(a) Chromosomal DNA refers to the entire genome of an organism and depends on the genome for replication. It may be single stranded or double stranded and linear or circular. While plasmid DNA is extrachromosomal DNA that can replicate itself independently and always double-stranded circular DNA.
(b) DNA has deoxyribose pentose sugar and adenine and thymine as purines. It is found in the nucleus, mitochondria, and chloroplast only. While RNA has ribose pentose sugar and adenine and uracil as purines and found in nucleus and cytoplasm only. DNA replicates to form DNA and transfers genetic information from one generation to next whereas RNA is formed by DNA when required and directs the synthesis of protein in the body.
(c) Exonucleases are the enzymes that remove nucleotides from 5' or 3' end of DNA while endonucleases make cut within the DNA sequence by breaking the phosphodiester bond, not from its one of the end.

The population can grow exponentially for a certain period of time and then assumes a steady state as the resource availability becomes limiting at some point of time.  

Every environment has resources to support a particular maximum number of individuals, called its carrying capacity; beyond that there is no increase in the size/density of a population.
A population showing logistic growth shows a sigmoid curve, when the number of individuals is plotted as a function of time.
It is described by the equation,
dN/dt = \(rN\left( \frac { K-N }{ K } \right) \), 
Where, N = Population density at time t.
r = Intrinsic rate of natural increase.
K = Carrying capacity.
This growth model is more realistic in nature because no population can sustain the exponential growth indefinitely.

Three important characteristics of a population are:
(i) Population size and population density
(ii) Birth or natality rate
(iii) Death or mortality rate.
(i) Population size.  The size of population keeps changing with time depending on the factors like:
(a) Food availability
(b) Weather
(c) Predation pressure and
(d) Competition.
The population density in a given habitat during a given period, changes due to four basic processes namely
(a) Natality,
(b) Mortality,
(c) Immigration and
(d) Emigration.
While natality and immigration contribute to an increase in the size and density of a population, mortality and emigration contribute to a decrease in them.
So the equation for population growth is:
\(N_{ t+1 }=N_{ t }+[(B+I)-(D+E)],\)
where, N = population density at time t.
B = Birth rate.
I = Immigration.
D = Death rate.
E  = Emigration.
If B + I is more than D + E, the population density increases.
If B + I is less than D + E, the population density decreases.
(ii) Birth or Natality rate. It is generally expressed as number or births per 1,000 individuals of a population per year. It increases the population size (total number of individuals of a population) and population density.
Natal or Birth Rate                  
If B + I is more than D + E, the population density increases.
\(=\frac { Total\quad Number\quad of\quad Live\quad Births\quad in\quad a\quad year }{ Total\quad Population\quad in\quad the\quad Middle\quad of\quad the\quad year } X1000\)
(iii) Death or Mortality rate. It is opposite of Mortality (Death) Rate natality rate. It is commonly expressed as the number of deaths per 1,000 individuals of a population per year.
\(=\frac { No.of\quad Deaths\quad in\quad a\quad year\qquad }{ Total\quad Population\quad in\quad the\quad Middle\quad of\quad the\quad year } X1000\\ \)

(i) The zygote starts dividing only after a certain amount of endosperm is formed as an adaptation to provide assured nutrition to the developing embryo; hence we can say it remains dormant for some time.
(ii) In groundnut, the developing embryo utilises the endosperm completely. There is no residual endosperm in the seed and so the seed is exalbuminous. In castor, the endosperm is not completely used up by the developing embryo, there is some amount of endosperm left in the seeds and the seeds are albuminous.
(iii) The micropyle facilitates the entry of water- and oxygen into the seed during germination.
(iv) The loss of water (up to 10-15% of weight) reduces the metabolic activity and seeds can enter a state of dormancy during unfavorable environment.
(v) Since, the thalamus (part other than ovary) contributes to fruit formation, these fruits are called false fruits and not true fruits.