body cell contains 23 pairs of chromosomes, with 22 pairs of autosomes and one pair of sex chromosome. The autosomes are similar in male and female but one sex chromosome is different in both. In females, sex chromosomes are same XX and heteromorphic in males, i.e, XY. Sex chromosomes control the sex of an individual. One male haploid gamete and one female haploid gamete form a diploid cell gamete by sharing equal amounts of genetic material from both paternal and maternal parents. If the zygote receives one X chromosome from a female and another X chromosome from male then the child will be female, i.e, XX. And when the zygote receives one X chromosome from a female and another Y chromosome from male then the child will be male.
Outline a project which aims to find the dominant coat colour in dogs.
How is the sex of the child determined in human beings?
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?
How do Mendel’s experiments show that traits are inherited independently?
If a trait A exists in 10% of a population of an asexually reproducing species and a trait B exists in 60% of the same population, which trait is likely to have arisen earlier?
Explain how sexual reproduction gives rise to more viable variations than asexual reproduction. How does this affect the evolution of those organisms that reproduce sexually?
Explain the terms analogous and homologous organs with examples.
How do Mendel’s experiments show that traits may be dominant or recessive?
How does the creation of variations in a species promote survival?
Will geographical isolation be a major factor in the speciation of an organism that reproduces asexually? Why or why not?
Did Döbereiner’s triads also exist in the columns of Newlands’ Octaves? Compare and find out.
What is a good source of energy?
Why is diffusion insufficient to meet the oxygen requirements of multi-cellular organisms like humans?
What are trophic levels? Give an example of a food chain and state the different trophic levels in it.
What changes can you make in your habits to become more environment-friendly?
What is the difference between a reflex action and walking?
What is the importance of DNA copying in reproduction?
Why should a magnesium ribbon be cleared before burning in air?
Define the principal focus of a concave mirror.
You have been provided with three test tubes. One of them contains distilled water and the other two contain an acidic solution and a basic solution, respectively. If you are given only red litmus paper, how will you identify the contents of each test tube?
Why is respiration considered an exothermic reaction? Explain.
What does one mean by exothermic and endothermic reactions? Give examples.
Name the type of mirror used in the following situations.
(a) Headlights of a car.
(b) Side/rear-view mirror of a vehicle.
(c) Solar furnace.
Support your answer with reason.
The xylem in plants are responsible for
(a) transport of water. (c) transport of amino acids.
(b) transport of food. (d) transport of oxygen.
Compare and contrast fossil fuels and the Sun as direct sources of energy.
On what basis would you classify energy sources as
(a) renewable and non-renewable?
(b) exhaustible and inexhaustible?
Are the options given in (a) and (b) the same?
If all the waste we generate is biodegradable, will this have no impact on the environment?
What are outside raw materials used for by an organism?
What are the components of the transport system in highly organised plants?
What criteria do we use to decide whether something is alive?