Give an example of characteristics being used to determine how close two species are in evolutionary terms.
The more characteristics of two species have in common, they seem to be more closely related. And the more closely they are related, more recently they shared a common ancestor or the evolutionary relationship.
Mostly the homologous characteristics derive from how close two species are in evolutionary terms. For example, mammals have four limbs as birds, reptiles and amphibians possess. Basic structures of the limbs are very similar and they are modified to do different functions. The characteristics can be similar in different organisms because of sharing the common ancestors which helps to identify the evolutionary relationship among two close related species. Another example is the common connection link between the reptiles and birds. The connecting link between the reptiles and the birds are known as archaeopteryx. Aves have the evolutionary characters which are derived from the reptiles, in which the forelimbs of the reptiles modified into the feathers or the wings.
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?
What are the differences between aerobic and anaerobic respiration? Name some organisms that use the anaerobic mode of respiration.
Draw a schematic diagram of a circuit consisting of a battery of three cells of 2 V each, a 5 Ω resistor, an 8 Ω resistor, and a 12 Ω resistor, and a plug key, all connected in series.
What are the different ways in which glucose is oxidised to provide energy in various organisms?
Compare and contrast fossil fuels and the Sun as direct sources of energy.
Draw a labelled diagram of an electric motor. Explain its principle and working. What is the function of a split ring in an electric motor?
In Activity 13.7, how do we think the displacement of rod AB will be affected if (i) current in rod AB is increased; (ii) a stronger horse-shoe magnet is used; and (iii) length of the rod AB is increased?
Give any two ways in which non-biodegradable substances would affect the environment.
What changes can you make in your habits to become more environment-friendly?
Why are we looking at alternate sources of energy?
Explain the formation of scum when hard water is treated with soap.