Explain the importance of fossils in deciding evolutionary relationships.
Fossils are formed during the formation of sedimentary rocks, dead animals of the sea and the lakes, rivers when they sink down and get buried in the rocks. When there is no oxygen, they prevent the decay of an animal. The animals then preserved in the rocks, which form the fossils. The hard matter remains of the dead animals preserved layer by layer in the sedimentary rocks. The deeper layer had more older fossils and the upper layer had more recent fossils. Palaeontology is the study of past life based on the fossil records. Palaeontology furnishes the evidence for the evolution which tells about the organism that lives in today’s time or that lived in the past and how they originated by showing the fossil records. Ages of the fossils can be determined by some methods like relative dating method, absolute dating method etc. By which age of fossils determine how long they have been in the evolutionary relationships.
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?
Will geographical isolation be a major factor in the speciation of an organism that reproduces asexually? Why or why not?
How does the creation of variations in a species promote survival?
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?
Which of the following groups contain only biodegradable items?
(a) Grass, flowers and leather
(b) Grass, wood and plastic
(c) Fruit-peels, cake and lime-juice
(d) Cake, wood and grass
Why are we looking at alternate sources of energy?
Draw the structure of a neuron and explain its function.
Will current flow more easily through a thick wire or a thin wire of the same material, when connected to the same source? Why?
Explain different ways to induce current in a coil.
Why does the Sun appear reddish early in the morning?
Why do HCl, HNO3, etc., show acidic characters in aqueous solutions while solutions of compounds like alcohol and glucose do not show acidic character?
The human eye forms the image of an object at its
(a) cornea. (b) iris. (c) pupil. (d) retina.
In the Modern Periodic Table, calcium (atomic number 20) is surrounded by elements with atomic numbers 12, 19, 21 and 38. Which of these have physical and chemical properties resembling calcium?
A milkman adds a very small amount of baking soda to fresh milk.
(a) Why does he shift the pH of the fresh milk from 6 to slightly alkaline?
(b) Why does this milk take a long time to set as curd?