Q28 of 30 Page 1

(a) What is genetics?

(b) What are genes? Where are the genes located?


(c) State and define three factors responsible for the rise of a new species.


(a) Genetics is a branch of biology concerned with the study of genes, genetic variation, and heredity in organisms.

(B) A gene is the basic physical and functional unit of heredity. Genes are made up of DNA. Some genes act as instructions to make molecules called proteins. Genes are located in the chromosomes.


(c) Speciation is the formation of new and distinct species in the course of evolution.


Three factors:


(A) Natural Selection: Natural selection is the differential survival and reproduction of individuals due to differences in phenotype. It is a key mechanism of evolution, the change in the heritable traits characteristic of a population over generations


(B) Genetic Drift: Genetic drift is the change in the frequency of an existing gene variant in a population due to random sampling of organisms. The alleles in the offspring are a sample of those in the parents, and chance has a role in determining whether a given individual survives and reproduces.


(c) Geographical Isolation: Geographic isolation is a term that refers to a population of animals, plants, or other organisms that are separated from exchanging genetic material with other organisms of the same species.


More from this chapter

All 30 →
26

The position of certain elements in the Modern Periodic Table are shown below.

Using the above table answer following questions giving reasons in each case:


(i) Which element will form only covalent compounds?


(ii) Which element is a non-metal with valency 2?


(iii) Which element is a metal with valency 2?


(iv) Out of H, C and F which has largest atomic size?


(v) To which family does H, C and F belong?


OR


Define atomic size. Give its unit of measurement. In the modern periodic table what trend is observed in the atomic radius in a group and a period and why is it so?


 27

(a) Why is there a difference in the rate of breathing between aquatic organisms and terrestrial organisms? Explain.

(b) Draw a diagram of human respiratory system and label – pharynx, trachea, lungs, diaphragm and alveolar sac on it.


OR


(a) Name the organs that form the excretory system in human beings.


(b) Describe in brief how urine is produced in human body.


 29

Draw a ray diagram in each of the following cases to show the formation of image, when the object is placed:

(i) between optical centre and principal focus of a convex lens.


(ii) anywhere in front of a concave lens.


(iii) at 2 F of a convex lens. State the signs and values of magnifications in the above-mentioned cases (i) and (ii).


OR


An object 4.0 cm in size, is placed 25.0 cm in front of a concave mirror of focal length 15.0 cm


(i) At what distance from the mirror should a screen be placed in order to obtain a sharp image?


(ii) Find the size of the image.


(iii) Draw a ray diagram to show the formation of image in this case.


 30

(a) What is an electromagnet? List any two uses.

(b) Draw a labelled diagram to show how an electromagnet is made.


(c) State the purpose of soft iron core used in making an electromagnet.


(d) List two ways of increasing the strength of an electromagnet if the material of the electromagnet is fixed.