1. Germplasm - Protoplasm contained inside the germ cells that is transmitted from one generation to other is called germplasm.
2. Branching descent-It the formation of different types of species from a common ancestor due to variations and adaptations to varying ecological niches.

DDT is an insecticide-kills most of the insects, but some become resistant varieties, in much less time scale of just month or years. It is a chance event in nature-so chance mutation.

Hardy-Weinberg principle states that allele frequencies in a population are stable and remain constant generation after generation; it is called genetic equilibrium.
Genetic drift
Genetic drift refers to the random changes in the allele frequencies of a population, in the allele frequencies of a population, that occur only by chance.
When the change in the allele frequency is so different in the original drifted population that it becomes a new species, the original population becomes founders and such an effect, is called founder effect.

(a) Homo erectus.
(b) Neanderthal man.
(c) Homo habilis.
(d) Dryopithecus and Ramapithecus.

Psilophyton is the ancestor of
(i) Horsetails (sphenopsids)
(ii) Ferns
(iii) Ginkgo
(iv) Conifers
(v) Gnetales
(vi) Progymnosperms (Cycads,Dicots, etc.)

Theory of chemical evolution or abiogenesis was proposed by Oparin and Haldane.
It states that the first form of life could have come from pre-existing non-living organic molecules (like RNA, proteins, etc.) and that formation of life was preceded by chemical evolution, i.e. formation of diverse organic molecules from inorganic constituents.
Miller's experiment:
He created conditions similar to the primitive earth in the laboratory.
Electric discharge was produced (by using electrons) in a closed flask, containing methane, hydrogen, ammonia and water vapour.
The temperature was kept at \(800\)\(^{ \circ }{ C }\). 
 After a week, he observed formation of amino acids.
Such molecules must have reacted among themselves to form giant, self-replicating molecules, the first form of life.

(a) Culture: It is defined as an accumulation of knowledge and accomplishment of Knowledge and accomplishment. Following evidences suggest that Homo erectus had a culture.
1. The tools found amongst fossil remains of this species show that its members were capable of making tools and transmitting this knowledge to next generations.
2. He had achieved techniques for hunting and utilising wild game.
3. Ability of Homo erectus to accumulate and transmit culture is the fact that members were widely dispersed and apparently successful in living in a variety of environment.
(b) Culture of Neanderthal man represent advancement from Homo erectus as his tools were of wider variety and was capable of creating fire when needed.
His methods of burial suggest a much more sophisticated type of reasoning ability.
Thus the above facts show that along with organic evolution there occurred cultural evolution.
Nature selection operates in the following ways according to Darwin's theory:
(1) All planted and animals reproduce in geometrical pattern. The number of organisms produced are much more that can survive due to limited space and food.
(2)  Due to same basic requirement competition between organisms take place and those who are better adapted to environment survive while the rest die.
(3)  The individuals having useful variation overpower those without or having harmless variations and these variations are transmitted to further generations.

The steps of chemical evolution are as follows:
(1) Origin of planets.
(2) Presence of elements.
(3) Interaction of elements to form inorganic compounds such as H ₂, H₂O,CO, HCN and CH. ₄.
(4) Formation of simple organic compounds such as sugars, amino acids, fatty acids, glycerol, purines and pyrimidines-as a result of interaction and energy from UV light and lightning. This as even well supported by Urey-Miller experiment.
(5) Simple organic molecules and even primitive inorganic molecules got dissolved and mixed in sea water.
(6) Formation of complex organic compounds. Amino acids joined to form polypeptides, and simple protein, simple sugars got converted into starches, fatty acids combined with glycerol to form fats and nucleotides joined to form nucleic acid.
(7) Formation of molecular aggregates was well supported by Sydney Fox and termed coacervates. Enzymes like substances were formed.
(8) These coacervates grow by absorbing molecules from surroundings and nucleic acid took control, turning  them into the first primitive living system
(9) Free genes diversified joined producing heterotrophs perhaps resembling viruses.
(10) Lipoproteinic membrane was formed around eobionts to form first living cells.
(11) Some of heterotrophs evolved further and became capable of making their own food by chemosynthesis and / or photosynthesis.
(12) First simple one called organisms were similar to today's cyanobacteria.

(a) Hardy-Weinberg Principle:
(i)  It states that the allele frequencies in a population are stable and remain constant from generation to generation; it is called genetic equilibrium.
(ii) The sum total of all the allelic frequencies is one.
(b) Genetic drift:
(i) Genetic drift refers to the changes in allele frequencies that occur only one by chance events.
(ii) Sometimes the change in allele frequency is so different in the new sample of population, that they become a different species.
(iii) The originally drifted population becomes the founder and such an effect is called founder effect.